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Neuro-Otology -  

Vestibular Disorders
Lecture 2 of 3  NEXT»

History

Vertigo, strictly defined, refers to an hallucination of movement. When the symptom complex is one of spinning or rotation, the cause is almost always the inner ear or peripheral vestibular system. Although some patients experience a definite sense of environmental spin or self-rotation, most do not present solely with true spinning vertigo. The most common complaint is dizziness, a term that represents a variety of symptoms (Table 7.1). The examiner should elicit an exact description of what the patient is experiencing. Is it a spinning sensation that could be characterized as vertigo, pointing to the peripheral vestibular apparatus? Is it a sensation of falling without rotation? Is it a sensation of unsteadiness or imbalance? Is there a particular direction in which the patient tends to fall? When the patient's complaint is actually incoordination or clumsiness, the cause may be cerebellar dysfunction or peripheral neuropathy. When the symptom complex is "lightheadedness" or "swimmy-headedness," the examiner should think of presyncope or syncope and consider systemic factors such as postural hypotension, vasodepressor syncope, or cardiac arrhythmia.

Table 7.1

After trying to define the true qualitative nature of the symptom complex, one must proceed to a consideration of temporal factors. Is the patient's experience a continuous one? Are there episodes of severe symptomatology with symptom-free intervals? If the symptoms are episodic, do they occur only when the patient is upright?

Patients often have difficulty describing their symptoms. Initially, it is important to have patients provide their own descriptions before the examiner biases the outcome by suggesting descriptive phrases. Some patients are asked to describe their symptoms without using the word dizziness cannot further characterize the symptoms.

In addition to determining whether the symptom complex is episodic, one should define duration, length of symptoms, and any associated complaints such as tinnitus, hearing loss, double vision, slurred speech, numbness, or paralysis. A history of episodic disequilibration accompanied by diplopia, slurred speech, perioral numbness, dimming of vision, and occasional drop attacks would suggest transient vertebrobasilar ischemia, Are there associated symptoms such as headache, and have these occurred at earlier times? If the patient experienced severe episodes of imbalance in early life, followed by occipital or generalized headaches, especially throbbing, the history would suggest basilar artery migraine. Did the dizziness follow head trauma, a systemic illness accompanied by aminoglycoside antibiotic therapy, or a mild upper respiratory infection? Episodic positional vertigo with brief episodes of spinning while turning over in bed suggests a common condition, benign paroxysmal positional vertigo (BPPV). Did the symptom complex occur following ear surgery or infection, deep-sea diving, or a concussive blow to the ear? Such a history, with or without hearing loss, would suggest a perilymph fistula.

There are a significant number of patients whose balance disorders are aggravated or even caused by anxiety. If the disequilibration or dizziness is of long duration, it is often difficult to tell whether the symptom complex is caused by anxiety or depression or whether the anxiety or depression are secondary to the dizziness. One always tries to make a positive diagnosis of a neurosis or chronic anxiety disorder on the basis of other symptomatology and historic information. There may be a history of previous episodes of serious depression or anxiety attacks, and these should be elucidated before concluding that dizziness is secondary to anxiety.

Neurologists and neuro-otologists follow a large number of patients with chronic vertiginous sensations who remain undiagnosed. These patients complain of constant or intermittent disequilibration, often aggravated by position change, as well as by visual stimuli such as moving traffic and patterned wallpaper or by passing food displays in supermarkets. Many of these patients have become agoraphobic; they hesitate to leave their homes and particularly fear driving a car that will be passed by other automobiles. Some of these persons have had a single attack of acute peripheral vestibulopathy but have never made appropriate central compensation or adapted to their peripheral,abnormality. Although mechanisms for compensation remain unclear, most patients, particularly those younger than 30, rapidly recover from an acute peripheral vestibulopathy. Elderly patients or patients with a previously existing intrinsic brainstem abnormality will rarely make adequate compensation for an acute peripheral vestibulopathy. These patients continue to complain of severe disequilibration and have exacerbated symptoms with a variety of visual inputs. They often have completely normal examinations and vestibular tests.

Figures 7.1 and 7.2 illustrate what might happen following an acute peripheral vestibular abnormality. In some individuals, as diagramed in the right-hand panel of Figure 7.2, there is decreased ability to compensate for peripheral vestibular abnormality. One possibility would be a congenital inability to make CNS compensation, but others include (a) an acquired central inability to compensate due to CNS lesions, as from multiple sclerosis or previous brainstem stroke; (b) a fluctuating peripheral vestibular problem, as in Ménière's's disease; (c) relative inactivity without much afferent input; and (d) a peripheral vestibular apparatus providing inaccurate, although nonfluctuating, afferent information. Careful history taking may reveal childhood meningitis, a remote head injury, or particular susceptibility to motion sickness in childhood. During history taking, these possibilities should be explicitly sought.

fig. 7.1a fig. 7.1b

Figure 7.1. Left, Vestibular afferent input during normal horizontal head rotation to the right. Increased firing rate from right peripheral vestibular apparatus. Ocular deviation shows slow-phase deviation to the left. VN, vestibular nuclei. (Adapted from Baloh 1984 and Daroff 1977). Right, Acute left peripheral vestibulopathy with resultant acute vertiginous sensation simulating head rotation to the right. Slow-phase ocular deviation to the left (small arrow) and fast phase of nystagmus to the right (bold arrow) and away from the side of the peripheral vestibular injury.
 
fig. 7.2a fig. 7.2b

Figure 7.2. Left, Normal adaptation for prior left peripheral vestibulopathy. Despite a reduced firing rate from the left side, the central nervous system (CNS) has compensated for the disparity, and there is no nystagmus or vertigo. Right, Abnormal compensation for prior left peripheral vestibulopathy. The patient continues to experience vertiginous sensations and may have nystagmus with a fast phase to the right (solid arrow).

Examination of the Dizzy Patient

GENERAL EXAMINATION

Every patient with a disorder of equilibration or true vertigo should have a screening general physical examination. Patients who exhibit symptoms suggesting presyncope or actual syncope must have particular attention paid to their cardiovascular systems. Not only should patients have their blood pressure measured in the resting, sitting, and standing position, but they also should have their blood pressure measured at 1-minute intervals up to 5 minutes after assuming the upright position, as delayed postural hypotension is not uncommon. Exercise-induced hypotension is an important observation and should lead to consideration of conditions such as the Shy-Drager syndrome, diabetic autonomic neuropathy, and cardiac defects such as aortic stenosis and obstructive cardiomyopathy. Whenever episodic symptomatology is associated with a question of alteration of consciousness or lightheadedness, particular attention should be paid to the possibility of cardiac dysrhythmia. Most patients with cardiac dysrhythmias do not report associated sensations of irregular heartbeat, thumping in the chest, or fluttering; however, examination
may reveal an irregular cardiac rhythm or cardiac murmur.

During the general examination, attention should be paid to systemic conditions that could give rise to a general feeling of malaise or weakness interpreted by the patient as a disorder of balance. Conditions leading to sudden syncope may be revealed on the general physical examination. Patients with suspected extracranial vascular disease not only should have the head and neck auscultated for bruits, but also should have a general examination of the peripheral vascular system, including the cranial and carotid pulses and evaluation for significant varicose veins that might lead to venous pooling and hypotensive episodes.

