CHAPTER 92 Treatment of Intractable Vertigo
Classification of Vestibular Disorders
Vestibular disorders are classified as central or peripheral. Central disorders involve the brainstem and cerebellum, whereas peripheral disorders involve the vestibular nerve and labyrinth. The causes, symptoms, and treatments differ between the two categories. The hallmarks of each category are summarized in Table 92-1.1,2
| CHARACTERISTIC | CENTRAL VERTIGO | PERIPHERAL VERTIGO |
|---|---|---|
| Onset | Insidious | Sudden |
| Auditory symptoms (hearing loss, tinnitus, aural fullness) | Rarely present | Common |
| Neurologic deficits | Common | Rare |
| Severity of symptoms |
Central Vestibular Disorders
Vertebrobasilar Insufficiency
Patients with vertebrobasilar occlusive disease most commonly suffer from weakness in the extremities, ataxia, and oculomotor or oropharyngeal cranial nerve palsies. In these patients, vertigo is also a frequent finding.3 Patients with cerebellar infarctions may complain of vertigo, diplopia, nystagmus, nausea, and ataxic gait. Wallenberg’s syndrome, produced by unilateral infarction of the dorsolateral medulla, is manifested as vertigo, hoarseness, ataxia, Horner’s syndrome, and loss of pain and temperature sensation ipsilaterally in the face but contralaterally in the trunk and limbs.3 Subclavian steal syndrome is an unusual variant of vertebrobasilar insufficiency that may cause vertigo, although the association is controversial.4
Migrainous Vertigo
Migrainous vertigo is the second most common cause of recurrent vertigo and occurs in approximately 10% of all patients with migraine headaches. The disorder arises at any age and has a strong female preponderance.5,6 During acute episodes, patients often exhibit nystagmus and a Romberg sign. Auditory symptoms are rarely present, but vague ear fullness is rather common. The clinical findings may be quite variable, thus making precise diagnosis difficult, particularly given the fact that many times there is no associated headache. In fact, there is no broad consensus regarding diagnostic criteria for this disorder. Epidemiologic data indicate that (1) symptoms may be associated with typical migraine symptoms, including auras, photophobia, phonophobia, and severe headache; (2) the vertigo may be spontaneous or provoked by motion and last from seconds to several days; and (3) the temporal relationship between headache and the onset of vertigo may vary considerably. At present, there is no clear consensus regarding the treatment of migrainous vertigo, although many different therapeutic regimens have been studied.7
Tumors
Tumors of the cerebellopontine angle are rare but potentially important causes of vertigo. These tumors more commonly produce ataxia and disequilibrium; however, they are believed to produce vertigo by a variety of mechanisms, including compression of the cerebellum or brainstem, invasion of the bony labyrinth, compression of the membranous labyrinth, or neoplastic transformation of the vestibular nerve itself.8,9 Vestibular schwannomas, for instance, may cause unilateral hearing loss, tinnitus, and disequilibrium or vertigo, depending on the nature of the labyrinthine involvement. Intralabyrinthine schwannoma, a less common variant of vestibular schwannoma with only 47 reported cases since 1917, produces vertigo in the majority of patients.10
Paraneoplastic Syndromes
Several paraneoplastic syndromes have been associated with vertigo, probably through an autoimmune mechanism.11 Paraneoplastic encephalomyelitis is an autoimmune disease associated with small cell lung cancer. The disease is typically manifested as vertigo with other cranial nerve deficits secondary to degeneration of vestibular and cranial nerve nuclei. Paraneoplastic cerebellar degeneration is associated with lung cancer, lymphoma, and breast and ovarian cancer. Patients experience rapidly progressive symptoms, including vertigo, ataxia, oscillopsia, diplopia, dysarthria, and dysphagia. Magnetic resonance imaging typically reveals atrophy of the cerebellum.12 In some cases the vestibular symptoms produced by these disorders may precede the diagnosis of malignancy.13
Demyelinating Disorders
Multiple sclerosis (MS) is a relatively uncommon cause of central vertigo. Although dizziness is a frequent complaint of patients suffering from MS, only 5% to 10% of these patients experience true vertigo. Importantly, benign paroxysmal positional vertigo (BPPV) is frequently underappreciated in MS patients because the signs and symptoms of MS blur the distinction between central and peripheral causes of vertigo.14,15
Peripheral Vestibular Disorders
Benign Paroxysmal Positional Vertigo
