Insertion trauma of a new cochlear implant electrode: evaluated by histology in fresh human temporal bone specimens

Abstract

Background Combining acoustic and electrical stimulation has been successfully used in patients with low-frequency residual hearing. Electrode insertion trauma, such as electrode translocation could result in loss of residual hearing. Objectives The aim of the study is to evaluate the LCI-20PI electrode array insertion trauma to the intra-cochlear structures in fresh human temporal bone specimens. Materials and methods The LCI-20PI electrode arrays were inserted into scalae tympani through round window membrane in 10 cochleae from ten fresh human cadavers. The intracochlear trauma was evaluated histologically by a scale of 0–4: 0 – no observable trauma, 1 – elevation of basilar membrane, 2 – rupture of basilar membrane or spiral ligament, 3–dislocation into scala vestibuli and 4 – fracture of modiolus or osseous spiral lamina. The insertion depth was measured by radiography. Results Histological results revealed no observable trauma in seven specimens; basal membrane elevation and rupture in two specimens; the electrode array misled into scala vestibuli in one specimen. The insertion depth varied from 228° to 288°. Conclusions and significance The insertion of the LCI-20PI electrode arrays caused no trauma in the majority of the fresh temporal bone specimens. No translocation of the electrode arrays from the scala tympani to the scala vestibuli was observed.