The neurologic examination should be directed by the patient's history. In patients with clear-cut episodic vertigo, the neurologic examination will usually be normal, with the exception of the ocular motor findings to be described. However, when the patient's symptom complex is more vaguely defined and includes disequilibration or unsteadiness, particular attention must be paid to examination of the motor system, reflexes, sensation, and cerebellar function.

All patients with undiagnosed disorders of equilibration, however described, should have a complete neurologic examination. Portions of the neurologic examination are described briefly below, followed by suggestions of which entities might cause abnormality.

MENTAL STATUS EXAMINATION

Signs of diffuse alteration in consciousness may suggest overmedication, metabolic encephalopathy, or an acquired dementing process. Focal disturbances in intellectual function, such as a subtle aphasia, may lead to the consideration of multi-infaract dementia with accompanying brainstem infarctions or of a mass lesion in the dominant hemisphere.

CRANIAL NERVE EXAMINATION

Alterations in visual sensory function can be a primary or exacerbrating cause of disequilibration. Even the recent addition of a new refractive correction, particularly lenses for presbyopia, may be an added or primary cause of imbalance. Visual field defects such as unsuspected bitemporal or homonymous field defects from infarcts or tumors may cause patients to run into objects or feel disoriented in space. The presence of papilledema or absent venous pulsations on funduscopy should be an immediate clue to raised intracranial pressure. Altered corneal sensation can be the clue to a previously unsuspected cerebellopontine angle mass. Simple auditory screening tests may reveal a previously unsuspected hearing loss and should always lead to formal audiologic testing. Abnormalities on examination of cranial nerves IX through XII raise the differential diagnosis of multiple cranial neuropathies caused by collagen vascular disease, tumors of the base of the skull, or nasopharyngeal carcinoma.

OCULAR MOTOR EXAMINATION

The presence of spontaneous or induced nystagmus is of critical importance in the diagnosis of peripheral, central, or systemic causes of imbalance. Nystagmus types of particular note are described in the section on the directed neuro-otologic examination. Defective downward gaze is often the first condition often accompanied by disequilibration. The presence of asymmetric slowing of the adducting eye indicating an internuclear ophthalmoplegia is a subtle but important clue to the presence of brainstem multiple sclerosis, brainstem infarction, or mass lesion of the posterior fossa.

MOTOR SYSTEM EXAMINATION

The examination of motor function can reveal focal or diffuse weakness indicating CNS or neuromuscular disorders. A subtle hemiparesis may be the true cause of the patient's balance complaint. Diffuse hyperreflexia reflects cerebral or spinal cord dysfunction and, in combination with cerebellar abnormality, might lead to the diagnosis of a spinocerebellar degeneration.

SENSORY EXAMINATION

Examination of sensation can reveal a significant peripheral neuropathy leading to a diagnosis of diabetes or toxic neuropathy. Selective loss of sensory modalities conveyed by the posterior column, such as proprioception and vibration, may indicate that the patient has vitamin B12 deficiency or early tabes dorsalis. Such patients are relatively steady during the Romberg test with eyes open but rapidly lose balance and fall in any direction when visual compensation is elminated by eye closure.

CEREBELLAR SYSTEM EXAMINATION

Obvious limb or body ataxia should be an immediate clue to the CNS abnormality as the cause for the patient's imbalance. Unsteadiness during Romberg testing with eyes open and only slight exaggeration on eye closure indicates a cerebellar abnormality. Cerebellar dysfunction is usually accompanied by abnormality during gait testing or even difficulty maintaining balance while seated. Patients with symptomatic peripheral vestibulopathy tend to fall toward the side of the abnormality during eye closure with the head straight ahead. Unilateral limb ataxia is almost always an indicator of focal posterior fossa abnormality, such as infarct, demyelination, abscess, or tumor.

DIRECTED NEURO-OTOLOGIC EXAMINATION

A directed neuro-otologic examination should be performed, particularly when there are abnormalities of the auditory, ocular motor, and vestibular systems. Audiologic testing is discussed below. During the neurologic examination, there may be subtle signs of peripheral vestibular dysfunction indicated by nystagmus. On external examination, the nystagmus fast phase is away from the ear with the vestibular abnormality. During the funduscopic examination, particular attention should be paid to the movement of the optic disc. A rhythmic, subtle, horizontal, slow- and fast-component nystagmus is frequently present in patients with new peripheral vestibular dysfunction. The nystagmus is brought out by reducing fixation during the funduscopic examination. For example, with the patient staring at a dimly lit target in the distance, the presence of a slow ocular drift to the left and a fast phase to the right of the optic disc should indicate to the examiner that the patient has a subtle left beating nystagmus in the primary position. The findings indicate a right peripheral vestibular abnormality. Fast, upward, rhythmic, vertical movement of the optic disc seen during funduscopic examination signifies the presence of downbeat nystagmus. The examiner should then search carefully for the presence of downbeat nystagmus during examination of oblique and downward gaze. The need to search for presence of any type of nystagmus during the directed neuro-otologic examination cannot be overemphasized. The directed neuro-otologic examination should include a detailed otoscopic examination of the external auditory canal and the tympanic membrane. The presence of a retracted or scarred eardrum suggests prior middle ear infection. The presence of a blue mass behind the tympanic membrane points to a glomus jugular tumor.

The patient should be tested for balance during standing, walking, and turning, and for the presence of past-pointing. Past-pointing is a tendency for the repetitively elevated and lowered outstretched fingers to drift unidirectionally. Past-pointing is a clear indication of tonic imbalance in the vestibular system. If, during Romberg testing, the patient tends to fall in a certain direction, can this direction be altered by changing head position? The ability to alter the direction of the fall during Romberg testing by head turning indicates a peripheral vestibular abnormality. For example, a patient with an acute left peripheral vestibulopathy will tend to fall to the left during eye closure with the head straight ahead, but will fall backward (toward the abnormal ear) with the head turned left, and will fall forward during eye closure when the head is turned to the right.

The physician should test for the presence of an intact vestibulo-ocular reflex (VOR) and observe whether the patient is able to maintain steady ocular fixation during funduscopic examination as the head is gently rotated from side to side. The patient with an intact VOR can still maintain fixation on distance objects during head turn. The absence of this ability produces an apparent nystagmus, most easily observed during funduscopic examination, which is good evidence for a defective VOR. A different test of vestibulo-ocular control is for the patient to fix on his or her own thumb while rotating the head in the same direction. During this maneuver, the patient must suppress the vestibulo-ocular response to permit combined head and eye tracking. The loss of this ability may be a subtle clue to cerebellar system dysfunction. The patient should also be examined for the presence of nystagmus when visual fixation is reduced by wearing Frenzel glasses, which blur the patient's vision. The lenses also magnify the eye, allowing better detection of low-amplitude nystagmus.

If the patient has no cervical problems, a head-shaking test can be performed. The patient is asked to shake the head rapidly 20 times back and forth while wearing Frenzel glasses. Then the patient is observed to determine whether there is any primary position horizontal nystagmus. The maneuver may bring out a latent nystagmus indicating vestibular imbalance. The fast phase of the nystagmus would be away from the ear with the peripheral vestibulopathy.

