Multi-channel cochlear implant histopathology: Are fewer spiral ganglion cells really related to better clinical performance?

Abstract

Conclusion: Our findings show that all cochlear implanted temporal bones had a varied degree of trauma and inflammatory reaction from cochlear implantation. No definitive relationship was observed from our limited number of specimens between residual spiral ganglion cells (SGCs) in implanted temporal bones and clinical speech performance. Objectives: We hypothesize that there is a relationship between residual SGCs in cochlear implanted temporal bones and clinical speech performance. Our aim was to examine the histopathology of multi-channel cochlear implant temporal bones and to evaluate the relationship of residual SGC counts to clinical hearing performance. Methods: Temporal bones from four cochlear implant patients were examined histologically. Comparisons were made between implanted and nonimplanted temporal bones. Clinical performance data were obtained from patient charts. Results: There were varying amounts of inflammation in the basal turn of the cochleae in all four implanted temporal bones. Trauma to the facial nerve at the facial recess was noticed in one case. Surviving dendrites varied from 5% to 30% among four cases, with no relationship to clinical performance. The speech recognition scores, measured with Central Institute of the Deaf (CID) sentence score, varied among patients from 4% to 89%, while the patient with the highest SGCs had the best clinical outcome.