Introduction

Vestibular neuritis is characterized by the acute onset of vertigo with associated nausea, vomiting, and generalized imbalance. The acute phase is often severe and can last from a few hours to several days, while a more subtle sense of imbalance and unsteadiness may linger for weeks. Auditory symptoms are uncommon, although patients may occasionally report fullness and tinnitus. Patients with accompanying hearing loss are believed to have a slightly different pathophysiological entity termed acute labyrinthitis.

The precise etiology of vestibular neuritis remains elusive. Several theories have been postulated and supported, at least partially, within the literature. Dix and Hallpike in the 1950s suggested that an infectious process affecting “Scarpa’s” ganglion or the vestibular nerve might be responsible. Lindsay and Hemenway felt that an ischemic process might be responsible, although they found no direct evidence of vascular occlusion. More recent efforts have suggested that a viral agent may be the underlying cause. While individual studies have demonstrated the presence of herpes simplex virus DNA within vestibular nerve fibers and “Scarpa’s” ganglion, others have demonstrated histologic changes within the vestibular nerve suggestive of viral-induced atrophy and inflammation. Anatomic studies have also demonstrated that the superior vestibular nerve, which supplies the utricle, superior, and horizontal semicircular canals, is more likely to be involved in cases of vestibular neuritis. Goebel and colleagues have shown an anatomic basis for this observation related to the increased length, reduced diameter, and increased bony trabeculae of the bony canal housing the superior vestibular nerve (and its divisions) as compared with the inferior vestibular nerve.

Despite an inability to clearly identify the cause of vestibular neuritis, a thorough understanding of its clinical course and management has been established. The typical onset is one of intense vertigo, oftentimes described upon awakening. Patients may have a tendency to fall toward the involved side and will frequently demonstrate spontaneous nystagmus whose direction is similar in various positions of gaze. Head or body movements exacerbate the symptoms, and patients will often try to minimize any such movements by lying completely still. While the initial vertigo symptoms do subside over a period of days, patients will often have a longer period of continued imbalance. This imbalance may manifest as difficulty making quick movements or turns, slight swaying during walking, or a generalized feeling of unsteadiness. Patients also often complain of a heavy feeling in their head or simply feeling “off” for days to weeks after the initial episode. Benign paroxysmal positional vertigo (BPPV) is more common in patients who have suffered from vestibular neuritis, but it can occur at varying intervals after the acute attack. Why BPPV seems to occur more frequently in these patients is not known, Schucknecht suggested that utricular otoconia might be loosened with the initial neuritis. Repeated bouts of vestibular neuritis have also been described, which many contend lends evidence toward a possible viral reactivation process as seen in herpes zoster oticus.

As with most vestibular disorders of peripheral origin, a diagnosis of vestibular neuritis is primarily reached through a complete and thorough history and physical examination. A history of chronic ear disease should be elicited, as complications of chronic otitis media are quite common and may present with vertigo (ie, labyrinthine fistula or cerebellar abscess). The duration of the vertigo attack is a critical component in the history of any patient with a complaint of dizziness and is particularly helpful in diagnosing vestibular neuritis. However, variability in the duration of the initial attack of vertigo is possible (ie, hours to days), while recurrent episodes of intense vertigo may occur with years of time between individual events. Equally important as the duration of the vertigo attack is whether any neurologic symptoms are present. As there are several potentially dangerous causes of dizziness, one must always maintain a high degree of suspicion ( Box 1 ). Directed questioning regarding associated symptoms is of paramount importance in ruling out vertigo of central etiology. In particular, one should ask about any weakness or change in sensation (pain, temperature, or numbness) of the limbs or face, slurred speech, vision changes, memory loss, or ataxia. These symptoms are indicative of a central insult and require a distinctly different management paradigm than that used in patients with vestibular neuritis. Brainstem/cerebellar infarct or hemorrhage may present with some form of dizziness but will invariably be accompanied by other neurologic symptoms. These patients will oftentimes be unable to stand or walk. In such cases, imaging is diagnostic, with magnetic resonance imaging (MRI) being the preferred modality. Although rare, compromise of the posterior cerebral circulation may manifest with neck pain (from trauma or vertebral artery dissection) and associated dizziness and requires prompt neurosurgical consultation.

