A patient with Meniere's disease has episodic vertigo, tinnitus, and low-frequency sensorineural hearing loss. The pathophysiology involves endolymphatic hydrops. Which ion transport abnormality underlies endolymph accumulation?

• A Increased potassium secretion by stria vascularis cells raises endolymph osmolarity drawing water into scala media
• B Impaired endolymph reabsorption in the endolymphatic sac due to reduced aquaporin-2/Na+/K+-ATPase activity causing volume accumulation ✓
• C Autoimmune damage to Reissner's membrane impairs the barrier between endolymph and perilymph
• D Increased vasopressin-driven water entry into endolymph via V2 receptors on stria vascularis cells

Explanation

Endolymphatic hydrops in Meniere's disease results from impaired reabsorption of endolymph in the endolymphatic sac, the primary site of endolymph drainage. The endolymphatic sac possesses specialized ion-transport machinery (Na+/K+-ATPase, aquaporins, carbonic anhydrase) to resorb endolymph. Dysfunction — from immune injury, viral infection, or drainage obstruction — leads to progressive volume and pressure increase in the membranous labyrinth. Option A is physiologically reversed (stria vascularis normally maintains the potassium-rich endolymph but via active transport, not by raising osmolarity to draw water). Options C and D are not established primary mechanisms.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.