Electrocochleography (ECochG) has received increased interest in the recent years,
especially during cochlear implant (CI) electrode insertion and postoperative predictions
of outcome. The Advanced Bionics (AB) system is capable of measuring ECochGs via the
intra-cochlear electrode array for an acoustically delivered low-frequency sinusoidal
stimulus. This information is used as feedback to the surgeon during insertion of
the electrode array. Furthermore, these measurements can be performed postoperatively.
The aim of this case series presentation was to evaluate clinical feasibility and
satisfaction in EAS patients with recordable ECochG signals.
ECochG signals in 10 subjects with residual hearing receiving either the AB HiResUltra
SlimJ or Mid-Scala electrode arrays was measured during insertion. After complete
insertion, ECochG responses to tone bursts at 125, 250, 500, 1 kHz and 2 kHz were
recorded and an assumption of threshold made via an implemented algorithm. The threshold
estimation procedure was repeated at 1, 3 & 6 months post activation. After initial
activation, the electro-acoustic (EAS) stimulation of the CI was programmed in subjects
with remaining residual hearing. Speech perception outcomes were measured using monosyllabic
words presented at 65 and 80 dB SPL.
As this is an ongoing study, preliminary results reveal that ECochG signals are not
measurable in all patients with residual hearing. ECochG signals, when detectable
during surgery remain stable and are well correlated to post-operatively measured
audiograms.
Initial experience shows ECochG to be practical to apply both intra- and post-operatively.
Further recordings are required to determine whether ECochGs remain stable over the
fitting process within the first year.
