A 52-year-old woman presents with recurrent episodes of severe vertigo lasting 20 minutes to 3 hours, accompanied by unilateral hearing loss, tinnitus, and aural fullness. Audiometry shows low-frequency sensorineural hearing loss. Which investigation is most specific for confirming endolymphatic hydrops in suspected Meniere disease?

Explanation

## Investigation of Choice in Meniere Disease ### Electrocochleography (ECochG) **Key Point:** Electrocochleography is the most specific non-invasive test for detecting endolymphatic hydrops, the pathophysiological hallmark of Meniere disease. **High-Yield:** ECochG measures the ratio of summating potential (SP) to action potential (AP). In endolymphatic hydrops, the SP/AP ratio is elevated (>0.4), reflecting increased endolymphatic pressure and displacement of the basilar membrane. **Clinical Pearl:** ECochG can be performed transtympanically (more accurate) or extratympanically (less invasive). The transtympanic approach places an electrode on the promontory, achieving superior signal-to-noise ratio and diagnostic accuracy. ### Why ECochG Is Superior | Investigation | Detects | Specificity for Hydrops | Invasiveness | |---|---|---|---| | **Electrocochleography** | Endolymphatic hydrops directly | High (SP/AP ratio) | Minimally invasive | | Caloric test | Vestibular function asymmetry | Low (non-specific) | Non-invasive | | Audiometry | Sensorineural hearing loss | Low (many causes) | Non-invasive | | MRI with gadolinium | Endolymphatic space enlargement | Moderate (invasive imaging) | Invasive | ### Diagnostic Criteria Context **Key Point:** Meniere disease diagnosis relies on: 1. Episodic vertigo (≥20 min) 2. Audiometrically documented hearing loss 3. Tinnitus and/or aural fullness 4. **Exclusion of other causes** ECochG provides objective evidence of the underlying pathophysiology (hydrops) and helps exclude mimics like vestibular migraine or superior semicircular canal dehiscence. **Mnemonic:** **ECHO** = **E**lectrocochleography **C**onfirms **H**ydrops in **O**tic disease (Meniere). ### Clinical Application ECochG is particularly valuable when: - Clinical presentation is atypical or incomplete - Bilateral symptoms raise diagnostic uncertainty - Need to differentiate Meniere from other causes of vertigo with hearing loss [cite:Harrison 21e Ch 468]