Transcanal Computed Tomography Views for Transcanal Endoscopic Lateral Skull Base Surgery: Pilot Cadaveric Study

Abstract

Objectives\u2003Transcanal endoscopic operative approaches provide for a minimally invasive surgical portal to the lateral skull base. Traditional preoperative imaging evaluation involves computed tomography (CT) acquisition in the axial and coronal planes that are not optimized for the transcanal surgical corridor. Herein, we describe a novel CT-based “transcanal view” for preoperative surgical planning and intraoperative navigation. Study Design\u2003Present study is a cadaveric imaging study. Methods\u2003Cadaveric temporal bones (n\u2009=\u20096) from three specimens underwent high-resolution CT (0.625\u2009mm slice thickness). Using three-dimensional (3D) Slicer 4.8, reformatted “transcanal” views in the plane of the external auditory canal (EAC) were created. Axial and coronal reformats were used to compare and measure distances between anatomic structures in the plane of the EAC. Results\u2003The degree of oblique tilt for transcanal CT reformats was 6.67\u2009±\u20091.78 degrees to align the EAC in axial and coronal planes. Anticipated critical landmarks were identified easily using the transcanal view. Mean values were 8.68\u2009±\u20090.38\u2009mm for annulus diameter, 9.5\u2009±\u20090.93\u2009mm for isthmus diameter, 10.27\u2009±\u20090.73\u2009mm for distance between annulus and isthmus, 2.95\u2009±\u20090.13\u2009mm for distance between annulus and stapes capitulum, 5.12\u2009±\u20090.35\u2009mm for distance between annulus and mastoid facial nerve, and 19.54\u2009±\u20091.22\u2009mm for EAC length. Conclusions\u2003This study is the first to illustrate a novel “transcanal” CT sequence intended for endoscopic lateral skull base surgery. Future studies may address how incorporation of a transcanal CT reformat may influence surgical decision making.