Intratympanic gentamicin therapy is used for refractory Meniere's disease. Which semicircular canal function is most impaired first, and what is the mechanism of action?

• A Cochlear hair cells are selectively destroyed, eliminating tinnitus and hearing fluctuation
• B Gentamicin selectively ablates type I vestibular hair cells (dark cells) in the cristae, reducing endolymph production and causing chemical labyrinthectomy ✓
• C Gentamicin blocks the endolymphatic duct, reducing endolymph pressure without hair cell destruction
• D Gentamicin acts on the stria vascularis to increase potassium reabsorption

Explanation

Intratympanic gentamicin (ITG) in low-dose protocols exploits the selective sensitivity of vestibular hair cells (particularly type I hair cells in the cristae ampullares) to aminoglycoside toxicity. Gentamicin causes chemical ablation of vestibular sensory epithelium, reducing afferent signals from the offending labyrinth and providing vertigo control. It also reduces endolymph production by damaging the dark cells (endolymph-secreting cells) of the vestibular labyrinth. At low doses, cochlear toxicity is minimized. The Eustachian tube is not involved. Endolymphatic duct blockage is not the mechanism.

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.