The Histopathology of Revision Cochlear Implantation

Abstract

The current study evaluates histopathologic changes in the temporal bones of 4 human subjects who underwent revision cochlear implantation. Specimens were removed at autopsy, fixed and prepared for histological study by standard techniques. Specimens were serially sectioned, reconstructed by two-dimensional methods, and the tracks of the initial and revision cochlear-implant electrodes identified. The tracks were of three types: a ‘common track’ (shared by the reimplantation electrode and initial electrode), ‘two tracks’ (where the reimplantation electrode was in a different track than that of the initial electrode) and ‘one track’ (where the reimplantation electrode extended beyond the initial electrode, forming a single track). Associated histopathologic findings (new bone formation, fibrosis or inflammatory cells, and cochlear fluid) were evaluated for the three types of tracks. In all 4 subjects, the insertion depth of the revision cochlear implant was deeper than that of the initial cochlear implant. The primary track of the initial implantation did not interfere with insertion of a revision cochlear implant, and the trajectory of the revision electrode did not always follow the primary track. In cochlear segments with a common track or two tracks, the mean (across-subject) percent area of the extraelectrode cochlear duct filled with abnormal (new bone or fibrotic) tissue (43.2%) was significantly greater than the mean percent area occupied by fluid (13.4%; t = 3.12, d.f. = 19.9, p = 0.003).

Round Window Versus Cochleostomy Technique in Cochlear Implantation

“…In cases with multiple surgeries, initial trauma was most likely due to the first implantation, as we have not seen evidence of damage from removal of an electrode. There is some conflicting evidence regarding the status of the sheath that surrounds an implant electrode after removal and reimplantation (17, 18). In this study, attention was paid in each multiple surgery case to determine whether a new electrode track was present.…”

Revision Cochlear Implantation With Different Electrodes Can Cause Incomplete Electrode Insertion and Poor Performance

“…Chute has insisted that both the level of cochlear neoosteogenesis and the electrode insertion depth might affect the postoperative hearing rehabilitation (24). On the contrary, evaluation of the histopathology of temporal bones of 4 human subjects who underwent revision CI revealed that a newly inserted electrode can make a new route in the cochlear duct as a common track or 2 tracks according to its pathology (21). They concluded that the electrode insertion depth at revision CI is not limited by the depth of insertion of the initial implant.…”

Molecular and Cellular Mechanisms of Loss of Residual Hearing after Cochlear Implantation

“…38 Finally, it disrupts the architecture of the organ of Corti and provokes subsequent hair cell and neuronal loss, further compromising the maintenance of residual hearing. 39 The development of cochlear fibrosis can be as- Fibrotic scar formation after cochlear implantation. Acute inflammatory reaction is triggered by insertion trauma that induces recruitment of inflammatory cells such as macrophages or lymphocytes to site, thus promoting elimination of cellular debris and secretion of cytokines and growth factors.…”