5Ménière's disease

The biggest clinical use of ECochG, and the most debated. An elevated SP/AP ratio is the canonical signature of endolymphatic hydrops — but the test misses 30–50% of patients, and an abnormal result is no longer required to make the diagnosis. This module walks through how to use it well, knowing what it can and cannot do.

Prosper Ménière first described the syndrome of fluctuating sensorineural hearing loss, episodic vertigo, tinnitus, and aural fullness in 1861. A century later, post-mortem temporal-bone work established endolymphatic hydrops — distension of the endolymphatic compartment, with bulging of Reissner's membrane into scala vestibuli — as its consistent histopathological finding.[1967] Endolymphatic hydrops is a necessarycondition for Ménière's disease but not a sufficient one: hydrops is also found incidentally at post-mortem in patients without symptoms, which is one reason ECochG sensitivity is bounded below 100%.[2010]

FClinical diagnosis

Ménière's disease is a clinical diagnosis. The 2015 Bárány Society / Equilibrium Committee criteria — now the international standard, superseding the 1995 AAO-HNS guidelines[1995] — define two levels of certainty:[2015]

ECochG is not part of the diagnostic criteria. It serves as a supportive test where the clinical picture is uncertain, where the symptoms overlap with vestibular migraine (a common diagnostic problem), or where intervention is being considered and an objective marker is wanted.[2023] In a 2010 survey of US otologists and neurotologists, fewer than 4% required an abnormal ECochG to make the diagnosis of endolymphatic hydrops.[2010]

FWhy ECochG changes in hydrops

Endolymph accumulates in scala media. Reissner's membrane distends into scala vestibuli, the basilar membrane is pushed slightly toward scala tympani, and the resting position of the mechanoelectrical transduction system shifts. The hair cells now operate from an asymmetric baseline.[2010] Click stimulation causes a stronger DC-shift component (the SP rises) because the MET input-output curve is being read from a biased operating point. The AP — generated by the auditory nerve — is not directly affected by this mechanical bias, so the AP amplitude usually stays put or, in more advanced disease with neural loss, falls. Either way, the SP/AP ratio rises.

THydrops mechanism

The mechanical chain in endolymphatic hydrops is short and instructive: endolymph volume rises in scala media, Reissner's membrane distends upward into scala vestibuli, the basilar membrane is biased toward scala tympani, and the MET system operates from an asymmetric resting position. The figure below contrasts a normal cochlear cross-section with a hydropic one at roughly stage 3 severity — the same view that drives the SP elevation seen on ECochG.

Drag the slider from no hydrops through to advanced disease. Reissner's membrane bulges upward into scala vestibuli as endolymph volume rises, the basilar membrane is pushed slightly toward scala tympani, and the organ of Corti tilts as it reads from an asymmetric resting position. The predicted SP/AP ratio in the readout uses a smooth saturating model: the Ferraro 0.40 cutoff is crossed at around 30% severity, and the curve flattens above 70% as the geometry stops changing usefully.[2010, 1967]

TDiagnostic measurements

Several measurements are in clinical use, in order of historical adoption and approximate sensitivity:

CSensitivity, specificity, and the limits of the test

Decades of work have converged on a stable picture. Click SP/AP amplitude alone has a sensitivity of 53–70% and specificity of 80–90% for definite Ménière's against the 1995 AAO-HNS criteria.[2013] Combining click and tone-burst measurements — SP/AP amplitude ratio plus area ratio plus latency-difference plus interaural comparison — pushes sensitivity to 84–92% in the best meta-analyses while preserving specificity at 85–90%.[2019] A modern head-to-head adds further nuance: transtympanic click SP/AP area ratio reaches 88.5% sensitivity / 70% specificity, with tone-burst SP amplitude trading some sensitivity for cleaner plateau measurement.[2024] Recent multimodal studies that combine ECochG with cVEMP, oVEMP, and vHIT report overall positive rates near 99%, with ECochG positive in about 55% of confirmed MD cases.[2025]

Several factors limit the test's standalone diagnostic power:

• Hydrops is intermittent in early disease. ECochG done between vertigo episodes may capture the hydrops at a low point and read normal. Several authors recommend testing close to an active episode.
• ECochG abnormalities do not correlate with disease stage. A patient with severe stage IV disease may have a less elevated ratio than a stage I patient — and labs that have looked for stage correlation have generally failed to find it.
• Severe hearing loss distorts the ratios. Once the PTA exceeds 50 dB nHL, AP amplitude shrinks and the SP/AP ratio becomes unreliable.[2017]
• Inter-clinic comparison is treacherous. Different electrodes, different stimulus protocols, different SP measurement conventions produce different absolute ratios — so a 0.45 ratio from one lab is not necessarily comparable to a 0.45 ratio from another.[2017]

TClick vs tone burst — side by side

The same Ménière's ear, recorded with both protocols. The click SP is a thin shoulder you must measure with care; the tone-burst SP is a plateau you can read off the trace directly. The advantage of the tone burst is reproducibility, not amplitude — and the case for combining both measurements is that they capture slightly different aspects of hydrops physiology.

FClinical case

FTSelf-assessment