Effect of Cochlear Implantation on Residual Spiral Ganglion Cell Count as Determined by Comparison with the Contralateral Nonimplanted Inner Ear in Humans

It is generally assumed that at least a minimal number of spiral ganglion cells is essential for successful speech perception with a cochlear implant. Although the insertion of a multichannel cochlear implant frequently results in loss of residual hearing in the implanted ear, this outcome does not imply that significant damage to residual populations of spiral ganglion cells has occurred. The purpose of the current study was to compare spiral ganglion cell counts in implanted and nonimplanted cochleas in 11 patients for whom both temporal bones were available and in whom a multichannel cochlear implant had been placed unilaterally. The temporal bones were processed for light microscopy by standard techniques. The cochleas were reconstructed by 2-dimensional methods. Spiral ganglion cell counts of the implanted and nonimplanted sides were compared by a paired t-test (2-tailed). The mean spiral ganglion cell counts for implanted and nonimplanted ears were not statistically different in the most basal three segments of the cochlea. However, the mean spiral ganglion cell count in segment 4 (apical segment) and the mean total spiral ganglion cell count were lower in the implanted cochleas than in the nonimplanted cochleas (p < .01). The results of this study suggest a modest decrease in the total spiral ganglion cell count in the implanted ears as compared to the nonimplanted ears, principally in the apical segment. Possible interpretations of this finding are discussed.

[1]  Y. Raphael,et al.  Effects of chronic high-rate electrical stimulation on the cochlea and eighth nerve in the deafened guinea pig , 1997, Hearing Research.

[2]  P J Abbas,et al.  Multivariate Predictors of Audiological Success with Multichannel Cochlear Implants , 1993, The Annals of otology, rhinology, and laryngology.

[3]  D. Sutton,et al.  Cochlear Implant Effects on the Spiral Ganglion , 1983, The Annals of otology, rhinology, and laryngology.

[4]  J. Nadol,et al.  Correlation of Acoustic Threshold Measures and Spiral Ganglion Cell Survival in Severe to Profound Sensorineural Hearing Loss: Implications for Cochlear Implantation , 1998, The Annals of otology, rhinology, and laryngology.

[5]  John K. Niparko,et al.  Evaluation of the Temporal Bones of a Multichannel Cochlear Implant Patient , 1991, The Annals of otology, rhinology, and laryngology.

[6]  B. Clopton,et al.  Estimates of Essential Neural Elements for Stimulation through a Cochlear Prosthesis , 1980, The Annals of otology, rhinology & laryngology. Supplement.

[7]  D. Nosan,et al.  Lymphangioma presenting as a delayed posttraumatic expanding neck mass. , 1995, American journal of otolaryngology.

[8]  R. Snyder,et al.  Chronic intracochlear electrical stimulation induces selective survival of spiral ganglion neurons in neonatally deafened cats , 1991, Hearing Research.

[9]  T. Balkany,et al.  Loss of residual hearing after cochlear implantation , 1989, The Laryngoscope.

[10]  Graeme M. Clark,et al.  Factors Predicting Postoperative Sentence Scores in Postlinguistically Deaf Adult Cochlear Implant Patients , 1992, The Annals of otology, rhinology, and laryngology.

[11]  R. Lousteau,et al.  Increased spiral ganglion cell survival in electrically stimulated, deafened guinea pig cochleae , 1987, The Laryngoscope.

[12]  R Schrimpf,et al.  Sclerosing lesions of the temporal bone , 1982, The Laryngoscope.

[13]  B. Woodson,et al.  Prediction of uvulopalatopharyngoplasty response using cephalometric radiographs. , 1997, American journal of otolaryngology.

[14]  G M Clark,et al.  The histopathological effects of chronic electrical stimulation of the cat cochlea , 1983, The Journal of Laryngology & Otology.

[15]  J. Nadol,et al.  Otopathology in a case of multichannel cochlear implantation , 1994, The Laryngoscope.

[16]  G M Clark,et al.  The histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient. Correlation with psychophysics and speech perception results. , 1988, Acta oto-laryngologica. Supplementum.

[17]  L Whitford,et al.  Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants. , 1996, Audiology & neuro-otology.

[18]  R. Altschuler,et al.  Protective Effect of Electrical Stimulation in the Deafened Guinea Pig Cochlea , 1991, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.

[19]  A. Hodges,et al.  Conservation of residual hearing with cochlear implantation. , 1997, The American journal of otology.

[20]  R. Shepherd,et al.  Chronic electrical stimulation of the auditory nerve in cats. Physiological and histopathological results. , 1983, Acta oto-laryngologica. Supplementum.

[21]  R. Shepherd,et al.  Cochlear pathology following reimplantation of a multichannel scala tympani electrode array in the macaque. , 1995, The American journal of otology.

[22]  M A Marsh,et al.  Temporal bone histopathology of a patient with a nucleus 22-channel cochlear implant. , 1992, The American journal of otology.

[23]  Donald K. Eddington,et al.  Histopathology of Cochlear Implants in Humans , 2001, The Annals of otology, rhinology, and laryngology.

[24]  R J Glynn,et al.  Survival of Spiral Ganglion Cells in Profound Sensorineural Hearing Loss: Implications for Cochlear Implantation , 1989, The Annals of otology, rhinology, and laryngology.

[25]  D Ballantyne,et al.  Delayed loss of residual hearing in Clarion® cochlear implant users , 2003, The Journal of Laryngology & Otology.

[26]  P. Blamey,et al.  Are spiral ganglion cell numbers important for speech perception with a cochlear implant? , 1997, The American journal of otology.

[27]  F. Linthicum,et al.  Cochlear implant. Histopathological guide to indications and contraindications: a post mortem study on temporal bones. , 1999, European review for medical and pharmacological sciences.