Internal neurolysis for atypical facial pain: Clinical outcomes and validation of an intraoperative trigeminal pathology scoring system

Background: Atypical facial pain (AFP) differs from typical trigeminal neuralgia (TTN) in clinical features and pathophysiology. Internal neurolysis (IN) has been proposed as a treatment for refractory AFP; however, objective intraoperative assessment methods remain limited. Methods: We retrospectively analyzed 20 consecutive patients with AFP who underwent IN. Intraoperative findings revealed superior cerebellar artery (SCA) compression in five cases, venous compression in four, and no vascular compression in 11. When vascular compression was identified, the vessel was dissected and mobilized before performing IN. For comparison, we reviewed a cohort of patients with TTN and SCA compression who underwent microvascular decompression with arterial transposition. Intraoperative sclerosis was graded (0–6 points) according to appearance, stiffness, and adhesion. Pain severity was evaluated using the Barrow Neurological Institute (BNI) pain score. Results: A total of 20 patients underwent IN for AFP, including 12 females and eight males, with a mean age of 62.5 years (range, 32–82 years). Postoperatively, 15 patients (75%) achieved BNI I–II, indicating significant pain relief, while 5 patients (25%) achieved BNI III, reflecting moderate residual pain. Median follow-up was 18 months (range, 6–24 months). No major surgical complications were observed. Higher sclerosis scores and moderate-to-severe adhesions were significantly associated with favorable BNI outcomes ( P = 0.03). Conclusion: IN is an effective and safe treatment for refractory AFP, particularly in patients with trigeminal sclerosis. Comparison with patients with TTN highlights distinct pathophysiology and treatment strategies, while SCA transposition is curative in TTN, AFP requires dissection and IN.