Advantages of a new, atraumatic, self-retaining electrode for direct cochlear nerve monitoring

Direct cochlear nerve monitoring during posterior fossa surgery offers the surgeon real-time information concerning auditory stams. However, routine utilization of this monitoring technique has been hampered by electrode designs that have not allowed the maintenance of a consistent contact between the nerve and electrode. We report on our experience with a new electrode designed to maintain consistent, atraumatic contact with the cochlear nerve and discuss the advantages of this electrode over existing wick and ball type electrodes.The utilization of this electrode during 18 posterior fossa surgeries, performed at Kaiser Permanenie Hospital, San Diego, including 8 vestibular schwannoma resections, allowed for consistent recording of high amplitude cochlear compound action potentials. Long-term exposure to pulsating cerebrospinal fluid (CSF) did not displace the electrode. Minimal cochlear nerve action potential amplitude change was noted with the electrode imrnersed in CSF. The electrode caused no trauma to the nerve, even in cases where it was accidentally dislodged from the nerve. It is hoped that by overcoming the problems previously associated with direct cochlear nerve monitoring, this electrode will allow for increased use of this advantageous monitoring technique. As a by product of the real-time data provided to the surgeon, we anticipate increased rates of hearing preservation during cerebellopontine angle surgery.