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.