In intractable Meniere's disease failing conservative treatment, intratympanic gentamicin ablation works by:

• A Reducing endolymph production by toxic destruction of the dark cells of the utricle and semi-circular canals
• B Anti-inflammatory action reducing endolymphatic hydrops through glucocorticoid-like effects
• C Blocking voltage-gated calcium channels in endolymphatic sac epithelial cells, reducing endolymph secretion
• D Selectively destroying the type I vestibular hair cells of the cristae, reducing afferent input and vertigo while relatively sparing cochlear hair cells ✓

Explanation

Gentamicin is preferentially toxic to vestibular (type I > type II) hair cells over cochlear hair cells because vestibular hair cells express higher levels of uptake transporters (MET channels) and have lower antioxidant capacity. This selective vestibulotoxicity destroys the afferent peripheral vestibular signal from the diseased labyrinth, allowing central compensation and cessation of episodic vertigo. The risk is cochleotoxicity (SNHL), which increases with multiple doses; low-dose single-shot protocols are used to minimise this. Dark cells secrete endolymph but are less the primary target.

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.