ANSWERS

1. Motor cortex and the descending pyramidal pathways.

The motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements. Classically the motor cortex is an area of the frontal lobe located in the dorsal precentral gyrus immediately anterior to the central sulcus.

Components of the motor cortex are,

Primary motor cortex-located in dorsal part of the frontal lobe,it funuction with other motor areas to plan and execute movements.this area contain large amount of neurons know as betz cells.these cells along woth other neurons send long axon down the spinal cord to synapse into the interneuron circuit of the spinal cord and directly to the onto the alpha motor neurons in the spinal cord which connect to the muscles.

Pathways:As the motor axons travel down through the cerebral white matter, they move closer together and form part of the posterior limb of the internal capsule.

They continue down into the brainstem, where some of them, after crossing over to the contralateral side, distribute to the cranial nerve motor nuclei. (Note: a few motor fiberssynapse with lower motor neurons on the same side of the brainstem).

After crossing over to the contralateral side in the medulla oblongata (pyramidal decussation), the axons travel down the spinal cord as the lateral corticospinal tract.

Fibers that do not cross over in the brainstem travel down the separate ventral corticospinal tract, and most of them cross over to the contralateral side in the spinal cord, shortly before reaching the lower motor neurons

Premotor cortex-

In the frontal lobe of the brain just anterior to the primary motor cortex. The functions of the premotor cortex are diverse and not fully understood.

It projects directly to the spinal cord and therefore may play a role in the direct control of behavior, with a relative emphasis on the trunk muscles of the body.

It may also play a role in planning movement, in the spatial guidance of movement, in the sensory guidance of movement, in understanding the actions of others, and in using abstract rules to perform specific tasks

Supplementary motor cortex-

part of the primate cerebral cortex that contributes to the control of movement. It is located on the midline surface of the hemisphere just in front of (anterior to) the primary motor cortex leg representation.

Neurons in the SMA project directly to the spinal cord and may play a role in the direct control of movement.

Possible functions attributed to the SMA include the postural stabilization of the body, the coordination of both sides of the body such as during bimanual action, the control of movements that are internally generated rather than triggered by sensory events, and the control of sequences of movements

Posterior motor cortex

plays an important role in planned movements, spatial reasoning, and attention.

Damage to the posterior parietal cortex can produce a variety of sensorimotor deficits, including deficits in the perception and memory of spatial relationships, in accurate reaching and grasping, in the control of eye movement, and in attention. The two most striking consequences of PPC damage are apraxia and hemispatial neglect

2. Examination of muscle appearance and power.

The power should be tested in all limbs, comparing each side. Asystematic evaluation will enable the recognition of a particular pattern of weakness that will be in keeping with either a cerebral, spinal cord, plexus or peripheral nerve weakness.

Weakness due to a corticospinal tract lesionis most marked in the abductors and extensors of the upper limbs and the ﬂexors of the lower limbs. It is normally associated with increased tone and exaggerated reﬂexes. Weakness due to lower motor neurone lesions is usually more severe than when the upper motor neurone is involved and is seen in the distribution of the nerve affected. It is associated with wasting, hypotonia and diminished reﬂexes. Fasciculation is an irregular, non-rhythmical contraction of muscle fascicles which is most easily seen in the deltoid or calf muscles. It occurs classically in motor neurone disease but may also occur in lower motor neurone lesions, e.g. in the lower limbs following long-standing lumbar root compression.

The tone in the upper limbs should be tested using a ﬂexion–extension movement of the wrist, by holding the patient’s terminal phalanges and by pronation–supination of the forearm. The tone in the lower limbs should be tested by ﬂexion of the hip, knee and ankle.

Decreased tone This is due to: •a lower motor neurone lesion involving the spinal roots or anterior horn cell of the spinal cord • lesions of the sensory roots of the reﬂex arc, e.g. tabes dorsalis • cerebellar lesions, which cause ipsilateral hypotonia • myopathies • spinal shock (the acute phase of a severe spinal lesion usually due to trauma).

Increased tone This will be produced by any upper motor neurone lesion involving the corticospinal tracts above the level of the anterior horn cell in the spinal cord. There are three major types of hypertonicity. 1 ‘Clasp knife’ spasticity, in which the resistance is most pronounced when the movement is ﬁrst made. It is usually more marked in the ﬂexor muscles of the upper limbs and extensor muscles of the lower limbs and is a sign of an upper motor neurone lesion. 2 ‘Lead pipe’ rigidity, in which there is equal resistance to all movements. This is a characteristic feature of a lesion of the extrapyramidal system but is also seen in severe spasticity from an upper motor neurone lesion. 3 ‘Cog wheel’ rigidity, in which there is an alternating jerky resistance to movement and which occurs in degenerative lesions of the extrapyramidal system, particularly Parkinson’s disease. ‘Clonus’ is best demonstrated by ﬁrm rapid dorsiﬂexion of the foot and is indicative of marked increased tone.

3. Examination of tendon reflexes.

The deep tendon reﬂex requires the stimulus, sensory pathway, motor neurone, contracting muscle and the synapses between the neurones in order to elicit a response.

Reduced or absent tendon reﬂex This may occur due to any breach in the reﬂex arc: • sensory nerve—polyneuritis • sensory root—tabes dorsalis • anterior horn cell—poliomyelitis • anterior root—compression • peripheral motor nerve—trauma • muscle—myopathy.

Increased deep tendon reflex

Due to lesions of the pyramidal system, increased deep tendon reﬂexes may be excessively prolonged, with a larger amplitude in a cerebellar lesion. In myxoedema the relaxation phase of the reﬂex is retarded. Each deep tendon reﬂex is associated with a particular segmental innervation and peripheral nerve as listed in Table 1.3. The superﬁcial abdominal reﬂex has a segmental innervation extending from T9 in the upper abdominal region to T12 in the lower area. The reﬂex may be absent in pyramidal lesions above the level of segmental innervation, particularly in spinal lesions. However, the reﬂex may also be difﬁcult to elicit when the abdominal muscles have been stretched or damaged by surgical operations, or in a large, pendulous, obese abdomen.

Plantar reﬂex This should result in the great toe ﬂexing the metatarsophalangeal joint. The Babinski response consists of extension of the great toe at the metatarsophalangeal joint, and usually at the interphalangeal joint, and indicates disturbance of the pyramidal tract

4. Examination of superficial reflexes and muscle tone.

Check the 3^rd 2^nd question.

5. Examination of coordination.

Coordination should be tested in the upper and lower limbs. In the upper limb it is best assessed using the ‘ﬁnger–nose’ test and in the lower limb using the ‘heel–knee’ test. It is important to determine whether abnormalities of coordination are due to defects in: • cerebellar function •proprioception • muscular weakness.

6. Examination of gait.

An essential part of the examination is to observe the patient’s gait. This is best done not only as a formal part of the examination but also when the patient is not aware of observation. The type of gait is characteristic of the underlying neurological disturbance. Ahemiparesis will cause the patient to drag the leg and, if severe, the leg will be thrown out from the hip, producing the movement called circumduction. A high stepping gait occurs with a foot drop (e.g. L5 root lesion due to disc prolapse, lateral popliteal nerve palsy, peroneal muscular atrophy). The patient raises the foot too high to overcome the foot drop and the toe hits the ground ﬁrst. In tabes dorsalis the high stepping gait is due to a profound loss of position sense but

a similar gait, of lesser severity, will result from involvement of the posterior column of the spinal cord or severe sensory neuropathy which interferes with position sense. The gait is worse in the dark and the heel usually strikes the ground ﬁrst. In Parkinson’s disease or other extrapyramidal diseases the patient walks with a stooped, shufﬂing gait. The patient may have difﬁculty in starting walking and stopping. Aslight push forward will cause rapid forward movement (protopulsion). In the ataxic gait, the patient is unstable due to cerebellar disturbance. Amidline vermis tumour will result in the patient reeling in any direction. If the cerebellar hemisphere is involved then the patient will tend to fall to the ipsilateral side. Awaddling gait is associated with congenital dislocation of the hips and muscular dystrophy. The hysterical gait is often bizarre and is diminished when the patient is unaware of any observation.

7. Paralysis: upper motor neuron lesion.

Signs:  Weakness or paralysis  Spasticity

 Loss of superficial abdominal reflexes  Increased tendon reflexes  Little, if any, muscle atrophy  An extensor plantar (Babinski) response

Such signs occur with involvement of the upper motor neuron at any point, but further clinical findings depend upon the actual site of the lesion. Note that it may not be possible to localize a lesion by its motor signs alone. Localization of underlying lesion. 1) A parasagittal intracranial lesion produces an upper motor neuron deficit that characteristically affects both legs and may later involve the arms. 2) A discrete lesion of the cerebral cortex or its projections may produce a focal motor deficit involving, for example, the contralateral hand. Weakness may be restricted to the contralateral leg in patients with anterior cerebral artery occlusion or to the contralateral face and arm if the middle cerebral artery is involved. A more extensive cortical or subcortical lesion will produce weakness or paralysis of the contralateral face, arm, and leg and may be accompanied by aphasia, a visual field defect, or a sensory disturbance of cortical type. 3) A lesion at the level of the internal capsule, where the descending fibers from the cerebral cortex are closely packed, commonly results in a severe hemiparesis that involves the contralateral limbs and face. 4) A brainstem lesion commonly – but not invariably – leads to bilateral motor deficits, often with accompanying sensory and cranial nerve disturbances, and disequilibrium. A more limited lesion involving the brainstem characteristically leads to a cranial nerve disturbance on the ipsilateral side and a contralateral hemiparesis; the cranial nerves affected depend on the level at which the brainstem is involved. 5) A unilateral spinal cord lesion above the fifth cervical segment (C5) causes an ipsilateral hemiparesis that spares the face and cranial nerves. Lesions between C5 and the first thoracic segment (T1) affect the ipsilateral arm to a variable extent as well as the ipsilateral

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leg; a lesion below T1 will affect only the ipsilateral leg. Because, in practice, both sides of the cord are commonly involved, quadriparesis or paraparesis usually results. If there is an extensive but unilateral cord lesion, the motor deficit is accompanied by ipsilateral impairment of vibration and position sense and by contralateral loss of pain and temperature appreciation (BrownSequard syndrome).

With compressive and other focal lesions that involve the anterior horn cells in addition to the fiber tracts traversing the cord, the muscles innervated by the affected cord segment weaken and atrophy.

Therefore, a focal lower motor neuron deficit exists at the level of the lesion and an upper motor neuron deficit exists below it – in addition to any associated sensory disturbance.

8. Paralysis: lower motor neuron lesion and myopathic disorders.

Weakness or paralysis  Wasting and fasciculations of involved muscles  Hypotonia (flaccidity)  Loss of tendon reflexes when neurons subserving them are affected

 Normal abdominal and plantar reflexes – unless the neurons subserving them are directly involved, in which case reflex responses are lost

Localization of the Underlying Lesion. In distinguishing weakness from a root, plexus, or peripheral nerve lesion, the distribution of the motor deficit is of particular importance. Only those muscles supplied wholly or partly by the involved structure are weak. The distribution of any accompanying sensory deficit similarly reflects the location of the underlying lesion. It may be impossible to distinguish a radicular (root) lesion from discrete focal involvement of the spinal cord. In the latter situation, however, there is more often a bilateral motor deficit at the level of the lesion, a corticospinal or sensory deficit below it, or a disturbance of bladder, bowel, or sexual function. Certain disorders selectively affect the anterior horn cells of the spinal cord diffusely or the motor nerves; the extensive lower motor neuron deficit without sensory changes helps to indicate the site and nature of the pathologic involvement

C. Neuromuscular transmission disorders. Pathologic involvement of either the pre- or postsynaptic portion of the neuromuscular junction may impair neuromuscular transmission. Signs:  Normal or reduced muscle tone  Normal or depressed tendon and superficial reflexes  No sensory changes  Weakness, often patchy in distribution, not conforming to the distribution of any single anatomic structure; frequently involves the cranial muscles and may fluctuate in severity over short periods, particularly in relation to activity

D. Myopathic disorders.

Signs:  Weakness, usually most marked proximally rather than distally  No muscle wasting or depression of tendon reflexes until at least an advanced stage of the disorder  Normal abdominal and plantar reflexes  No sensory loss or sphincter disturbances In distinguishing the various myopathic disorders, it is important to determine whether the weakness is congenital or acquired, whether there is a family history of a similar disorder, and whether there is any clinical evidence that a systemic disease may be responsible. The distribution of affected muscles is often especially important in distinguishing the various hereditary myopathies.