Differential Diagnosis of Dizziness

Because ongoing or episodic conditions accompanied by vertigo, unsteadiness, or presyncope are produced by multiple and often subtle causes, it is not surprising that a significant number of patients cannot be readily diagnosed. A major differential diagnostic classification would include broad categories such as (a) peripheral vestibulopathy, (b) central neurologic disorders, nod (c) systemic or medical conditions. There is some ambiguity in the use of the term central, which has been used by otolaryngologists to include causes that are central or proximal to the vestibular end-organ and therefore include the vestibular portion of the eighth nerve. Neurologists, however, consider conditions that affect the vestibular nerve, such as tumors, as peripheral in location because they are on a cranial nerve and are extraaxial. Because masses or neoplasms can enlarge to involve other structures in the cerebellopontine angle, particularly the hrainstem, conditions that affect the eighth nerve are discussed for convenience in the central category.

Peripheral Causes of Vertigo

Peripheral causes result from dysfunction of vestibular end-organs (semicircular canals, utricle, and saccule) (Table 7.2).

Table 7.2

PERIPHERAL VESTIBULOPATHY

Peripheral vestibulopathy encompasses terms such as vestibular neuronitis, labyrinthitis, and viral neurolabyrinthitis. Such terms imply an inflammatory mechanism, which is unproved. Vestibular neuronitts, strictly speaking, is characterized by single or recurrent sudden episodes of true vertigo lasting from hours to days and often associated initially with vomiting. When the condition is associated with hearing loss, the entire labyrinth is assumed to be involved, and the term labyrinthitis is used. Despite this technical distinction, many neuro-otologists, otologists, and neurologists use the terms vestibular neuronitis and labyrinthitis interchangeably, whether or not auditory symptoms are present. In such patients the vertiginous sensation may be provoked by head movement, but not necessarily by a particular head position.

Whether isolated viral involvement of the vestibular nerves is a cause of acute or episodic vertigo is controversial, Many prefer the term acute or recurrent peripheral vestibulopathy. In the acute phase, many patients present with sudden severe vertigo, nausea, and vomiting, without any hearing disturbance or facial weakness, The acute symptoms usually resolve in a few days to a week but may recur in weeks or months. If true vertigo is part of the symptom complex, the condition is most likely to be associated with some disorder of the peripheral end-organ. However, patients with either acute peripheral vestibulopathy or, more commonly, recurrent attacks may experience only a sensation of lightheadedness or floating or a feeling of "walking on tennis balls." Even if the patient has had hundreds of episodes, it is important to determine whether any of them were associated with spinning vertigo. Over time, the nature of the patient's symptom complex may change, even with peripheral vestibulopathy, from vertiginous sensations to those of pure unsteadiness or disequilibration.

Epidemic and seasonal outbreaks of acute vertigo have suggested an infectious origin due to viral disease, but this largely remains unproved. Viral labyrinthitis can also be part of a systemic viral infection such as mumps, measles, infectious mononucleosis, or upper respiratory tract viral infections. Isolated viral infections of the labyrinth are also believed to cause the sudden onset of hearing loss and/or vertigo in both children and adults. Otitic herpes zoster is an infection characterized by pain in the ear, followed in 1 to 110 days by a vesicular eruption in the external ear. When the seventh and eighth nerves are affected, there is a combination of facial weakness, hearing loss, and vertigo known as the Ramsay Hunt syndrome. Whenever vertigo is associated with severe ear pain or facial pain, one must consider this possibility. A dysesthetic area of skin may precede by many days the appearance of the skin eruption.

BENIGN POSITIONAL VERTIGO

Benign positional vertigo refers to a symptom complex classically described as indicating benign peripheral (end-organ) disease. These symptoms, differentiated from central neurologic symptoms, are outlined in Table 7.3. The signs and symptoms of benign positional vertigo are transient and rarely last longer than 40 seconds. They frequently occur when a certain position is assumed, such as lying down or turning in bed. Other causes of vertigo are also intensified by position change. Depending on whether the symptom (vertigo) or sign (nystagmus) is being emphasized, this condition is termed paroxysmal positional vertigo (BPPV) or benign paroxysmal positional nystagmus (BPPN). In a major review of 240 cases, Baloh and associates described the clinical and eye movement-recording features in patients with BPPV. In each case, after a rapid position change from sitting to head-hanging position, a stereotyped torsional paroxysmal nystagmus was observed. The time to onset of the nystagmus, the latency, was from 0 to 40 seconds, with an average of approximately 8 seconds. The initial phase of the nystagmus was rotary and upward, with the upper pole of the eye beating toward the ground on visual inspection. From the examiner's observation, the nystagmus should appear counterclockwise, with the left ear down. The average age of onset was 54 years, and the most common identifiable causes were head trauma (17%) and viral neurolabyrinthitis (15%).

Table 7.3

Troost and Patton described historic factors that should lead to the consideration of BPPV: (a) symptoms associated with certain head positions; (b) rotational vertigo of episodic nature; (c) an antecedent episode of severe rotary vertigo, with or without nausea and vomiting, associated with upper respiratory infection that suggests prior viral neuro-labyrinthitis; (d) a history of head traumabefore attacks of vertigo; (e) most severe symptomatology early in the day, with lessening symptoms as the day progresses; and (f) a relative absence of spontaneous symptoms without head movement or positional change. Physical examination findings include (a) vertical-rotary BPPN produced by provocative maneuvers (Fig. 7.3); (b) latency to onset of symptoms once precipitating head position is achieved; (c) short-duration nystagmus (3 to 30 seconds); and (d) adaptation of nystagmus an symptoms (i.e., disappearance with repeated maneuvers). Additionally, BPPN is not a constant feature of the physical examination, being present on some examinations but absent at other times. Typical nystagmus upon assumption of certain head postures is considered the single most important physical finding in making the diagnosis of BPPV (Fig. 7.4).

fig. 7.3

Figure 7.3. Provocative maneuvers for positional vertigo and nystagmus. The patient is abruptly moved from a seated position to one with the head hanging 45° below the horizontal and rotated 45° to one side. He or she Is then observed for positional nystagmus. The maneuvers are repeated with the head straight back and turned to the other side. (From Troost BT, Patton JM. Exercise therapy for positional vertigo. Neurology 1992;42:1441-1444.)

fig. 7.4

Figure 7.4. In benign paroxysmal positional nystagmus, the nystagmus fast phase is horizontal-rotary directed toward the undermost ear when gaze is directed toward the undermost ear (upper panel). The nystagmus fast phase is upward toward the forehead when gaze is directed to the uppermost ear (middle panel). With the eyes in the central orbital position, the nystagmus fast phase is vertical upward and rotary toward the down ear (bottom panel). (From Troost BT, Patton JM. Exercise therapy for positional vertigo. Neurology 1992;42:1441-1444.)

Posttraumatic vertigo immediately follows head trauma in most cases, implying end-organ damage in the absence of other CNS signs. The interval between injury and onset of symptoms can, however, be days or even weeks. The mechanism for the delay of symptoms is uncertain but includes hemorrhage into the labyrinth, with later development of serous labyrinthitis. Another mecha-nism for delayed posttraumatic positional vertigo is cupulolithiasis, in which the calcareous deposits (otoconia) of a damaged organ of the labyrinth are displaced to a sensitive region of the posterior canal, making it more susceptible to stimulation in certain head positions. In posttraumatic vertigo, the symptoms may be those of general peripheral vestibulopathy or benign positional vertigo. Generally, the prognosis is good, with symptoms gradually resolving within weeks to months. As pointed out by Baloh and colleagues, disabling persistent positional vertigo unresponsive to medical therapy occurs more commonly than was previously recognized. Many patients respond to exercise therapy, as described below, and rarely need selective section of the nerve to the posterior semicircular canal.

