A 52-year-old woman presents with recurrent episodes of severe vertigo lasting 20 minutes to 3 hours, accompanied by unilateral tinnitus, aural fullness, and fluctuating sensorineural hearing loss. Clinical examination and basic audiometry suggest inner ear pathology. Which investigation is most specific for confirming the diagnosis of Meniere disease?

Explanation

## Investigation of Choice in Meniere Disease **Key Point:** Electrocochleography (ECoG) is the most specific diagnostic test for Meniere disease. It detects endolymphatic hydrops by measuring the ratio of summating potential (SP) to action potential (AP). ### Why ECoG is Diagnostic ECoG measures electrical potentials generated by the cochlea in response to sound stimuli. In Meniere disease, endolymphatic hydrops causes: 1. **Increased summating potential (SP)** — due to cochlear partition displacement from fluid overload 2. **Relatively preserved action potential (AP)** — auditory nerve function remains intact early 3. **Elevated SP/AP ratio** — typically >0.4 (normal <0.35) is diagnostic of hydrops **High-Yield:** ECoG is non-invasive, does not require imaging, and directly reflects the underlying pathophysiology (endolymphatic hydrops) rather than just symptoms. ### Diagnostic Criteria for Meniere Disease ECoG abnormalities support the diagnosis when combined with: - Recurrent spontaneous vertigo (≥2 episodes lasting 20 min–12 hours) - Audiometric evidence of sensorineural hearing loss (low-frequency initially) - Tinnitus and/or aural fullness - No other neurological cause **Clinical Pearl:** ECoG is particularly valuable in early or atypical presentations where imaging is normal but clinical suspicion remains high. ### Comparison of Investigations in Meniere Disease | Investigation | Purpose | Diagnostic Value | |---|---|---| | **ECoG** | Detects endolymphatic hydrops | **Most specific** — directly confirms hydrops | | **Caloric test** | Assesses vestibular function | Shows reduced caloric response; non-specific | | **Audiometry** | Documents hearing loss pattern | Supports diagnosis; not specific | | **HRCT temporal bones** | Excludes structural lesions | Rules out retrocochlear pathology; normal in Meniere | | **MRI with CISS** | Visualizes endolymphatic hydrops | Emerging; not yet standard | **Mnemonic:** **ECHO** — **E**lectrocochleography **C**onfirms **H**ydrops in **O**tic disease (Meniere). ### Clinical Context In this patient, the classic triad of vertigo, hearing loss, and tinnitus with aural fullness is highly suggestive of Meniere disease. ECoG would objectively confirm endolymphatic hydrops and differentiate Meniere from other causes of recurrent vertigo (benign paroxysmal positional vertigo, vestibular migraine, superior semicircular canal dehiscence).