Conclusion: A 20 mm hole made backwards from the midpoint of the asterion to the mastoid process is suitable for a retrosigmoid keyhole approach with the aid of an endoscope. The endoscope-assisted retrosigmoid keyhole approach can be considered an effective and safe method for removal of vestibular schwannoma.
Objective: To investigate the feasibility of the endoscope-assisted retrosigmoid keyhole approach for exposing the cerebellopontine angle (CPA) and internal auditory canal (IAC).
Methods: With the aid of an endoscope, we simulated surgical procedures in 30 sides of 15 formalin-fixed cadaver heads.
Results: (1) For 24 (80%) sides, the midpoint of the top notch to the mastoid process was in the anterior edge of the sigmoid sinus; for 27 sides (90%) the midpoint of the asterion to the mastoid process was in the posterior edge of the sigmoid sinus. (2) The IAC and CPA were exposed by the retrosigmoid keyhole approach with the aid of the endoscope.