[The influence of insertion depth on the preservation of residual hearing after cochlear implantation].
BACKGROUND
Cochlear implantation may be indicated in patients with bilateral severe sensory hearing loss. Patients with minimal residual hearing have more benefit from cochlear implantation than from optimal fitted hearing aids. However, it has to be considered that inner ear structures might be damaged during electrode insertion.


METHODS
We analysed the influence of insertion depth on the preservation of residual hearing in 47 cochlear implant patients (type of implant: Nucleus 22 M or 24 M) by using the pure tone audiometry. Frequency-specific analyses of pre- and postoperative audiograms on the implanted side were performed, evaluating only frequencies above 500 Hz. The insertion depth was documented by stiffening rings outside the cochlea.


RESULTS
Residual hearing was more obtained in cases with complete insertion of the electrode array than in those cases with incomplete insertion. In the frequencies 1000 and 4000 Hz these results are significant.


CONCLUSIONS
In our opinion, the perceived resistance producing intracochlear damages and preventing the complete electrode-insertion at the same time is an explanation for the significantly poorer results of the patients with incomplete insertion.
Neumann
M
M
Universitätsklinik für Hals-, Nasen- und Ohrenheilkunde, Freiburg. neumann@hno.ukl.uni-freiburg.de
Aschendorff
A
A
Schipper
J
J
Laszig
R
R
Klenzner
T
T
D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D002648:Child; D019929:Cochlear Implantation / Q000379:methods*; D007758:Ear, Inner / Q000293:injuries* / Q000503:physiopathology; D004567:Electrodes, Implanted / Q000009:adverse effects; D004867:Equipment Design; D005260:Female; D006312:Hearing Loss, Bilateral / Q000503:physiopathology / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D010897:Pitch Discrimination / Q000502:physiology