Vascular trauma during cochlear implantation: A contributor to residual hearing loss?

OBJECTIVE: This study was performed to investigate the vascular structures of the cochlea that are potentially vulnerable to mechanical trauma during cochlear implant surgery. BACKGROUND: Despite improvements in surgical technique and electrode design, residual hearing is lost in a significant percentage of cochlear implant patients. Although a variety of factors may contribute, it is widely believed that mechanical trauma plays an important role. This study focused on the vasculature of scala tympani and its potential susceptibility to injury during implant surgery. METHODS: Anatomic study of normal human temporal bones prepared by either conventional cross sectioning or by microdissection for examination by light or scanning electron microscopy. RESULTS: Blood vessels located at or near the perilymphatic surface of scala tympani are predominately of the venous type, and they are situated so as to be at risk for trauma during implantation. Those vessels include veins on the lateral wall and floor of scala tympani, the modiolar wall and the undersurface of the osseous lamina and basilar membrane. CONCLUSION: Injury or occlusion of blood vessels associated with scala tympani may adversely affect inner ear function, potentially contributing to hearing loss following cochlear implantation.