Treatment
Patients with phobic postural vertigo are highly responsive to vestibular rehabilitation, counseling, and exercise. Initially, it is explained to patients that their vertigo is related to disturbed sensory integration. Further, it is emphasized that behavioral strategies that were appropriate during a period of vestibu-lopathy or other stressful life event may ultimately become maladaptive if they persist. An exercise program and desensiti-zation with psychotherapy are prescribed.
Pharmacotherapy can be a useful adjunct. The usual choice is a vestibular suppressant such as clonazepam or diazepam. These agents should be used at the lowest dose possible because they can also retard the process of vestibular compensation. For patients with a concomitant mood or anxiety disorder, selective serotonin reuptake inhibitors are often useful.
Vertebrobasilar insufficiency
Two thirds of patients with vertebrobasilar insufficiency will complain of dizziness at some point during the disease.48 Of patients with completed posterior-circulation strokes, 15% to 20% will have had antecedent isolated attacks of dizziness. These attacks generally last on the order of minutes. It is important to recognize that vestibulopathy related to vertebrobasilar insuffi- ciency can be the result of ischemia in the brain stem, cerebellum, or inner-ear labyrinth, secondary to disease in the branches of the basilar artery. With completed strokes, the vertigo can persist for hours or longer.
Table 10 Differential Diagnosis of Meniere Disease
|
Type of Disorder |
Diagnosis |
|
Vascular |
Giant cell arteritis |
|
Migraine headache |
|
|
Microvascular compression |
|
|
Posterior-circulation stroke |
|
|
Vertebrobasilar transient ischemic attack |
|
|
Infectious |
HIV |
|
Syphilis |
|
|
Inflammatory/ immune mediated |
Cogan syndrome |
|
Lupus |
|
|
Multiple sclerosis |
|
|
Chronic inflammatory demyelinating polyneuropathy |
|
|
Sarcoidosis |
|
|
Susac syndrome |
|
|
Idiopathic progressive bilateral sensorineural hearing loss |
|
|
Structural |
Neoplasia |
|
Perilymphatic fistula |
|
|
Other |
Superior canal dehiscence |
|
Episodic ataxia type 2 |
|
|
Seizure |
|
|
Thyroid disease |
Pathophysiology
The principal source of blood supply to the labyrinth is the anterior inferior cerebellar artery. This branch of the basilar trunk gives rise to the internal auditory artery, which ultimately divides into the anterior and posterior vestibular arteries. The anterior branch perfuses the anterior and horizontal SCCs, as well as the utricle, and the posterior branch serves the posterior SCC, the cochlea, and the saccule. Hence, an embolic event that specifically involves the anterior vestibular artery can engender a partial labyrinthine infarction, producing vertigo without hearing loss49 or vertigo with bilateral hearing loss.50 Transient bilateral hearing loss may herald a catastrophic basilar artery occlusion.51 Complete labyrinthine infarction can produce profound and lasting hearing loss and vestibular loss. Even though this would be considered a peripheral rather than a central lesion, the risk of further posterior-circulation strokes is the same as that after a pontine or cerebellar infarction.
Diagnosis
Vertebrobasilar ischemia that affects the brain stem and cerebellum can produce a broad array of neurologic manifestations. These include nystagmus, diplopia, tinnitus, sensory changes, ataxia, dysarthric speech, facial pain, Horner syndrome, weakness, and postural abnormalities. The nystagmus can be highly varied and can have characteristics of either a central or a peripheral type.
Because vertebrobasilar insufficiency is potentially life threatening, it should be actively excluded as a cause of dizziness in patients with a compatible clinical picture, especially those with cerebrovascular risk factors such as hypertension and diabetes. Magnetic resonance imaging of the brain is useful to look for evidence of posterior fossa lesions suggestive of stroke. High-resolution magnetic resonance angiography is increasingly utilized to visualize the patency of the basilar and vertebral arteries. With further refinements, this imaging technique may largely replace conventional angiography as the gold standard for assessing the anatomy of the posterior cerebral vasculature. Patients with cerebellar or brain stem hemorrhagic stroke may present similarly but with a more prolonged duration of symptoms. Emergent imaging is indicated in such cases.
