Pilot Study of Injection of OnabotulinumtoxinA Toward the Sphenopalatine Ganglion for the Treatment of Classical Trigeminal Neuralgia

Background: The sphenopalatine ganglion (SPG) has previously been targeted in trigeminal neuralgia (TN), but its role in this condition has not been established. Objective: To investigate the safety of injecting onabotulinumtoxinA (BTA) toward the SPG using the MultiGuide^® in 10 patients with refractory classical TN, and collect preliminary efficacy data. Methods: Twenty-five international units (IU) of BTA were injected toward the SPG in a prospective, open-label study in 10 patients with refractory classical TN. All patients were recruited and treated on an out-patient basis at St. Olav's University Hospital in Trondheim (Norway). Primary outcome: adverse events (AEs). Primary efficacy outcome: number of TN attacks at weeks 5-8 after injection compared to baseline. A treatment responder was predefined as at least 50% reduction in the median number of attacks per day between baseline and weeks 5-8. Other efficacy outcomes were intensity of attacks (numeric rating scale, 0 to 10) and functional level (1 to 4; 1 best and 4 worst) at weeks 5-8 after injection compared to baseline. Percentage of the day with concomitant persistent pain was registered at baseline and at weeks 1-4, 6, 8, and 12 after injection. Patient global impression of change (PGIC) was ascertained at month 3. Results: For the primary endpoint, we analyzed data for all 10 patients. For efficacy outcomes we analyzed data for 9 patients (1 patient violated protocol). We registered 13 AEs, none of which were serious. The median number of TN attacks during the 4-week baseline and weeks 5-8 after injection was 5.5 (range: 1.0-51.5) and 5 (range: 0-225.0), respectively (P =.401). Four patients were treatment responders. The median intensity of attacks at baseline and weeks 5-8 after injection was 6 (range: 3.0-8.5) and 3 (range: 0.0-9.0) respectively (P =.024). The median functional level at baseline was 2 (range: 1.0-3.3) and at month 2, 1 (range 1.0-4.0; P =.750). Median percentage of the day with concomitant persistent pain was 75% (minimum 37.5%, maximum 100%) at baseline and 18.75% (minimum 0%, maximum 100%) at week 8 (P =.023). Conclusions: Injection of BTA toward the SPG using the MultiGuide^® in patients with TN appears to be safe and well tolerated. This study was negative for the main efficacy endpoint (reduction in the number of attacks from baseline to weeks 5-8). Further studies examining the role of the SPG in TN are necessary.