BPPV is the most common cause of recurrent vertigo. It can occur throughout life, with the peak age at onset between the fifth and sixth decades. The annual incidence of BPPV is 107 cases per 100,000 population, and it is twice as common in women as in men. Risk factors for BPPV include a history of vestibular neuritis or head trauma, although most cases are idiopathic.16–20
BPPV is thought to result from canalithiasis in the majority of cases. Otoconia from the utricle dislodge and enter the endolymph of the semicircular canal system, most commonly the posterior semicircular canal, and stimulate flow of endolymph in response to changes in head position.17 An alternative form is cupulolithiasis, in which the dislodged otoconia adhere to the cupula ampullaris, thereby creating an abnormal mechanical stimulus that produces protracted deviation of the cupula in response to changes in the gravitational vector.21
Canalithiasis accounts for vertigo elicited by particular rotational movements of the head. Common positional triggers include lying down, extension of the neck to look up, bending forward, and sitting up from a supine position. A typical vertiginous episode lasts from 10 to 30 seconds and is often associated with nausea and visible nystagmus. Episodes of vertigo often occur in clusters with asymptomatic intervals between attacks. Several randomized placebo-controlled trials have demonstrated that a significant proportion of cases resolve spontaneously within a few months of onset, but the percentage of patients with self-limited cases varies considerably among these trials, ranging from 27% to 84%.21
BPPV caused by posterior semicircular canalithiasis may be revealed through the Dix-Hallpike maneuver. Proposed in 1952, this bedside maneuver quickly moves the patient from an upright seated to a supine position and then turns the patient’s head to one side and slightly extended at the neck. The procedure is then repeated by turning the head to the other side and observing the patient for nystagmus.21 Patients with horizontal canal BPPV may not demonstrate nystagmus with this maneuver.22
Meniere’s Disease
Endolymphatic hydrops, or Meniere’s disease, was first described by the Parisian physician Prosper Meniere in 1861.23 Meniere’s disease is relatively rare, with a prevalence of 218 per 100,000 persons. However, it is a relatively common cause of acute recurring episodic vertigo. Meniere’s disease may be overdiagnosed in the primary care setting.24–26
The classic manifestation consists of recurrent episodes of spontaneous rotational vertigo coupled with fluctuating hearing loss, tinnitus, and aural fullness. The vertiginous episodes generally last several hours and are associated with nausea and vomiting. Hearing loss is typically progressive, predominantly affects the lower frequencies initially, and may ultimately lead to unilateral deafness (Fig. 92-1). Bilateral hearing loss develops in approximately 50% of patients.17 Management of bilateral cases is exceedingly complex.
Since its description, Meniere’s disease has been the subject of intense scientific inquiry. Even so, understanding its pathogenesis remains elusive. Current theories suggest that dysfunction of mechanisms governing the production and reabsorption of endolymph leads to distention and periodic rupture of the membranous labyrinth, which causes unilateral vestibular dysfunction. The cause of the dysfunction is unknown, although a viral insult in predisposed individuals has been proposed.2
Labyrinthitis
The most common cause of labyrinthitis is viral infection. Viral labyrinthitis is classically described as a sudden onset of severe vertigo associated with nausea, vomiting, and auditory symptoms, including tinnitus and hearing loss. Identification of the viral pathogens responsible for viral labyrinthitis is an ongoing scientific endeavor, the principal challenge being the demonstration of Koch’s postulates for a variety of presumptive agents.2,27
Bacteria can infiltrate the labyrinth through direct extension from a nearby focus of infection (otitis media, otomastoiditis, or meningitis) to cause a more serious form of labyrinthine infection. Serous labyrinthitis is characterized by the sudden onset of vertigo in association with otitis media, but it causes only mild to moderate hearing loss. Suppurative bacterial labyrinthitis results in severe hearing loss, vertigo, nausea, and vomiting. Patients with suppurative labyrinthitis often appear toxic and febrile.28 Although viral labyrinthitis is a self-limited condition, bacterial labyrinthitis requires intravenous antibiotics and sometimes urgent surgical labyrinthectomy to prevent serious complications such as meningitis. Permanent hearing loss is inevitable.
