A patient with Meniere's disease has failed dietary restriction and diuretics. The ENT surgeon considers intratympanic gentamicin therapy. The primary mechanism of action of intratympanic gentamicin in Meniere's disease is:

• A Selective ablation of type I vestibular hair cells, reducing vestibular input and vertigo episodes ✓
• B Reducing endolymph production by destroying the stria vascularis
• C Blocking sodium channels in the endolymphatic sac
• D Reducing perilymph pressure by opening the cochlear aqueduct

Explanation

Intratympanic gentamicin reaches the inner ear via the round window membrane and selectively ablates type I vestibular hair cells (which have higher sensitivity to aminoglycosides than cochlear hair cells at low doses). This reduces the abnormal vestibular input from the diseased labyrinth, thereby controlling the episodic vertigo. The therapy exploits the differential ototoxicity of aminoglycosides — at carefully titrated doses, vestibular hair cell destruction is preferential over cochlear hair cell damage. However, risk of sensorineural hearing loss exists, and treatment is therefore reserved for disabling unilateral Meniere's.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.