9. Hypertonic-hypokinetic syndrome.

The most disabling feature of this disorder is hypokinesia (sometimes called bradykinesia or akinesia) - a slowness of voluntary movement and a reduction in automatic movement, such as swinging the arms while walking.

The patient's face is relatively immobile (masklike fades), with widened palpebral fissures, infrequent blinking, a certain fixity of facial expression, and a smile that develops and fades slowly. The voice is of low volume (hypophonia) and tends to be poorly modulated. Fine or rapidly alternating movements are impaired, but power is not diminished if time is allowed for it to develop.

The handwriting is small, tremulous, and hard to read. Rigidity, or increased tone – ie, increased resistance to passive movement – is a characteristic clinical feature of parkinsonism. The disturbance in tone is responsible for the flexed posture of many patients with parkinsonism.

The resistance is typically uniform throughout the range of movement at a particular joint and affects agonist and antagonist muscles alike – in contrast to the findings in spasticity, where the increase in tone is often greatest at the beginning of the passive movement (clasp-knife phenomenon) and more marked in some muscles than in others.

In some instances, the rigidity in parkinsonism is described as cogwheel rigidity because of ratchet like interruptions of passive movement that may be due, in part, to the presence of tremor.

Abnormal gait and posture. The patient generally finds it difficult to get up from bed or an easy chair and tends to adopt a flexed posture on standing. It is often difficult to start walking: so that the patient may lean farther and farther forward while walking in place before being able to advance.

The gait itself is characterized by small, shuffling steps and absence of the arm swing that normally accompanies locomotion; there is generally some unsteadiness on turning, and there may be difficulty in stopping. In advanced cases, the patient tends to walk with increasing speed to prevent a fall (festinating gait) because of the altered center of gravity that results from the abnormal posture.

The 4- to 6-Hz tremor of parkinsonism is characteristically most conspicuous at rest; it increases at times of emotional stress and often improves during voluntary activity.

It commonly begins in the hand or foot, where it takes the form of rhythmic flexionextension of the fingers or of the hand or foot or of rhythmic pronation-supination of the forearm. It frequently involves the face in the area of the mouth as well. Although it may ultimately be present in all of the limbs, it is not uncommon for the tremor to be confined to one limb or to the two limbs on one side-for months or years before it becomes more generalized. In some patients tremor never becomes prominent.

10. Abnormal movements.

Abnormal movements (hypotonic-hyperkinetic syndrome) can be classified as tremor, chorea, athetosis or dystonia, ballismus, myoclonus, or tics.

The abnormal movements are not present during sleep. They are generally enhanced by emotional stress and by voluntary activity. In some cases, abnormal movements or postures occur only during voluntary activity and sometimes only during specific activities such as writing, speaking, or chewing.

A tremor is a rhythmic oscillatory movement best characterized by its relationship to voluntary motor activity – ie, according to whether it occurs at rest, during maintenance of a particular posture, or during movement. Tremor is enhanced by emotional stress and disappears during sleep. Tremor that occurs when the limb is at rest is generally referred to as static tremor or rest tremor. If present during sustained posture, it is called a postural tremor; while this tremor may continue during movement, movement does not increase its severity. When present during movement but not at rest, it is generally called an intention tremor. Both postural and intention tremors are also called action tremors. An 8- to 12-Hz tremor of the outstretched hands is a normal finding. Physiologic tremor may be enhanced by fear or anxiety. A more conspicuous postural tremor may also be found following excessive physical activity or sleep deprivation. Intention tremor occurs during activity. If the patient is asked to touch his or her nose with a finger, for example, the arm exhibits tremor during movement, often more marked as the target is reached.

This form of tremor is sometimes mistaken for limb ataxia, but the latter has no rhythmic oscillatory component. Intention tremor results from a lesion affecting the superior cerebellar peduncle. Rest tremor usually has a frequency of 4-6 Hz and is characteristic of parkinsonism whether the disorder is idiopathic or secondary (ie, postencephalitic, toxic, or drug-induced in origin). The rate of the tremor, its relationship to activity, and the presence of rigidity or hypokinesia usually distinguish the tremor of parkinsonism from other forms. Tremor in the hands may appear as a "pill-rolling" maneuver-rhythmic, opposing circular movements of the thumb and index finger. There may be alternating flexion and extension of the fingers or hand, or alternating pronation and supination of the forearm; in the feet, rhythmic alternating flexion and extension are common.

The word “chorea” denotes rapid irregular muscle jerks that occur involuntarily and unpredictably in different parts of the body.

In florid cases, the often forceful involuntary movements of the limbs and head and the accompanying facial grimacing and tongue movements are unmistakable. Voluntary movements may be distorted by the superimposed involuntary ones.

In mild cases, however, patients may exhibit no more than a persistent restlessness and clumsiness. Power is generally full, but there may be difficulty in maintaining muscular contraction such that, for example, hand grip is relaxed intermittently (milkmaid grasp). The gait becomes irregular and unsteady, with the patient suddenly dipping or lurching to one side or the other (dancing gait).

Speech often becomes irregular in volume and tempo and may be explosive in character. In some patients, athetotic movements or dystonic posturing may also be prominent. Chorea disappears during sleep.

Hemiballismus is unilateral chorea that is especially violent because the proximal muscles of the limbs are involved. It is most often due to vascular disease in the contralateral subthalamic nucleus and commonly resolves spontaneously in the weeks following its onset.

It is sometimes due to other types of structural disease; in the past, it was an occasional complication of thalamotomy. Pharmacologic treatment is similar to that for chorea.

The term “athetosis” generally denotes abnormal movements that are slow, sinuous, and writhing in character. When the movements are so sustained that they are better regarded as abnormal postures, the term dystonia is used, and many now use the terms interchangeably. The abnormal movements and postures may be generalized or restricted in distribution.

In the latter circumstance, one or more of the limbs may be affected (segmental dystonia) or the disturbance may be restricted to localized muscle groups (focal dystonia).

Myoclonic jerks are sudden, rapid, twitch-like muscle contractions. Generalized myoclonus has a widespread distribution, while focal or segmental myoclonus is restricted to a particular part of the body. Myoclonus can be spontaneous, or it can be brought on by sensory stimulation, arousal, or the initiation of movement (action myoclonus).

Myoclonus may occur as a normal phenomenon (physiologic myoclonus) in healthy persons, as an isolated abnormality (essential myoclonus), or as a manifestation of epilepsy (epileptic myoclonus). It can also occur as a feature of a variety of degenerative, infectious, and metabolic disorders (symptomatic myoclonus).

Tics are sudden, recurrent, quick, coordinated abnormal movements that can usually be imitated without difficulty. The same movement occurs again and again and can be suppressed voluntarily for short periods, although doing so may cause anxiety. Tics tend to worsen with stress, diminish during voluntary activity or mental concentration, and disappear during sleep.

Transient simple tics are very common in children, usually terminate spontaneously within 1 year (often within a few weeks), and generally require no treatment.

Chronic simple tics can develop at any age but often begin in childhood, and treatment is unnecessary in most cases. The benign nature of the disorder must be explained to the patient. Persistent simple or multiple tics of childhood or adolescence generally begin before age of 15 years.

There may be single or multiple motor tics and often vocal tics but complete remission occurs by the end of adolescence. The syndrome of chronic multiple motor and vocal tics is generally referred to as Gilles de la Tourette's syndrome, after the French physician who was one of the first to describe its clinical features

11. Cerebellar ataxia.

Ataxia is incoordination or clumsiness of movement that is not the result of muscular weakness. It is caused by vestibular, cerebellar, or sensory (proprioceptive) disorders. Ataxia can affect eye movement, speech (producing dysarthria), individual limbs, the trunk, stance, or gait. Cerebellar ataxia is produced by lesions of the cerebellum itself or its afferent or efferent connections in the cerebellar peduncles, red nucleus, pons, or spinal cord. Because of the crossed connection between the frontal cerebral cortex and the cerebellum, unilateral frontal disease can also occasionally mimic a disorder of the contralateral cerebellar hemisphere. The clinical manifestations of cerebellar ataxia consist of irregularities in the rate, rhythm, amplitude, and force of voluntary movements. Cerebellar ataxia is commonly associated with hypotonia, which results in defective posture maintenance. Limbs are easily displaced by a relatively small force and, when shaken by the examiner, exhibit an increased range of excursion. The range of arm swing during walking may be similarly increased. Tendon reflexes take on a pendular quality, so that several oscillations of the limb may occur after the reflex is elicited, although neither the force nor the rate of the reflex is increased. When muscles are contracted against resistance that is then removed, the antagonist muscle fails to check the movement and compensatory muscular relaxation does not ensue promptly. This results in rebound movement of the limb. In addition to hypotonia, cerebellar ataxia is associated with incoordination of voluntary movements. Simple movements are delayed in onset, and their rates of acceleration and deceleration are decreased. The rate, rhythm, amplitude, and force of movements fluctuate, producing a jerky appearance. Because these irregularities are most pronounced during initiation and termination of movement, their most obvious clinical manifestations include terminal dysmetria, or "overshoot," when the limb is directed at a target, and terminal intention tremor as the limb approaches the target.

Dysdiadochokinesia denotes rapid alternating movements that are clumsy and irregular in terms of rhythm and amplitude.

More complex movements tend to become decomposed into a succession of individual movements rather than a single smooth motor act (asynergia). Movements that involve rapid changes in direction or greater physiologic complexity, such as walking, are most severely affected. Speech becomes dysarthric and takes on an irregular and explosive quality in patients with lesions that involve the cerebellar hemispheres. Because of the cerebellum's prominent role in the control of eye movements, ocular abnormalities are a frequent consequence of cerebellar disease. These include nystagmus and related ocular oscillations, gaze pareses, and defective saccadic and pursuit movements. Anatomic basis of distribution of clinical signs. Midline lesions. The middle zone of the cerebellum – the vermis and flocculonodular lobe and their associated subcortical (fastigial) nuclei – is involved in the control of axial functions, including eye movements, head and trunk posture, stance, and gait. Midline cerebellar disease therefore results in a clinical syndrome characterized by nystagmus and other disorders of ocular motility, oscillation of the head and trunk (titubation), instability of stance, and gait ataxia.

Selective involvement of the superior cerebellar vermis, as commonly occurs in alcoholic cerebellar degeneration, produces exclusively or primarily ataxia of gait, as would be predicted from the somatotopic map of the cerebellum.

Hemispheric lesions. The lateral zones of the cerebellum (cerebellar hemispheres) help to coordinate movements and maintain tone in the ipsilateral limbs.

The hemispheres also have a role in regulating ipsilateral gaze. Disorders affecting one cerebellar hemisphere cause ipsilateral hemiataxia and hypotonia of the limbs as well as nystagmus and transient ipsilateral gaze paresis (an inability to look voluntarily toward the affected side).

Cerebellar dysarthria may also occur with paramedian lesions in the left cerebellar hemisphere. Diffuse lesions.

Many cerebellar disorders – typically toxic, metabolic, and degenerative conditions – affect the cerebellum diffusely. The clinical picture in such states combines the features of midline and bilateral hemisphere disease.

12. Sensory and vestibular ataxia.

Sensory ataxia results from disorders that affect the proprioceptive pathways in peripheral sensory nerves, sensory roots,

posterior columns of the spinal cord, or medial lemnisci (Fig. 4.4). Thalamic and parietal lobe lesions are rare causes of contralateral sensory hemiataxia. Sensations of joint position and movement (kinesthesis)

originate in pacinian corpuscles and unencapsulated nerve endings in joint capsules, ligaments, muscle, and periosteum. Such sensations are transmitted via heavily myelinated A-fibers of primary afferent neurons, which enter the dorsal horn of the spinal cord and ascend uncrossed in the posterior columns.

