NEURO-OTOLOGY (Continued)

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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{Back to Outline}

Posterior fossa lesions in a variety of locations are unusual causes of isolated vertigo. The symptoms are usually positional vertigo of the central type (see Table 3). Magnetic resonance imaging (MRI) with coronal and sagittal reconstructions permits identification of small tumors close to the tissue-bone interface, a region often blurred by bone artifact in CT scans.

Acquired disease of the brainstem and cerebellum produces a variety of types of nystagmus, which 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 presence of vertical oscillopsia should alert the physician to look for primary position upbeat or downbeat nystagmus. These nystagmus types are reliable indicators of CNS abnormality due to structural intrinsic midline cerebellar disease or drugs.

Seizure Disorders{Back to Outline}

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. Rare seizure patients have isolated auras of the symptoms listed in Table 1 including spinning vertigo.

SYSTEMIC OR MEDICAL CAUSES{Back to Outline}

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. Some are outlined in (Table 5):

Side effects of drug ingestion frequently cause dizziness in the broadest 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 5 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 which themselves can add to disequilibration or dizziness.

Hypotension{Back to Outline}

The multiple causes of presyncope or postural hypotension are often responsible for complaints of vertigo or dizziness (Mathias, 1995). Again, careful historical 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 lightheadedness 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 be explained by this mechanism.

Endocrine Disorders{Back to Outline}

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 SENSORY ABNORMALITIES{Back to Outline}

What this means is that some people, particularly the elderly, may experience "dizziness" due to decreased sensory function : diminution of of inner ear function, decreased hearing , poor eye sight, and decreased ability to feel their legs (peripheral neuropathy). When all your sensory systems related to balance are decreased you don't feel oriented in space, are subject to falls, and have difficulty with activities of daily living. You may tell physicians - " I'm dizzy", "I can't keep my balance" , "I feel like I'm going to fall", etc.

The technical explanation of what is going on follows: The vestibular system functions to provide: (1) spatial orientation at rest or during acceleration, (2) visual fixation during head and/or body movement (the vestibulo-ocular reflex), and (3) 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 (Brandt 1991) 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.

Thus many people who have multiple sensory defects are in fact, "dizzy" or "imbalanced" due to the subtle combination of different sensory defects. Medication is usually not helpful unless there is clear episodic vertigo (spinning) due to inner ear dysfunction. Patients can be helped however, by increasing their sensory input by using a "dragging cain". Using a cane, not to support a weak leg, but by dragging it along the ground, increases sensory input through the arm where the cane is held. The individual has a better sense of stability and "where the ground is" and many times can walk more steadily and safely.

DIZZINESS IN CHILDHOOD{Back to Outline}

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 Meniere's Disease occur in childhood. The youngest reported case being age 3.

LABORATORY EVALUATION OF DIZZINESS (TESTS){Back to Outline}

The primary techniques for evaluating vestibular function are electronystagmography (ENG) (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){Back to Outline}

Electronystagmography (ENG) is the most readily available test for assessing the vestibular system. Eye movements are recorded by means of the corneo-retinal 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 of the induced nystagmus. Peak slow phase velocity (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 when compared with the other. A difference of > 20% to 25% in one ear, when 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 of less than 8% to 10% for both warm and cool stimulation.

Typical ENG recordings are shown in Figure 5: Figure 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 drift. 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 right demonstrating rightward-beating nystagmus. The electronystagmogram would be interpreted as showing minor reduction in right ear responses due to slightly reduced responses in right ear warm caloric testing. The asymmetry would be less then 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 postional nystagmus provoked by certain head movements.

(b) The average speed of the fast eye movement is recorded. Slow saccades are an indicator of central nervous system disease such as degeneration in the brainstem.

(c) When smooth pursuit tracking eye movements is interrupted by a series of small saccades, it is known as cogwheel or saccadic pursuit, a non-specific abnormality and may be caused by drowsiness, drugs, or central nervous system disease.

(d) A major asymmetry in the optokinetic response is an indicator of unilateral parieto-occipital central nervous system 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{Back to Outline}

The patient is rotated in a chair controlled by a computer with eye movements measured. Patients are rotated in the dark with eyes open while performing mental tasks assigned to distract them from mental imagery which may 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 of the rotation in one direction with those in the opposite direction. Another measurement made 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. Therefore, 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, therefore, 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 non-specific marker indicating some degree of prior peripheral vestibular abnormality.

Posturography{Back to Outline}

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 based on which systems are defective. Posturography is a promising technology currently in use and under evaluation for assessment of balance disorders, and may be useful in rehabilitation.

Additional Diagnostic Tests{Back to Outline}

Patients with undiagnosed vertigo should have metabolic screening tests including blood count, electrolytes, glucose and thyroid function testing. Many physicians involved in the evaluation of dizzy patients will also perform lipid screens for the presence of 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 to include 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 audiological 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.

Neuroradiological Investigation{Back to Outline}

In the past, the primary neuroradiological techniques for determining CNS abnormality and, in particular, cerebellopontine angle tumors included tomography of the temporal bone, computed tomographic scanning (CT), 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. Magnetic resonance imaging (MRI) has largely supplanted CT scanning for cerebellopontine angle tumors. For general neurological 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 when there are persistent symptoms suggesting a CNS disorder. Some MRI scans are shown in the following three figures:

THERAPY FOR PERIPHERAL VESTIBULAR DISORDERS{Back to Outline}

The emphasis here will be on medical and to a lesser extent, surgical treatment of peripheral vestibular dysfunction and vertigo.

