Tip Fold-over in Cochlear Implantation: Case Series

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Abstract

Objective:

To describe the incidence, clinical presentation, and performance of cochlear implant (CI) recipients with tip fold-over.

Study Design:

Retrospective case series.

Setting:

Tertiary referral center.

Patients:

CI recipients who underwent postoperative computed tomography (CT) scanning.

Intervention(s):

Tip fold-over was identified tomographically using previously validated software that identifies the electrode array. Electrophysiologic testing including spread of excitation or electric field imaging (EFI) was measured on those with fold-over.

Main Outcome Measure(s):

Location of the fold-over; audiological performance pre and postselective deactivation of fold-over electrodes.

Results:

Three hundred three ears of 235 CI recipients had postoperative CTs available for review. Six (1.98%) had tip fold-over with 5/6 right-sided ears. Tip fold-over occurred predominantly at 270 degrees and was associated with precurved electrodes (5/6). Patients did not report audiological complaints during initial activation. In one patient, the electrode array remained within the scala tympani with preserved residual hearing despite the fold-over. Spread of excitation supported tip fold-over, but the predictive value was not clear. EFI predicted location of the fold-over with clear predictive value in one patient. At an average follow-up of 11 months, three subjects underwent deactivation of the overlapping electrodes with two of them showing marked audiological improvement.

Conclusion:

In a large academic center with experienced surgeons, tip fold-over occurred at a rate of 1.98% but was not immediately identifiable clinically. CT imaging definitively showed tip fold-over. Deactivating involved electrodes may improve performance possibly avoiding revision surgery. EFI may be highly predictive of tip fold-over and can be run intraoperatively, potentially obviating the need for intraop fluoroscopy.

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