Transcanal and Transmastoid Computed Tomography Reformatted Views for Lateral Skull Base Endoscopic Ear Surgery

By June 7, 2019

Lubner, Rory J.1,2; Knoll, Renata M.1,3; Lee, Daniel J. 1,3; Remenschneider, Aaron K.1,3,4; Barber, Samuel R.1,5; Kozin, Elliott D.1,3
1 Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA.
2 Warren Alpert Medical School of Brown University, Providence, RI, USA.
3 Department of Otolaryngology, Harvard Medical School, Boston, MA, USA.
4 Department of Otolaryngology, University of Massachusetts Medical Center, Worcester, MA, USA.
5 Department of Otolaryngology, University of Arizona College of Medicine, Tucson, AZ, USA.

Introduction: Endoscopic surgical techniques are increasingly being used for lateral skull base surgery as a replacement for, or adjunct to, binocular operative microscopes. While conventional imaging modalities involve computed tomography (CT) in the axial, coronal, and sagittal planes, these views are sub-optimal for real-time endoscopic ear surgery (EES) approaches. Herein, we establish novel CT-based views using transcanal and transmastoid reformats for skull base surgical planning and real-time intraoperative navigation.

Methods: Cadaveric temporal bones (n=6) underwent high-resolution CT imaging (0.625mm slice thickness).  Using 3D Slicer 4.8, reformatted transcanal and transmastoid views were created. A transform module first performed a lateral rotation of 90 degrees to display the axial series in the surgical position. Next, transformed series had anterior-posterior rotations to align in the planes of transcanal and transmastoid approaches, respectively. Pertinent anatomy was then identified.

Results: Reformatted series (n=6) were aligned using standard reformatted planes. Slices were reviewed from lateral to medial to identify middle and inner ear anatomy in respective reformatted views. Anatomical landmarks were easily identified using both views.

Conclusions: This study is the first to illustrate a novel CT reformats intended for endoscopic skull base surgical planning and real-time navigation. Transcanal and transmastoid views may have advantages intraoperatively for surgical navigation of endoscopic lateral skull base procedures. Future studies may address how novel CT reformats may influence surgical decision making.