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Is Word Recognition Correlated With the Number of Surviving Spiral Ganglion Cells and Electrode Insertion Depth in Human Subjects With Cochlear Implants?

Authors

  • Aayesha M. Khan MD,

    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    2. Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
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  • Ophir Handzel MD, LLB,

    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    2. Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
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  • Barbara J. Burgess,

    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    2. Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
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  • Doris Damian PhD,

    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    Current affiliation:
    1. Dr. Damian is currently with Beyond Genomics, Waltham, Massachusetts.
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  • Donald K. Eddington PhD,

    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    2. Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
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  • Joseph B. Nadol Jr MD

    Corresponding author
    1. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A.
    2. Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A.
    • Joseph B. Nadol, Jr., MD, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, Massachusetts 02114, U.S.A.
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  • Supported by NIDCD/NIH grant 5-R01 DC00152–23 and by the American Physicians Fellowship for Medicine in Israel (o.h.).

Abstract

Objectives/Hypothesis: Speech perception scores using cochlear implants have ranged widely in all published series. The underlying determinants of success in word recognition are incompletely defined. Although it has been assumed that residual spiral ganglion cell population in the deaf ear may play a critical role, published data from temporal bone specimens from patients have not supported this hypothesis. The depth of insertion of a multichannel cochlear implant has also been suggested as a clinical variable that may be correlated with word recognition. In the current study these correlations were evaluated in 15 human subjects.

Study Design: Retrospective review of temporal bone histopathology.

Methods: Temporal bones were fixed and prepared for histological study by standard techniques. Specimens were then serially sectioned and reconstructed by two-dimensional methods. The spiral ganglion cells were counted, and the depth of insertion of the cochlear implant as measured from the round window was determined. Correlation analyses were then performed between the NU6 word scores and spiral ganglion cell counts and the depth of insertion.

Results: The segmental and total spiral ganglion cell counts were not significantly correlated (P > .50) with NU6 word scores for the 15 subjects. Statistically significant correlations were not achieved by separate analysis of implant types. Similarly, no significant correlation between the depth of insertion of the electrode array and postoperative NU6 word score was identified for the group.

Conclusion: Although it is unlikely that the number of residual spiral ganglion cell counts is irrelevant to the determination of word recognition following cochlear implantation, there are, clearly, other clinical variables not yet identified that play an important role in determining success with cochlear implantation.

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