Proprioceptive information from the legs is conveyed in the medially located fasciculus gracilis, and that from the arms is conveyed in the more laterally situated fasciculus cuneatus.

These tracts synapse on second-order sensory neurons in the nucleus gracilis and nucleus cuneatus in the lower medulla. The second-order neurons decussate as internal arcuate fibers and ascend in the contralateral medial lemniscus.

They terminate in the ventral posterior nucleus of the thalamus, from which third-order sensory neurons project to the parietal cortex. Numbness or tingling in the legs is common in patients with sensory ataxia. Clinical findings include defective joint position and vibration sense in the legs and sometimes the arms, unstable stance with Romberg's sign, and a gait of slapping or steppage quality.

Because proprioceptive deficits may, to some extent, be compensated for by other sensory cues, patients with sensory ataxia may report that their balance is improved by watching their feet when they walk or by using a cane or the arm of a companion for support.

They thus find that they are much more unsteady in the dark and may experience particular difficulty in descending stairs. Sensory ataxia from polyneuropathy or posterior column lesions typically affects the gait and legs in symmetric fashion; the arms are involved to a lesser extent or spared entirely. Vertigo, nystagmus, and dysarthria are characteristically absent.

Causes of sensory ataxia

Polyneuropathy

Autosomal dominant sensory

ataxic neuropathy

Cisplatin (cis-platinum)

Dejerine-Sottas disease

Diabetes

Diphtheria

Hypothyroidism

Immune-mediated neuropathies

Isoniazid

Paraneoplastic sensory

neuronopathy

Pyridoxine

Refsum's disease

Myelopathy

Acute transverse myelitis

AIDS (vacuolar myelopathy)

Multiple sclerosis

Tumor or cord compression

Vascular malformations

Polyneuropathy or myelopathy

Friedreich's ataxia Neurosyphilis (tabes dorsalis)

Nitrous oxide

Vitamin B12 deficiency

Vitamin E deficiency

Vestibular Ataxia Ataxia associated with vertigo suggests a vestibular disorder, whereas numbness or tingling in the legs is common in patients with sensory ataxia. Vestibular ataxia can be produced by the same central and peripheral lesions that cause vertigo. Nystagmus is frequently present and is typically unilateral and most pronounced on gaze away from the side of vestibular involvement. Dysarthria does not occur. Vestibular ataxia is gravity-dependent: incoordination of limb movements cannot be demonstrated when the patient is examined lying down but becomes apparent when the patient attempts to stand or walk. A. Joint position sense. In patients with sensory ataxia, joint position sense is always impaired in the legs and may be defective in the arms as well. Testing is accomplished by asking the patient to detect passive movement of the joints, beginning distally and moving proximally, to establish the upper level of deficit in each limb. Abnormalities of position sense can also be demonstrated by positioning one limb and having the patient, with eyes closed, place the opposite limb in the same position. B. Vibratory sense. Perception of vibratory sensation is frequently impaired in patients with sensory ataxia. The patient is asked to detect the vibration of a 128-Hz tuning fork placed over a bony prominence. Again, successively more proximal sites are tested to determine the upper level of the deficit in each limb or over the trunk. The patient's threshold for appreciating the vibration is compared with the examiner's own ability to detect it in the hand that holds the tuning fork. C. Reflexes. Tendon reflexes are typically hypoactive, with a pendular quality, in cerebellar disorders; unilateral cerebellar lesions produce ipsilateral hyporeflexia. Hyporeflexia of the legs is a prominent manifestation of Friedreich's ataxia, tabes dorsalis, and polyneuropathies that cause sensory ataxia. Hyperactive reflexes and extensor plantar responses may accompany ataxia caused by multiple sclerosis, vitamin BI2 deficiency, focal brainstem lesions, and certain olivopontocerebellar or spinocerebellar degenerations.

13. Anatomical substrate of sensation.

The sensory pathway between the skin and deeper structures and the cerebral cortex involves three neurons, with two synapses occurring centrally (Fig. 2.1). The cell body of the first sensory neuron of the spinal nerve is in the dorsal root ganglion.

Each cell located there sends a peripheral process that terminates in a free nerve ending or encapsulated sensory receptor and a central process that enters the spinal cord. Sensory receptors are relatively specialized for particular sensations and, in addition to free nerve endings (pain), include Meissner's corpuscles, Merkel's corpuscles, and hair cells (touch); Krause's end-bulbs (cold); and Ruffini's corpuscles (heat).

The location of the first central synapse depends upon the type of sensation but is either in the posterior gray column of the spinal cord or in the upward extension of this column in the lower brainstem.

The second synapse is located in the ventral posterolateral (VPL) nucleus of thalamus, from which there is sensory radiation to the cerebral cortex. In the spinal cord, fibers mediating touch, pressure, and postural sensation ascend in the posterior white columns to the medulla, where they synapse in the gracile and cuneate nuclei.

From these nuclei, fibers cross the midline and ascend in the medial lemniscus to the thalamus. Other fibers that mediate touch and those subserving pain and temperature appreciation synapse on neurons in the posterior horns of the spinal cord, particularly in the substantia gelatinosa.

The fibers from these neurons then cross the midline and ascend in the anterolateral part of the cord; fibers mediating touch pass upward in the anterior spinothalamic tract, whereas pain and temperature fibers generally travel in the lateral spinothalamic tract.

Fibers from this anterolateral system pass to the thalamic relay nuclei and to nonspecific thalamic projection nuclei and the mesencephalic reticular formation. Fibers from the lemniscal and anterolateral systems are joined in the brainstem by fibers subserving sensation from the head.

Cephalic pain and temperature sensation are dependent upon the spinal nucleus of the trigeminal (V) nerve; touch, pressure, and postural sensation are conveyed mostly by the main sensory and mesencephalic nuclei of this nerve.

14. Examination of primary sensory modalities.

A. Light touch. The appreciation of light touch is evaluated with a wisp of cotton wool (a finger, a feather, a piece of tissue paper, or the like), which is brought down carefully on a small region of skin. The patient lies quietly, with the eyes closed, and makes a signal each time the stimulus is felt. The appreciation of light touch depends on fibers that traverse the posterior column of the spinal cord in the gracile (leg) and cuneate (arm) fasciculi ipsilaterally, passing to the medial lemniscus of the brainstem, and on fibers in the contralateral anterior spinothalamic tract.

B. Pain & temperature. The ability to feel pain should be tested by pinching a fold of skin or by asking the patient to indicate whether the point of a pin (not a hypodermic needle, which is likely to puncture the skin and draw blood) feels sharp or blunt.

Temperature appreciation is evaluated by application to the skin of containers of hot or cold water.

Pain and temperature appreciation depend upon the integrity of the lateral spinothalamic tracts. The afferent fibers cross in front of the central canal after ascending for two or three segments from their level of entry into the cord.

C. Deep pressure. Deep pressure sensibility is evaluated by pressure on the tendons, such as the Achilles tendon at the ankle.

D. Vibration. Vibration appreciation is evaluated with a tuning fork (128 Hz) that is set in motion and then placed over a bony prominence; the patient is asked to indicate whether vibration, rather than simple pressure, is felt. Many elderly patients have impaired appreciation of vibration below the knees.

E. Joint position. Joint position sense is tested by asking the patient to indicate the direction of small passive movements of the terminal interphalangeal joints of the fingers and toes. Patients with severe impairment of joint position sense may exhibit slow, continuous movement of the fingers (pseudoathetoid movement) when attempting to hold the hands outstretched with the eyes closed. For clinical purposes, both joint position sense and the ability to appreciate vibration are considered to depend on fibers carried in the posterior columns of the cord, although there is evidence that this is not true for vibration.

15.Examination of complex sensory functions.

A. Romberg's test. The patient is asked to assume a steady stance with feet together, arms outstretched, and eyes closed and is observed for any tendency to sway or fall. The test is positive (abnormal) if unsteadiness is markedly increased by eye closure as occurs, for example, in tabes dorsalis. A positive test is indicative of grossly impaired joint position sense in the legs.

B. Two-point discrimination. The ability to distinguish simultaneous touch at two neighboring points depends upon the integrity of the central and peripheral nervous system, the degree of separation of the two points, and the part of the body that is stimulated. The patient is required to indicate whether he or she is touched by one or two compass points, while the distance between the points is varied in order to determine the shortest distance at which they are recognized as different points. The threshold for two-point discrimination approximates 4 mm at the fingertips and may be several centimeters on the back. When peripheral sensory function is intact, impaired two-point discrimination suggests a disorder affecting the sensory cortex.

C. Graphesthesia, stereognosis, & barognosis. Agraphesthesia, the inability to identify a number traced on the skin of the palm of the hand despite normal cutaneous sensation, implies a lesion involving the contralateral parietal lobe. The same is true of inability to distinguish between various shapes or textures by touch (astereognosis) or impaired ability to distinguish between different weights (abarognosis).

D. Bilateral sensory discrimination. In some patients with apparently normal sensation, simultaneous stimulation of the two sides of the body reveals an apparent neglect of (or inattention to) sensation from one side, usually because of some underlying contralateral cerebral lesion.

16. Sensory disturbances in patients with peripheral nerve and root lesions.

A. Mononeuropathy.

In patients with a lesion of a single peripheral nerve, sensory loss is usually less than would have been predicted on anatomic grounds because of overlap from adjacent nerves . Moreover, depending upon the type of lesion, the fibers in a sensory nerve may be affected differently. Compressive lesions, for example, tend to affect preferentially the large fibers that subserve touch.

B. Polyneuropathy. In patients with polyneuropathies, sensory loss is generally symmetric and is greater distally than proximally – as suggested by the term stocking-and-glove sensory loss. As a general rule the loss will have progressed almost to the knees before the hands are affected. Certain metabolic disorders (such as Tangier disease, a recessive trait characterized by the near absence of highdensity lipoproteins) preferentially involve small nerve fibers that subserve pain and temperature appreciation. Sensory loss may be accompanied by a motor deficit and reflex changes.

C. Root lesions. Nerve root involvement produces impairment of cutaneous sensation in a segmental pattern, but because of overlap there is generally no loss of sensation unless two or more adjacent roots are affected.

Pain is often a conspicuous feature in patients with compressive root lesions. Depending on the level affected, there may be loss of tendon reflexes (C5-6, biceps and brachioradialis; C7-8, triceps; L3-4, knee; S1, ankle), and if the anterior roots are also involved, there may be weakness and muscle atrophy.

17. Sensory disturbances in patients with spinal cord lesions.

In patients with a spinal cord lesion, there may be a transverse sensory level. Physiologic areas of increased sensitivity do occur, however, at the costal margin, over the breasts, and in the groin, and these must not be taken as abnormal. Therefore, the level of a sensory deficit affecting the trunk is best determined by careful sensory testing over the back rather than the chest and abdomen.

A. Central spinal cord lesion. With a central spinal cord lesion – such as occurs in syringomyelia, following trauma, and with certain cord tumors – there is characteristically a loss of pain and temperature appreciation with sparing of other modalities. This loss is due to the interruption of fibers conveying pain and temperature that cross from one side of the spinal cord to the spinothalamic tract on the other. Such a loss is usually bilateral, may be asymmetric, and involves only the fibers of the involved segments. It may be accompanied by lower motor neuron weakness in the muscles supplied by the affected segments and sometimes by a pyramidal and posterior column deficit below the lesion.

B. Anterolateral spinal cord lesion. Lesions involving the anterolateral portion of the spinal cord (lateral spinothalamic tract) can cause contralateral impairment of pain and temperature appreciation in segments below the level of the lesion. The spinothalamic tract is laminated, with fibers from the sacral segments the outermost. Intrinsic spinal cord (intramedullary) lesions often spare the sacral fibers, while extramedullary lesions, which compress the spinal cord, tend to involve these fibers as well as those arising from more rostral levels.

C. Anterior spinal cord lesion. With destructive lesions involving predominantly the anterior portion of the spinal cord, pain and temperature appreciation are impaired below the level of the lesion from lateral spinothalamic tract involvement. In addition, weakness or paralysis of muscles supplied by the involved segments of the spinal cord results from damage to motor neurons in the anterior horn.