DRUG TOXICITY

Patients with dizziness produced by vestibulotoxic drugs are presumed or documented to have persistent injury to the peripheral end-organ. Among the agents causing such end-organ injury are the aminoglycosides. Streptomycin and gentainicin are most detrimental to the vestibular end-organ; kanamycin, tobramycin, and neomycin cause more damage to the auditory end-organ. Patients usually report progressive unsteadiness, particularly when visual input is diminished, as happens at night or in a darkened room. Vestibular testing documents a progressive bilateral loss of vestibular function. The aminoglycosides are concentrated in the endolymph and perilymph; thus the hair cells are exposed to high concentrations of the drugs. Extreme caution should be used in patients with renal disease, because most of these agents are primarily eliminated by the kidney. This type of end-organ toxicity should be contrasted with that produced by the large group of drugs with widespread reversible central and peripheral nervous system effects (Table 7.4). These drugs cause transient disequilibration that subsides with cessation of the medication.

Table 7.4

MÉNIÈRE'S SYNDROME

Ménière's syndrome is characterized by attacks of severe vertigo, tinnitus, fluctuating hearing loss, and ill-described aural sensations of fullness, with spontaneous recovery in hours to days. Initially, the patient develops a sensation of fullness and pressure along with decreased hearing and tinnitus in a single ear. This is followed by severe vertigo, which reaches peak intensity within minutes and slowly subsides over hours. A sense of disequilibration persists for days after an acute episode. Occasionally, sufferers from Ménière's syndrome experience such severe attacks that they suddenly fall to the ground. Consciousness is not lost in such episodes, although awareness of surroundings may be altered by the intensity of the accompanying sensation and nausea, which has been called Tumarkin's crisis. The most consistent pathologic finding in Ménière's syndrome is an increase in the volume of the endolymphatic fluid and distention of the canals, hence the term endolymphatic hydrops. Although some specific causes such as bacterial, viral, and syphilitic infections may lead to the same pathologic changes and symptoms, most cases are idiopathic. Ménière's disease usually develops between the ages of 30 and 50 and is slightly more common in women than in men. The prognosis is for progressive reduction in heating along with increasing frequency of attacks. Some patients stabilize with no subsequent attacks of severe vertigo, but they are left with residual hearing loss. Fifty percent of Ménière's patients become bilateral. The hearing loss often progresses to a moderate degree of deficit and then stabilizes.

OTHER PERIPHERAL VESTIBULAR CONDITIONS

Many other disorders affect the peripheral labyrinth, including acute otitis media, chronic ear infection, hereditary degenerative disorders of the end-organ, and local tumors. Conditions such as a vertebrobasilar transient ischemic attack (TIA) or focal ischemic stroke of the end-organ, particularly in an elderly patient, are often cited as a cause of vertigo. Such isolated involvement is difficult to document, and vertebrobasilar insufficiency should not be diagnosed without associated brainstem symptoms and signs.

Central Causes of Vertigo

Central pathologic causes of vertigo result from dysfunction of the vestibular portion of the eighth cranial nerve, the vestibular nuclei within the brainstem, and their central connections (Table 7.5). Neural connections with the central vestibular nuclei include interaction with the vestibular portions of the cerebellum (primarily the cerebellar flocculus), the visual sensory system, and afferent connections from muscle, joint, and tactile receptors. Normal persons will experience physiologic vertiginous sensations when visual and vestibular inputs are in conflict or when they are initially exposed to heights. Central pathologic causes of vertigo are less common than either peripheral or systemic causes, the vertiginous symptoms are usually less prominent, and additional neurologic signs are usually present on examination.

Table 7.5

BRAIN-STEM ISCHEMIA AND INFARCTION

The posterior circulation supplies blood to the brainstem, cerebellum, and peripheral vestibular apparatus, in addition to other structures. It is not surprising that vertebrobasilar insufficiency may be accompanied by vertigo. In general, brainstem TIAs should be accompanied by neurologic symptoms or signs in addition to vertigo or dizziness before a clear-cut diagnosis is entertained. However, it is clear that isolated episodes of vertigo lasting many minutes may be due to posterior circulation dysfunction. Symptoms include transient clumsiness, weakness, loss of vision, diplopia, perioral numbness, ataxia, drop attack, and dysarthria. Common signs of vertebrobasilar ischemia include disorders of motor function such as weakness, clumsiness, or paralysis. A crossed defect (a motor or sensory deficit on one side of the face and the opposite side of the body) is good evidence of brainstem dysfunction. If the occipital lobes are the site of ischemia, transient visual loss in the form of complete or partial homonymous hemianopia will occur. Ataxia, imbalance, unsteadiness, or disequilibrium not necessarily associated with spinning vertigo may occur because of labyrinthine or cerebellar ischemia.

However, it is incorrect to believe that dizziness must be present before a TIA of the posterior circulation can be diagnosed. Isolated symptoms like those described may occur without dizziness. On the other hand, it has been overemphasized that such symptoms must always accompany dizziness when the vertiginous symptoms are due to brainstem TIA. In elderly patients with no laboratory evidence of peripheral vestibulopathy or systemic disease, episodic disequilibration or dizziness may be due to vertebrobasilar disease.

Sudden hearing loss with moderate dizziness may be due to infarction in the distribution of the internal auditory artery. In isolation, this symptom complex is uncommon in elderly patients with atherosclerotic verte-brobasilar disease and is more suggestive of diseases affecting small and intermediate-diameter arteries, such as syphilis, systemic lupus erythematosus, or periarteritis nodosa. In the atherosclerotic patient, such symptoms are usually accompanied by other signs of brainstem or cerebellar dysfunction, which allow a more certain diagnosis. If actual brainstem infarction occurs, neurologic signs are often present on examination. Such signs may not be obvious and should be carefully sought. They include nystagmus of the central type, hyperreflexia, internuclear ophthalmoplegia, homonymous visual field defects, dysarthria, vertebral bruits, and ataxia. Symptoms of dizziness are also quite common in proximal extracranial occlusion of the vertebral arteries and in the subclavian steal syndrome.

Up to this point, the emphasis has been on the accompanying signs and symptoms that almost always occur with vertebrobasilar disease. However, acute severe vertigo, mimicking labyrinthine disease, is an early symptom of acute cerebellar infarction in the distal territory of the posterior inferior cerebellar artery. To differentiate this condition from labyrinthine disease, particular attention is directed to the type of nystagmus that is present. Acute peripheral vestibulopathy usually causes unidirectional nystagmus, with the fast phase in the opposite direction. This is similar to the situation described by the mnemonic COWS (Cold, Opposite, Warm, Same) for remembering the direction of the nystagmus fast phase during thermal irrigation of the ear. The fast phase is away from the side of the cold water irrigation. Cold water mimics a peripheral destructive lesion of the labyrinth, and almost all lesions are destructive. Therefore, with a peripheral labyrinthine disturbance, the nystagmus fast phase is in the opposite direction, or away from the involved ear. The nystagmus increases during gaze in the direction of the fast phase, or contralateral to the peripheral vestibulopathy. Swaying or falling occurs toward the side of the lesion (opposite the nystagmus fast phase). The nystagmus direction is said to be fixed in that it tends to be unidirectional, away from the side of the peripheral vestibulopathy, and tends to remain horizontal on upward gaze.

