Endoscopic endonasal superomedial orbitectomy: How far is safe and possible?

Abstract

During the endoscopic endonasal approach (EEA) to the anterior cranial base, the lateral boundaries are the lamina papyracea (medial orbital walls) bilaterally but further extension in the coronal plane is possible by performing a superomedial orbitectomy. The aims of this study are to describe the technique of the endoscopic endonasal transethmoidal supraorbital approach to the anterior cranial base and to calculate the extension in the coronal plane added with the superomedial orbitectomy. Thirty superomedial orbitectomies via EEA were completed in 15 fresh-frozen heads. After finishing the procedure, a bifrontal craniotomy with removal of both frontal lobes was performed in order to measure the width of the supraorbital EEA in the coronal plane. We divided the anterior cranial base into five zones related to distinct anatomical segments: sinusal zone, post-sinusal zone, anterior ethmoidal, inter-ethmoidal zone, and posterior ethmoidal zone. Measurements of each segment of the anterior cranial base were taken. In all specimens, it was possible to perform a superomedial orbitectomy without excessive retraction of the orbital contents. The inter-ethmoidal zone is the segment where the lateral extension was widest. The mean total width in this area was 45.4 mm. The superomedial orbitectomy added a mean of 8 mm on each side to the total anterior skull base exposure. The endoscopic endonasal superomedial orbitectomy added important extension in the coronal plane during an EEA to the anterior cranial base. The inter-ethmoidal zone has shown the greatest lateral extension. N/A Laryngoscope, 130:1151-1157, 2020.