Cochlear Implant Electrode Choice in Challenging Surgical Cases: Malformation, Residual Hearing, Ossification, or Reimplantation

Abstract

The limits of cochlear implantation candidacy have been expanding over the last decade and recent studies show that patients with inner ear anomalies, significant residual hearing, ossified cochlea, or far advanced otosclerosis can benefit from implant. The cochlear implant companies are coming up with various electrode designs. The purpose of this study is to review the factors that can affect the choice of electrode array in the expanding indications of cochlear implantation and suggest some surgical tips. A comprehensive preoperative evaluation is crucial. Detailed audiologic examination and radiologic assessment of inner ear structures with high-resolution computed tomography and/or magnetic resonance imaging is necessary. The choice of electrode array should be made regarding the type of cochlea in the presence of inner ear anomalies. If the patient has residual hearing in low-frequencies, electrode array and surgical insertion technique should be as atraumatic as possible to protect apical part of the cochlea. Appropriate selection of electrodes and surgical techniques are necessary if the cochlea is obstructed by fibrosis or ossified. The surgeon also should consider the possibility of reimplantation in the future and select the initial electrode after comprehensive evaluation. There is a diversity of electrode arrays for different indications. The selection of the most accurate electrode depends on the audiological tests, etiology of hearing loss, and cochlear anatomy. Surgeon must be prepared preoperatively for various clinical situations and unexpected surgical circumstances. One should keep in mind that making the right electrode choice will impact the outcomes of unusual or challenging cases.