Treatment
In patients with established vertebrobasilar insufficiency, a critical aspect of therapy is the reduction of modifiable risk factors, such as smoking, hypertension, and hyperlipidemia. An-tiplatelet or anticoagulation therapy must also be carefully considered [see 11:IV Cerebrovascular Disorders].
Drug-induced vertigo
Many drugs can produce dizziness by their effects on the vestibular system and cerebellum [see Table 11]. Alcohol changes the specific gravity of endolymph in the cupula and can lead to nystagmus and vestibulopathy. It also impairs cerebellar function, which can produce ataxia, speech changes, postural instability, and nystagmus. Lithium therapy can result in cerebellar dysfunction and can be a cause of downbeating nystagmus.
Table 11 Drugs That Can Cause Vertigo
|
Drug or Category |
Mechanism |
|
Alcohol |
Peripheral: alteration of endolymph specific gravity |
|
Central: gaze-evoked nystagmus, cellular atrophy |
|
|
Anticholinergics, antihy-pertensives, smooth muscle relaxants (e.g., alpha blockers) |
Orthostatic hypotension |
|
Anticonvulsants |
Cerebellar dysfunction |
|
Aminoglycoside antibiotics |
Vestibular hair cell damage (causes imbalance rather than vertigo) |
|
High-dose aspirin |
Ototoxic damage to vestibular hair cells |
|
Chemotherapeutic agents (e.g., cisplatin) |
Hair cell damage |
Other agents commonly associated with dizziness include tranquilizers and antihypertensive medications, which cause dizziness by producing orthostatic hypotension; anticonvul-sant agents, which produce cerebellar dysfunction; and antibiotics, which can damage vestibular hair cells bilaterally, leading to gait instability and oscillopsia. Additional sources of vestibular toxicity include high-dose aspirin52 and chemothera-peutic agents such as cisplatin.
One of the most ototoxic agents is gentamicin, which can produce profound vestibular dysfunction by causing bilateral damage to inner-ear hair cells. The symmetrical damage explains the absence of vertigo and nystagmus. In one study, vestibulopathy was found to begin as long as 1 week after gentamicin was discontinued, and onset was delayed in 32 of 36 patients.53 Half of the affected patients did not have abnormal peak or trough antibiotic levels. Metronidazole given concurrently with genta-micin may increase the risk of vestibulotoxicity.54 Dynamic visual-acuity testing can be helpful in early recognition of gentam-icin-associated vestibular toxicity. Prompt termination of gentamicin treatment may confer a more complete recovery in such patients. There may be a genetic predisposition to gentamicin ototoxicity related to an abnormality in ribosomal messenger RNA, although most cases of ototoxicity occur in patients who do not have this mutation.
Vestibular migraine
Migraine headache often has neurologic accompaniments, the most common of which are visual distortions. The second most common neurologic manifestation of migraine is vestibulopathy, principally characterized by vertigo.56 Central nystagmus is the typical type observed in patients with migraine.57 The most extreme form of vestibular migraine, basilar artery migraine, was first described and named by Bickerstaff. This migraine occurs in adolescents and young adults; typically presents as visual loss or aura, vertigo, ataxia, dysarthria, and dysesthesia lasting up to 45 minutes; and is always followed by a throbbing headache, frequently with vomiting.58 Much less dramatic, but more common, is so-called migrainous vertigo, which combines vestibular symptoms with characteristic features of migraine.59
In up to 30% of patients with vestibular migraine, vertigo occurs completely independently of headache (i.e., acephalgic migraine). A family history of migraine is common, as is a personal history of car sickness in childhood. Uncommonly, sudden hearing loss is attributable to migraine.60 On the other hand, patients considered to have Meniere syndrome who have no documented hearing loss may in fact have migraine. Patients who complain of "sinus headaches" that include vestibular symptoms most likely have vestibular migraine. Most patients with vestibular migraine have episodes of dizziness that generally last for minutes, although in some, the episodes last for hours. The vertigo may be position induced and can occur in association with central-pattern nystagmus. Some women have a greater disposition for vestibular migraine around the time of their menses (so-called catamenial migraine).
