Vestibular neuritis and labyrinthitis

INTRODUCTION — Vestibular neuritis is also known as vestibular neuronitis, labyrinthitis, neurolabyrinthitis, and acute peripheral vestibulopathy [1]. A group of leading international experts has proposed the term "acute unilateral vestibulopathy" (AUVP) as the preferred name for this condition [2]. It is a self-limited disorder, and most patients recover completely. Nonetheless, its symptoms of vertigo, nausea, vomiting, and gait impairment can be disabling in the short term.

Vestibular neuritis also shares clinical features with less benign disorders, particularly acute vascular lesions of the central nervous system, from which it must be accurately differentiated in order to avoid morbidity and mortality.

This topic will review the pathophysiology, clinical manifestations, diagnosis, and treatment of vestibular neuritis. The evaluation and differential diagnosis of vertigo are discussed separately. (See "Evaluation of the patient with vertigo" and "Causes of vertigo".)

PATHOPHYSIOLOGY — Vestibular neuritis is generally understood to be a viral or postviral inflammatory disorder affecting the vestibular portion of the eighth cranial nerve [2]. There are few pathologic data to support this mechanism in patients with this disorder, and a history of a preceding viral illness is elicited in less than one-half of patients [3-6]. One advanced magnetic resonance imaging (MRI) study revealed a pattern of enhancement consistent with an inflammatory process in 20 of 29 patients with vestibular neuritis [7].

CLINICAL MANIFESTATIONS — Vestibular neuritis, also known as vestibular neuronitis and labyrinthitis, represents an acute, spontaneous, peripheral vestibular ailment, characterized by the rapid onset of severe vertigo with nausea, vomiting, and gait instability.

Physical examination findings are consistent with an acute vestibular imbalance (figure 1):

●Spontaneous vestibular nystagmus that is unidirectional and horizontal or horizontal-torsional, is suppressed with visual fixation, and does not change direction with gaze. The fast phase of nystagmus beats away from the affected side.

●Positive head impulse test. With rapid turning of the head toward the side of the lesion by the examiner, the patient is unable to maintain visual fixation (figure 2). In one series, this was present in 82 percent of patients [8]. Patients in this series with a positive head impulse sign were also more likely to have persistent symptoms. While a positive head impulse test supports the diagnosis of vestibular neuritis, it does not definitively rule out a central nervous system disorder [9]. (See "Evaluation of the patient with vertigo", section on 'Other vestibular signs'.)

●Gait instability with preserved ability to ambulate. If the patient sways or falls, it is opposite to the direction of the fast component of the nystagmus, ie, toward the affected side.

●Other neurologic signs and symptoms (dysarthria, dysphagia, limb weakness, sensory loss, facial droop, limb dysmetria) are absent. Vertical diplopia or skew eye deviation may be present due to an imbalance in otolithic-ocular reflexes, although the presence of a significant vertical diplopia or skew deviation suggests that the patient has had a stroke. (See "Evaluation of the patient with vertigo", section on 'Other vestibular signs'.)

●Auditory function is preserved; when the symptoms and signs of vestibular neuritis are combined with unilateral hearing loss, the condition is called labyrinthitis.

In one study of 101 patients, three clinical signs, in particular, were useful in distinguishing vestibular neuritis from a cerebrovascular event [10]. The presence of either a normal head impulse test, direction changing nystagmus, or a skew deviation had a 100 percent sensitivity and a 96 percent specificity for stroke. These findings, codified as the HINTS examination (Head Impulse test, direction changing Nystagmus, Test of Skew), have been found to have a similarly high sensitivity and specificity for distinguishing peripheral from central vertigo in patients with an acute vestibular syndrome (figure 1) [11-15]. However, in all studies, examiners were either specialists or specifically trained in this examination.

DIFFERENTIAL DIAGNOSIS — Many conditions cause vertigo (table 1). The clinical features of common causes of vertigo are summarized in the table (table 2). The differential diagnosis of vertigo is discussed separately. (See "Causes of vertigo" and "Evaluation of the patient with vertigo".)

The principal differential diagnostic concern in a patient presenting with acute sustained vertigo is a vascular event in the central nervous system affecting the cerebellum and/or brainstem [16,17]. This possibility should be considered in all patients with vascular risk factors, because of the relatively high risk of recurrent vascular events [18].

