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Intratympanic Gentamicin Injections for the Treatment of Ménière’s Disease

Ménière’s disease was first described in 1861 by Prosper Ménière. The disease is characterized by episodic vertigo, hearing loss, tinnitus, and ear fullness. Ménière was the first to recognize that the vestibular apparatus could be the source of this balance disturbance.To diagnose Ménière’s disease, a patient has tohave two or more spontaneous vertigo attacks lasting more than 20 minutes, hearing loss demonstrated on pure toneaudiometry on at least one occasion and tinnitus or sensationof fullness in the ear, when other causes have been excluded, usually by magnetic resonance imaging.

It is believed that endolymphatic hydrops is part of the pathogenesis.

This causes a distortion and distension of the membranous endolymph-containing portions of the labyrinthine system, compressing the perilymphatic spaces. Ruptures of the fragile membranes of the inner ear lead to a mixing of endolymph and perilymph, with a loss of the physiologic ionic gradients, altering the function of the hearing and balance portions of the inner ear.Other proposed etiologic factors include hypoplasia of the vestibular aqueduct, viral etiology, and vascular etiology.

Therapy is directed at reduction of symptoms. Medical management usually includes a salt restriction diet, a diuretic, and betahistine hydrochloride.Betahistine is thought to act by reducing endolymphatic pressure through improved microvascular circulation in the stria vascularis of the cochlea or by inhibition of activity in the vestibular nuclei.Vertigo persists despite optimal medical therapy in approximately 10 percent of patients with Ménière’s disease, and this necessitates further treatment.Traditionally, those in whom the disease did not respond to medical management have been treated by surgery, with endolymphatic sac decompression, labyrinthectomy, or vestibular nerve section.

Intratympanic gentamicin application is another option for treatment. It reduces the frequency and severity of the vertigo attacks.Gentamicin is thought to affect the hair cells of the crista, the ampullae, and the cochlea, causing degeneration and reduction of the endolymph’s volume.Gentamicin is more vestibulo-toxic than cochleotoxic and will decrease vertigo symptomswith a lower risk of damage to hearing than other aminoglycosides.

Intratympanic instillation of gentamicin allows treatment of one ear with no systemic effects or risk to the contra-lateral ear. The drug is inserted into the middle ear, and then it is diffuses into the inner ear primarily through the round window. Pure tone audiometry and a brain and temporal bone magnetic resonance imaging prior to treatment. The patient is placed in a comfortable supine position, with thehead turned away from the ear to be injected. This position ismaintained for 20 minutes following the injection, and the patientis instructed not to swallow or clear the middle ear during thisperiod. The tympanic membrane is locally anesthetized, and 1.5 mL (60 mg) of gentamicin is injected into the affected ear.After each single gentamicin application, patients arekept under observation for balance symptoms. Cochlearfunction is monitored by pure tone audiometry. Twoweeks after treatment patients are assessed, and, if theystill had vertigo, they receive another similar gentamicininjection, until the vertigo subsides. This protocol is referredto as the variable method of titration.

Conclusion

Intratympanic gentamicin is an effective minimally invasive treatment for patients with disabling Ménière’s disease who are not well controlled with medical management. Only a minority of patients experienced some hearing loss in the affected ear, and it was demonstrated that the treatment improved the quality of life of all patients treated. The variable titration method of intratympanic gentamicin is demonstrated to have a high success rate in the treatment of Ménière’s disease in patients resistant to medical treatment. and most of them achieved complete relief of vertigo. Tinnitus and ear fullness were improved or unchanged in the majority of patients. In most patients, hearing was not affected. We believe that the use of the variable titration protocol avoids the unnecessary cochleotoxic effect of the gentamicin.

Article verified by Dr. Alok Banka

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