The treatment of vestibular migraine is similar to that of other forms of migraine [see 11:VIII Headache] and includes elimination of habitual use of caffeine and over-the-counter analgesics and prophylactic treatment with beta blockers, tricyclic antidepressants, calcium channel blockers, valproic acid, and, occasionally, acetazolamide. Triptans may play a role in therapy, but their efficacy has not yet been determined.61,62
Perilymphatic fistula and superior canal dehiscence syndrome
Perilymphatic fistulas are abnormal communications between perilymph and the outside world.63 Generally, these fistulas occur between the middle and inner ear at the oval or round windows. Precipitating causes include head trauma, Valsalva maneuvers that increase intracranial pressure, vigorous exercise, stapes surgery, barotrauma, erosive lesions in the petrous bone (e.g., a neoplastic lesion or cholesteatoma), inflammatory conditions such as syphilis, and congenital conditions.
Superior canal dehiscence (SCD) syndrome involves the opening of a third window into the labyrinth because of the absence of bone overlying the superior canal.64 Although the syndrome probably results from congenital thinness of the temporal bone in this area, symptoms may not appear until adulthood, often after head trauma.
Diagnosis
Patients with perilymphatic fistula show hearing loss that is generally similar to that which occurs in Meniere disease. Position-induced vertigo and nystagmus may also occur. Vertigo and nystagmus can also be induced by tragal compression or with swallowing. A useful clinical test for diagnosing fistula involves insufflation of the external ear, which in some patients can produce nystagmus (Hennebert sign). This has been incorporated into platform posturographic testing.
Vertigo in patients with perilymphatic fistula is often secondary to activation of the SCC. Patients with either perilym-phatic or otolithic fistula can experience vertigo that is provoked by exposure to loud noise (the Tullio phenomenon), a response that may also be seen in Meniere disease. Patients with SCD also experience the Tullio phenomenon, sometimes even from their own voice. A Valsalva maneuver performed against pinched nostrils, which results in increased middle-ear pressure, will induce a nystagmus consistent with excitation of the superior canal—namely, a mixed torsional-vertical nystagmus with fast phases directed downward and with the upper pole beating toward the affected ear. Hearing loss is often mixed, with both a conductive and a sensorineural component, predominantly in the lower frequencies. Some patients report that when a tuning fork is placed on the ankle, they can hear it in the affected ear. A useful laboratory test, although not widely available, is measurement of the vestibular evoked myo-genic potential (VEMP).66 This test measures electromyograph-ic activity in the sternocleidomastoid muscle by modulating loud clicks in each ear. The VEMP is elicited at a lower threshold than normal in an ear with SCD.
Treatment
Patients with a fistula are generally treated conservatively, with bed rest, fluid hydration, elevation of the head, and avoidance of straining that may cause a Valsalva response. If conservative measures fail, surgical occlusion of the fistula site can be attempted. This generally involves patching the oval and round windows with fatty tissue. Success is variable.
Surgical resurfacing of the arcuate eminence, the area of bone overlying the superior canal, can effectively reduce or eliminate symptoms of SCD.63 This involves a craniotomy and middle fossa approach.
