If dexamethasone perfusion of the inner ear has failed to control the vertigo of Meniere’s disease, the ear specialist may offer gentamicin perfusion of the inner ear as the next step in treatment. Gentamicin treatment is minimally invasive and also very effective in controlling the vertigo attacks in over 90% of Meniere’s disease cases that have failed medical therapy.
Different surgical protocols are used, but essentially a liquid solution of the antibiotic Gentamicin is placed through the ear drum into the middle ear space of the diseased ear. The Gentamicin is absorbed through the round window membrane in the middle ear and passes through this membrane and into the inner ear which contains the nerve endings of hearing and balance. Gentamicin is selectively more toxic to the nerve endings of balance than those of hearing and on a cellular level damages enough of the balance nerves to stop the vertigo attacks.
As the drug is absorbed, many patients experience a period of mild to moderate disequilibrium that usually starts 3-4 days after the initiation of treatment. The disequilibrium will resolve in most patients over a period of several weeks after treatment with Gentamicin is stopped. In many cases, only a short 5-7 day course of treatment with Gentamicin is necessary. The temporary disequilibrium is described typically as the sensation most people feel coming off a small boat. The patient will automatically adjust with a broad-based gait (walking with legs apart). It is important for the patient to remain as active as possible since the inner ear will more quickly adjust to the new signals it is now receiving from the treated ear. Active movement speeds the centers in the brain to re-equilibrate to the new signal pattern coming from the inner ear.
Gentamicin perfusion is an optimal treatment for the patient with significantly decreased hearing in the involved ear, uncontrolled vertigo, and normal or near normal hearing in the opposite ear. In these patients the overwhelming objective is to make the vertigo attacks stop and Gentamicin perfusion will stop the attacks in over 90% of cases. However, a treatment dilemma may occur in the patient with aggressive, severe vertigo attacks that cannot be controlled with medical therapy who also has normal or near normal hearing in the Meniere’s affected ear.
Unfortunately, it is not possible to accurately predict which patients will experience hearing loss due to the Gentamicin treatment. Studies over the past 10 years cite further hearing loss due to the Gentamyicin treatment in between 10-20% of patients treated. If further hearing loss occurs from Gentamicin perfusion the loss is usually not severe, however severe or even profound hearing loss in the treated ear can occur after even one Gentamicin perfusion.
Continuing research is underway to determine the optimum Gentamicin dosage that preserves hearing, but controls vertigo. Some patient, 12-18 months after initial Gentamicin treatment, may have a recurrence of vertigo episodes and may require additional treatment(s).