Cerebellar hemorrhage or infarction — An important consideration in the differential diagnosis of a patient with acute sustained vertigo is a vascular event (infarction or hemorrhage) in the cerebellum [19,20]. As many as 25 percent of patients older than 50 years presenting to the emergency department with this clinical picture have a cerebellar infarction rather than vestibular neuritis, although the percentage is usually reported as much lower [21-23]. As this alternative diagnosis represents a potentially immediately life-threatening condition, it is important to consider this possibility in every patient who presents with acute sustained vertigo. Patients with acute cerebellar lesions may have distinctive clinical features from that of vestibular neuritis (figure 1) [19,20,24]:

●The nystagmus is not suppressed with visual fixation. It may be other than horizontal or horizontal-torsional, and may change direction with gaze.

●Patients are usually unable to stand or walk unsupported. The direction of falling is not necessarily opposite to the direction of the nystagmus.

●There may also be limb dysmetria, dysarthria, or headache.

●Head impulse test is usually normal [9].

●Symptoms may be unremitting for 72 hours or more.

●Patients with a vascular event are typically older and/or have atherosclerosis risk factors (hypertension, diabetes, smoking).

Despite these caveats, the distinction between vestibular neuritis and acute cerebellar lesions is not always apparent; patients with acute vertigo are often quite ill, and the examination may be limited. When the diagnosis is unclear, a neuroimaging study, typically MRI, may be necessary [4,20,25,26].

Brainstem infarction — The most common stroke syndrome producing vertigo is a lateral medullary infarction producing a constellation of symptoms and signs known as a Wallenberg syndrome:

●Ipsilateral Horner syndrome

●Dissociated sensory loss (loss of pain and temperature sensation on the ipsilateral face and contralateral limbs and trunk)

●Abnormal eye movements

●Ipsilateral loss of corneal reflex

●Hoarseness and dysphagia

●Ipsilateral limb ataxia

While these signs are usually apparent after a careful neurologic examination, these signs may be overlooked by patients and non-neurologists because the vertigo, nausea, and vomiting may overwhelm the clinical picture. In one study, more than half of patients with an acute vestibular syndrome subsequently found to be due to lateral medullary infarction did not have any of the above signs documented on clinical examination [27]. (See "Posterior circulation cerebrovascular syndromes", section on 'Lateral medullary infarction'.)

More restrictive brainstem infarctions have been described that affect isolated vestibular structures [28]. Thus, their clinical manifestations are very similar to vestibular neuritis. While many of these infarcts are due to small arterial disease, and are managed by atherosclerosis risk factor management and antiplatelet therapy alone, some proportion (up to 50 percent in one series) has been found to be due to nonlacunar mechanisms (vertebral artery dissection or atrial fibrillation), suggesting that a high index of suspicion and accurate diagnosis is important [27].

DIAGNOSIS — A diagnosis of vestibular neuritis is largely based on the clinical presentation of an acute sustained vestibular syndrome with examination features consistent with a peripheral lesion as discussed above. There are no specific diagnostic tests.

Neuroimaging is indicated to rule out alternative diagnoses if the examination is not entirely consistent with a peripheral lesion, if there are prominent risk factors for stroke, if there are focal neurologic signs or symptoms, or if there is a new headache accompanying the vertigo (figure 1) [4,29]. A younger patient with acute sustained vertigo, with no other neurologic signs or symptoms, and with nystagmus and an examination that is consistent with a peripheral origin (see 'Clinical manifestations' above) does not need imaging if there is improvement within 48 hours [4].

The procedure of choice is MRI with diffusion-weighted imaging (DWI) and angiography (MRA). MRI with DWI can detect infarction in the posterior fossa on the first day. MRA has a specificity and sensitivity exceeding 95 percent in detecting stenosis or occlusion of the posterior circulation [30]. Small strokes in the brainstem or cerebellum may be missed on the initial MRI-DWI; thus, if the initial MRI is negative and the diagnosis of a central lesion is suspected, a repeat study should be ordered >72 hours after the onset of symptoms with perfusion weighted sequences if available [15,27].

