A novel scoring system as a preoperative predictor for pain-free survival after microsurgery for trigeminal neuralgia

OBJECTIVE Pain relief following microvascular decompression (MVD) for trigeminal neuralgia (TN) may be related to pain type, degree of neurovascular conflict, arterial compression, and location of compression. The objective of this study was to construct a predictive pain-free scoring system based on clinical and radiographic factors that can be used to preoperatively prognosticate long-term outcomes for TN patients following surgical intervention (MVD or internal neurolysis [IN]). It was hypothesized that contributing factors would include pain type, presence of an artery or vein, neurovascular conflict severity, and compression location (root entry zone). METHODS At the authors' institution 275 patients with type 1 or type 2 TN (TN1 or TN2) underwent MVD or IN following preoperative high-resolution brain MRI studies. Outcome data were obtained retrospectively by chart review and/or phone follow-up. Characteristics of neurovascular conflict were obtained from preoperative MRI studies. Factors that resulted in a probability value of < 0.05 on univariate logistic regression analyses were entered into a multivariate Cox regression analysis in a backward stepwise fashion. For the multivariate analysis, significance at the 0.15 level was used. A prognostic system was then devised with 4 possible scores (0, 1, 2, or 3) and pain-free survival analyses conducted. RESULTS Univariate predictors of pain-free survival were pain type (p = 0.013), presence of any vessel (p = 0.042), and neurovascular compression severity (p = 0.038). Scores of 0, 1, 2, and 3 were found to be significantly different in regard to pain-free survival (log rank, p = 0.005). At 5 and 10 years there were 36%, 43%, 61%, and 69%, and 36%, 43%, 56%, and 67% pain-free survival rates in groups 0, 1, 2, and 3, respectively. While TN2 patients had worse outcomes regardless of score, a subgroup analysis of TN1 patients with higher neurovascular conflict (score of 3) had significantly better outcomes than TN1 patients without severe neurovascular conflict (score of 1) (log rank, p = 0.005). Regardless of pain type, those patients with severe neurovascular conflict were more likely to have arterial compression (99%) compared to those with low neurovascular conflict (p < 0.001). CONCLUSIONS Pain-free survival was predicted by a scoring system based on preoperative clinical and radiographic findings. Higher scores predicted significantly better pain relief than lower scores. TN1 patients with severe neurovascular conflict had the best long-term pain-free outcome.