In certain syndromes of the posterior circulation, the initial presentation with acute vertigo suggests peripheral vestibulopathy. With incipient cerebellar infarction, the sway or fall is toward the side of the lesion. The accompanying nystagmus may be variable in direction but is most prominent during gaze toward the lesion. In other words, with central lesions, the fast phase of the nystagmus is in the direction of gaze (direction changing nystagmus) but becomes more prominent when gaze is directed ipsilateral to the lesion. Ocular motor findings are often present in brainstem disease, such as limitation of vertical gaze, upbeat or downbeat nystagmus, or disconjugate nystagmus.

Multiple sclerosis should only be diagnosed following the documentation of disseminated CNS lesions such as optic neuritis, transverse myelitis, internuclear ophthalmoplegia or other brainstem signs, and magnetic resonance imaging (MRI) changes, Occasionally, signs and symptoms suggesting multiple sclerosis, including disequilibration and dizziness, may be mimicked by an intrinsic brainstem tumor in a young patient.

CEREBELLOPONTINE ANGLE TUMORS

Tumors of the cerebellopontine angle rarely present solely with episodic vertigo. The most common tumor in this location results from a proliferation of the Schwann cells, hence the name schwannoma. Most of these tumors arise on the vestibular portion of the eighth cranial nerve within the internal auditory canal. They progressively enlarge, deforming the internal auditory meatus and compressing adjacent neural structures such as the acoustic portion of the eighth nerve, the facial nerve, the trigeminal nerve, the brainstem, and the cerebellum. Other tumors occurring in the cerebellopontine angle include meningiomas, epidermoids, and metastases.

The most common symptoms associated with eighth nerve tumors are progressive hearing loss and tinnitus. Vertigo occurs in approximately 20%, but a symptom of imbalance or disequilibration is more common. Rarely, a patient with a vestibular nerve tumor may present with subtle hearing loss, tinnitus, and episodic vertigo. All those with progressive unilateral hearing loss, and particularly those with any vestibular symptoms, should be carefully examined for additional neurologic signs such as a depressed corneal reflex.

CRANIAL NEUROPATHY

Multiple or isolated cranial neuropathies occur in focal or systemic disease, including vasculitis, granulomatous disease, and meningeal carcinomatosis. The cause is often elusive. Evidence of systemic involvement is elicited by history, physical examination, and laboratory evaluation. Cogan's syndrome may be considered with cranial neuropathies. The condition is characterized by nonsyphilitic keratitis associated with vertigo, tinnitus, ataxia, nystagmus, rapidly progressive deafness, and systemic involvement.

POSTERIOR FOSSA LESIONS

Posterior fossa lesions in a variety of locations are unusual causes of isolated vertigo. The symptoms are usually positional vertigo of the central type (Table 7.3). MRI with coronal and sagittal reconstructions permits identification of small tumors close to the tissue-bone artifact in computed tomography (CT) scans.

Acquired disease of the brainstem and cerebellum produces a variety of types of nystagmus, wich sometimes present as a complaint of oscillopsia, an illusion of environmental movement characterized by bouncing or jiggling of objects. Although oscillopsia is a common complaint with bilaterally reduced vestibular function, as from ototoxicity, the present of vertical oscillopsia should alert the physician to look for primary-position upbear or downbeat nystagmus. These nystagmus types are reliable indicators of CNS abnormally due to structural intrinsic midline cerebellar disease or drugs.

SEIZURE DISORDERS

Seizure disorders, especially complex partial epilepsy, are rare causes of dizziness or vertigo. The history almost always reveals additional symptoms such as loss of awareness, automatic behavior, or generalized seizure activity following an aura of vertigo. However, rare seizure patients, documented by additional history and EEG, have isolated auras of the symptoms listed in Table 7.1.

Systemic or Medical Causes of Vertigo

Systemic causes have been given a separate category to include more widespread conditions that secondarily affect peripheral and/or central vestibular structures to produce vertigo or dizziness (Table 7.6).

Table 7.6

DRUGS

Side effects of drug ingestion frequently cause dizziness in the broadcast definition of the term. Vestibulotoxic drugs, as previously described, can produce true vertigo. The dizziness produced by other drugs is more a sense of weakness, disequilibration, or "fuzzy headedness." The agents listed in Table 7.6 are among the most common offenders. Every attempt should be made to determine the type and quantity of medication being taken by the dizzy patient. Frequently, the elimination or reduction of medication such as a mild tranquillizer will produce improvement. The dizzy patient may have been treated with a variety of medications that themselves can add to disequilibration or dizziness.

HYPOTENSION

The multiple causes of presyncope or postural hypotension are often responsible for complaints of vertigo or dizziness. Again, careful historic review and documentation of physical findings such as postural hypotension or cardiac arrhythmia direct further investigation and therapy. Presyncope is described as lightheadedness, among other phrases, and is actually a common mechanism for dizziness or even vertiginous sensations. Postural hypotension is a common side effect of antihypertensive agents, diuretics, and dopaminergic agents. When the symptom is intermittent, a history of light-headedness following change from recumbent or sitting posture to an erect position, but not the reverse, is more helpful than blood pressure measurements. In adolescents, a hyposensitive carotid sinus reflex during the growth spurt is not rare, and transient symptoms of postural dizziness might he explained by this mechanism.

ENDOCRINE DISORDERS

Among the endocrinopathies that cause disorders of equilibration are diabetes and hypothyroidism. The mechanism in diabetes is probably the autonomic neuropathy and orthostatic hypotension that may accompany the disease. Though much less common as a specific cause, hypothyroidism should be considered when the symptoms of vertigo remain undiagnosed. Indeed, dizziness is not an infrequent presenting complaint in patients with thyroid deficiency. The remaining systemic conditions rarely present with isolated vertigo but are included as additional primary or secondary causes.

MULTIPLE AFFERENT SENSORY LOSS

The vestibular system functions to provide (a) spatial orientation at rest or during acceleration, (b)visual fixation during head and/or body movement (the vestibulo-ocular reflex), and (c) feedback control of muscle tone to maintain posture. These functions and their control mechanisms are interconnected in a complex fashion. Thus, the symptoms of episodic vertigo reflect disturbances in more than one system. The combination of multiple sensory deficits can produce disorientation or disequilibration that is interpreted as dizziness or vertigo. This often occurs in the elderly, in whom vision (cataracts), hearing (presbycusis), and proprioception (peripheral neuropathy) may all be impaired. There is an entity known as presbylibrium, or imbalance resulting from aging, which may be due to a selective progressive deterioration of the peripheral vestibular apparatus or a combination of sensory deficits.

Even an intact person is easily confused by afferent sensory information, as exemplified by the sensation of spinning or true vertigo experienced during full-field optokinetic stimulation. Almost every individual while quietly seated will experience a compelling illusion of rotation while viewing a moving environment of optokinetic stripes (the circular-vection illusion). Thus, it is not surprising that patients with subtle abnormalities of peripheral or central vestibular mechanisms experience definite momentary periods of disorientation while viewing a moving patterned environment. Some experience episodic vertigo during vehicular travel.

The age-related degeneration of vestibular receptors, presbylibrium, contributes to vertigo. Although most younger patients readily compensate for unilateral peripheral vestibular damage, older patients frequently cannot or have very gradual improvement, indicating either bilateral peripheral vestibular dysfunction or a separate central abnormality that decreases their ability to compensate.

