Feasibility of the Ultrasonic Bone Aspirator in Retrosigmoid Vestibular Schwannoma Removal

Objective: Postoperative headache is an undesirable consequence of retrosigmoid vestibular schwannoma (VS) removal. An ultrasonic bone aspirator (UBA) may reduce headache by minimizing subarachnoid bone dust dispersion. The feasibility of removing internal auditory canal (IAC) bone with a UBA is unknown. This study assessed volume and duration of IAC bone removal in clinical and laboratory settings. Study Design: (1) Retrospective review of radiologic data and intraoperative videos. (2) Cadaveric temporal bone model. Setting: (1) Tertiary care medical center. (2) Laboratory. Subjects Methods: We calculated the volume of IAC bone drilled during retrosigmoid VS removal using postoperative computed tomography scans. We then measured the time spent actively drilling IAC bone by analyzing operative videos. Finally, we measured bone ablation rates in a cadaveric temporal bone model using a drill and UBA. Results: The mean SD volume of IAC bone removed during surgery was 0.32 +/- 0.17 mL (n = 9). The time spent actively removing IAC bone with a drill was only 10.4 +/- 3.5 minutes, less than a third of the total IAC opening time of 34.2 +/- 13.1 minutes (n = 5). On cadaveric specimens, the UBA removed bone at 0.21 +/- 0.03 or 0.35 +/- 0.07 mu L/s at 15% or 50% power, respectively (n = 4). This extrapolates to 15.0 +/- 3.0 to 25.0 +/- 3.9 minutes to remove the same 0.32 mL from surgery. Conclusions: The volume and duration of IAC bone removal during retrosigmoid VS surgery are small. Using a UBA at low power instead of a drill would extend the length of surgery by 5 to 15 minutes, with the theoretical potential for reducing headache.