Retrograde cochlear implantation in postmeningitic basal turn ossification

Postmeningitic basal turn ossification is a challenge for successful cochlear implantation despite the availability of sophisticated implants and advanced drill-out procedures. A less complex concept consisting of a cochleostomy near the apex with retrograde array insertion is evaluated clinically and experimentally with emphasis on imaging of intracochlear array morphology.

Retrospective case-control study.

Outcome, hearing performance, and radiological findings including three-dimensional (3D) reconstructions were assessed in the long term in eight retrograde implanted ears of seven postmeningitic deaf patients and compared to an etiology- and device-matched control group of 17 basal turn implanted ears of 14 patients. Experimental insertions into three autopsy-derived human temporal bones were evaluated using high-resolution microtomography, 3D reconstruction, and histology.

No complications occurred. At the long-term follow-up, the average monosyllabic word test scores were 41% for the study group and 67% for the control group (P = .03). Radiological follow-up revealed insertion sites into either the apical or middle turn and frequent intracochlear array direction changes (n = 5). Experimental implantations in temporal bones resulted in folding-free, retrograde, middle turn insertions (n = 3).

The retrograde cochlear implantation is a safe and efficient alternative approach in basal turn ossification. Despite a high occurrence of intracochlear array direction changes, open set speech discrimination was achieved in all patients. Postoperative computed tomography is recommended for fitting the speech processor according to intracochlear array positions. The experimental insertion in temporal bones helped to optimize the approach.