DIZZINESS IN CHILDHOOD

The most common causes of vertigo and dizziness in childhood and infancy are similar to those in the adult: acute peripheral vestibulopathy, trauma, and infection. Vertigo following air travel is more common in children than in adults because of the frequency of accompanying middle ear infection and effusion. Migraine is a significant cause of episodic dizziness or vertigo in childhood and should be considered even when the symptoms of headache are minimal.

Benign paroxysmal vertigo in childhood is a variety of vestibular neuronitis. Although unaccompanied by loss of consciousness, children may fall during the course of an attack. The episodes may last minutes to hours or recur for many weeks or even months, gradually decreasing in severity. The preservation of consciousness during an attack distinguishes the condition from temporal lobe seizures with a vestibular component and from vestibulogenic epilepsy in which an attack is triggered by labyrinthine stimulation. Congenital anomalies of the inner ear and brainstem are rare causes as is vascular disease or tumor in childhood. Rarely, typical signs and symptoms of Ménière's disease occur in childhood, the youngest reported patient being age 3.

Laboratory Evaluation of Dizziness

The primary techniques for evaluating vestibular function are electronystagmography (including caloric, specific ocular motor, and rotational testing) and posturography. Various screening tests are required with undiagnosed vertigo, and neuroradiologic imaging is indicated when a central cause is suspected.

ELECTRONYSTAGMOGRAPHY (ENG)

ENG is the most readily available test for assessing the vestibular system. Eye movements are recorded by means of the corneoretinal potential by surface electrodes, with the results printed on strip-chart recording paper or analyzed by a computer. A primary function of the ENG is to determine whether there is unilateral weakness or decreased caloric responses bilaterally. Each ear is irrigated separately with warm and cool stimulation, produced by either water or by air. The resulting nystagmus is analyzed manually or by computer to determine the slow phase velocity (SPV) of the induced nystagmus. Peak SPV resulting from the warm and cool stimulation of one ear is compared with that from the other ear. The most important finding during ENG is a significant reduction in the response on one side compared with the other. A difference of more than 20 to 25% in one ear, compared with the other, is a clear indication of hypofunction in one peripheral vestibular apparatus. The ear with the weaker response is said to have a reduced vestibular response or unilateral weakness. A bilateral weakness is defined as an SPV below 8% to 10% for both warm and cool stimulation. Typical ENG recordings are shown in Figure 7.5.

fig. 7.5a fig. 7.5b
fig. 7.5c fig. 7.5d
fig. 7.5e fig. 7.5f
fig. 7.5g fig. 7.5h

Figure 7.5. Electronystagmogram (ENG). Typical bitemporal electrode recording using AC coupling. A. Calibration. Upward sweep of trace indicates eye movement to right; decay in position of trace is due to AC dal. A DC-coupled recording, standard in some laboratories, would show maintenance of this position before the eye returns to midline. B. Smooth-pursuit tracking eye movement trace shows sinusoidal side-to-side movement Interspersed with minor saccadic interruption. C. Right-ear cold caloric test demonstrating left-beating nystagmus. D. Left-ear cold caloric testing demonstrating right-beating nystagmus. E. Right-ear warm caloric testing demonstrating right-beating nystagmus. F. Left-ear warm caloric testing demonstrating left-beating nystagmus. G. Optokinetic testing with tape moving to tight demonstrating rightward-beating nystagmus. The electronystagmogram would be Interpreted as showing minor reduction in right ear responses because of slightly reduced responses in right-ear warm caloric testing. The asymmetry would be less than 30% and therefore not of clinical significance.

Equally important information gained from the use of the ENG includes (a) documentation of spontaneous and induced nystagmus, (b) quantitation of fast eye movements, (c) smooth pursuit tracking, (d) optokinetic responses, and (e) gaze testing. These are briefly discussed below.

a. Positional nystagmus induced by certain head movements may be documented by the ENG, including the latency to onset. There is usually a delay in onset of the nystagmus or latency with peripheral types of positional nystagmus. The ENG may document a primary position horizontal or vertical nystagmus. Vertical primary position nystagmus suggests central nervous system disease. One type of induced nystagmus is positional nystagmus provoked by certain head movements.

b. The average speed of the fast eye movement is recorded. Slow saccades indicate CNS disease, such as degeneration in the brainstem.

c. When smooth pursuit tracking eye movements are interrupted by a series of small saccades (a nonspecific abnormality known as cogwheel, or saccadic, pursuit), it may be caused by drowsiness, drugs, or CNS disease.

d. A major asymmetry in the optokinetic response indicates unilateral parieto-occipital CNS dysfunction.

e. Nystagmus produced during ocular excursions, in any direction, is known as gaze-evoked nystagmus. Gaze-evoked nystagmus can result from drugs such as sedatives or anticonvulsants or from cerebellar and brainstem abnormality.

ROTATIONAL TESTING

The patient is rotated in a chair controlled by a computer and eye movements are measured. Patients are rotated in the dark with eyes open while performing mental tasks assigned to distract them from mental imagery that might suppress eye movement. During a chair rotation to the right, the eyes move to the left and then recenter with a fast phase. Thus, the slow component (phase) is in the direction opposite the spin, and the fast component of the resultant nystagmus is in the direction of the rotation. The fast components are eliminated by computer, and a slow phase is reconstructed and compared with the speed of the chair rotation. In this way, a gain (slow eye movement speed ÷ chair rotation speed) at different frequencies is obtained. Measurement is made of symmetry, which compares the response to rotation in one direction with that in the opposite direction, Also measured during rotational testing is the time relationship between the slow eye movement and the slow movement of the chair. This difference is called the phase lag. Various phase lags are also plotted against the frequency of rotation of the chair. Thus, both gain and phase plots are produced during rotational testing. Rotational testing provides little information about the site of the lesion, as opposed to caloric testing in the ENG. However, it is quite beneficial in quantitating bilaterally reduced vestibular function such as occurs with ototoxicity. Rotational testing, there fore, is helpful in determining response patterns in patients with bilateral vestibular loss, A symmetric response of a person with a previous unilateral peripheral vestibular abnormality indicates vestibular compensation, and abnormal phase-lag is a nonspecific marker indicating some degree of prior peripheral vestibular abnormality.

POSTUROGRAPHY

Posturography is a means of quantifying the Romberg test. Changes in body sway during Romberg testing with feet directly together, both with eyes open and eyes closed, are measured by means of a computer. Most recently, a dynamic posture platform has been introduced. The patient is surrounded by a movable visual field and stands on a posture platform that is mobile. By manipulating the visual field, visual cues that help maintain posture may be eliminated. Similarly, by moving the posture platform in response to movement of the feet, attempts are made to remove proprioceptive cues. The test results in all conditions are reported, and an interpretation is made on the basis of which systems are defective. Posturography, a promising technology currently in use and under evaluation for assessment of balance disorders, may be useful in rehabilitation.

ADDITIONAL DIAGNOSTIC TESTS

Patients with undiagnosed vertigo should have metabolic screening tests including a blood count, electrolytes and glucose determinations, and thyroid function testing. Many physicians involved in the evaluation of dizzy patients also perform lipid screens for hypercholesterolemia or increased triglycerides. The laboratory investigation, like the physical examination, is directed particularly by the patient's history. If there is a history of presyncope or syncope, the patient must have a cardiac evaluation, including at least an electrocardiogram and rhythm strip. A more suggestive history would lead to a Holter 24-hour monitor or an event monitor, during which the patient wears a battery-powered apparatus that can be activated at times of symptoms. This device then records the cardiac rhythm. The presence of auditory symptoms requires a complete audiologic evaluation as described below. Multiple or recurrent cranial neuropathy would lead to a variety of screening tests for collagen vascular disease or skull-based pathology or meningitic processes.

