Purely endoscopic endonasal resection of extracranial trigeminal schwannomas: a descriptive systematic review and institutional case series

Background: Trigeminal schwannomas (TSs) are uncommon, benign tumors that arise from the trigeminal nerve. They can spread to the middle cranial fossa, posterior fossa, and extracranially (pterygopalatine fossa (PPF), infratemporal fossa, orbita). Among these, extracranial involvement is the least frequent. Before the advent of endoscopic techniques, these tumors were primarily removed using conventional microsurgical approaches. Due to both the rarity of extracranial localization and the increasing use of endoscopic techniques in suitable cases, reports of TSs with extracranial involvement treated via a purely endoscopic endonasal approach (EEA) remain limited, typically appearing as case reports or a small subset within larger case series. This study systematically reviews the literature on extracranial TSs managed exclusively with EEA and presents two illustrative cases from our institution. Methods: A systematic search of the PubMed database was performed in accordance with PRISMA guidelines to identify studies that utilized a purely EEA for extracranial TS cases. Additionally, a retrospective review of 6118 EEA procedures conducted at our institution identified two patients with histopathologically confirmed extracranial TSs. Clinical presentation, surgical approach, outcomes, and complications were analyzed. Results: A total of 147 records were identified through database searches and reference lists. After removing duplicate records, 144 full-text articles were assessed for eligibility. Of these, 124 studies were excluded with justification, resulting in 23 studies being included in the review. When combined with our institutional cases, data from a total of 52 patients were analyzed. Facial numbness was the most common presenting symptom (70.5 %). The mean tumor diameter was 38.6 +/- 13.3 mm, and the gross total resection rate was 93.1 %. In our cases, both patients successfully underwent tumor resection via EEA without postoperative neurological deficits. Conclusions: EEA provides a direct, minimally invasive route for managing extracranial TSs while reducing the morbidity associated with transcranial approaches. Although optimal for purely extracranial tumors, lesions extending into the middle or posterior fossa may require a combined approach. Therefore, individualized surgical planning is essential for achieving optimal outcomes in TS management.