Transtympanic Electrocochleography Detects Endolymphatic Hydrops In Meniere's Disease

From: Doctor's Guide, Canada - 16 Dec 2002

A DGReview of :"Transtympanic electrocochleography: a 10-year experience"
Otology & Neurotology

12/16/2002
By Mark Greener

Transtympanic electrocochleography reliably detects endolymphatic hydrops in Meniere's disease, while prolonged action potential latency shifts aid the diagnosis.

Researchers from the Shea Ear Clinic, Memphis, Tennessee, United States, retrospectively reviewed transtympanic electrocochleography performed on 2,421 ears in 2,140 patients over 10 years. The authors regarded enlarged summating potential/action potential ratios, broadened action potential waveforms or prolonged action potential latency shifts as indicating endolymphatic hydrops.

In response to clicks, 76.1 percent of ears showed enlarged summating potential/action potential ratios (>0.40). Seventy percent of the ears showed broadened action potential waveforms (>3 msec). Moreover, 78.4 percent of ears showed either enlarged summating potential/action potential ratios or broadened action potential waveforms. Using tonebursts, 64.8 percent of ears showed enlarged summating potential/action potential ratios. Combining clicks and tonebursts produced enlarged summating potential/action potential ratios in 81.7 percent of ears.

The researchers commented that tonebursts allowed an assessment of frequency selectivity. For example, 62.2 percent of ears affected by Meniere's disease showed prolonged action potential latency shifts(>0.2 msec). Enlarged summating potential/action potential ratios showed a statistically significant correlation with action potential latency shifts.

The proportion of patients with enlarged summating potential/action potential ratios rose with increasing severity. Seventy-one percent of patients with stage 1 Meniere's disease showed enlarged summating potential/action potential ratios. This proportion increased to 82, 85 and 90 percent at stages 2, 3 and 4 respectively.

Enlarged summating potential/action potentials seemed to be associated with disease duration. Forty-three percent of those that suffered from Meniere's disease for less than a year showed enlarged summating potential/action potentials. The proportion rose to 100 percent in those who'd suffered from the condition for more than 30 years.

Finally, the authors commented that cochlear microphonic indicated hair cell survival. Sixty-nine percent of the ears with hearing levels greater than 40 dB showed a large cochlear microphonics.

The authors concluded that transtympanic electrocochleography reliably detects endolymphatic hydrops in Meniere's disease. Furthermore, a prolonged action potential latency shift evoked by clicks is a useful addition to the diagnosis of Meniere's disease.
Otol Neurotol 2002;23:799-805. "Transtympanic electrocochleography: a 10-year experience"

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