Neuroradiologic Investigation

In the past, the primary neuroradiologic techniques for determining CNS abnormality and, in particular, cerebellopontine angle tumors included tomography of the temporal bone, CT scanning, and posterior fossa myelography with air or other contrast material. Currently, the high resolution obtainable on CT scanning has largely eliminated the need for tomography of the temporal bone. MRI has largely supplanted CT scanning for cerebellopontine angle tumors. For general neurologic screening, a CT scan, with and without contrast, is appropriate in patients suspected of having a CNS disorder on the basis of history or physical examination. The workup must include an MRI (Figs. 7.6, 7.7, 7.8) when there are persistent symptoms suggesting a CNS disorder. The best available images of the cerebellopontine angle and brainstem are clearly afforded via MRI.

fig. 7.6

Figure 7.6. MRI scan showing marked atrophy of cerebellum in a patient who had progressive unsteadiness.

fig. 7.7

Figure 7.7. Typical MRI scan of patient with multiple sclerosis showing periventricular white mattere abnormality (arrow). White matter lesions extending in a perpendicular fashion from the ventricle are virtually pathognomonic for multiple rosis.

fig. 7.8

Figure7.8. High-resolution MRI scan of the posterior fossa demonstrating cranial nerves VII and VIII to the viewer's right and a large cerebellar pontine angle vestibular schwannoma on the viewer's left (arrows).

Therapy for Peripheral Vestibular Disorders

The emphasis in this section is on medical and, to a lesser extent, surgical treatment of peripheral vestibular dysfunction and vertigo.

MEDICAL TREATMENT

Therapy is outlined in Table 7.7 for symptomatic treatment of dizziness presumed to be of peripheral origin. When a definitive diagnosis such as vestibular schwannoma, auloimmune disorder, perilymph fistula, or systemic vasculitis has been made, the therapy must be directed to the underlying disorder.

Table 7.7

Although most of the drugs used for dizziness are loosely referred to as vestibular suppressants, their mechanism of action may not be defined, and it is often unclear which agents will be effective in a given patient. The primary vestibular afferent system could be suppressed directly or indirectly through the inhibitory portion of the vestibular efferent system. An important effect of some agents may be to act on other sensory systems such as proprioceptive or visual inputs to the vestibular nuclei of the brainstem.

Few controlled studies have investigated the response of patients with presumed peripheral vestibular dysfunction. Most of the drugs used are empirical, based on studies of the prevention of motion sickness in normal subjects or on the various regimens used by otologists for Ménière's syndrome. Each drug class is discussed separately below.

Antihistamines are among the most commonly employed agents in the treatment of dizziness. The initial drug usually employed is meclizIne hydrochloride in doses up to 50 mg three times per day. Since the main side effect of antihistamines is drowsiness, the smallest dose should be used initially, even as low as 12.5 mg two to three times per clay.

For dizziness, antihistamines in the H1 antagonist group are used. Possibly the blockers, effective in motion sickness, act by central antagonism of acetylcholine (ACh), as does scopolamine. An excellent drug as asecond choice is Promethazine, a phenothiazine with the strongest ACh-blocking action. The usual starting dose is 25 mg three times per day, but if this amount produces drowsiness and still has a positive effect, the drug dosage may be reduced to 12.5 mg three times a day.

Anticholinergics that block the muscarinic effect of ACh have been widely used and studied for the prevention of motion sickness. Atropine acts centrally to stimulate the medulla and cerebrum, but the closely related alkaloid scopolamine is more widely used. Transdermal delivery of scopolamine may prevent or mitigate the nausea and vomiting associated with motion sickness, but not the dizziness. In general, transdermal scopolamine is not useful in patients with acquired vestibulopathy. Frequent side effects are blurred vision and dry mouth, in addition to occasional confusion. Some patients have significant difficulty when they try to discontinue scopolamine patches. A side effect of low-dose scopolamine or atropine is the transient bradycardia (4 to 8 beats fewer per minute) associated with the peak action of oral scopolamine at 90 minutes and diminishing thereafter.

Sympathomimetics have been used in the treatment of motion sickness, particularly in combination with anticholinergics. The sole agent in this class that may have an application in combination with other drugs is ephedrine. Tolerance may develop after a few weeks of treatment.

Antiemetics may be used when prominent nausea is an accompanying feature of the patient's complaint. Many of the antihistaminic nd anticholinergic drugs listed here are also used for their antiemetic actions. Prochlorperazine (Compazine) should be used with caution, particularly by the intramuscular route, because of the high incidence of dystonic reactions. Because promethazine (Phenergan) has a significant antiemetic effect, this drug is particularly useful when there is prominent nausea.

Tranquilizers is the general name for drugs from different classes with central and probably peripheral effects. They include henzodiazepines, butyrophenones, and phenothiazines. Diazepam is one of the most widely prescribed drugs for the treatment of dizziness. Many believe it should not be the first choice, primarily because of the significant potential for habituation and depression and because it can be the actual cause of dizziness. Nonetheless, it does remain the first choice of many otoneurologists or otologists. Other longer-acting benzodiazepines may be helpful in certain patients, but no study has substantiated their effectiveness. Haloperidol in small oral doses (0.5 mg three times a day) is effective in many patients with peripheral vestibular dysfunction who are not helped by other antidizziness medications.

Combination preparations and other agents include those listed in Table 7.6 and are frequently useful, particularly the combination of ephedrine and promethazine. Some other agents and regimens used primarily in the medical management of Meniere's disease are listed. Low-sodium diets and diuretics have been helpful with some patients. In the belief that in some cases an effect on blood supply to the peripheral end-organ might be a factor, agents such as cyclandelate have been used. The general approach to the patient with an acute or chronic vestibulopathy is to first use an antihistamine such as meclizine hydrochloride, If this is not helpful, the next step is to use promethazine (Phenergan), and if this is ineffective, low doses of haloperidol or low-dose Valium, always keeping in mind the potential for habituation with benzodiazepines.

EXERCISE THERAPY

It is important to recognize that BPPV is responsible for at least 50% of all causes of vertigo, and exercise therapy may be curative in up to 90% of patients. The primary therapeutic option is one form or other of exercise therapy. The severity of the individual attacks and accompanying nausea may be lessened by medical therapy; however, this does not prevent future attacks,
Exercise therapy is indicated for all patients with BPPV. There are two general approaches to therapy: (a) a single treatment session in an outpatient office setting and (b) a series of exercises performed by the patient at home. Each is briefly described below.

