What is Viral Neuronitis / Labyrinthitis?
A vestibular neuronitis or labyrinthitis can result from an infection of the inner ear. More often than not, this infection is caused by a virus. In rare occurrences, the infection may be bacterial; however, bacterial ear infections are typically localized to the middle ear and commonly occur in childhood.
When a patient suffers from a vestibular neuronitis or labyrinthitis, the virus is usually localized to one ear. The foreign virus will cause an immune response that leads to inflammation and irritation of the inner ear. The inner ear houses the vestibulocochlear nerve (8th cranial nerve) which is responsible for balance, equilibrium, and hearing. When an inflammatory response onsets, the patient will typically report symptoms of vertigo, dizziness, imbalance, nausea, or vomiting. In some cases, the patient will also report changes in their hearing profile including hearing loss, ringing in the ears, or a feeling of pressure (aural fullness). If only the vestibular nerve is inflamed, this is called a viral neuronitis. If both the cochlear and vestibular nerves are affected by the virus, this is called a viral labyrinthitis.
Most patients experience both an acute and chronic phase of the disorder. During the acute phase, symptoms typically onset suddenly as a severe attack of vertigo that may last anywhere from a couple of hours to a couple of days. Many patients experience severe nausea and vomiting as well. During the chronic phase of the disorder, patients may suffer from a lingering disequilibrium that gradually improves over a period of weeks to months.
How is Viral Neuronitis / Labyrinthitis Diagnosed?
During the acute phase of the disease, patients are advised to present to their physician’s office for evaluation as soon as possible for optimal diagnosis and treatment. To aid in the diagnosis of a viral neuronitis or labyrinthitis, the clinician will first obtain a detailed symptom history. They will also evaluate the patient for abnormal eye movements called nystagmus, which are recorded in our office with infrared video oculography on our multi-axial rotational chairs. The most common nystagmus pattern that will present during the acute phase of a viral labyrinthitis is a sustained horizontal nystagmus—meaning the eyes consistently beat to the right or left in any testing position. The clinician will also obtain a comprehensive audiogram (hearing test) to assess for any asymmetric hearing loss. MRI and CT imaging may also be ordered to rule out other intracranial or retrocochlear pathologies.
During the chronic phase of the disease, further testing can be performed to assess for lasting damage to the vestibulocochlear nerve. The clinician may choose to obtain repeat infrared video oculography or audiometric testing. They may also order a test called a videonystagmograph (VNG). This test is designed to assess the function of the vestibular nerve by measuring the symmetry in the caloric response between the two ears. A vestibular evoked myogenic potential (VEMP) is a test that can also be used to assess the saccule (another part of the inner ear) for any damage that may have occurred secondary to the virus’ inflammatory response.
How is Viral Neuronitis / Labyrinthitis Treated?
In order for patients to receive optimal treatment, it is advised that patients present to the clinic as soon as possible to ensure a timely and accurate diagnosis. Once the diagnosis has been made, pharmacologic intervention is the best form of treatment during the acute phase of the disease. If patients present to the clinic close enough to onset or during the symptomatic period, they will likely be started on a course of anti-viral medication such as Acyclovir or Valacyclovir. They will also be given a short course of steroids to reduce any underlying inflammatory processes. If diagnosed and treated soon enough, most patients will make a full recovery.
If patients are in the chronic phase and continue to have symptoms of disequilibrium and imbalance, they may be referred to a vestibular rehabilitation program. The goal of vestibular rehabilitation is to retrain the brain to recognize and process signals from the damaged vestibular system in coordination with vision and proprioception. Patients will also practice vestibular ocular reflex (VOR) exercises that will retrain the eye, inner ear, and brain to work together to maintain balance and equilibrium.