Medical Treatment{Back to Outline}

Therapy is outlined for symptomatic treatment of dizziness presumed to be of peripheral origin (Table 7):

*Usual adult starting dose, can be increased by factor of 2 to 3. The most common side effect is drowsiness.

**The combination preparations Donphen and Donnatal each contain a mixture of atropine alkaloids with approximately 1/4 grain (15-16.2 mg) phenobarbital.

***Note the very low dose when compared to usual antipsychotic levels. Still, the patient should be observed for dystonias.

When a definitive diagnosis such as vestibular schwannoma, autoimmune disorder, perilymph fistula, or systemic vasculitis has been made, the therapy must be directed to the underlying disorder.

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 of the various regimens employed by otologists for Meniere's syndrome. Each of the drug classes are discussed separately. {Back to Outline}

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 50mg 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 day.

For dizziness, antihistamines falling into the H1 antagonist group are used. Possibly the H1 blockers, effective in motion sickness, act by central antagonism of acetylcholine, as does scopolamine. An excellent drug as a second choice is Promethazine, (Phenergan® ), 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 less 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 and 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 given to include drugs from different classes having central and probably peripheral effects. Drugs include benzodiazepines, butyrophenones, and phenothiazines. Diazepam (Valium® ) 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 6 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 would be first to employ an antihistamine such as meclizine hydrochloride. If this is not helpful, the next step would be to use promethazine (Phenergan® ), and if this is ineffective, low doses of haloperidol or low dose diazepam always keeping in mind the potential for habituation with benzodiazepines.

Exercise Therapy{Back to Outline}

It is important to recognize that Benign Positional Paroxysmal Vertigo (BPPV) is responsible for at least fifty percent of all cases of vertigo and exercise therapy may be curative in up to ninety percent 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, (The Epley Maneuver and its variations) and

(b) a series of exercises performed by the patient at home (The Brandt-Daroff exercises). Each will be briefly described.

a). Office single treatment approach. Among the single treatment approaches are the Canal Repositioning Maneuver (CRP) and its modifications (Figure 9, Panel 1-6, Modified for this Web page exclusively, after Epley).

Figure 9. Positioning sequence for left posterior semicircular canal (in red) shows orientation of left labyrinth and gravitating canaliths (in violet).
1,The patient is seated with operator behind. An ultrasonic oscillator may be used and is started at this point.

2, Head is placed over end of table, 45 degrees to left, with head extended. (Canaliths gravitate to center of posterior semicircular canal, the "cleared" portion now shown in green.)
3, Head is rotated 45 degrees to right; head is kept well extended in process of coming from position 1. (Canaliths reach common crus.)

4, Head (and body) are rotated until facing downward 135 degrees from supine. (Canaliths traverse common crus.)

5, Patient is brought to sitting position; head is kept turned to right in process of coming from position 3. (Canaliths enter utricle.)
6, Head is turned forward with chin down about 20 degrees.

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 times, the examiner notices a characteristic rotary vertical nystagmus accompanying the vertigo when the head is placed in the offending position (see Figures 3 and 4, earlier).

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 degrees with the left ear down. In each position, there may be nystagmus induced as a result of change from the prior head position. The patient is kept in the position until the nystagmus or symptoms subside, typically ten to fifteen seconds.

2. The head is slowly rotated so that the right ear is now turned 45 degrees down, keeping 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 fifteen 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 twenty-four to forty-eight hours, some recommend that the patient remain upright as much as possible. Another variation is to apply a handheld mechanical oscillator to the head in each position. The overall success of this single treatment is reported to be fifty to seventy-five percent.

b). Home Exercise Therapy (Brandt-Daroff exercises).

The patient is first instructed carefully about the type of exercise to be performed (Figure 10):

Figure 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 position, 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 two times a day.

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 (Figure 10). The patient then moves from the sitting position, rapidly, and rest the head on a pillow or other support. They should not move so forcefully that it might produce a neck injury.

2. The patient then returns rapidly to an upright seated position and remains there for thirty seconds or until symptoms subside.

3. The patient rapidly lies down on the other side and remains there for approximately thirty 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 thirty minutes. Some patients have intense symptoms at the onset of the BPPV, including vomiting. It is clear that the patients who experience extreme discomfort during the maneuvers will not be 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 fifty percent 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 handheld 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 twenty percent 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 ninety percent, even with patients who have been symptomatic for years.

Surgical Treatment of Peripheral Vestibular Disorders{Back to Outline}

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 Meniere'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, Meniere'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 Meniere's disease.

Various shunting procedures have been used in the treatment of Meniere'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 6 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{Back to Outline}

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 earlier. 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 earlier, may prove quite effective. When a specific diagnosis, for example, 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, or others which prevent vasodilatation, or drugs which 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 would be a patient without the accompanying symptoms of disequilibration. 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 suppressant 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 is also dependant 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{Back to Outline}

Surgical therapy is primarily directed toward removal of the tumors, which can affect the peripheral or central vestibular apparatus. A variety of destructive procedures for removal of the semicircular canals or section of the vestibular nerve have been utilized for intractable vertigo, particularly in Meniere's disease. Description of these procedures is beyond the scope of this Chapter and may be found in texts on Otology, Otolarygology and Neuro-Otology. {Back to Outline}

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