## Pathophysiology of Meniere Disease **Key Point:** Endolymphatic hydrops is the hallmark pathophysiological finding in Meniere disease, characterized by abnormal accumulation of endolymph within the inner ear. ### Mechanism of Endolymphatic Hydrops The condition results from: 1. **Overproduction** of endolymph by the stria vascularis, OR 2. **Impaired reabsorption** of endolymph by the endolymphatic sac, OR 3. **Combination** of both mechanisms This leads to increased pressure within the membranous labyrinth, causing: - Distension of the cochlear duct → fluctuating hearing loss (especially low frequencies) - Distension of the semicircular canals → episodic vertigo - Rupture of Reissner's membrane → mixing of endolymph and perilymph ### Clinical Correlation with Pathology | Feature | Mechanism | |---------|----------| | Fluctuating hearing loss | Pressure changes in cochlear duct | | Low-frequency hearing loss | Cochlear duct distension | | Episodic vertigo | Increased pressure in semicircular canals | | Tinnitus | Endolymphatic pressure changes | | Progressive permanent loss | Repeated ruptures → hair cell damage | **High-Yield:** Endolymphatic hydrops is confirmed by electrocochleography (elevated summating potential/action potential ratio) and MRI with gadolinium (shows enlarged endolymphatic space). **Clinical Pearl:** The fluctuating nature of hearing loss in early Meniere disease is pathognomonic — it reflects reversible pressure changes rather than permanent hair cell loss, which only occurs with repeated ruptures. [cite:Robbins 10e Ch 29]
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