With more extensive disease, involvement of the corticospinal tracts in the lateral funiculi may cause a pyramidal deficit below the lesion. There is relative preservation of posterior column function. Ischemic myelopathies caused by occlusion of the anterior spinal artery take the form of anterior spinal cord lesions.

D. Posterior spinal column lesion. A patient with a posterior column lesion may complain of a tight or bandlike sensation in the regions corresponding to the level of spinal involvement and sometimes also of paresthesias (like electric shocks) radiating down the extremities on neck flexion (Lhermitte's sign). There is loss of vibration and joint position sense below the level of the lesion, with preservation of other sensory modalities. The deficit may resemble that resulting from involvement of large fibers in the posterior roots.

E. Spinal cord hemisection. Lateral hemisection of the spinal cord leads to Brown-Sequard's syndrome. Below the lesion, there is an ipsilateral pyramidal deficit and disturbed appreciation of vibration and joint position sense, with contralateral loss of pain and temperature appreciation that begins two or three segments below the lesion.

18. Sensory disturbances in patients with brainstem and hemispheric lesions.

Brainstem lesions. Sensory disturbances may be accompanied by a motor deficit, cerebellar signs, and cranial nerve palsies when the lesion is in the brainstem. In patients with lesions involving the spinothalamic tract in the dorsolateral medulla and pons, pain and temperature appreciation are lost in the limbs and trunk on the opposite side of the body.

When such a lesion is located in the medulla, it also typically involves the spinal trigeminal nucleus, impairing pain and temperature sensation on the same side of the face as the lesion. The result is a crossed sensory deficit that affects the ipsilateral face and contralateral limbs.

In contrast, spinothalamic lesions above the spinal trigeminal nucleus affect the face, limbs, and trunk contralateral to the lesion. With lesions affecting the medial lemniscus, there is loss of touch and proprioception on the opposite side of the body. In the upper brainstem, the spinothalamic tract and medial lemniscus run together so that a single lesion may cause loss of all superficial and deep sensation over the contralateral side of the body. Thalamic lesions. Thalamic lesions may lead to loss or impairment of all forms of sensation on the contralateral side of the body. Spontaneous pain, sometimes with a particularly unpleasant quality, may occur on the affected side. Patients may describe it as burning, tearing, knifelike, or stabbing, but often have difficulty characterizing it. Any form of cutaneous stimulation can lead to painful or unpleasant sensations. Such a thalamic syndrome (Dejerine-Roussy syndrome) can also occasionally result from lesions of the white matter of the parietal lobe or from cord lesions.

Sensory cortex lesions. Disease limited to the sensory cortex impairs discriminative sensory function on the opposite side of the body. Thus, patients may be unable to localize stimuli on the affected side or to recognize the position of different parts of the body.

They may not be able to recognize objects by touch or to estimate their size, weight, consistency, or texture. Cortical sensory disturbances are usually more conspicuous in the hands than in the trunk or proximal portions of the limbs

19. Pain syndromes.

Pain from infective, inflammatory, or neoplastic processes is a feature of many visceral diseases and may be a conspicuous component of certain neurologic or psychiatric diseases. It can also occur with no obvious cause.

In evaluating patients with pain, it is important to determine the level of the nervous system at which the pain arises and whether it has a primary neurologic basis. In taking the history, attention should be focused on the mode of onset, duration, nature, severity, and location of the pain; any associated symptoms; and factors that precipitate or relieve the pain.

Treatment depends on the underlying cause and clinical context of the pain and is discussed below. A brief comment is necessary, however, about stimulation-produced analgesia and, in particular, about spinal cord stimulation (previously known as dorsal column stimulation) and peripheral nerve stimulation.

These approaches were based on principles encapsulated by the Gate Control theory, in which activation of large myelinated fibers was held to interrupt nociceptive transmission in the spinal cord, but their precise mechanism of action is uncertain. Spinal cord stimulation is known to affect certain neurotransmitter systems, particularly substance P and γ-aminobutyric acid (GABAergic) systems.

A. Peripheral nerve pain. Pain arising from peripheral nerve lesions is usually localized to the region that is affected pathologically or confined to the territory of the affected nerve. It may have a burning quality, and when mixed (motor and sensory) nerves are involved, there may be an accompanying motor deficit. Painful peripheral neuropathies include those caused by diabetes, polyarteritis, alcoholic-nutritional deficiency states, and the various entrapment neuropathies.

Treatment of pain associated with peripheral neuropathies is discussed in the section on diabetic neuropathy earlier. The term causalgia correctly is used for the severe persistent pain, often burning in quality, that results from nerve trauma.

Such pain often radiates to a more extensive territory than is supplied by the affected nerve and is associated with exquisite tenderness. Onset of pain may be at any time within the first 6 weeks or so after nerve injury. Pain may be accompanied by increased sweating and vasoconstriction of the affected extremity, which is commonly kept covered up and still by the patient. Reflex sympathetic dystrophy is a more general term that denotes sympathetically mediated pain syndromes precipitated by a wide variety of tissue injuries, including soft tissue trauma, bone fractures, and myocardial infarction.

Medical approaches to treatment include sympathetic blockade by injection of local anesthetics into the sympathetic chain or by regional infusion of reserpine or guanethidine. One such procedure may produce permanent cessation of pain-or repeated sympathetic blocks may be required. Surgical sympathectomy is beneficial in up to 75% of cases. Spinal cord stimulation has also been successful in some instances for the treatment of reflex sympathetic dystrophy or causalgia.

B. Radicular pain. Radicular pain is localized to the distribution of one or more nerve roots and is often exacerbated by coughing, sneezing, and other maneuvers that increase intraspinal pressure. It is also exacerbated by maneuvers that stretch the affected roots.

Passive straight leg raising leads to stretching of the sacral and lower lumbar roots, as does passive flexion of the neck. Spinal movements that narrow the intervertebral foramina can aggravate root pain.

Extension and lateral flex ion of the head to the affected side may thus exacerbate cervical root symptoms. In addition to pain, root lesions can cause paresthesias and numbness in a dermatomal distribution; they can also cause segmental weakness and reflex changes, depending upon the level affected. Useful modes of treatment include immobilization, nonsteroidal anti-inflammatory drugs or other analgesics, and surgical decompression.

C. Thalamic pain. Depending upon their extent and precise location, thalamic lesions may lead to pain in all or part of the contralateral half of the body. The pain is of a burning nature with a particularly unpleasant quality that patients have difficulty describing.

It is aggravated by emotional stress and tends to develop during partial recovery from a sensory deficit caused by the underlying thalamic lesion. Mild cutaneous stimulation may produce very unpleasant and painful sensations.

This combination of sensory loss, spontaneous pain, and perverted cutaneous sensation has come to be called Dejerine-Roussy syndrome. Similar pain can be produced by a lesion that involves the parietal lobe or the sensory pathways at any point in the cord (posterior columns or spinothalamic tract) or in the brainstem. Treatment with analgesics, anticonvulsants (carbamazepine or phenytoin), or antidepressants and phenothiazines in combination is occasionally helpful.

20. Functional anatomy of the spinal cord.

The spinal cord is located inside the vertebral canal, which is formed by the foramina of 7 cervical, 12 thoracic, 5 lumbar, and 5 sacral vertebrae, which together form the spine. It extends from the foramen magnum down to the level of the first and second lumbar vertebrae (at birth down to second and third lumbar vertebrae).

The spinal cord is composed of 31 segments: 8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5 sacral (S), and 1 coccygeal (Co), mainly vestigial (Fig. 3.1). The spinal nerves comprise the sensory nerve roots, which enter the spinal cord at each level, and the motor roots, which emerge from the cord at each level. The spinal nerves are named and numbered according to the site of their emergence from the vertebral canal.

C1-7 nerves emerge above their respective vertebrae. C8 emerges between the seventh cervical and first thoracic vertebrae. The remaining nerves emerge below their respective vertebrae.

The dorsal rami of C1-4 are located in the suboccipital region.

C1 participates in the innervation of neck muscles, including the semispinalis capitis muscle.

C2 carries sensation from the back of the head and scalp along with motor innervation to several muscles in the neck. C3-C5 contribute to forming the phrenic nerve and innervating the diaphragm.

C5-T1 provide motor control for the upper extremities and related muscles. The thoracic cord has 12 segments and provides motor control to the thoracoabdominal musculature. The lumbar and sacral portions of the cord have 5 segments each. L2-S2 provide motor control to lower extremities and related muscles.

The conus medullaris is the cone-shaped termination of the caudal cord. The pia mater continues caudally as the filum terminate through the dural sac and attaches to the coccyx. The coccyx has only one spinal segment. The cauda equina (Latin for horse tail) is the collection of lumbar and sacral spinal nerve roots that travel .

The external part of the spinal cord consists of white matter, while the internal part is composed of gray matter.

The white matter includes the 3 funiculi, posterior, lateral, and anterior. Each contains ascending and descending tracts . A tract is usually named by a composite of its origin and destination.

The gray matter can be divided into 10 laminae/layers or into 4 parts: anterior or ventral horn (ie, motor neurons; laminae VIII, IX, and part of VII), posterior or dorsal horn (ie, sensory part; laminae I-VI), intermediate zones (ie, associate neurons; lamina VII), and lateral horns (ie, part of the intermediate zone, present in the thoracic and lumbar segments, where sympathetic neurons are located).

The cell bodies of the sensory nerves are located in the dorsal root ganglia. Each dorsal root contains the input from all the structures within the distribution of its corresponding body segment (ie, somite).

Dermatomal maps portray sensory distributions for each level. These maps differ somewhat according to the methods used in their construction.

Charts based on injection of local anesthetics into single dorsal root ganglia show bands of hypalgesia to be continuous longitudinally from the periphery to the spine. Maps derived from other methods, such as observation of herpes zoster lesion distributions or surgical root section, show discontinuous patterns. In addition, innervation from one dermatomal segment to another overlaps considerably, more so for touch than for pain. As the dermatomes travel from the back to the chest and abdomen, they tend to dip inferiorly.

21. Autonomic pathways and disturbances of bladder, bowel, and sexual function.

Preganglionic sympathetic neurons are located in the intermediolateral cell column (lamina VII), which lies in the lateral aspect of the gray matter at levels T1-L3. Preganglionic fibers pass through the ventral roots, spinal nerves, and white communicating rami, ending in the sympathetic paravertebral ganglia at different levels. They are cholinergic. Second-order neurons then reach the end organ and in most cases use norepinephrine as their neurotransmitter. Sacral preganglionic neurons are located in and near the intermediolateral nucleus of S2-S4. They are cholinergic and emerge from the spinal cord, synapsing in the end organ ganglia. Postganglionic neurons are cholinergic and control defecation, urination, and erection. The clinical manifestations of bladder, bowel, and sexual disturbances depend on the site of the lesion (peripheral/central, unilateral/bilateral): Spinal cord transection above the sacral level cuts off the bladder and bowel from the supraspinally derived (cortical) impulses subserving the voluntary control of micturition and defecation, but all of the afferent and efferent nerve pathways of the bladder remain intact, including the spinal reflex arc for bladder emptying. The result is a spastic (automatic) neurogenic bladder, which empties itself reflexively whenever it is filled to a certain volume. Penile erection remains possible, though there may be retrograde ejaculation into the bladder. Lesions of the conus medullaris and cauda equine (as well as sacral plexus and pelvic plexus) inactivate the sacral centers for micturition and defecation. The result is atony of the bladder (a flaccid neurogenic bladder) and bowel musculature, leading to severe impairment of emptying. Bladder filling can no longer be perceived, either consciously or unconsciously. Tone is preserved in the sympathetically elevated vesical sphincter; the bladder, therefore, continues to fill until the passive intravesical pressure overcomes the closing force of the sphincter. The continually overfilled bladder lets out small amounts of urine at short intervals (overflow incontinence). Defecation, meanwhile, occurs passively and in uncontrolled fashion through a patulous anal sphincter. In the male, lesions of these structures cause erectile impotence. Psychosexually mediated arousal remains possible in rare cases because of the preserved sympathetic efferent innervation through the hypogastric plexus. Thus, a small number of affected men are still able to have an emission of semen, but without ejaculation, and without rhythmic contraction of the pelvic floor muscles.

