Gamma knife radiosurgery for trigeminal neuralgia: the initial experience of the Barrow Neurological Institute

Purpose: To assess the efficacy and complications of Gamma Knife radiosurgery for trigeminal neuralgia. Methods and Materials: The Barrow Neurological Institute (BNI) Gamma Knife facility has been operational since March 17, 1997. A total of 557 patients have been treated, 89 for trigeminal neuralgia (TN). This report includes the first 54 TN patients with follow-up exceeding 3 months. Patients were treated with Gamma Knife stereotactic radiosurgery (RS) in uniform fashion according to two sequential protocols. The first 41 patients received 35 Gy prescribed to the 50% isodose via a single 4-mm isocenter targeting the ipsilateral trigeminal nerve adjacent to the pons. The dose was increased to 40 Gy for the remaining 13 patients; however, the other parameters were unvaried. Outcome was evaluated by each patient using a standardized questionnaire. Pain before and after RS was scored as level I–IV per our newly-developed BNI pain intensity scoring criteria (I: no pain; II: occasional pain, not requiring medication; III: some pain, controlled with medication; IV: some pain, not controlled with medication; V: severe pain/no pain relief). Complications, limited to mild facial numbness, were similarly graded by a BNI scoring system. Results: Among our 54 TN patients, 52 experienced pain relief, BNI score I in 19 (35%), II in 3 (6%), III in 26 (48%), and IV in 4 (7%). Two patients (4%) reported no relief (BNI score V). Median follow-up was 12 months (range 3–28). Median time to onset of pain relief was 15 days (range 0–192), and to maximal relief 63 days (range 0–253). Seventeen (31%) noted immediate improvement (≤ 24 h). Prior to RS, all patients were on pharmacologic therapy felt to be optimal or maximal. Twenty-two (41%) were able to stop medications entirely (BNI score I or II). Another 16 (30%), with BNI Score III relief, decreased medication intake by at least 50%. Patients with classical TN pain symptoms were more likely to stop medications than those with atypical features, 49% (21 of 43) versus 9% (1 of 11). This difference was significant at p = 0.040. Statistically, the finding most predictive for pain relief was new facial numbness following RS. Each of the 5 patients with new numbness after RS developed BNI score I relief, contrasting with 35% for the 49 patients with no new numbness ( p = 0.019). Complications have been limited to delayed, mild facial sensory loss. Before RS, 17 patients had numbness from prior invasive procedures, none of whom repo