The Nucleus Contour electrode array: a radiological and histological study.

OBJECTIVES

To evaluate the handling and insertion trauma of the recently developed Nucleus perimodiolar Contour electrode array (Cochlear Ltd., Pty, Lane Cove, New South Wales, Australia) in human temporal bones compared with the Nucleus standard straight electrode array.

STUDY DESIGN

E-perimental control group.

METHODS

Twenty-nine fresh-frozen bones were implanted with different electrode arrays by an experienced cochlear implant surgeon, and evaluated both radiologically and histologically.

RESULTS

Intracochlear insertion of the standard Nucleus straight electrode array was found to be atraumatic, confirming previous findings in the literature. Insertion of the Nucleus Contour electrode array resulted in instances of localized basilar membrane penetration causing the electrode array to move from the scala tympani into the scala vestibuli. However, this trauma did not result in any observable damage to the osseous spiral lamina or the modiolus. Basilar membrane penetration was observed in six of eight cochlear bones when a standard cochleostomy size (approximately 0.8 mm) and site (anterior and superior to the round window) were used. However, when the surgical technique was modified to use a slightly larger cochleostomy ( approximately 1.8 mm) situated closer to the round window and employ a partial stylet withdrawal technique during electrode insertion, the frequency of penetrations was restricted to two of seven bones. This trauma rate is comparable to that observed with other cochlear implants designs.

CONCLUSIONS

Following our results, the design of the Nucleus Contour electrode appears to fulfill the safety requirements for an intracochlear electrode array, provided that the surgical insertion technique is modified in the manner outlined.