Management of large Trigeminal Schwannoma: long-term oncologic and functional outcome from a multicentric retrospective cohort

Abstract

Objective: Trigeminal schwannoma (TS), though a rare and benign tumor, becomes a significant surgical challenge due to its intricate location. This study aims to detail the long-term functional outcomes and tumor control post-surgical resection.

Method: We analyzed a multicentric retrospective cohort of 39 patients operated on for a TS in five tertiary centers between January 1993 and July 2022.

Results: Six TS (15%) were in the middle fossa (type M), two (5%) in the posterior fossa (type P), and two (5%) were extracranial (type E). Twenty-nine (75%) were Dumbbell shape: Eighteen (47%) were MP type, seven (18%) were MPE type, and four (10%) were ME type. Fifth nerve symptoms were the foremost preoperative complaint: hypesthesia (51%), trigeminal neuralgia (36%), and paresthesia (30%). We report a favorable evolution course for 61% of preexisting deficits (half of patients with preoperative paresthesia and neuralgia improved while only 5% of preoperative hypesthesia improved). Postoperative hypesthesia was the most frequent de novo deficit 14 (74%) and resolved in solely half the cases. Various approaches were used according to tumor type. Gross total resection (GTR), Subtotal resection (STR), and partial resection (PR) were achieved in respectively 33% (N = 13), 10% (N = 4), and 56% (N = 22) of patients. The mean clinical and radiological FU was 63 months (12 - 283 months). GTR led to no sign of recurrence (mean FU: 60 months - range: 12-283 months). For STR or PR (67%): 23 (88%) were assigned to a Wait-&-rescan policy (WS group) which offered stability in 70% (N = 16). Three cases (8%) underwent a complementary GKS (GammaKnife) on the residual lesion (GK group) without tumor change.

Conclusion: For large TS, the completeness of resection must consider the potential functional burden of surgery. With giant infiltrating lesions, a strategy of planned subtotal resection, complemented by radiosurgery, either complementary or uppon regrowth, may provide similar oncological outcomes.

Keywords: Endoscopic endonasal; Gamma knife surgery; Literature review; Skull base surgery; Trigeminal Schwannoma; Trigeminal hypoesthesia.