Computed tomography (CT) scanning with thin cuts through the cerebellum is an alternative when MRI scanning is not available or in patients with metallic implants. The scan is usually normal in the first hours after an infarct; however, intraparenchymal hemorrhage or significant edema compressing the fourth ventricle will usually be evident immediately. Thus, in patients who require brain imaging, a brain CT scan should therefore be performed if an MRI scan is not immediately available.

TREATMENT — Potential treatments for vestibular neuritis include acute disease-specific treatment with glucocorticoids and antiviral agents, symptomatic treatments, and vestibular rehabilitation. There are few formal studies of these therapies in patients with vestibular neuritis.

Acute disease-specific treatment — Treatment with glucocorticoids during the acute period of vertigo was shown in at least one clinical trial to improve the recovery of peripheral vestibular function in patients with acute labyrinthitis. However, subsequent studies, albeit with many limitations, have not found a clear benefit of glucocorticoid therapy.

Despite these somewhat conflicting results and remaining questions, it seems reasonable to treat presumed acute vestibular neuritis with glucocorticoid therapy if there are no contraindications. We typically prescribe a 10-day course of prednisone; 60 mg daily on days 1 through 5, 40 mg on day 6, 30 mg on day 7, 20 mg on day 8, 10 mg on day 9, and 5 mg on day 10. It is also reasonable not to treat with glucocorticoids in patients at risk for adverse effects.

A controlled trial randomly assigned 141 patients with vestibular neuritis to one of four treatment groups: methylprednisolone, valacyclovir, methylprednisolone plus valacyclovir, or placebo [31]. The main outcome measure of vestibular function was the extent of unilateral caloric paresis; this was determined by measuring the mean peak slow-phase nystagmus velocity after caloric irrigation. The following observations were noted:

●Treatment with methylprednisolone (22-day tapering dose schedule) significantly improved vestibular function at 12-month follow-up compared with placebo.

●Treatment with valacyclovir 1000 mg three times daily for seven days did not improve outcome.

●Treatment with the combination of methylprednisolone plus valacyclovir was no more effective than methylprednisolone alone.

A meta-analysis examined the efficacy of glucocorticoids in four randomized controlled studies (149 patients) [32]. There was an overall significant effect of glucocorticoid therapy on complete caloric recovery at 1 month but not at 12 months. Small sample size and methodologic issues with the included studies precluded firm conclusions regarding the benefit of glucocorticoids, particularly on long-term outcomes. Subsequent small trials with similar methodologic problems have also not shown a clear benefit of glucocorticoid therapy [33-36], although observational studies continue to suggest a benefit, including one that showed that earlier treatment (within 24 versus 48 hours) was associated with a higher likelihood of normal caloric testing three months later [37,38].

Symptomatic treatment — Symptomatic treatments to reduce vertigo, nausea, and vomiting are often employed in the first few days of vestibular neuritis. These include antiemetics, antihistamines, anticholinergics, and benzodiazepines (table 3). A nonoral route is generally preferred. Lower doses should be attempted, with upward titration as needed. (See "Treatment of vertigo", section on 'Symptomatic treatment'.)

There is little evidence supporting the use of one agent over another. In general, antihistamines and anticholinergics are preferred over benzodiazepines, because they are somewhat less sedating. One trial compared intravenous dimenhydrinate, 50 mg, with lorazepam, 2 mg, in 74 patients with acute peripheral vestibulopathy. After two hours, patients treated with dimenhydrinate had better ability to ambulate and were more likely to feel ready to go home compared with patients treated with lorazepam (86 versus 69 percent), who also felt drowsier after treatment [39]. Another study compared intramuscular dimenhydrinate, 50 mg, with droperidol, 2.5 mg, in 40 patients with acute peripheral vertigo and found similar efficacy of the two agents; after 30 minutes, approximately 40 percent of patients felt sufficiently improved to go home without further treatment [40].

While they provide necessary symptomatic relief in the first 24 to 48 hours, these medications are believed to be somewhat contraindicated after that time. By suppressing vestibular activity, they are believed to impair the central compensation response and delay long-term recovery.

