Vestibular Neuronitis

A dysfunction of the vestibular system that causes sudden and severe VERTIGO (sensation of spinning) with accompanying NAUSEA, VOMITING, and balance disturbances. The prevailing view is that viral infections cause vestibular neuronitis. Because hearing remains unaffected, doctors believe the INFECTION inflames the vestibular NERVE, the branch of the eighth cranial nerve (vestibulocochlear nerve) leading from the vestibular structures to the BRAIN. INFLAMMATION causes the vestibular nerve to transmit confused and erroneous signals to the brain. The brain responds to the incoming signals as though they were legitimate, instructing the body to react to movement that is not occurring or failing to direct reaction when there is movement. This confusion results in vertigo and a sense of spatial disorientation. Vestibular neuronitis most commonly occurs in adults between the ages of 40 and 60.

Symptoms and Diagnostic Path
The distinguishing symptoms of vestibular neuronitis are severe vertigo and one-sided balance disturbances without TINNITUS or HEARING LOSS. Any hearing-related symptoms suggest a different diagnosis. The vertigo causes nausea and often vomiting. Attempts to move, or to move the head, result in repeated vertigo. The symptoms often are debilitating, with the person falling toward the affected side when attempting to walk and sometimes when attempting to sit upright. Symptoms appear abruptly though often follow a cold or occur among groups of people who are in close contact. An initial episode of symptoms can last 7 to 10 days.

The diagnostic path is fairly straightforward; any pattern of vestibular disturbance that includes additional symptoms is likely to have a different cause. Confirming diagnostic signs the doctor looks for include

• horizontal NYSTAGMUS (rapid movements of the EYE with certain positions or movements)
• diminished or absent response to caloric testing (alternating warm and cool water infused into the auditory canal)

Imaging procedures are not likely to offer diagnostic information unless the doctor is uncertain of the diagnosis, in which case MAGNETIC RESONANCE IMAGING (MRI) or COMPUTED TOMOGRAPHY (CT) SCAN can rule out other conditions such as ACOUSTIC NEUROMA.

Treatment Options and Outlook
The VIRUS causing the vestibular neuronitis must run its course, which typically takes 10 to 14 days. During this time, certain ANTIHISTAMINE MEDICATIONS used to treat motion sickness can provide relief from the vertigo and associated nausea. These antihistamines include the prescription medications hydroxyzine (Atarax, Vistaril) and promethazine (Phenergan) and the over-the-counter products dimenhydrinate (Dramamine), meclizine (Antivert, Bonine) and diphenhydramine (Benadryl). The two prescription medications diazepam (Valium) and clonazepam (Klonopin) appear to act on the vestibular system directly to subdue the vertigo, though cause more sedation than antihistamines and can be addictive when used for an extended period of time. ACUPUNCTURE gives some people relief. Most people recover completely and are free from residual consequences in three to four weeks. A small percentage experiences recurrent episodes over the following months to years, though the severity of symptoms diminishes with each episode.

Risk Factors and Preventive Measures
Because doctors do not know for certain what causes vestibular neuronitis, they cannot identify risk factors or preventive measures. Prompt diagnosis and treatment help relieve symptoms more quickly but do not appear to alter the course of the inflammation or affect the likelihood of RECURRENCE.