Sudden hearing loss is defined as a hearing loss of 30 dB or more across at least three consecutive frequencies within the past 72 hours. It differs from other types of hearing loss in that it is characterized by a sudden deterioration in hearing in individuals who were previously completely healthy. The individual may wake up in the morning and realize that one ear is not hearing. Or, during the day, they may suddenly feel a dullness in one ear and sense that it has suddenly closed off. In many patients, tinnitus accompanies the hearing loss. Sudden hearing loss is usually unilateral, though it can rarely affect both ears.
HOW IS THE DIAGNOSIS OF SUDDEN HEARING LOSS MADE, AND WHAT TESTS SHOULD BE CONDUCTED?
Patients must undergo an ENT examination. This is because, in some cases, a wax plug blocking the outer ear canal can cause hearing loss. Alternatively, a tear in the eardrum may be the cause of hearing loss. Once these causes are ruled out, the patient should undergo audiological testing to determine the type and degree of hearing loss. Hearing loss may range from mild to moderate, or it may result in complete hearing loss.
In addition to hearing tests, blood tests should also be performed for these patients. An MRI of the ear must be performed for every patient. This is because acoustic neuromas are the cause in 1% of patients with AIK.
WHAT CAUSES SUDDEN HEARING LOSS
The exact cause of sudden hearing loss (SHL) is unknown. However, studies suggest that a viral infection of the inner ear and the auditory nerve may be a likely cause. The viruses most commonly implicated are those of the herpes family.
Sudden decreases in blood flow to the inner ear can also lead to SHL.
HOW IS SUDDEN HEARING LOSS TREATED
There are many methods and medications used in the treatment of sudden hearing loss. However, meta-analyses have shown that the only medication proven to be effective is corticosteroids. For this reason, corticosteroids are included in all treatment protocols. Corticosteroids can be administered intravenously or orally, or via what is known as intratympanic steroid administration—an injection through the eardrum into the middle ear.
In addition to corticosteroids, the use of high-molecular-weight dextran to increase blood flow to the inner ear is also quite common. Furthermore, hyperbaric oxygen therapy has become increasingly widespread in recent years.
In a study we conducted, we compared patients who received systemic steroid therapy alone with those who received systemic steroid therapy combined with concurrent intratympanic steroid therapy, and with those who received systemic steroid therapy combined with 10 sessions of concurrent hyperbaric oxygen therapy. We found no difference in recovery rates among these three groups.
HOW MUCH DOES SUDDEN HEARING LOSS IMPROVE?
Approximately 70% of patients with sudden hearing loss experience full or partial recovery with treatment. The milder the hearing loss, the higher the chance of recovery. The earlier treatment begins, the greater the chance of recovery. While some studies have shown that the presence of tinnitus and vertigo alongside hearing loss negatively affects the prognosis, there are also studies indicating the opposite.
What Is Rescue Therapy for Sudden Hearing Loss?
In cases where systemic steroid therapy (administered orally or intravenously) does not improve the condition, treatment may be continued with intratympanic steroid therapy. Some patients treated in this manner have shown improvement. For patients who do not improve, hyperbaric oxygen therapy is also an option as a salvage treatment.