Vestibular Neuritis
The clinical manifestation of vestibular neuritis involves the acute onset of vertigo over a period of hours, which becomes quite severe for several days before it gradually subsides. There may be a flu-like prodrome. Auditory symptoms (tinnitus, aural fullness, and hearing loss) are characteristically absent, which helps distinguish the disorder from labyrinthitis.29 The most likely cause of vestibular neuritis is viral infection of the superior division of the vestibular nerve. Patients who suffer from vestibular neuritis are predisposed to secondary forms of BPPV, an association suggestive of a viral mechanism for otoconial displacement.
Vestibular neuritis is often described as a self-limited condition that persists for several weeks, depending on the rate of vestibular compensation. However, chronic morbidity is a significant problem given that 30% to 40% of patients will suffer from persistent dizziness secondary to incomplete vestibular compensation, a condition termed uncompensated vestibular neuritis.29,30 This distinction is particularly important for surgeons evaluating patients with intractable vertigo because patients with uncompensated vestibular neuritis are typically poor surgical candidates.
Perilymphatic Fistula
Perilymphatic fistula (PLF) is an abnormal connection between the fluid-filled inner ear and the air-filled tympanic cavity. First proposed a century ago by Meniere, PLF remains a controversial diagnosis among neuro-otologists.31 Previous studies have documented variable signs and symptoms, and it is often difficult to identify a definite site of leakage. Nonetheless, a recent meta-analysis of these studies has revealed certain clinical patterns: (1) patients complain of sudden loss or rapid deterioration of their hearing, (2) the hearing loss tends to involve fluctuations in speech discrimination, (3) dizziness is the most common symptom and is usually described as a continuous disequilibrium with occasional episodes of positional vertigo, and (4) most patients have a combination of symptoms.31–33 A significant proportion of documented cases exhibited the symptom constellation of fluctuating hearing loss, tinnitus, dizziness, and aural fullness. This clustering of symptoms is very similar to Meniere’s disease, thus confounding accurate diagnosis and treatment of these patients.34
Superior Semicircular Canal Dehiscence Syndrome
Superior semicircular canal dehiscence (SSCD) syndrome was first described in 2000. The putative pathophysiology of SSCD is thinning of the squamous temporal bone, which predisposes to dehiscence of the superior semicircular canal. In effect, acoustic energy is shunted away from the basilar membrane toward the structural defect in the otic capsule bone. SSCD syndrome is characterized by aural fullness, hyperacusis, autophony, and conductive or mixed hearing loss with a low-frequency component.35,36 Patients characteristically exhibit the Tullio phenomenon (noise-induced dizziness and eye movements) and the Hennebert sign (movement of the eyes in response to impulses of pressure in the external auditory canal). The sensitivity to loud sounds and changes in ambient pressure typically causes episodic vertigo and oscillopsia. On audiometric testing, bone conduction thresholds in the involved ear are better than in the other and may be supranormal in the low frequencies. Acoustic reflexes are present despite the apparent conductive hearing loss. Thin-section temporal bone computed tomography (CT) scans reformatted in the plane of the superior canal are diagnostic. Electrocochleography and vestibular evoked myogenic responses are particularly helpful in confirming the diagnosis in patients with a suspicious clinical picture or borderline CT findings.