Physical examination should be performed to confirm the absence or presence of neurologic involvement. In addition to a complete head and neck examination with an otoscopic examination and testing of all cranial nerves, tuning fork testing, cerebellar testing, gait assessment, and a full neurologic examination should be performed. Chronic ear disease and any associated complications are usually discernible from a combination of history and physical examination including a careful microscopic otoscopic examination. High-resolution computed tomography (CT) imaging of the temporal bones should be obtained if intracranial pathology of otologic origin is suspected, and the appropriate treatment should be instituted accordingly. Any neurologic abnormalities on physical examination should prompt further investigation into a central cause with dedicated imaging of the brain, preferably in the form of MRI. Patients with vestibular neuritis may sway toward the side of the involved ear while standing, but an inability to stand without assistance is also indicative of a central lesion and demands dedicated imaging. Cases of vestibular neuritis present with characteristic spontaneous nystagmus that is both horizontal and rotary, has a fast phase directed toward the uninvolved ear, and improves with fixation. Head thrust testing toward the affected ear will often demonstrate catch-up saccades indicating a peripheral vestibular insult. Formal vestibular testing, though not performed in practice in the acute setting, has been performed in research settings and typically demonstrates reduced caloric responses. Imaging studies are not required in classic cases of vestibular neuritis, but as outlined previously, the presence of any additional or unusual symptoms demands an assessment for the presence of a central lesion.

In clinics specializing in vestibular disorders, vestibular neuritis accounts for between 3% and 10% of diagnoses. An annual incidence of vestibular neuritis approximating 3.5 cases per 100,000 persons was reported by Sekitani and colleagues, but further literature on the subject is lacking. In this same report, which was based on a large Japanese population, the peak age distribution for vestibular neuritis was between 30 and 50 years, with a range of 3 to 88 years. Furthermore, approximately 12% of patients in this study were over age 65. Dix and Hallpike, in their review of 100 cases of vestibular neuritis, found that 94% of cases occurred among patients between the ages of 20 and 59. While middle-aged individuals do seem to be more commonly affected, the authors’ experience would suggest that vestibular neuritis likely accounts for a larger percentage of vestibular diagnoses than outlined in these reports. This may be a consequence of differences in geographic referral patterns, variations in health care access, and a general lack of follow-up in patients achieving rapid resolution of symptoms. Additionally, it is possible that some practitioners may confuse vestibular neuritis with other diagnoses, including migraine-associated vertigo (MAV). MAV is most often seen in patients having some prior history of headaches or a family history of migraines (see article by Cherchi and Hain in this publication). In patients with MAV, the headache itself may occur before or after the onset of dizziness, while the sensation of dizziness may represent true vertigo or merely a sense of disequilibrium. The variability of symptom duration in patients with MAV, with dizziness lasting from several hours to even a whole day, may explain why there might be some difficulty in properly distinguishing between this entity and cases of vestibular neuritis. MAV occurs in both adults and children, although in pediatric cases it is commonly referred to as benign paroxysmal vertigo of childhood (see articles by McCaslin and colleagues, and O’Reilly and colleagues in this publication). Cases of pediatric vestibular neuritis have been reported, yet such a diagnosis among children is fairly uncommon. Reasons for this apparent predilection for middle-aged individuals is not known, and further investigation into the etiology of vestibular neuritis, viral or otherwise, is likely to aid in understanding this disease process.

Management of patients with vestibular neuritis is primarily supportive. The acute phase is best managed with vestibular suppressants, antiemetics, and in some cases, intravenous hydration. Common medications employed in this acute phase have been extensively reviewed elsewhere. Patients who are more susceptible to dehydration, including children, the elderly, and individuals with underlying systemic disorders, may require hospitalization for a brief period of time. It has been suggested that the early administration of steroids may improve the rate and extent of recovery of vestibular function, although controversy remains as to the best method of assessing vestibular recovery and whether there is truly an improvement in clinical symptomatology. The use of antiviral medications has also been proposed as an adjunctive treatment, yet evidence supporting their effectiveness is lacking.

Once the acute phase of vestibular neuritis has passed, treatment efforts are aimed at improving central compensation through vestibular rehabilitation. In addition to minimizing the use of vestibular suppressants, early exercise is encouraged, and patients are instructed on various vestibular exercises designed to enhance ocular stability and improve the tolerance of various head and body movements. The degree of compensation is somewhat variable and likely depends on a number of factors, including patient age and underlying functional status, degree of initial vestibular injury (and any subsequent end-organ recovery), as well as patient motivation. While many patients may be able to compensate with the help of home vestibular exercise programs, others may require formal vestibular rehabilitation under the supervision of a dedicated vestibular therapist (see article by Alrwaily and Whitney in this publication). Elderly individuals and patients with prolonged recovery would likely be excellent candidates for such a course of treatment. In rare instances, when prolonged vestibular therapy is not effective and patients are debilitated by their symptoms, surgical intervention may be warranted. In such patients, the authors feel that an MRI of the brain as well as videonystagmography should be performed preoperatively to document the absence of an eighth nerve or central lesion and to determine the degree of peripheral vestibular dysfunction. Surgical options in the setting of chronic vestibular neuritis include vestibular nerve section if hearing is present, or labyrinthectomy in cases of a dead or unserviceable ear. Although surgical intervention is considered a solution of last resort, it can be quite effective in improving patient symptoms.