Botulinum toxin type A for cephalic cutaneous allodynia in chronic migraine: a randomized, double-blinded, placebo-controlled trial

Cephalic allodynia (CA) can be observed in 50-70% of patients with chronic migraine (CM). The aim of this trial was to assess the efficacy of botulinum toxin type A (Botx-A) in the treatment of CA associated with CM. In this placebo-controlled trial, patients were randomized either into Botx-A or 0.9% saline injections and efficacy measures were assessed every 4 weeks for 3 months. Efficacy endpoints were number of migraine episodes associated with CA, changes from baseline in visual analogical scale scores for pain (VAS) and frequency of common analgesics use for migraine. A total of 38 subjects were randomized to saline (n=18) or Botx-A (n=20). There were no significant differences in baseline between active intervention or placebo groups regarding mean age, number of headache episodes [mean 12.1 (9.22) and 17.00 (9.69) respectively; P=0.12], pain severity as measured by the VAS or frequency of analgesic use for headache episodes. Efficacy analysis showed that Botx-A injections led to an important decrease from baseline in the mean migraine episodes associated with CA after 12 weeks (5.20 versus 11.17; P=0.01). Also, VAS scores and frequency of analgesics use for headache were significantly reduced in the Botx-A group. This study suggests that Botx-A injections are superior to saline in the treatment of CA associated with CM, with mild self limited side effects