Botulinum toxin type A injections for myofascial pain syndrome and tension-type headache

Myofascial pain syndrome (MPS) is characterised by acute and specific pain affecting the piriformis, iliopsoas or scalenus anterior muscles. Tension-type headache (TH) is a common pathological condition, which can be chronic or episodic. Based on its muscle-relaxant properties, botulinum toxin type A (BTX-A) has demonstrated efficacy in a variety of conditions involving dysregulated muscle contractions. Patients with MPS (n = 40) or TH (n = 20) were recruited to two randomised, single-blind studies, respectively. Each patient received either BTX-A or methylprednisolone, injected into the affected muscles after administration of a local anaesthetic. Pain was assessed at baseline, and 30 and 60 days post-treatment using a standard visual analogue scale. At 30 days post-injection, the mean pain score in all treatment groups was reduced compared with baseline in both studies, although the difference between treatment groups was not significant at this time in either study. However, by 60 days post-injection, the mean pain score has continued to fall in the BTX-A treatment groups, compared with a waning of the steroid therapeutic activity in the controls. The net effect was a highly significant difference between the two treatments in both the MPS (P <0.0001) and TH (P <0.0005) studies. No major adverse events were reported. In conclusion, BTX-A produces a more prolonged pain relief than methylprednisolone in patients suffering from MPS or TH.