Use of endoscopic transorbital and endonasal approaches for 360° circumferential access to orbital tumors

OBJECTIVE Orbital tumors are often surgically challenging because they require an extensive fronto-temporo-orbital zygomatic approach (FTOZ) and a multidisciplinary team approach to provide the best outcomes. Recently, minimally invasive endoscopic techniques via a transorbital superior eyelid approach (ETOA) or endoscopic endonasal approach (EEA) have been proposed as viable alternatives to transcranial approaches for orbital tumors. In this study, the authors investigated the feasibility of 360 degrees circumferential access to orbital tumors via both ETOA and EEA. METHODS Between April 2014 and June 2019, 16 patients with orbital tumors underwent either ETOA or EEA at the authors' institution. Based on the neuro-topographic "four-zone model" of the orbit with its tumor epicenter around the optic nerve in the coronal plane, ETOA (n = 10, 62.5%) was performed for tumors located predominantly superolateral to the nerve and EEA (n = 6, 37.5%) for those located predominantly inferomedial to the nerve. Eight patients (50%) presented with intraconal tumors and 8 (50%) with extraconal ones. The orbital tumors included orbital schwannoma (n = 6), cavernous hemangioma (n = 2), olfactory groove meningioma (n = 1), sphenoorbital meningioma (n = 1), chondro-sarcoma (n = 1), trigeminal schwannoma (n = 1), metastatic osteosarcoma (n = 1), mature cystic teratoma (n = 1), seba-ceous carcinoma (n = 1), and ethmoid sinus osteoma (n = 1). The clinical outcomes and details of surgical techniques were reviewed. RESULTS Gross-total resection was achieved in 12 patients (75%), near-total resection in 3 (18.8%), and subtotal re-section in 1 (6.2%). Eight (88.9%) of the 9 patients with preoperative proptosis showed improvement after surgery, and 4 (66.7%) of the 6 patients with visual symptoms demonstrated improvement. Four (40%) of the 10 patients treated with ETOA experienced partial third nerve palsy immediately after surgery (3 transient and 1 persistent). There have been no postoperative CSF leaks or infections in this series. CONCLUSIONS Without transcranial approaches requiring temporalis muscle dissection and orbitozygomatic oste-otomy, the selection of ETOA or EEA based on a concept of a four-zone model with its epicenter around the optic nerve successfully provides a minimally invasive 360 degrees circumferential access to the entire orbit with acceptable morbidity. https://thejns.org/doi/abs/10.3171/2020.6.JNS20890