Reprint from LARYNGOSCOPE, Vol. 104, No.3, March 1994 Otopathology in a Case of Multichannel Cochlear Implantation Joseph B. Nadol, Jr., MD; Darlene R. Ketten, PhD; Barbara J. Burgess FREQUENCY (Hz) 62.5125 250 500 1K 2K 4K 8K 16K CASE REPORT This 62-year-old woman became deaf following a pro- found a decrease in the number of spiral ganglion cells on the implanted side. Other reports have demon- strated no significant effect of implantation or stimu- lation on survival of spiral ganglion cells in either humans 3 ,7 or experimental animals. 8 - 1o Still other reports 11 ,12 have shown an improved survival ofresid- ual spiral ganglion cells on the implanted versus nonimplanted side in deafened experimental ani- mals. The temporal bones from a patient who died 10 weeks following implantation of a Richards Ineraid® device were studied by light microscopy. This repre- sents the second case report of the histopathologic findings following cochlear implantation using the Richards Ineraid device 7 and the first report following implantation of the currently used "single bundle" electrode array. In addition, this study was performed using a new embedding and sectioning strategy13 allowing the implanted cochlea to be sectioned with the electrode array in situ, avoiding artifacts caused by removing the electrode array prior to embedding. Discrimination AS 0% AD 0% 0 10 20 30 iii 40 :!:? Qj 50 > 60 C> c 70 .;;: 1II II) 80 :I: 90 100 110 120 INTRODUCTION Histologic studies of the temporal bones of pa- tients who had previouslyunde;:gone cochlear implan- tation have provide' concerning trauma to supporting eleme ts of-tlie cochlea due to electrode insertion, tissue reac' I to the presence ofimplanted electrodes, and, perhaps t important, secondary degeneration of spiral ganglion lIs. Previous studies have demonstrated significant rauma to the spiral ligament and basilar membrane, particularly at the round window near the site of insertion and in the 8-to-15-mm region of the upper basal turn. l -6 A vari- able tissue response, ranging from perielectrode fi- brosis to new bone formation, has been reported. 3 - 5 ,7 The effects of implantation on the spiral ganglion cell population are less clear. Some studies 4 ,6 have From the Department ofOtology and Laryngology, Harvard Medical School, and the Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston. Supported by NIDCD Grant #POI DC00361. Editor'sNote: This Manuscript was acceptedfor publication March 2, 1993. The histopathology of the temporal bones of a patient who died of unrelated causes 10 weeks follow- ing cochlear implantation using a Richards Ineraid® device is presented. Deafness was caused by a pro- longed course of intravenous gentamycin therapy 5 years prior to implantation. The electrode array of the cochlear implant was left in situ throughout histologic preparation and sectioning. Despite displacement and disruption of supporting structures of the inner ear, particularly in the 6-to-15-mm range as measured from the round window, there was no significant difference in the mean densities of spiral ganglion cells in the im- planted and unimplanted sides. This case is presented as evidence that despite . significant disruption of supporting elements of the inner ear, which is common during cochlear implan- tation, to be little effect on the residual spiral ganglion cell count, at least in the short term. Send Reprint Requests to Joseph B. Nadol, Jr., MD, Massachusetts Eye & Ear Infirmary, 243 Charles St., Boston, MA 02114. Fig. 1. Preoperative audiogram in this 62-year-old patient deaf- ened by intravenous gentamycin therapy. Laryngoscope 104: March 1994 "', Nadol, et a/.: Otopathology 299