OBJECTIVE Minimally-invasive image-guided approach to cochlear implantation (CI) involves drilling a narrow, linear tunnel to the cochlea. Reported herein is the first clinical implementation of this approach. STUDY DESIGN Prospective, cohort study. METHODS On preoperative CT, a safe linear trajectory through the facial recess targeting the scala tympani was planned. Intraoperatively, fiducial markers were bone-implanted, a second CT was acquired, and the trajectory was transferred from preoperative to intraoperative CT. A customized microstereotactic frame was rapidly designed and constructed to constrain a surgical drill along the desired trajectory. Following sterilization, the frame was employed to drill the tunnel to the middle ear. After lifting a tympanomeatal flap and performing a cochleostomy, the electrode array was threaded through the drilled tunnel and into the cochlea. RESULTS Eight of nine patients were successfully implanted using the proposed approach with six insertions completely within scala tympani. Traditional mastoidectomy was performed on one patient following difficulty threading the electrode array via the narrow tunnel. Other difficulties encountered included use of the back-up implant when an electrode was dislodged during threading via the tunnel, tip fold-over, and facial nerve paresis (House-Brackmann II/VII at 12 months) secondary to heat during drilling. Average time of intervention was 182±36 minutes. CONCLUSION Minimally-invasive, image-guided CI is clinically achievable. Further clinical study is necessary to address technological difficulties during drilling and insertion and to assess potential benefits including decreased time of intervention, standardization of surgical intervention, and decreased tissue dissection potentially leading to shorter recovery and earlier implant activation.

Objective Percutaneous cochlear implantation (PCI) surgery uses patient-specific customized microstereotactic frames to achieve a single drill-pass from the lateral skull to the cochlea avoiding vital anatomy. We demonstrate the use of a specific microstereotactic frame, called a “Microtable”, to perform PCI surgery on cadaveric temporal-bone specimens. Study Design Feasibility study using cadaveric temporal-bones. Subjects and Methods PCI drilling was performed on six cadaveric temporal-bone specimens. The main steps involved were (1) placing three bone-implanted markers surrounding the ear, (2) obtaining a CT scan, (3) planning a safe surgical path to the cochlea avoiding vital anatomy, (4) constructing a microstereotactic frame to constrain the drill to the planned path, and (5) affixing the frame to the markers and using it to drill to the cochlea. The specimens were CT scanned after drilling to show the achieved path. Deviation of the drilled path from the desired path was computed, and the closest distance of the mid- axis of the drilled path from critical structures was measured. Results In all six specimens, we drilled successfully to the cochlea preserving the facial nerve and ossicles. In 4/6 specimens, the chorda tympani was preserved, and in 2/6 specimens, it was sacrificed. The mean ± standard deviation error at the target was found to be 0.31±0.10 mm. The closest distances of the mid-axis of the drilled path to structures were 1.28±0.17 mm to facial nerve, 1.31±0.36 mm to chorda tympani, and 1.59±0.43 mm to ossicles. Conclusion In a cadaveric model, PCI drilling is safe and effective.

Access to the cochlea requires drilling in close proximity to bone-embedded nerves, blood vessels, and other structures, the violation of which can result in complications for the patient. It has recently been shown that microstereotactic frames can enable an image-guided percutaneous approach, removing reliance on human experience and hand–eye coordination, and reducing trauma. However, constructing current microstereotactic frames disrupts the clinical workflow, requiring multiday intrasurgical manufacturing delays, or an on-call machine shop in or near the hospital. In this paper, we describe a new kind of microsterotactic frame that obviates these delay and infrastructure issues by being repositionable. Inspired by the prior success of bone-attached parallel robots in knee and spinal procedures, we present an automated image-guided microstereotactic frame. Experiments demonstrate a mean accuracy at the cochlea of 0.20 ± 0.07 mm in phantom testing with trajectories taken from a human clinical dataset. We also describe a cadaver experiment evaluating the entire image-guided surgery pipeline, where we achieved an accuracy of 0.38 mm at the cochlea.

Objectives To report a novel modification of the cochlear drill-out procedure that utilizes customized microstereotactic frames as drill guides. Patient(s) A 34-year-old man with an 18-year history of profound bilateral hearing loss and completely ossified cochleae that underwent a prior unsuccessful conventional cochlear drill-out procedure in the contralateral ear. Interventions Image-guided cochlear implantation using customized microstereotactic frames to drill linear basal and apical cochlear tunnels. Main outcome measures Transfacial recess cochlear drill-out procedure with full electrode insertion. Results Two linear paths were drilled using customized microstereotactic frames targeting the proximal and distal basal turn followed by a full split array insertion. Postoperative imaging confirmed two cochlear tunnels straddling the modiolus with adequate clearance of the facial nerve and internal carotid artery. The patient received auditory benefit with device use and did not experience any surgical complication. Conclusions Successful cochlear implantation in the setting of total scalar obliteration poses a significant challenge. Image guidance technology may assist in navigating the ossified cochlea facilitating safe and precise cochlear tunnel drilling.

Purpose Validation of a novel minimally-invasive, image-guided approach to implant electrodes from three FDA-approved manufacturers—Medel, Cochlear, and Advanced Bionics—in the cochlea via a linear tunnel from the lateral cranium through the facial recess to the cochlea. Methods Custom microstereotactic frames that mount on bone-implanted fiducial markers and constrain the drill along the desired path were utilized on seven cadaver specimens. A linear tunnel was drilled from the lateral skull to the cochlea followed by a marginal, round-window cochleostomy and insertion of the electrode array into the cochlea through the drilled tunnel. Post-insertion CT scan and histological analysis were used to analyze the results. Results All specimens (N=7) were successfully implanted without visible injury to the facial nerve. The Medel electrodes (N=3) had minimal intracochlear trauma with 8, 8, and 10 (out of 12) electrodes intracochlear. The Cochlear lateral wall electrodes (straight research arrays) (N=2) had minimal trauma with 20 and 21 of 22 electrodes intracochlear. The Advanced Bionics electrodes (N=2) were inserted using their insertion tool; one had minimal insertion trauma and 14 of 16 electrodes intracochlear while the other had violation of the basilar membrane just deep to the cochleostomy following which it remained in scala vestibuli with 13 of 16 electrodes intracochlear. Conclusions Minimally invasive, image-guided cochlear implantation is possible using electrodes from the three FDA-approved manufacturers. Lateral wall electrodes were associated with less intracochlear trauma suggesting that they may be better suited for this surgical technique.