Electrophysiological and imaging diagnostics of the scale dislocation during cochlear implantation

Introduction:

Cochlear implant surgery may lead to a scale dislocation of the electrode array as it perforates the basilar membrane and subsequently comes to lie in the scala vestibuli. The aim of this work was to investigate whether scale dislocations can be detected by electrophysiological measurements.

Methods:

The investigations were performed retrospectively on 30 adult patients with a Nucleus® Slim Modiolar and 25 with a Contour Advance array (Cochlear® Ltd.). The electrode position was assessed by postoperative CT or DVT imaging. Intraoperative and one month after first fitting measured electrode impedances, ECAP and ESR thresholds were examined.

Results:

Dislocations occurred at a median insertion angle of 141 degrees (Q25 = 125 degrees, Q75 = 175 degrees), whereas the array was already no longer certainly in the scala tympani at a median of 67 degrees (Q25 = 53 degrees, Q75 = 84 degrees). There are no differences between both groups for intraoperatively and one month after first fitting measured ECAP thresholds at small insertion angles (0 to 50 °). For angles between 51 and 350 °, dislocations showed significantly higher (p < 0.001) ECAP and ESR thresholds than the scala tympani insertions.

Discussion:

In this work it could be shown that patients with a scale dislocation have higher ECAP and ESR thresholds than patients with a full scala tympani insertion. Since these differences already occur at smaller insertion angles, it can be concluded that both electrophysiological characteristics provide additional information for detection of dislocations compared to radiological imaging.

Publikationsverlauf

Publikationsdatum:
23. April 2019 (online)