Structural abnormalities associated with vertigo
A variety of structural abnormalities have been associated with the development of vertigo. Cerebellopontine angle tumors (e.g., acoustic neuromas) and Arnold-Chiari malformation may present as new-onset vertigo associated with asymmetry in sensorineural hearing thresholds or with new-onset or atypical headache. Consequently, such findings are accepted indications for brain imaging with contrast. Other structural lesions that can produce vertigo include primary brain tumor, meta-static lesion, neurofibroma, traumatic labyrinthine fracture, der-moid and epidermoid lesions, and vascular malformation.
Some patients who have stereotypical paroxysmal episodes of vertigo may suffer from a vascular compression syndrome.68 This syndrome is produced by a vascular ectasia in one of the posterior-circulation arteries that leads to compression of the caudal brain stem or cranial nerve VIII. Such patients experience rotational or fore-and-aft vertigo. Attacks last seconds to minutes, are generally provoked by particular head positions, and can be associated with hyperacusis or tinnitus. Results of vestibular or auditory function testing may be abnormal. Hy-perventilation or exercise-induced symptoms are typical of, but not specific for, microvascular compression syndromes. Most patients respond to membrane-stabilizing agents such as car-bamazepine, phenytoin, clonazepam, and baclofen. Medically refractory cases may be responsive to vascular decompression surgery.69
Cerebellar ataxia
Patients with cerebellar disease from any cause may complain of vertigo and oscillopsia because of spontaneous or positional nystagmus. Subacute development of imbalance, dysarthria, and incoordination over weeks to months should prompt a search for paraneoplastic antibodies and an occult malignancy.70 A family history should be sought and molecular testing for the various spinocerebellar atrophies considered under the appropriate circumstances. Episodic ataxia type 2 (EA2; familial acetazolamide-responsive episodic or periodic ataxia syndrome) is an autosomal dominant condition caused by mutations in the calcium channel gene (CACNA1A), located on chromosome 1971 [see 11:X Inherited Ataxias]. This is the same gene that is involved in spinocerebellar ataxia type 6 and familial hemiplegic migraine. Treatment with acetazolamide is generally effective in reducing the frequency and severity of attacks. However, patients often have interictal abnormalities, including downbeating nystagmus. Fortunately, 4-aminopyrid-ine (4AP) or the related compound 3,4-diaminopyridine have been reported to decrease downbeating nystagmus.72 Some patients benefit from treatment with clonazepam, baclofen, or gabapentin. Bilateral vestibular loss and cerebellar ataxia can occur as part of the same syndrome and can be recognized by a failure of visual-pursuit mechanisms to enhance the VOR during head rotation in light.73
Vestibular seizure
In rare cases, patients present with stereotypical episodes of vertigo on the basis of seizure activity.74 These episodes have been referred to as tornado epilepsy. Such attacks appear to involve discharges from primary vestibular cortical zones that produce symptoms of vertigo and, on occasion, the perception of environmental tilt. It is of interest that Penfield,75 in his original human cortical stimulation experiments, was able to elicit vertigo by stimulation of the parietal insular regions of the brain, though frontal areas have also been implicated.76 Fortunately, these seizures often respond to treatment with standard anticonvulsant agents [see 11:XII Epilepsy]. It should be noted that a normal interictal electroencephalogram does not exclude the presence of an epileptic focus. Nystagmus, however, is not uncommon during a seizure and may have some localizing value.77
Multiple sclerosis
Although vertigo is an uncommon initial presentation of MS, accounting for less than 5% of cases, up to 20% of MS patients will experience vertigo at some time over the course of the illness. Vertigo secondary to demyelination most commonly arises from lesions in the vestibular nucleus and the root entry zone of cranial nerve VIII.78 Nystagmus from such lesions can appear to be of central or peripheral origin (e.g., mixed tor-sional-horizontal, pendular, or pure vertical).79 When a patient with MS has vertigo resulting from inflammatory lesions, appropriate treatment includes corticosteroids and vestibular suppressants. BPPV must be excluded in any MS patient with vertigo, given the ease of BPPV diagnosis and the high response rate to treatment.
