Transtympanic electrocochleography: a 10-year experience.
OBJECTIVE
To report the authors' experience with transtympanic electrocochleography during the past 10 years.


METHODS
Retrospective case review.


METHODS
Otology/neurotology referral center.


METHODS
Transtympanic electrocochleography was performed on 2,421 ears of 2,140 patients from May 1990 to April 2000.


METHODS
Clicks and tonebursts were used in electrocochleography testing. Summating potential/action potential ratio was calculated. Action potential latency shift by rarefaction and condensation clicks was measured. Cochlear microphonic was recorded.


METHODS
An enlarged summating potential/action potential ratio (>0.40), broadened action potential waveform (>3 msec) or prolonged action potential latency shift (>0.2 msec) was considered to be indicative of endolymphatic hydrops. The presence of cochlear microphonic indicated hair cell survival.


RESULTS
In response to clicks, an enlarged summating potential/action potential ratio was found in 76.1% of ears and a broadened action potential waveform in 70%. Either an enlarged summating potential/action potential ratio or a broadened action potential waveform was observed in 78.4% of ears. In response to tonebursts, an enlarged summating potential/action potential ratio was found in 64.8%. The combined use of clicks and tonebursts yielded an enlarged summating potential/action potential ratio in 81.7%. Electrocochleography using tonebursts had the advantage of frequency selectivity. A prolonged action potential latency shift was found in 62.2% of ears with Ménière's disease. A significant association between an enlarged summating potential/action potential ratio and an action potential latency shift was noted (chi = 5.357, p = 0.021). An enlarged summating potential/action potential ratio was found 71% in Stage 1 of Ménière's disease, 82% in Stage 2, 85% in Stage 3, and 90% in Stage 4 (chi = 19.442, p = 0.000). An enlarged summating potential/action potential ratio was associated with the duration of the disease, 43% in the under 1-year group, and 100% in the more than 30-years group (chi = 33.555, p = 0.000). A large cochlear microphonic was present in 69% of ears with hearing levels greater than 40 dB.


CONCLUSIONS
Transtympanic electrocochleography using clicks and tonebursts is a reliable test to detect the presence of endolymphatic hydrops in Ménière's disease. A prolonged action potential latency shift evoked by rarefaction and condensation clicks is a useful addition to the application of electrocochleography in the diagnosis of Ménière's disease.
Ge
Xianxi
X
Shea Ear Clinic, Memphis, Tennessee 38119, USA. xianxige@yahoo.com
Shea
John J
JJ
D000200:Action Potentials / Q000502:physiology; D001300:Audiometry, Evoked Response / Q000295:instrumentation*; D003051:Cochlea / Q000503:physiopathology*; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D007762:Labyrinthitis / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008575:Meniere Disease / Q000175:diagnosis* / Q000503:physiopathology*; D010040:Otosclerosis / Q000175:diagnosis / Q000503:physiopathology; D012189:Retrospective Studies; D014012:Tinnitus / Q000175:diagnosis / Q000503:physiopathology; D014432:Tympanic Membrane