Vestibular rehabilitation — Vestibular exercises have been shown to be efficacious in improving symptoms and functioning as measured by a variety of symptom- and examination-based scores in patients with unilateral peripheral vestibular injury [41]. In our clinical experience, these measured improvements are clinically meaningful. (See "Treatment of vertigo", section on 'Vestibular rehabilitation'.)

Most studies of vestibular rehabilitation have not been specific to etiology. However, one study randomly assigned 39 patients with vestibular neuritis to physical therapy versus standard care [42]. Evaluation at 30 days revealed that balance function was substantially improved in treated patients [42]. Other measures of central compensation appeared similar between the groups.

Vestibular rehabilitation is most likely to be efficacious when the patient is referred for a vestibular physical therapy evaluation and completes an individually designed program.

CLINICAL COURSE AND PROGNOSIS — Patients with vestibular neuritis generally suffer from severe vestibular symptoms for one to two days, followed by a gradual diminution of symptoms and a return of equilibrium. While the acute illness rarely lasts more than several days to a few weeks, residual imbalance and nonspecific dizziness may persist for months [43]. Early improvement in symptoms is believed to be largely due to central compensation. Tests of vestibular function, such as caloric testing, often show improvement and ultimately recovery as well, but with a significant lag time compared with clinical symptoms.

Recovery of responsiveness to vestibular stimulation including caloric stimulation and head impulse testing does not consistently correlate with long-term symptoms [44]. Two studies have found that abnormal head impulse testing correlates with ongoing symptoms and predicts a more protracted course, especially if it remains positive in follow-up examinations [45,46], whereas other studies found no correlation between abnormal head impulse testing and persistent dizziness [44,47].

Usually patients suffer from vestibular neuritis only once. In one case series of 103 patients followed for almost 10 years, just two patients had a recurrence, both in the contralateral ear [48]. However, in one series, 15 percent of patients with vestibular neuritis later developed benign paroxysmal positional vertigo (BPPV) [49]. Panic disorder has been found to develop in 10 percent of patients with vestibular neuritis over two years [50].

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Vertigo (a type of dizziness) (The Basics)" and "Patient education: Labyrinthitis (The Basics)")

●Beyond the Basics topics (see "Patient education: Vertigo (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Pathogenesis – Vestibular neuritis is believed to be an acute viral or postviral inflammatory disorder of the vestibular portion of the eighth cranial nerve. (See 'Pathophysiology' above.)

●Clinical presentation – Vestibular neuritis presents with acute onset of vertigo with nausea, vomiting, and gait impairment. In pure vestibular neuritis, auditory function is preserved; when this syndrome is combined with unilateral hearing loss, it is called labyrinthitis. (See 'Clinical manifestations' above.)

●Evaluation and differential diagnosis – The syndrome of acute-onset, sustained vertigo is not specific to vestibular neuritis but is also a presentation of vascular events in the cerebellum or brainstem. (See 'Differential diagnosis' above.)

Examination features can help distinguish these features; specifically, the presence of either a normal head impulse test (figure 2), direction-changing nystagmus, or a skew deviation suggests that the diagnosis is likely a vascular event and mandates an urgent neuroimaging study (MRI). MRI should also be performed in patients with acute sustained vertigo who are older (>60 years) or have headache, any focal neurologic signs, or vascular risk factors. There is no confirmatory test for vestibular neuritis. (See 'Diagnosis' above.)

●Treatment – In patients with clinical features entirely consistent with vestibular neuritis and no contraindications to steroids, we suggest a glucocorticoid taper (Grade 2C). While short-term recovery seems to be improved with this therapy, a benefit on long-term outcomes is uncertain. Thus, it is reasonable to choose not to treat patients with glucocorticoids, particularly if there are risk factors for adverse effects. (See 'Treatment' above.)

●Symptomatic management – We suggest using vestibular suppressants and antiemetics to limit symptoms in the first 24 to 48 hours (Grade 2C). We stop acute symptomatic treatments within 48 hours if the patient's symptoms allow, as some data suggest that these medications interfere with central compensation and long-term recovery. (See 'Symptomatic treatment' above.)

●Role of vestibular rehabilitation – We suggest early institution of a vestibular rehabilitation program after acute symptoms subside, as this may hasten long-term recovery, particularly of balance (Grade 2B). (See 'Treatment' above and "Treatment of vertigo".)