Is word recognition correlated with the number of surviving spiral ganglion cells and electrode insertion depth in human subjects with cochlear implants?
OBJECTIVE
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.


METHODS
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.


CONCLUSIONS
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.
Khan
Aayesha M
AM
Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02114, USA.
Handzel
Ophir
O
Burgess
Barbara J
BJ
Damian
Doris
D
Eddington
Donald K
DK
Nadol
Joseph B
JB
D000368:Aged; D000369:Aged, 80 and over; D002452:Cell Count; D002470:Cell Survival; D019929:Cochlear Implantation / Q000379:methods; D003054:Cochlear Implants; D003638:Deafness / Q000473:pathology / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013067:Speech Perception / Q000502:physiology*; D013136:Spiral Ganglion / Q000473:pathology*; D013701:Temporal Bone / Q000473:pathology