22. Complete spinal cord transection syndrome.

In the acute phase, the classic syndrome of complete spinal cord transection at the high cervical level consists of respiratory insufficiency, quadriplegia, upper and lower extremity areflexia, anesthesia below the affected level, neurogenic shock (hypotension without compensatory tachycardia), loss of rectal and bladder sphincter tone, and urinary and bowel retention leading to abdominal distention, ileus, and delayed gastric emptying. This constellation of symptoms is called spinal shock. Horner syndrome (ie, ipsilateral ptosis, miosis, and anhydrosis) is also present with higher lesions because of interruption of the descending sympathetic pathways originating from the hypothalamus. Patients experience problems with temperature regulation because of the sympathetic impairment, which leads to hypothermia. Lower cervical level injury spares the respiratory muscles. High thoracic lesions lead to paraparesis instead of quadriparesis, but autonomic symptoms are still marked. In lower thoracic and lumbar lesions, hypotension is not present but urinary and bowel retention are. In the subacute phase, the flaccidity of spinal shock is replaced by the return of intrinsic activity of spinal neurons and spasticity develops. This usually happens in humans within 3 weeks of injury. However, the spinal shock phase may be prolonged by other medical complications, such as infections. Quadriplegia and sensory loss below the level of injury persist, but spinal reflexes return. Because modulation from supraspinal centers is lost, hyperreflexia with increased tone and extensor plantar responses are noted. At any given level, with more extensive involvement of the anterior horn, flaccidity with loss of reflex activity and atrophy is present in a lower motor neuron pattern (as is common in diseases such as poliomyelitis). Usually the initial hypotension after high lesions resolves, although orthostatic hypotension persists. For lesions above the lumbosacral centers for bladder control, the initial urinary retention is replaced by development of a spastic (automatic) neurogenic bladder. Lower lesions lead to permanent atonic bladder (a flaccid neurogenic bladder). Autonomic hyperreflexia in the subacute phase is characterized by massive firing of sympathetic neurons after distention, stimulation, or manipulation of the bladder and bowels. Cutaneous stimulation with painful or cold stimuli can also lead to massive sympathetic firing. This is a life-threatening condition because blood pressure may increase as high as 300 mm Hg, leading to intracerebral hemorrhage, confusional states, and death. A response to the massive sympathetic discharge is generated at the brainstem level. However, interruption of descending projections to the spinal cord can prevent inhibition of the spinal cord sympathetic centers, which continue to fire inappropriately until the stimulus is removed. A vagal inhibitory reflex to the heart is generated, which leads to bradycardia and worsening symptoms.

23. Anterior cord syndrome. Central cord syndrome. Radiculopathy syndromes.

Anterior cord syndrome. The anterior cord syndrome is typically observed with anterior spinal artery infarction and results in paralysis below the level of the lesion, with loss of pain and temperature sensation below the level of the lesion and relative sparing of touch, vibration, and position sense (because the posterior columns receive their primary blood supply from the posterior spinal arteries).

Central cord syndrome. Central cord syndrome is observed most often in syringomyelia, hydromyelia, and trauma. Hemorrhage and intramedullary tumors such as central canal ependymoma are other causes. Since central cord syndrome is more common in the cervical cord, the arms are often weak with preservation of strength in the legs ("man-in-a-barrel syndrome"). Considerable recovery is common. This syndrome is associated with variable sensory and reflex deficits; often the most affected sensory modalities are pain and temperature because the lateral spinothalamic tract fibers cross just ventral to the central canal. This is sometimes referred to as dissociated sensory loss and is often present in a cape-like distribution. Lateral extension can result in ipsilateral Horner syndrome (because of involvement of the ciliospinal center), kyphoscoliosis (because of involvement of dorsomedian and ventromedian motor nuclei supplying the paraspinal muscles) and spastic paralysis (because of corticospinal tract involvement). Dorsal extension can result in ipsilateral position sense and vibratory loss due to involvement of dorsal column.

Radiculopathy syndromes. Patients with radicular involvement present with dermatomal sensory changes with dorsal root involvement and with myotomal weakness with ventral root involvement. In general, radicular pain (eg, root distribution or shooting pain) increases with increased intraspinal pressure (eg, coughing, sneezing, any Valsalva maneuver).

24. Brown-Séquard syndrome. Cauda equina and conus medullaris syndromes.

Brown-Séquard syndrome. Brown-Séquard syndrome may be considered equivalent to a hemicordectomy. Ipsilateral paralysis, loss of vibration and position sense below the level of the lesion, hyperreflexia, and an extensor toe sign all are noted. Ipsilateral segmental anesthesia is also observed at the lesion level. Loss of pain and temperature is observed contralaterally below the level of the lesion (beginning perhaps 2-3 segments below). Brown-Séquard syndrome is most common after trauma. However, the full spectrum of this syndrome is rare.

Cauda equina and conus medullaris syndromes. Patients with lesions affecting only the cauda equina can present with a polyradiculopathy in the lumbosacral area, with pain, radicular sensory changes, asymmetric lower motor neuron–type leg weakness, and sphincter dysfunction. This may be difficult to distinguish from plexus or nerve involvement. Lesions affecting only the conus medullaris cause early disturbance of bowel and bladder functions.

25. Visual system: functional anatomy and examination (visual acuity, fields, ophthalmoscopy).

The visual acuity should be tested using the standard Snellen type charts placed at 6m. The acuity is recorded as a fraction, e.g. 6/6 or 6/12, in which the numerator indicates the distance in metres from the chart and the denominator the line on the chart that can be read. 6/6 is normal vision. Refractive errors should be corrected by testing with the patient’s glasses or by asking the patient to view the chart through a pinhole.

The visual ﬁelds can be charted by confrontation, with the patient facing the examiner and objects of varying size being moved slowly into the visual ﬁeld .

Formal testing using perimetry should be undertaken in all cases of visual failure, pituitary tumour, parasellar tumour, other tumours possibly involving the visual pathways and demyelinating disease, or if there are any doubts after confrontation that the ﬁelds may be restricted. Perimetry can be performed using either a tangent screen, such as a Bjerrum screen a Goldmann perimeter.

The Bjerrum screen records the central ﬁeld of vision. By enlarging the central area out to 30°it is easier to detect scotomas and to measure the blind spot and, provided a small enough target is used, the tangent screen provides an accurate representation of the peripheral ﬁelds. An automated perimetry machine will enable an accurate and reproducible ﬁeld test that is particularly useful in cooperative patients. The pattern of visual ﬁeld loss will depend on the anatomical site of the lesion in the visual pathways • total visual loss—optic nerve lesion • altitudinous hemianopia—partial lesion of the optic nerve due to trauma or vascular accident • homonymous hemianopia—lesions of the optic tract, radiation or calcarine cortex • bitemporal hemianopia—optic chiasm lesions such as pituitary tumour, craniopharyngioma or suprasellar meningioma.

Fundal examination The fundus should be examined using the ophthalmoscope with particular attention to the:

• optic disc

• vessels

•retina.

A pale optic disc is due to optic atrophy which may be either primary, as a result of an optic nerve lesion caused by compression or demyelination, or consecutive, which follows severe swelling of the disc. Papilloedema is due to raised intracranial pressure and is evident by: •blurring of the disc margins

•ﬁlling in of the optic cup

• swelling and engorgement of retinal veins, with loss of normal pulsation of the veins

• haemorrhages around the disc margin (if severe).

26. Ocular motor system: functional anatomy and examination of eye movements.

The following are the general actions of the extraocular muscles

• Lateral rectus (6th nerve) moves the eye horizontally outwards.

• Medial rectus (3rd nerve) moves the eye horizontally inwards.

• Superior rectus (3rd nerve) elevates the eye when it is turned outwards.

• Inferior oblique (3rd nerve) elevates the eye when it is turned inwards.

• Inferior rectus (3rd nerve) depresses the eye when it is turned outwards.

• Superior oblique (4th nerve) depresses the eye when it is turned inwards. The patient should be tested for diplopia, which will indicate ocular muscle weakness before it is evident on examination. The following rules help determine which muscle and cranial nerve are involved.

• The displacement of the false image may be horizontal, vertical or both.

• The separation of images is greatest in the direction in which the weak muscle has its purest action.

•The false image is displaced furthest in the direction in which the weak muscle should move the eye.

27. Disorders of the visual system.

Disorders of eye movement may be due to impaired conjugate ocular movement. The centre for the control of conjugate lateral gaze is situated in the posterior part of the frontal lobe, with input from the occipital region. The ﬁnal common pathway for controlling conjugate movement is in the brainstem, particularly the median longitudinal bundle. Alesion of the frontal lobe causes contralateral paralysis of conjugate gaze (i.e. eyes deviated towards the side of the lesion) and a lesion of the brainstem causes ipsilateral paralysis of conjugate gaze (i.e. eyes deviated to side opposite to the lesion).

Nystagmusshould be tested by asking the patient to watch the tip of a pointer. This should be held ﬁrst in the midline and then moved slowly to the right, to the left and then vertically upwards and downwards.

Jerk nystagmus is the common type, consisting of slow drift in one direction and fast correcting movement in the other.

Horizontal jerk nystagmus is produced by lesions in the vestibular system which may occur peripherally in the labyrinth, centrally at the nuclei, in the brainstem or in the cerebellum.

In peripheral lesions the quick phase is away from the lesion and the amplitude is greater in the direction of the quick phase. In cerebellar lesions the quick phase is in the direction of gaze at that moment but the amplitude is greater to the side of the lesion.

By convention the quick phase is taken to indicate the direction of the nystagmus, so that if the slow phase is to the right and the quick phase to the left the patient is described as having nystagmus to the left. Vertical nystagmus is due to intrinsic brainstem lesions such as multiple sclerosis, brainstem tumours or phenytoin toxicity.

The so-called ‘downbeat’ nystagmus, which is characterized by a vertical nystagmus exaggerated by downgaze, is particularly evident in low brainstem lesions as caused by Chiari syndrome, where the lower brainstem has been compressed by the descending cerebellar tonsils.

28. Functional anatomy and examination of the trigeminal nerve.

The 5th cranial nerve (trigeminal nerve) is tested by assessing facial sensation over the three divisions of the cranial nerve; corneal sensation should be tested using a ﬁne piece of cotton wool. The motor function of the 5th nerve can be tested by palpating the muscles while the patient clenches their jaw, testing the power of jaw opening and lateral deviation of the jaw.

29. Lesions of the trigeminal nerve.

Trigeminal nerve function may be affected by supranuclear (upper motor neuron), nuclear, or peripheral lesions.

A. Supranuclear lesions. The motor nuclei receive bilateral supranuclear (corticobulbar) innervation. A unilateral upper motor neuron lesion (e.g. a hemispheric stroke) causes no clinically discernible weakness of the trigeminal nerve-innervated muscles. Bilateral upper motor neuron lesions (e.g. bilateral hemispheric strokes, occurring simultaneously or consecutively, or an upper brainstem lesion affecting both corticobulbar pathways) result in a pseudobulbar palsy with dysarthria, dysphagia, and a brisk jaw jerk.

