A novel scoring system for predisposing factors influencing surgical outcomes: comparing the endoscopic endonasal approach and transorbital approach for trigeminal schwannoma

OBJECTIVE: The optimal surgical approach for trigeminal schwannomas (TSs), particularly between the endoscopic endonasal approach (EEA) and endoscopic transorbital approach (ETOA), remains unclear. This study aimed to analyze radiological factors influencing surgical outcomes and establish criteria to guide approach selection. METHODS: A retrospective review of the records of TS patients treated with the EEA or ETOA at three tertiary centers from 2015 to 2023 was conducted. The authors introduced the orbito-ovale line (OOL) to classify tumors as low-lying or high-lying. A scoring system (range 0-5 points) incorporating five key radiological factors was developed, categorizing tumors as having a low score (0-2 points) or high score (3-5 points). RESULT: Among 74 patients, 54 (73.0%) underwent the ETOA, 19 (25.7%) the EEA, and 1 (1.4%) a combined approach. Gross- or near-total resection was achieved in 86.5% of cases. The ETOA consistently achieved favorable outcomes across both low- and high-score groups, while the EEA showed superior results in high-score cases but underperformed in low-score cases. High-lying tumors involving the middle cranial fossa (MCF) were predominantly treated with the ETOA, whereas low-lying tumors with extracranial involvement were managed with the EEA. The scoring system significantly correlated with outcomes in the EEA group (p = 0.018), with higher scores predicting better results. Surgical morbidity was low, with transient trigeminal neuropathy being the most common complication. CONCLUSIONS: Radiological features, particularly tumor location relative to the OOL and internal carotid artery displacement, significantly influence approach selection and surgical outcomes. The proposed scoring system provides a structured framework for optimizing preoperative decision-making and patient selection. While the ETOA demonstrated superior outcomes for MCF tumors, the EEA remains essential for cases with extracranial involvement.