Relative Pain Reduction and Duration of Nerve Block Response Predict Outcomes in Headache Surgery: A Prospective Cohort Study

BACKGROUND: Experts agree that nerve block (NB) response is an important tool in headache surgery screening. However, the predictive value of NBs remains to be proven in a prospective fashion. METHODS: Pre-NB and post-NB visual analogue pain scores (0 to 10) and duration of NB response were recorded prospectively. Surgical outcomes were recorded prospectively by calculating the Migraine Headache Index (MHI) preoperatively and postoperatively at 3 months, 12 months, and every year thereafter. RESULTS: The study population included 115 patients. The chance of achieving MHI percentage improvement of 80% or higher was significantly higher in subjects who reported relative pain reduction of greater than 60% following NB versus less than or equal to 60% [63 of 92 (68.5%) versus 10 of 23 (43.5%); P = 0.03]. Patients were more likely to improve their MHI 50% or more with relative pain reduction of greater than 40% versus 40% or less [82 of 104 (78.8%) versus five of 11 (45.5%); P = 0.01]. In subjects with NB response of greater than 15 days, 10 of 13 patients (77.0%) experienced MHI improvement of 80% or greater. Notably, all of these patients (100%) reported MHI improvement of 50% or greater, with mean MHI improvement of 88%. Subjects with a NB response of 24 hours or more achieved significantly better outcomes than patients with a shorter response (72.7% ± 37.0% versus 46.1% ± 39.7%; P = 0.02). However, of 14 patients reporting NB response of less than 24 hours, four patients had MHI improvement of 80% or greater, and seven, of 50% or greater. CONCLUSIONS: Relative pain reduction and duration of NB response are predictors of MHI improvement after headache surgery. NBs are a valuable tool to identify patients who will benefit from surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.