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

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We initially conducted a pilot study to evaluate the impact of botulinum toxin A (BtA) on increased masseteric mass associated with pain. After injection we assessed its impact on the muscle mass and the impact, if any, on reported pain, in a group of 10 patients who were refractory to conservative management. Results of this pilot study indicated that clenched and unclenched muscle dimensions showed no 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). The mean VAS score before the injection was 8.2, and at six weeks after the injection it was 1.8. Following the pilot study we focused only on patients' pain scores. Our main study included 48 patients (81 muscles) who suffered with pain secondary to increased masseteric size, and had recorded their pain score out of 10 on the VAS before placement of BtA into each affected muscle and again six weeks after the injection. Results showed a mean pre-injection pain score of 7.9 and a mean post-injection pain score of 2.9. Following the results of this study on reported pain alone, our Trust has allowed funding to provide the intramuscular injection of BtA in appropriately selected patients.