B. Nuclear lesions. Lesions involving the motor nucleus in the pons will cause ipsilateral weakness and wasting of the muscles of mastication. Masseter and temporalis can be seen and felt to be wasted, on jaw closure, and on jaw opening the jaw will deviate to the affected side because of weakness of the pterygoid muscles. Isolated involvement of the pontine primary sensory nucleus would be expected to produce ipsilateral loss of facial light-touch sensation, with preservation of pinprick sensation, but in practice lesions invariably also involve descending fibres and both sensory modalities are impaired. Lesions in this area affecting trigeminal motor and sensory function also frequently cause contralateral

hemiplegia and spinothalamic sensory loss. Common pathologies include vascular disease, demyelination, and tumour. Rarer causes are a variety of vascular malformations and (very rare) syringobulbia. Lesions in the medulla and upper cervical cord may affect the spinal trigeminal tract and nucleus, causing ipsilateral loss of facial pain (pinprick) and temperature sensation, with preservation of light-touch and the corneal reflex. By far the most common cause is infarction of the lateral medulla secondary to occlusion of the vertebral artery or the posterior inferior cerebellar artery (the lateral medullary syndrome of Wallenberg). Further symptoms include hiccoughs, dizziness, dysarthria, and dysphagia. Ipsilateral signs, in addition to the facial sensory loss, include Horner's syndrome, palatal and vocal cord paresis, and cerebellar ataxia. Contralaterally there is limb and trunk spinothalamic (pinprick and temperature) sensory loss. In syringomyelia a central cord lesion (a syrinx or cavity) gradually extends upwards from the cervical spinal cord into the medulla (when it is referred to as syringobulbia) and possibly as far as the pons. Spinal cord tumours may behave in the same fashion. In these situations there is bilateral involvement of the trigeminal tract and nuclei and, due to the topographic organization of nerve fibres, a particular pattern of facial sensory loss (to pinprick and temperature) evolves, which has been likened to an onion-skin or the wearing of a balaclava helmet. Thus, the sensory loss gradually progresses forwards and medially towards the nose.

C. Peripheral lesions. Numerous pathologies can affect the intracranial parts of the trigeminal nerve complex (the motor and sensory roots, trigeminal ganglion, and the three major nerve divisions). These include tumours (metastases, carcinomatous meningitis, acoustic neuromas, trigeminal neuromas, meningiomas, nasopharyngeal carcinoma), infections (viral, acute and chronic meningitis, abscesses, osteitis), Paget's disease, trauma, aneurysms, and granulomatous processes. Depending upon the site of the lesion, other cranial nerves may be involved and particular syndromes can be identified. A lesion affecting both the sympathetic nerve fibres around the internal carotid artery and the trigeminal ganglion may produce a Horner's syndrome (without anhydrosis as sudomotor fibres travel along the external carotid artery) and trigeminal nerve involvement (either with pain alone or with a demonstrable sensorimotor neuropathy). This combination is referred to as Raeder's paratrigeminal syndrome, and causes include carotid aneurysm, infection, tumours, and trauma. Such lesions may involve the optic nerve and cranial nerves III, IV, and VI in the parasellar region. Peripheral branches of the three main nerves may be damaged by blunt or penetrating, or surgical, trauma, resulting in areas of sensory disturbance, sometimes accompanied by continuous or neuralgic pain. Those most commonly affected are the supraorbital, infraorbital, and inferior alveolar nerves. The rather specific numb cheek and chin syndromes are discussed below. Trigeminal neuralgia is the most frequently encountered disorder of the trigeminal nerve. It may be symptomatic of an underlying structural disorder affecting the nerve, but in the majority of patients no specific cause is identified. It is more common in the second half of life, cases in younger people more often being symptomatic, is slightly more frequent in women.

30. Functional anatomy and examination of the facial nerve.

The facial nerve is tested by assessing facial movement. In an upper motor neurone facial weakness the weakness of the lower part of the

face is very much greater than the upper, with the strength of the orbicularis oculis being relatively preserved.

This is due to a lesion between the cortex and the facial nucleus in the pons. Lower motor neurone weakness is evident by equal involvement of the upper and lower parts of the face and is due to a lesion in, or distal to, the facial nerve nucleus in the pons.

The chorda tympani carries taste sensation from the anterior two-thirds of the tongue and this should be examined using test ﬂavours placed carefully on the anterior tongue.

31. Lesions of the facial nerve.

Lesions of the facial nerve, its nucleus or supranuclear pathways, may produce facial muscle weakness; but only peripheral lesions, affecting the facial nerve itself, affect taste sensation and autonomic function. As noted above, numbness is not an expected finding in facial-nerve lesions, although symptomatic complaints of sensory disturbance are common in Bell's palsy. A. Supranuclear lesions. The upper facial muscles have almost equal bilateral cortical representation, whereas the lower facial muscles receive mainly crossed fibres from the contralateral hemisphere. Thus, a unilateral upper motor neuron lesion causes contralateral facial weakness, with the lower part of the face being more affected than the upper (NB it is relative rather than absolute sparing of the upper facial muscles). As noted above, there is more than one pathway of supranuclear innervation and, depending upon the site of the lesion, spontaneous emotional movements may be more affected than voluntary movements, and vice versa.

B. Nuclear and peripheral lesions. A lesion of the nucleus or facial nerve generally causes equal weakness of all ipsilateral facial muscles and the clinical features are exemplified by Bell's palsy. Occasionally, partial lesions of the nucleus or nerve may selectively affect the lower facial muscles, thus mimicking the appearance seen with an upper motor neuron lesion. Considering the origins and sites of union with the facial nerve of the greater superficial petrosal nerve, the nerve to stapedius and the chorda tympani, the presence of impaired lacrimation, hyperacusis or an impaired stapedial reflex, or altered taste sensation can help in localizing the site of a facial-nerve lesion. The absence of such features is not of localizing value. The facial nucleus may be affected by pontine lesions, and the nerve by lesions in the cerebellopontine angle, within the petrous temporal bone and outside the skull.

1) Pontine lesions. These rarely affect the facial nucleus or nerve fibres in isolation, and associated features include ipsilateral lateral rectus or conjugate gaze palsy, trigeminal motor and sensory involvement, and contralateral hemiparesis and hemisensory loss. Common pathologies include vascular lesions, multiple sclerosis, and tumours, less common disorders being brainstem encephalitis, syringobulbia, and poliomyelitis. Bilateral facial paralysis due to agenesis of the facial nuclei (Mobius' syndrome) is a rare disorder that may be associated with other cranial nerve lesions and dysmorphic features.

2) Cerebellopontine angle lesion. The most common lesions at this site, which affect the facial nerve, intermediate nerve, and eighth nerve, are acoustic neuromas and meningiomas. Less common lesions include secondary tumours, nasopharyngeal carcinoma, developmental tumours, cholesteatomas, and any basal meningitic process (e.g. sarcoid).

3) Petrous temporal bone lesions. In the facial canal the nerve may be affected by infection spreading from the middle ear or mastoid, or by surgical procedures in that area. Inflammation and swelling of the facial nerve in the facial canal and at the stylomastoid foramen is presumed to be present in Bell's palsy. In the Ramsay Hunt syndrome swelling of the geniculate ganglion due to reactivation of latent herpes zoster infection may compress the motor fibres, or there may be direct infection of the motor nerve. The resultant facial palsy is accompanied by a rash, typically seen in the external auditory meatus, although it is often more extensive than this and involves the trigeminal distribution (e.g. the anterior pillar of the fauces) and cervical dermatomes. There is often pain around the ear.

4) Lesions outside the skull. Benign and malignant lesions of the parotid gland may involve some or all of the branches of the facial nerve. 5) Bilateral facial palsy. Bilateral, as well as unilateral, lower motor neuron facial weakness may be seen in Guillain-Barre syndrome, sarcoidosis (due to basal meningeal or parotid involvement), Lyme disease (often accompanied by facial rash and induration), HIV infection (at seroconversion), and Melkersson's syndrome. In the latter disorder, recurrent episodes of unilateral or bilateral facial swelling and facial palsy are associated with a deeply furrowed tongue.

32. Functional anatomy and examination of the vestibulocochlear nerve.

The 8th cranial nerve consists of:

• the cochlear nerve—hearing

•the vestibular nerve.

The cochlear nerve Hearing can be examined at the bedside by moving a ﬁnger in the meatus on one side, to produce a masking noise, and repeating words at a standard volume and from a set distance in the other ear.

Differentiation between conduction and sensorineural deafness can be aided using tests with a tuning fork. The Rinne’s test involves holding a vibrating tuning fork in front of the external meatus and then on the mastoid process. In nerve deafness both air and bone conduction are reduced, but air conduction remains the better. In conductive deafness bone conduction will be better than air conduction. In Weber’s test the vibrating tuning fork is placed on the centre of the forehead.

In nerve deafness the sound appears to be heard better in the normal ear, but in conductive deafness the sound is conducted to the abnormal ear. Formal audiometry should be performed if there are symptoms of impaired hearing.

The vestibular nerve The simplest test of vestibular function is the caloric test, which is usually performed in patients suspected of having a cerebellopontine angle tumour or as a test of brainstem function in patients with severe brain injury.

33. Lesions of the vestibulocochlear nerve.

A. Disorders of hearing. Deafness is usually caused by primary diseases of the middle ear, such as otosclerosis, otitis media, or trauma, or diseases of the inner ear, such as noise exposure, various genetic causes, congenital rubella, and age-related presbyacusis. Unilateral deafness is often not noticed unless patients find they are unable to hear the telephone earpiece with that ear. The main neurological cause of deafness is a tumour affecting the eighth cranial (auditory) nerve in its course between the brainstem and the internal auditory meatus. Partial deafness is a common sequel to bacterial meningitis or other infiltrating processes in the meninges surrounding the nerve.

Tinnitus is a symptom in which the person hears noises in the ears or head in the absence of any sound stimulus. The subjective sensations can take many forms which include buzzing, humming, hissing, roaring, clicking, or some similar description. It is usually constant, but some patients describe it as intermittent, pulsating, or fluctuating. Subjective tinnitus is an auditory sensation which is only heard by the patient, whereas objective tinnitus, which is much rarer, may be perceived by the examiner as well.

The latter includes vascular causes, such as fistulae or arteriovenous malformations, or mechanical causes, as in palatal myoclonus. Tinnitus is a symptom which, in addition to the common inner ear causes such as Meniere's disease, may herald a number of disorders, such as a glomus tumour, tumours of the internal auditory meatus or cerebellopontine angle, or a vascular abnormality in the temporal bone or skull.

B. Vestibular disorders.

1) Benign positional vertigo. The syndrome is characterized by brief (seconds to minutes) episodes of severe vertigo that may be accompanied by nausea and vomiting. Symptoms may occur with any change in head position but are usually most severe in the lateral decubitus position with the affected ear down. Episodic vertigo typically continues for several weeks and then resolves spontaneously; in some cases it is recurrent. Hearing loss is not a feature. Benign positional vertigo is the most common cause of vertigo of peripheral origin, accounting for about 30% of cases. The most frequently identified cause is head trauma, but in most instances, no cause can be determined. The pathophysiologic basis of benign positional vertigo is thought to be canalolithiasisstimulation of the semicircular canal by debris floating in the endolymph. Peripheral and central causes of positional vertigo can usually be distinguished on physical examination by means of the NylenBaniny or Dix-Hallpike maneuver. Positional nystagmus always accompanies vertigo in the benign disorder and is typically unidirectional, rotatory, and delayed in onset by several seconds after assumption of the precipitating head position. If the position is maintained, nystagmus and vertigo resolve within seconds to minutes. If the maneuver is repeated successively, the response is attenuated. In contrast, positional vertigo of central origin tends to be less severe, and positional nystagmus may be absent. There is no latency, fatigue, or habituation in central positional vertigo.

2) Meniere's disease is characterized by repeated episodes of vertigo lasting from minutes to days, accompanied by tinnitus and progressive sensorineural hearing loss. Onset is between the ages of 20 and 50 years in about three-fourths of cases, and men are affected more often than women. The cause is thought to be an increase in the volume of labyrinthine endolymph (endolymphatic hydrops), but the pathogenetic mechanism is unknown. At the time of the first acute attack, patients may already have noted the insidious onset of tinnitus, hearing loss, and a sensation of fullness in the ear. Acute attacks are characterized by vertigo, nausea, and vomiting and recur at intervals ranging from weeks to years. Hearing deteriorates in a stepwise fashion, with bilateral involvement reported in 10-70% of patients. As hearing loss increases, vertigo tends to become less severe. Physical examination during an acute episode shows spontaneous horizontal or rotatory nystagmus (or both) that may change direction. Although spontaneous nystagmus is characteristically absent between attacks, caloric testing usually reveals impaired vestibular function. The hearing deficit is not always sufficiently advanced to be detectable at the bedside. Audiometry shows low-frequency pure-tone hearing loss, however, that fluctuates in severity as well as impaired speech discrimination and increased sensitivity to loud sounds.