Trauma
Trauma can cause either peripheral or central vertigo, depending on the mechanism of injury. Head trauma can lead to vertigo by a variety of mechanisms, including fracture of the temporal bone, creation of epileptogenic foci, induction of posttraumatic migraine, and alteration in the vertebrobasilar circulation. Transverse fractures through the temporal bone may cause disruption of the membranous labyrinth or significant damage to the cochleovestibular nerve, or both, thereby provoking severe vertigo and profound sensorineural hearing loss (SNHL). In addition, trauma patients with labyrinthine injury will experience gait unsteadiness and veering toward the affected side for several days, along with nausea and vomiting. These symptoms usually subside within 6 weeks. Longitudinal temporal bone fractures, which typically spare the membranous labyrinth and cranial nerve VIII, can still produce vertigo and disequilibrium via shearing forces or a concussive injury to the labyrinth itself. Other potential features of temporal bone fractures include discomfort about the temporomandibular joint, facial nerve palsy, and cerebrospinal fluid (CSF) otorrhea.37 Posttraumatic epilepsy occurs in approximately 5% of patients with closed head injuries. Damage to the temporal lobe, in particular, may establish epileptic foci that cause the sensation of vertigo during seizures. Alterations in the vertebrobasilar arterial circulation may occur after trauma and predispose patients to basilar artery migraine, which may produce migrainous vertigo.38
Of note, head trauma patients are also susceptible to the development of BPPV and PLF. A recent study indicated that approximately 50% of traumatic brain injury patients who complain of positional vertigo actually have BPPV.39
Neck trauma, especially whiplash injury, can cause vertigo and disequilibrium. The onset of dizziness occurs 7 to 10 days after the traumatic event, and symptoms may persist for several years. Patients typically complain of neck pain and tenderness, as well as recurrent positional vertigo and visual disturbances triggered by rotation of the head. One putative mechanism is vertebrobasilar insufficiency, but a recent study of magnetic resonance angiography in patients with whiplash injury and vertigo yielded inconclusive results.40 It is also possible that the dizziness is mediated by a pathologic disturbance in the vestibulocollic reflex despite its relative lack of importance in healthy humans.
Nonsurgical Management of Vertigo
Vestibular Rehabilitation
Vestibular rehabilitation is a cornerstone of the treatment of many vertiginous disease processes and is particularly important in the postsurgical phase of recovery. The concept of vestibular rehabilitation for patients with iatrogenic unilateral loss of vestibular function or postconcussive disorders was first implemented in the 1940s by Cawthorne and Cooksey.41–43 Since that time, vestibular rehabilitation exercises have become more tailored to the individual patient, thereby increasing therapeutic efficacy, although some of the original exercises proposed by Cawthorne and Cooksey are still used by rehabilitation specialists today. There is considerable evidence to suggest that vestibular rehabilitation alone or in conjunction with other therapeutic modalities is highly efficacious in the treatment of a wide variety of vestibular disorders.44–48 However, the efficacy of vestibular rehabilitation can be compromised in the following situations: (1) bilateral loss of vestibular function, (2) central vestibular dysfunction or oversedation, (3) unstable conditions with fluctuating or progressive symptoms, and (4) medical comorbid conditions that affect proprioceptive or visual input to the central nervous system.43 Thus, patients with stable, unilateral lesions affecting the periphery of the vestibular system are most amenable to a program of vestibular rehabilitation, whereas those with central disorders require longer treatment periods and have poorer outcomes.43,44,49,50
Canalith Repositioning Maneuvers
BPPV is unusual relative to other forms of vertigo, and this condition can be promptly and effectively treated at the bedside with a series of canalith repositioning maneuvers, which were popularized by Epley in 1992.21,51,52 The objective of these maneuvers is to mobilize the displaced otoconial debris from the affected semicircular canal via a sequence of head positioning maneuvers such that the debris ultimately settles in the utricle. A meta-analysis concluded that the Epley maneuver is a safe and effective treatment strategy for BPPV in the short term, although the authors qualified this assertion with the fact that BPPV has a high rate of natural resolution and thus a type II error was possible. Moreover, there is no evidence that the Epley maneuver constitutes a definitive cure for BPPV because recurrences are common and there is a paucity of long-term follow-up of these patients.21
Pharmacologic Therapy
Glutamate appears to be the most important neurotransmitter of vestibular afferent impulses, although acetylcholine transmission via muscarinic receptors also plays a role. Histamine and γ-aminobutyric acid (GABA) receptors are also present in the vestibular nuclei. Most of the pharmacologic agents used for the treatment of vertigo are vestibular suppressants that exploit the known neurochemistry of the vestibular system, and such medications include benzodiazepines, antihistamines, and anticholinergic agents. In general, these drugs are designed to reduce the intensity of vertiginous spells and have little prophylactic benefit. The major side effect is sedation, although benzodiazepines have the additional side effect of respiratory depression in high doses. Vestibular suppressants should not be used on a chronic basis because they impair the process of vestibular compensation, and many of these medications foster physiologic dependence.53
Benzodiazepines potentiate the inhibitory action of GABA, thereby reducing pathologic vestibular input to the central nervous system. Benzodiazepines are considered by many clinicians to be the first line in the pharmacologic armamentarium for vertigo because they are the most effective class of medications for this symptom. Lorazepam and diazepam are particularly effective for the treatment of acute exacerbations of Meniere’s disease. The nongeneric form of lorazepam (Ativan) has the advantage of a sublingual delivery mode, which is valuable for patients with considerable nausea and emesis. Sometimes benzodiazepines are used for symptomatic management in the acute phase of a vestibular crisis caused by labyrinthitis or vestibular neuritis. Although benzodiazepines may actually facilitate the early stages of central compensation by helping mobilize the patient earlier,54 patients should not continue this medication after the acute symptoms resolve to avoid physiologic dependence and permit vestibular compensation to proceed to completion.
