Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study

Cochlear implantation is a surgical procedure for treating patients with hearing loss in which an electrode array is inserted into the cochlea. The traditional surgical approach requires drilling away a large portion of the bone behind the ear to provide anatomical reference and access to the cochlea. A minimally-invasive technique, called percutaneous cochlear implantation (PCI), has been proposed that involves drilling a linear path from the lateral skull to the cochlea avoiding vital structures and inserting the implant using that drilled path. The steps required to achieve PCI safely include: placing three bone-implanted markers surrounding the ear, obtaining a CT scan, planning a surgical path to the cochlea avoiding vital anatomy, designing and constructing a microstereotactic frame that mounts on the markers and constrains the drill to the planned path, affixing the frame on the markers, using it to drill to the cochlea, and inserting the electrode through the drilled path. We present in this paper a cadaveric study demonstrating the PCI technique on three temporal bone cadaveric specimens for inserting electrode array into the cochlea. A custom fixture, called a Microtable, which is a type of microstereotactic frame that can be constructed in less than five minutes, was fabricated for each specimen and used to reach the cochlea. The insertion was successfully performed on all three specimens. Postinsertion CT scans confirm the correct placement of the electrodes inside the cochlea without any damage to the facial nerve.