3) Acute peripheral vestibulopathy. This term is used to describe a spontaneous attack of vertigo of inapparent cause that resolves spontaneously and is not accompanied by hearing loss or evidence of central nervous system dysfunction. It includes disorders diagnosed as acute labyrinthitis or vestibular neuronitis, which are based on unverifiable inferences about the site of disease and the pathogenetic mechanism. A recent antecedent febrile illness can sometimes be identified, however. The disorder is characterized by vertigo, nausea, and vomiting of acute onset, typically lasting up to 2 weeks. Symptoms may recur, and some degree of vestibular dysfunction may be permanent.

During an attack, the patient – who appears ill – typically lies on one side with the affected ear upward and is reluctant to move his or her head. Nystagmus with the fast phase away from the affected ear is always present. The vestibular response to caloric testing is defective in one or both ears with about equal frequency.

Auditory acuity is normal. Acute peripheral vestibulopathy must be distinguished from central disorders that produce acute vertigo, such as stroke in the posterior cerebral circulation. Central disease is suggested by vertical nystagmus, altered consciousness, motor or sensory deficit, or dysarthria.

4) Head trauma is the most common identifiable cause of benign positional vertigo. Injury to the labyrinth is usually responsible for posttraumatic vertigo; however, fractures of the petrosal bone may lacerate the acoustic nerve, producing vertigo and hearing loss. Hemo-tympanum or CSF otorrhea suggests such a fracture.

5) Cerebellopontine angle tumor. The cerebellopontine angle is a triangular region in the posterior fossa bordered by the cerebellum, the lateral pons, and the petrous ridge. By far the most common tumor in this area is the histologically benign acoustic neuroma (also termed neurilemoma, neurinoma, or schwannoma), which typically arises from the neurilemmal sheath of the vestibular portion of the acoustic nerve in the internal auditory canal. Less common tumors at this site include meningiomas and primary cholesteatomas (epidermoid cysts). Symptoms are produced by compression or displacement of the cranial nerves, brainstem, and cerebellum and by obstruction of CSF flow. Because of their anatomic relationship to the acoustic nerve, the trigeminal (V) and facial (VII) nerves are often affected.

Hearing loss of insidious onset is usually the initial symptom. Less often, patients present with headache, vertigo, gait ataxia, facial pain, tinnitus, a sensation of fullness in the ear, or facial weakness. Although vertigo ultimately develops in 20-30% of patients, a nonspecific feeling of unsteadiness is encountered more commonly. In contrast to Meniere's disease, there is a greater tendency for mild vestibular symptoms to persist between attacks. Symptoms may be stable or progress very slowly for months or years.

34. Functional anatomy and lesions of the glossopharyngeal nerve (IX)

Although the glossopharyngeal nerve contains sensory, motor, and parasympathetic fibres, only its sensory function is testable at the bedside and for all practical purposes its other functions can be ignored. Functionally and anatomically it is closely related to the vagus nerve and, together with the accessory nerve, all three nerves may be affected by lesions in the jugular foramen. Isolated glossopharyngeal nerve lesions are rare, but this nerve alone is affected in the rare syndrome of glossopharyngeal neuralgia.

Three components of the glossopharyngeal nerve are of little interest in everyday clinical neurology. Special visceral afferent fibres subserve taste sensation from the posterior one-third of the tongue. Symptomatic loss of taste sensation from lesions of the nerve is not seen and there are no practical tests of this function at the bedside.

General visceral efferent fibres give rise to parasympathetic fibres which stimulate secretion from the parotid gland. Special visceral efferent fibres innervate the stylopharyngeus, but this muscle cannot be assessed clinically. Peripheral course. The glossopharyngeal nerve is formed by a series of radicles which enter and leave the medulla, in the posterior lateral sulcus, rostral to the vagus nerve. The nerve crosses the posterior fossa and leaves the skull, together with the vagus and accessory nerves, through the jugular foramen. It crosses in front of the internal carotid artery to reach the lateral wall of the pharynx.

The nerve contains two peripheral ganglia, the superior ganglion which lies in the jugular foramen and the inferior (petrosal) ganglion which is extracranial. The ganglia contain the cell bodies of primary sensory neurons that subserve general somatic and general visceral sensation. Sensory pathways. General visceral afferent fibres convey sensory impulses (tactile, thermal, and pain) from the posterior onethird of the tongue, tonsil, posterior wall of the upper pharynx and Eustachian tube, via the inferior ganglion, to the solitary fasciculus and its nucleus. Clinically, this particular sensory pathway is the most important function of the nerve and the only function readily assessed at the bedside.

General somatic afferent fibres carry sensation from the posterior part of the ear, via the superior ganglion, and terminate in the spinal trigeminal tract and nucleus. Clinically the most important function of the glossopharyngeal nerve is its provision of sensory input from the upper pharynx. It thus provides the afferent limb of the gag or palatal reflex, the efferent limb of which is provided by the vagus. This reflex is too gross a test of glossopharyngeal function. If a lesion is suspected, the sensation on each side of the posterior pharyngeal wall should be tested using an orange stick or a firmly secured pin. Most patients will gag, and the palate will be seen to move, but what is more important is for the patient to state whether the sensation is the same on both sides.

Supranuclear and nuclear lesions. Supranuclear lesions have no specific discernible effect on glossopharyngeal nerve function, although involvement of stylopharyngeus may contribute to pseudobulbar palsy. Nuclear lesions in isolation are rarely, if ever, seen and other cranial nerve nuclei, particularly the vagus, are usually also involved. The most common cause is a vascular lesion, with other causes including primary and secondary neoplasia and syringobulbia. Peripheral lesions. Between the medulla and jugular foramen the nerve may be affected by meningeal disease (e.g. inflammatory and neoplastic processes) and metastases. In the jugular foramen probably the most common lesion, which of course may also affect the vagus and accessory nerves, is a glomus tumour. Neuromas of any of these three nerves may arise in or near the jugular foramen and each nerve may be affected by basal skull fracture and basilar invagination. Metastatic disease may affect the nerve anywhere along its course, intracranially or extracranially. Glossopharyngeal neuralgia. Although much rarer, glossopharyngeal neuralgia shares many similarities with trigeminal neuralgia with respect to aetiology, treatment, and the characteristics of the paroxysms of pain. Most cases are idiopathic but neuralgia may be symptomatic of lesions affecting the glossopharyngeal nerve, particularly neoplastic disorders, and there is evidence that new cases, like trigeminal neuralgia, may be caused by compression of the nerve by an aberrantly situated artery. The paroxysms of pain may occur in clusters, with long periods of remission, or may be chronic. The pain is experienced in the back of the throat, below the angle of the jaw, and within the ear. The stabbing or lancinating quality is similar to that occurring in trigeminal neuralgia. Precipitants include eating, swallowing, talking, head turning, coughing, sneezing, and touching the outer ear. Syncope may occur in association with pain and is due to sinus bradycardia or asystole, reflecting the intimate associations between the glossopharyngeal and vagus nerves.

35. Functional anatomy of the vagus nerve (X)

The vagus nerve has the most extensive course of any of the cranial nerves and is anatomically complex, with different courses for the main nerve trunks and their branches on each side of the body. The nerve carries motor, sensory, and autonomic fibres, but with respect to structural lesions only the motor pathways are of great clinical importance. Disturbances of autonomic function are discussed elsewhere. Sensory and autonomic pathways.

General somatic afferent fibres subserve sensation from the skin over the back of the ear and the posterior wall of the external auditory meatus. The cell bodies are situated in the superior ganglion, which sits in or just below the jugular foramen, and centrally the fibres enter the spinal trigeminal tract in the medulla. General visceral afferent fibres, from the pharynx, larynx, trachea, oesophagus, and thoracic and abdominal viscera have their cell bodies in the inferior ganglion, and centrally the fibres enter the nucleus and tractus solitarius.

Preganglionic parasympathetic fibres (general visceral efferent) arise from the dorsal motor nucleus of the vagus nerve, situated in the floor of the fourth ventricle, and are destined to innervate the thoracic and abdominal viscera. Motor pathways. Special visceral efferent fibres innervate the voluntary striated muscles of the pharynx and larynx.

They originate in the nucleus ambiguus (which also gives rise to the special visceral efferent fibres of the glossopharyngeal nerve and cranial part of the spinal accessory nerve) which lies in the medullary reticular formation between the inferior olive and the spinal trigeminal nucleus. Peripheral course. The trunk of the vagus nerve is formed by a series of rootlets which emerge from the medulla, anterior to the inferior cerebellar peduncle, in line with the radicles of the glossopharyngeal and accessory nerves. The nerve leaves the skull through the jugular foramen, intimately associated with the accessory nerve and separated from the glossopharyngeal nerve only by a fibrous septum.

In the neck it lies in the carotid sheath, initially between the internal carotid artery and internal jugular vein, and then between the common carotid artery and internal jugular vein. Below the root of the neck the course of the nerve is different on the two sides of the body. On the right, the nerve crosses the subclavian artery and descends through the superior mediastinum posterior to the brachiocephalic vein and to the right of the trachea, to reach the posterior aspect of the lung root. On the left, the nerve passes between the common carotid and subclavian arteries to enter the thorax.

It descends through the superior mediastinum, behind the phrenic nerve and brachiocephalic vein and crosses the left side of the aortic arch, reaching the posterior surface of the lung root. The nerves branch behind the lung roots, and these branches unite with fibres from thoracic sympathetic ganglia to form the right and left posterior pulmonary plexuses. Fibres from these form the posterior and anterior oesophageal plexuses, respectively. Trunks, containing fibres from both vagus nerves, are re-formed from these plexuses and pass into the abdomen, through the oesophageal opening, where they undergo complex further branching before supplying the abdominal viscera.

On each side, the vagus nerve has important branches arising in the jugular foramen, neck, and thorax. From the superior ganglion arises a meningeal branch, which innervates the dura in the posterior fossa, and an auricular branch which subserves sensation from the posterior auricle and external auditory meatus. The pharyngeal branch arises from the inferior ganglion and is the main motor nerve to the pharynx and soft palate. The superior laryngeal nerve also arises from the inferior ganglion. It has two branches: the internal, which is the main sensory nerve of the larynx, and the external, which is motor to the inferior pharyngeal constrictor and cricothyroid muscles. The recurrent laryngeal nerves have a different origin and course on each side of the body. On the right, this nerve arises from the vagus at the root of the neck, in front of the subclavian artery. It winds below and behind that vessel and ascends beside the trachea and behind the common carotid artery.

At the level of the thyroid gland the nerve is closely related to the inferior thyroid artery. On the left, the nerve arises from the vagus at the level of the aortic arch. It winds under the arch and then ascends along the side of the trachea. On both sides the recurrent laryngeal nerves ascend in a groove between the oesophagus and trachea, pass closely next to the medial surface of the thyroid gland, and enter the larynx to supply all of the laryngeal muscles except the cricothyroid.

36. Lesions of the vagus nerve and its branches.

Supranuclear, nuclear, nerve trunk, and branch lesions may affect swallowing and phonation, the exact pattern of symptoms depending upon the site and chronicity of the lesion.

A. Supranuclear lesions. Because the nuclei receive both crossed and uncrossed corticobulbar fibres, unilateral supranuclear lesions do not usually cause persisting problems with phonation and swallowing, although dysphagia may be prominent following an acute hemispheric stroke. Bilateral lesions are associated with the syndrome of pseudobulbar palsy, in which dysphagia and dysarthria are due to disordered movements of the pharyngeal and laryngeal (and tongue) muscles rather than frank paralysis. Common causes include upper brainstem or bilateral hemispheric strokes, motor neuron disease, and demyelination.

