Can we justify the continued use of botulinum toxin A in the management of myofascial pain?

We initially performed a pilot study to evaluate the impact of botulinum toxin A (BtA) on increased masseteric mass with associated pain. We assessed the impact on the muscle mass and the impact, if any, on each patient’s reported pain before and after injection in a group of 10 patients who were refractory to conservative management methods. Results of this pilot study indicated that clenched and unclenched muscle dimensions showed no statistically significant reduction (-0.82 clenched and -1mm unclenched). However, what did prove to be significant was an improvement in their pain scores as measured on a Visual Analogue Scale (VAS). Pre-injection mean VAS score was 8.2 and 1.8 at 6 weeks post-injection. Following the pilot study we focused just on patients’ pain scores. Our main study included 48 patients (81 muscles) who suffered with pain secondary to increased masseteric size whom indicated their pain score out of 10 on the VAS prior to placement of BtA in to each affected masseter muscle, and a further pain-score recording 6 weeks post-injection. Results showed a mean pre-injection pain score of 7.9 and a mean post-injection pain score of 2.9. Our trust has allowed funding to provide the intramuscular injection of BtA in appropriately selected patients following the results of this study on reported pain alone, which has justified its continued use.