Maximal Area of Exposure for the Transcanal Endoscopic Access to the Internal Auditory Canal and Cerebellopontine Angle

By June 7, 2019

Anschuetz, Lukas1; Yacoub, Abraam1; Wimmer, Wilhelm1,2; Caversaccio, Marco1,2
1 Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, University Hospital and University of Bern, Bern, Switzerland;
2 ARTORG Center for Biomedical Engineering, Hearing Research Laboratory, University of Bern, Bern, Switzerland.

Recent developments in endoscopic lateral skull base surgery allows the removal of pathologies from the internal auditory canal (IAC) and the cerebellopontine angle trough a minimal-invasive transcanal and endoscopic route. However, the limits of this approach in terms of surgical exposure have not been investigated so far. We aim to assess the largest feasible transcanal corridor to the cerebellopontine angle.

Data from high-resolution CT scans of otherwise healthy temporal bones were extracted and the anatomical structures of interest manually segmented. A navigable three-dimensional model was generated. Thereafter, the main limits of dissection were assessed in n=10 dissections on whole head specimens (e.g. internal carotid artery, cochlear aqueduct, facial nerve). A total of six landmarks were used to indicate the boarders of dissection on the three-dimensional models and the maximal area of exposure calculated.

A total of 32 otherwise healthy temporal bone scans was analyzed and the largest surgically area on the medial surface of the middle ear using a transcanal endoscopic approach calculated. The mean assessed area of exposure was 135mm2(range: 90 – 205 mm2).

The maximal area of exposure during transcanal endoscopic surgery of the internal auditory canal and cerebellopontine angle exhibits a considerable anatomical variability. Mean values indicate an opening of approximately 19x15mm in the medial surface of the temporal bone offering a good anatomical control over contiguous structures.