B. Nuclear lesions.

A unilateral nuclear lesion will cause ipsilateral palatal, pharyngeal, and laryngeal paralysis. On phonation the soft palate does not rise on the affected side and the uvula is drawn to the normal side. Dysphagia is variable but usually mild. Phonation is affected not only because of laryngeal muscle weakness but also by accumulation of frothy mucus which collects near the opening of the oesophagus and overflows into the larynx as a result of impaired pharyngeal emptying. The voice and cough are weak and there is difficulty clearing the voice. Bilateral lesions, in the syndrome of bulbar palsy, produce much more severe symptoms. The speech is nasal and on attempting to swallow fluids regurgitate through the nose due to palatal weakness. There may be snoring and inspiratory stridor. Coughing is paralysed, leading to a high risk of bronchial aspiration. Acute bulbar palsy is life threatening and tracheostomy is required. Unilateral nuclear lesions rarely occur in isolation and are usually accompanied by involvement of other cranial nerve nuclei and long tracts.

Causes include vascular lesions (e.g. lateral medullary syndrome) and tumour. Bilateral nuclear lesions, sometimes asymmetric, may be due to vascular lesions, motor neuron disease, tumour, syringobulbia, encephalitis, poliomyelitis, and rabies.

C. Nerve-trunk lesions. The clinical features of a lesion affecting the vagus nerve trunk between its origin and the jugular foramen are as described above for a unilateral nuclear lesion. Thus, there is unilateral paralysis of the soft palate, pharynx, and larynx.

Causes include primary (glomus jugulare, meningioma) and secondary tumour, meningitic processes, and basal skull fracture. There is frequently involvement of other cranial nerves (IX, XI, and XII). The inferior ganglion lies just below the jugular foramen and from it arise the pharyngeal and superior laryngeal nerves, which supply the muscles of the soft palate and pharynx, and the tensors of the cords (cricothyroids).

A lesion of the vagus nerve trunk below the inferior ganglion thus spares these muscles and the pattern of laryngeal paralysis is the same as is seen with an isolated lesion of the recurrent laryngeal nerve.

D. Recurrent laryngeal nerve lesions. In practice, isolated vagus nerve trunk lesions are rare, but recurrent laryngeal nerve palsies are common. A unilateral lesion causes paralysis of the ipsilateral larynx and lower sphincter of the pharynx.

The vocal cord is immobile and lies near the midline. Dysphagia is not a major feature, because the pharyngeal nerve is unaffected, although following an acute lesion there may be transient difficulties swallowing fluids. In the acute phase there may also be dysphonia but despite the paralysed vocal cord compensatory mechanisms are so efficient that the voice may remain or soon return to normal.

The left recurrent laryngeal nerve is more commonly involved than the right, as a result of mediastinal lesions, particularly neoplasia but less frequently aortic aneurysm and enlargement of the left atrium.

In the neck the nerve may be affected unilaterally or bilaterally by trauma, surgery, cervical lymph gland enlargement (inflammatory or neoplastic), thyroid enlargement, and oesophageal carcinoma. Up to one-third of cases of recurrent laryngeal nerve palsy are idiopathic. They may be persistent or show partial or complete recovery.

37. Functional anatomy and lesions of the accessory nerve (XI)

This is a purely motor nerve. It is formed from cranial and spinal roots which, as the accessory nerve, run together for only a very short distance.

The cranial component is essentially part of the vagus nerve and is distributed mainly to the pharyngeal and recurrent laryngeal branches of that nerve, whereas the spinal component innervates sternomastoid and trapezius. The spinal nucleus of the accessory nerve lies in the lateral part of the anterior horn grey matter and extends from the pyramidal decussation to the fifth cervical segment.

The fibres arising from it emerge from the lateral aspect of the cord, between the dorsal and ventral roots, and unite to form a trunk which ascends posterior to the denticulate ligament and enters the skull through the foramen magnum, dorsal to the vertebral artery. The cranial root is formed by nerve fibres arising from the lower part of the nucleus ambiguus.

Rootlets emerge from the lateral medulla, below the origin of the vagus. The cranial and spinal components unite for a short distance and leave the skull through the jugular foramen, in close relationship to the vagus nerve to which the cranial root fibres are distributed. The spinal part runs backwards and laterally between the internal jugular vein and internal carotid artery and crosses the transverse process of the atlas. It passes deep to the sternomastoid muscle, which it supplies, and emerges from its posterior border from where it crosses the posterior triangle, lying on levator scapulae.

In this part of its course it is quite superficial, thus subject to trauma, and also related to cervical lymph nodes. The nerve then passes under the anterior border of the trapezius and unites with branches of the third and fourth cervical nerves (C3 and C4) to form a plexus which innervates the muscle. The pattern of innervation of the different parts of trapezius is probably quite variable but, in general, the accessory nerve appears to supply the upper part of the muscle, and fibres derived from C3 and C4 supply the lower part. Lesions. Unilateral sternomastoid weakness is asymptomatic because it normally acts in concert with other cervical muscles which can compensate.

Bilateral, but otherwise isolated, nerve lesions must be vanishingly rare. Bilateral sternomastoid weakness, with symptomatic weakness of neck flexion, is seen in myotonic dystrophy, inflammatory myopathies, various muscular dystrophies, myasthenia gravis, and motor neuron disease, but in all of these cases other cervical muscles are also involved.

Trapezius weakness is symptomatic. The shoulder droops slightly and there is mild scapular winging at rest, with the scapular rotated outwards and downwards. The winging is exacerbated by abduction of the arm, whereas winging due to serratus anterior weakness is most evident on forward flexion of the arm. The patient notices difficulty in shrugging the shoulder, abducting the arm above 90° and carrying the extended arm backwards. Bilateral trapezius weakness causes the head to fall forwards.

This is rarely the result of bilateral nervetrunk involvement but is seen in myasthenia gravis, motor neuron disease, and various myopathies.

A. Supranuclear lesions. The cortical representation is mainly ipsilateral for sternomastoid and contralateral for trapezius. Thus, following a major hemisphere stroke, trapezius is weak on the paralysed side but sternomastoid is weak on the side of the hemispheric event.

B. Nuclear and nerve-trunk lesions. The spinal cord nucleus is rarely involved in isolation. The anterior horn cells may be affected by motor neuron disease and poliomyelitis and the nuclei may be compressed by upper cervical cord tumours and syringomyelia. In the posterior fossa, lesions affecting the accessory nerve often also involve cranial nerves IX, X, and XII.

Common pathologies include primary and secondary tumours, meningitic processes, and basal skull fracture through the jugular foramen. Outside the skull the most common site of damage is in the posterior triangle (giving rise to trapezius but not sternomastoid weakness). The nerve may be damaged by trauma or during surgical procedures (particularly removal of cervical lymph glands) including carotid endarterectomy. Up to one-third of accessory nerve palsies are idiopathic, probably often as a forme fruste of neuralgic amyotrophy.

38. Functional anatomy and lesions of the hypoglossal nerve.

This motor nerve innervates all of the muscles of the tongue through general somatic efferent fibres. The nucleus, which is nearly 2 cm long, lies in the central grey matter of the medial eminence and extends from the stria medullaris to the most caudal part of the medulla. The axons arising from it pass ventro-laterally and emerge as a series of rootlets on the ventral aspect of the medulla between the inferior olivary complex and the pyramid.

The rootlets pass behind the vertebral artery and unite as they exit the skull through the hypoglossal canal, which lies about 1 cm anterior, inferior, and medial to the jugular foramen. Immediately outside the skull the nerve is in close proximity to cranial nerves IX, X, and XI, the internal jugular vein, and the internal carotid artery. At the level of the angle of the mandible it sweeps antero-laterally, looping below the occipital artery and crossing the external carotid artery and then the loop of the lingual artery just above the hyoid bone.

It then passes deep to the digastric muscle and terminates through multiple branches in the intrinsic and extrinsic tongue muscles. A unilateral lesion of the nucleus or nerve trunk causes ipsilateral wasting and weakness of the tongue. Fasciculation may be prominent, especially in infantile spinal muscular atrophy and classical motor neuron disease.

The epithelium is thrown into folds, which accumulate fur. In the acute stage, articulation and swallowing may be slightly impaired but chronic lesions are typically asymptomatic. The tongue deviates to the affected side on protrusion. Bilateral lower motor neuron lesions cause weakness of both sides of the tongue with inability to protrude the tongue, marked dysarthria, and mild swallowing difficulties.

Such bilateral lesions are rare in isolation and are usually part of the syndrome of bulbar palsy, in which other bulbar muscles are affected and in which there is significant dysphagia.

A. Supranuclear lesions.

The nuclei have bilateral cortical representation so that a unilateral upper motor neuron lesion may have no observable effect, although occasionally the tongue may deviate to the contralateral side. Bilateral upper motor neuron involvement is seen as part of the syndrome of pseudobulbar palsy.

The tongue is weak, clumsy, and contracted secondary to spasticity, but not wasted. Causes include bilateral hemispheric vascular disease, upper brain stem stroke and tumours, multiple sclerosis, and motor neuron disease.

B. Nuclear lesions.

Unilateral nuclear damage may be caused by tumours or vascular lesions, in both of which cases other structures are usually involved. Thus, a vascular event in the lower medulla might cause a unilateral hypoglossal nerve palsy and contralateral hemiplegia due to corticospinal tract involvement. Bilateral, but sometimes asymmetric, hypoglossal nuclear lesions may result from vascular lesions, tumours, syringobulbia, spinal muscular atrophy, motor neuron disease, and poliomyelitis.

C. Nerve-trunk lesions. In the posterior fossa the hypoglossal nerve rootlets may be affected, often together with cranial nerves IX, X, and XI, by primary (e.g. glomus jugulare, meningioma) and secondary neoplasms and basal meningitic processes. Unilateral or bilateral palsies may arise as a result of congenital or acquired bony abnormalities around the foramen magnum (basilar impression, Paget's disease). In the neck, the nerve may be damaged by external trauma, during surgery (including carotid endarterectomy), by tumours, and as a late consequence of radiotherapy to the region.

Vascular causes include aberrantly placed arteries, carotid artery dissection, and as a complication of central venous catheterization. As with cranial nerves X and XI, idiopathic cases occur.

39. Frontal lobe syndrome.

The manifestations of a frontal lobe syndrome in any patient depend on many factors, including baseline intelligence and education, site of the lesions, whether the lesions developed slowly or rapidly, age, possibly sex, and function of nonfrontal brain regions. Causes of frontal lobe dysfunction include mental retardation, cerebrovascular disease, head trauma, brain tumors, brain infections, neurodegenerative diseases including multiple sclerosis, and normal pressure hydrocephalus

The examiner must obtain a history from an informant who knows the patient well. One of the seeming paradoxes of frontal lobe dysfunction is that informants may complain about the patient's "inability to do anything," yet on at least cursory mental status testing, the patient appears normal or only mildly impaired. This dissociation should be a clue that frontal lobe dysfunction may be present. Symptoms of possible frontal lobe dysfunction that should be probed include change in performance at work and changes organizing and executing difficult tasks such as holiday dinners or travel itineraries.The examiner should inquire about the following changes:

Appropriateness of behavior: Does the patient say things that he or she would never have said before, such as "You are so fat" or "That is a really ugly dress"?

Patient's table manners: Does the patient now take food and start eating before everyone else or take food from other people's plates without asking?

Patient's empathy and ability to infer the mental state of others: This kind of dysfunction often leads to inappropriate behavior.

Possible apathy: Does the patient care less about hobbies, family members, and finances then previously?

An increase or decrease in the patient's sexuality or in his or her judgment about possible liaisons

In addition to these data, the examiner should obtain a careful developmental history, head trauma history, and social history, including educational and personal attainments. The examiner should also probe about possible substance abuse, whether the patient was a victim of past abuse (physical, sexual, psychiatric) and about major psychiatric stressor (eg, deaths of friends or family, divorce or separation, job loss or financial reversals). Indeed, a detailed past psychiatric history is required.

40. Temporal lobe syndrome.

The functional loss of major portions of the temporal lobes and rhinencephalon–amygdala, hippocampus, uncus and hippocampal gyrus Clinical Visual agnosia, tendency to examine all objects orally, lossof emotion, hypersexuality–heterosexual, autosexual and homosexual activity, and ↑ consumption of meat.

ANSWERS

Tuesday, June 28, 2016

Neurology