Jakubowski M et al. (2006) Exploding vs. imploding headache in migraine prophylaxis with Botulinum Toxin A. Pain 125: 286–295

Analyses of pooled data have failed to demonstrate a superiority of local intramuscular injections of botulinum toxin type A (BTX-A) over placebo for the prophylaxis of migraine; however, many clinicians have noted marked reductions in the frequency of migraine attack in certain patients following BTX-A therapy. Jakubowski et al. carried out a prospective study to identify neurological markers that might distinguish between responders and nonresponders.

Each participant (n = 42) received 100 units of BTX-A administered as 21 extracranial injections. Between weeks 4 and 12 following BTX-A treatment, 27 of the cohort could clearly be classified as responders (n = 14) or nonresponders (n = 13). Those responsive to BTX-A treatment reported reductions in attack frequency, attack duration, and headache intensity. The incidences of neck muscle tenderness, cutaneous allodynia and migraine symptoms were similar in responders and nonresponders. Notably, however, responders and nonresponders could be split into two groups on the basis of the description of their pain—93% of individuals responsive to BTX-A therapy described their migraine pain as either imploding (crushing) or ocular (eye-popping) headache, whereas 100% of nonresponders described a build-up of pressure inside their head (exploding headache). This result was retrospectively validated in an independent cohort of 36 migraine patients who had received BTX-A therapy. The amelioration of imploding headaches by BTX-A therapy indicates that this type of migraine pain is mediated, at least in part, by extracranial innervation.