gms | German Medical Science

Objective: The concept of Transorbital Neuroendoscopic Surgery (TONES) summarizes a group of approaches that allow for minimally invasive access routes to the anterior skull base (ASB). Advantages of these approaches include minimal morbidity, coplanar working angles towards the interorbital corridor and favorable biomechanics when addressing dural defects. The key structure limiting access to the interorbital ASB is the trochlea. The present study was conducted to analyze anatomy, technique, risks and benefits of trochlear release in TONES.

Method: A retrospective chart review was performed to analyze the incidence of postoperative diplopia after subperiosteal release of the trochlea in TONES. 12 patients with a minimal follow-up of 12 months who underwent TONES and release of the trochlea were identified. Type and location of pathology, and surgical technique were analyzed. Pre- and post-operative documentation with follow-up of 1 - 4 years of subjective and objective assessment of presence of diplopia was obtained, including SF 36 questionnaire results.

Results: The pathology included trauma, fibrous dysplasia and malignant tumor. 1/12 patients noted persistent postoperative diplopia. In this case a supero-posteriorly located fragment compressed the annulus of Zinn and could not be reached through the described approach. Transcranial pterional revision surgery allowed access and successful removal of the fragment.

Conclusions: Release of the trochlea provides a substantially wider access corridor in TONES, especially to the interorbital segment of the ASB. With appropriate surgical technique, release of the trochlea is a safe maneuver with minimal risk of postoperative diplopia. Meticulous subperiosteal dissection is required for uncompromised postoperative function.