OFFICE SINGLE-TREATMENT APPROACH. Among the single-treatment approaches are the canal repositioning maneuver (CRP) and its modifications (Fig. 7.9). One standard protocol is described below. This technique works best for patients in whom a specific head position produces attacks of vertigo, such as with the left ear down. Often, the examiner notices a characteristic rotary vertical nystagmus accompanying the vertigo when the head is placed in the offending position (Figs. 7.3 and 7.4).

fig.7.9

Figure 7.9. Positioning sequence for left PSC shows orientation of left labyrinth and gravitating canaliths. S, Start, patient is seated with operator behind patient. Oscillation is started. 1, Head is placed over end of table, 45° to left, with head extended. (Canaliths gravitate to center of posterior semicircular canal.) 2, Head is rotated 45° to right; head is kept well extended while coming from position 1. (Canaliths reach common crus.) 3, Head (and body) are rotated until facing downward 135° from supine. (Canaliths traverse common crus.) 4, Patient is brought to sitting position; head is kept turned to right while coming from position 3. (Canaliths enter utricle.) 5, Head is turned forward with chin down about 20°. (From Epley JM. Fine points of the canalith repositioning procedure for treatment of BPPV. Insights Otolaryngol 1994;2(9):7.)

Treatment Protocol for the Left Ear

  1. The patient is moved quickly from a seated position back over the end of the examination table, with the head extended and turned approximately 45° 'with the left ear down. In each position, there may be nystagmus induced as a re-sult of change from the prior head position. The patient is kept in the position until the nystagmus or symptoms subside, typically 10 to 15 seconds.
  2. The head is slowly rotated so that the right car is now turned 45° down, keep-ing the head extended.
  3. The head and body are rotated to the right until the patient is facing downward.
    This position is maintained for approximately 15 seconds.
  4. The patient is then brought gradually up to a seated position with the head turned to the right.
  5. The head is turned forward with the chin slightly depressed.

Over the next 24 to 48 hours, some recommend that the patient remain upright as much as possible. Another variation is to apply a hand-held mechanical oscillator to the head in each position. The overall success of this single treatment is reported to be 50 to 75%.

HOME EXERCISE THERAPY. The patient is first instructed carefully about the type of exercise to be performed (Fig. 7.10).

fig. 7.10

Figure 7.10. Exercise therapy. The patient begins in the seated position and then leans rapidly to the side, placing the head on the bed or table. The patient remains there until the vertigo subsides and then returns to the seated upright posi-tion, remaining there until all symptoms subside. The maneuver is repeated toward the opposite side, completing one full repetition. Ten to 20-repetitions should be performed three times a day. (From Troost BT, Patton JM. Exercise therapy for positional vertigo. Neurology 1992;42:1441-1444.)

Treatment Protocol for Either Ear

  1. In a seated position, on the edge of a couch or bed, the patient is asked to quickly lie on one side, placing the worst ear (if one can be discovered) down first (Fig. 7.9). The patient then moves rapidly from the sitting position and rests the head on a pillow or other support, without moving forcefully enough to produce a neck injury.
  2. The patient then returns rapidly to an up-right seated position and remains there for 30 seconds or until symptoms subside.
  3. The patient rapidly lies down on the other side and remains there for approximately 30 seconds or until the symptoms subside.
  4. The patient then returns to the upright seated position. This constitutes a single repetition.

Twenty repetitions should be performed two times per day. Each session lasts approximately 30 minutes. Some patients have intense symptoms at the onset of the BPPV, including vomiting. It is clear that patients who experience extreme discomfort during the maneuvers are not likely to pursue them on their own outside of an office or hospital setting. These patients may need hospital admission or hydration in an outpatient setting, with the concurrent administration of vestibular suppressant medications. Most patients are willing to perform exercises at home. This protocol is particularly useful for BPPV patients who have the following:

  1. Bilateral BPPV
  2. Uncertainty as to which ear is involved
  3. Failure of single office treatment protocols

Recovery can be quite rapid occurring during the first few days of exercise therapy. Others progressively improve over weeks and months, suggesting that the vestibular system may adapt to whatever abnormal perturbation is causing the symptoms.

Approximately 50% of patients who have well-defined vertigo and nystagmus in certain head positions will have improvement following the single-treatment maneuver. Variations include the use of a hand-held oscillator or longer durations in each single position. The home set of maneuvers, known as the Brandt-Daroff maneuvers, may take days, weeks, or even months to produce a cure, but progressive improvement of symptoms should be noticed by the patient within the first few weeks. It is estimated that approximately 20% of patients have recurrences within the first year, and either of the maneuvers described above may be repeated with high expectation of further improvement. The overall success rate of exercise therapy approaches 90%, even with patients who have been symptomatic for years.

SURGICAL THERAPY

Surgical therapy of chronic peripheral vestibular dysfunction includes exploration for fistulas, endolymphatic shunts, and destructive end-organ surgery. The details of these procedures may be found in standard otology texts. In patients with severe Ménière's disease for whom no medical therapy such as that described earlier has been effective and who have severe recurrent disabling attacks, a labyrinthectomy may be performed. Unfortunately, Ménière's disease may become bilateral, eventually resulting in the need for labyrinthectomy or vestibular nerve section on the contralateral side. A medical labyrinthectomy may be performed by the use of aminoglycoside drugs, those particularly destructive to the peripheral vestibular hair cells. Surgical or medical labyrinthectomy is usually a last resort in patients who have clearly defined severe attacks of peripheral vestibulopathy, presumably from Ménière's disease.

Various shunting procedures have been used in the treatment of Ménière's disease or endolymphatic hydrops. Although some patients can benefit, the long-term success with such shunting procedures, which include shunts to the mastoid region and to the subarachnoid space, has been only modest.

Some patients with benign paroxysmal positional vertigo do not have a benign course. Patients who experience classic but disabling symptoms persisting over months are candidates for exercise therapy as described earlier. On rare occasions, the exercise therapy is unsuccessful; such patients are candidates for section of the nerve from the posterior semicircular canal.

Management of Central and Systemic Vestibular Disorders

MEDICAL TREATMENT

Clearly the management of central vestibular disorders depends on the diagnosis. A simple separation into peripheral and central vestibular dysfunction is not always possible, as alluded to above. Some patients have inadequate central compensation for a peripheral vestibular abnormality and thus remain symptomatic. In such patients, medical therapy for peripheral vestibular dysfunction, as described above, may prove quite effective. When a specific diagnosis (e.g., postural hypotension secondary to diabetic peripheral neuropathy) is made, attention should be directed to treatment of the primary condition. Severe postural hypotension is notoriously difficult to manage. In general, the approach is to use agents that increase vasoconstriction, others that prevent vasodilation, or drugs that might increase cardiac output. Plasma volume may be increased by the use of mineralocorticoids such as fludrocortisone acetate, but they should be prescribed cautiously.

The patient who is diagnosed as having primary CNS disease, whether it be brainstem infarction or spinocerebellar degeneration, must be managed as a patient without the accompanying symptoms of disequilibration would be. Medical therapy of vertebrobasilar ischemia is directed at preventing new infarctions, primarily with antiplatelet agents and, on rare occasions, anticoagulation. Cerebellar dysfunction not caused by tumor may be treated symptomatically. Vestibular Nuppressant medication may add a modicum of improvement, and agents helpful in the therapy of essential tremor, such as beta-blocking drugs or primidone, may result in modest symptomatic improvement.

Therapy for systemic conditions producing vertigo also depends on the diagnosis. If systemic drug therapy, as with benzodiazepines, is actually the cause of disequilibration, then of course alteration in the medical regimen may prove efficacious. Withdrawal of all drugs, be they anticonvulsants or benzodiazepines, must proceed with caution to avoid precipitating the effects of withdrawal.

SURGICAL THERAPY

Surgical therapy is primarily directed toward removal of the tumors, which can affect the peripheral or central vestibular apparatus.


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