An evaluation of the risk of cerebrospinal fluid leakage as a function of the surgical approach to the cochlear nerve.

Abstract

Direct implantation into the cochlear nerve can bypass the potential limitations of conventional cochlear implants. Implantable electrical arrays increase the number of stimulation sites, broaden frequency selectivity, require less activating current, and are not dependent on cochlear anatomy. Cochlear nerve implantation demands a unique surgical exposure to the modiolus. This study comprises an assessment of the risk of generating an intraoperative cerebrospinal fluid (CSF) leak using this approach. Five fresh cadavers were obtained for dissection. Using dyed normal saline as an indicator, the central nervous system was pressurized to physiological parameters. Surgical approaches to the cochlear nerve were initiated. Leakage of indicator fluid for each approach was quantitatively and qualitatively assessed. Indicator dye in the surgical field was considered a CSF breech. Indicator fluid was collected and quantified. Eighty percent of the surgical approaches caused quantifiable leaks with rates ranging from 0.1 mL/minute to 6 mL/minute. For directly implanted microarrays, the utilization of a modified facial recess approach with cochleostomy and modiolar drillout carries significant risk for generating a CSF leak during the procedure.