Meclizine, dimenhydrinate, diphenhydrinate, and promethazine are type 1 histamine receptor antagonists. The mechanism by which these drugs reduce the severity of vertigo is unclear but most likely involves antagonism of either histamine receptors in the vestibular nuclei or central cholinergic activity. These drugs must cross the blood-brain barrier for therapeutic effect; thus, second-generation antihistamines are not efficacious in the treatment of vertigo. Meclizine is the most popular choice among clinicians, especially for Meniere’s disease.53
Currently, there is no evidence to support the use of antiviral medications for the treatment of vestibular neuritis despite the viral etiology of this disorder. A recent German study involving methylprednisolone and valacyclovir failed to show any therapeutic benefit from valacyclovir alone, although a benefit was observed with methylprednisolone.55 These findings have been corroborated by the work of Ariyasu, Morales-Luckie, and others, who demonstrated that oral steroids reduce the severity of vertiginous spells and expedite recovery from an acute episode of vestibular vertigo.56,57
Although Meniere’s disease is amenable to vestibular suppressants, the best conservative treatment strategy for this disorder consists of salt restriction and diuretics, both of which minimize hydropic change within the membranous labyrinth.58 The target range for salt consumption is 1.5 to 2 g daily. A dietitian can help patients select the appropriate foods to meet this objective. Patients should be advised that the therapeutic benefit of salt restriction may not become evident for several weeks. Some patients note that certain substances such as caffeine and nicotine may exacerbate their symptoms. Thiazide diuretics reduce the frequency of vertiginous spells in patients with Meniere’s disease but have a variable effect on hearing loss.59,60 Triamterene, a potassium-sparing diuretic, can be administered when thiazide diuretics are contraindicated. Generally, a combination of triamterene and hydrochlorothiazide is prescribed and continued for 3 to 6 months after resolution of the acute spells.
Currently, there is no consensus concerning the treatment of migrainous vertigo. Medications that are ordinarily administered for migraine prophylaxis (beta blockers, calcium channel blockers, tricyclic antidepressants, pizotifen, and flunarizine), as well as carbonic anhydrase inhibitors, have been used in the setting of migrainous vertigo with some degree of success.7,61
Surgical Management of Intractable Vertigo
Surgery for Benign Paroxysmal Positional Vertigo
BPPV often resolves spontaneously and is characteristically amenable to simple bedside maneuvers; however, in rare circumstances the condition is refractory to conservative therapies and is so debilitating that surgical intervention is warranted.62 There are two invasive modalities for the treatment of refractory BPPV: singular neurectomy and posterior semicircular canal occlusion.
Singular Neurectomy
Singular neurectomy involves transection of the posterior ampullary nerve (also known as the singular nerve), a branch of the inferior vestibular nerve that innervates the ampulla of the posterior semicircular canal. In effect, the procedure eliminates vestibular input from the posterior semicircular canal containing displaced otoconial debris. The procedure itself is technically challenging because it requires considerable expertise in temporal bone dissection and carries a significant risk for permanent SNHL. Gacek developed the procedure in the early 1970s. Since its inception, 342 singular neurectomies have been reported, the lion’s share by Gacek himself. According to his series, hearing was preserved in 97% of cases, but hearing outcomes have been markedly worse in other published studies by surgeons who have less experience with this procedure.62,63
