Introduction: Microvascular decompression(MVD) can be an effective intervention for trigeminal neuralgia(TN). Clinical and imaging predictors of surgical outcomes help guide candidate selection and optimize operative results. The purpose of this study was to create and validate utility of a simple preoperative TN grading system to predict long-term pain relief after MVD.
Methods: This retrospective cohort study included consecutive patients suffering unilateral TN who underwent MVD over a 5.5-year period. Exclusion criteria were prior MVD or ablative procedure and lack of follow up. A grading system was formulated using three preoperative characteristics(Table 1). The primary end-point was pain-free status without use of medication. Ability to predict long-term postoperative pain relief was analyzed by multiple regression and assessed by area under the receiver operating characteristic curve(AUC). Clinical utility to predict MVD success and reduce unnecessary surgeries was assessed by decision curve analysis.
Results: One-hundred and nineteen patients were analyzed. Median follow up was 45 months(IQR 19). At last follow up, 77% remained pain-free without medication. Factors predicting surgical success included classic TN(84%), positive response to carbamazepine and/or oxcarbazepine(87%), and presence and nature of neurovascular compression demonstrated on MRI(20% no contact or only venous, 19% arterial contact, 61% arterial deformity). All predictors were significant in both univariate and multivariate analyses(p<0.01). The composite grading system demonstrated accuracy(Brier 0.11) and good discriminatory ability for prediction of postoperative pain-free status without medications(AUC 0.87, 95% CI 0.80-0.95). Decision-curve analysis demonstrated net reduction of six cases likely to be unsuccessful per 100 patients evaluated with this grading system above a decision threshold of 50%.
Conclusions: Used in conjunction with other clinical information, this grading system is useful for preoperative prediction of both pain-free status without medications and failure following MVD across the spectrum of patients presenting with TN.
Patient Care: A simple grading scale for trigeminal neuralgia that predicts pain-free status after microvascular decompression may be easily used in clinical settings to improve selection of candidates for surgery. Use of this scale may prevent six unnecessary (unlikely to succeed) surgeries per 100 patients screened.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Identify three clinical and imaging factors predictive of pain-free status after microvascular decompression for trigeminal neuralgia.
2) Discuss clinical utility of grading systems and predictive factors in selection of candidates for surgery.
3) Apply a simple grading system to patients with trigeminal neuralgia under consideration for microvascular decompression.