Intracochlear Electrocochleography: Response Patterns During Cochlear Implantation and Hearing Preservation.
Christopher K Giardina, Kevin D Brown, Oliver F Adunka and 4 others
PMID 30335669WHAT IT FOUND
Drops in electrical cochlear responses during cochlear implant insertion did not reliably predict hearing loss.
Recordings succeeded in 28 of 36 subjects, and waveform phase or nerve and hair cell changes helped explain drops in preserved hearing.
Key findings
01Intracochlear ECochG recordings were successful in 28 of 36 subjects, and 8 failed because 60 Hz line noise saturated the amplifier.
02Among the 12 hearing-preservation subjects, 66% of preserved cases and 66% of lost cases fell into increase or steady ECochG categories, so a magnitude drop alone did not reliably indicate trauma.
03In the 12 hearing-preservation subjects, drops interpreted with phase or hair cell and nerve response changes identified hearing loss with 100% sensitivity and 89% specificity.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The hearing-preservation analysis used only 12 subjects, so the sensitivity and specificity numbers are not stable estimates. The clip method failed in 8 of 36 subjects because of line noise, so it may not be robust without technical adjustments. Twenty-four of 36 subjects were conventional implant candidates without a hearing-preservation goal. This left a small sample for trauma prediction. The study did not report speech perception outcomes. It cannot show how ECochG patterns relate to speech performance. Cochlear trauma was inferred from hearing loss, not from direct tissue examination. The rules that used phase or hair cell and nerve response changes were developed after examining the same small set of hearing-preservation cases. Postoperative hearing was measured at different times, and thresholds were sometimes taken from later visits when hearing improved.
Declared interests
The supplied text lists NIH extramural research support. No author conflict-of-interest declaration is included in the article text.
The easy way to misread this
Do not read a drop in ECochG magnitude as proof that cochlear trauma occurred or that hearing loss would follow. In the hearing-preservation group, drops occurred in both preserved and lost cases, and the best phase or response-shape rule was based on only 12 subjects.