Parsing head pain is about classifying the common complaints people bring to us. Classification of primary headaches implies a discoverable pathology. It is assumed that by creating procedures or drugs which correct that pathology, we can provide new ways of treating the common headache disorders. The recent approval of onabotulinum toxin A (OBA) for the treatment of chronic migraine (CM) may offer just such an opportunity. Yet by attempting to answer old questions, new ones have been raised amongst by this new treatment, some of which include:Is the effectiveness of botulinum toxin (BT) in CM based upon its analgesic properties or does it have something to do with the action of the toxin on the pathology underlying CM?Is it going to prove to be an effective tool for those patients who might need it most?
BT IN THE TREATMENT OF HEAD AND FACE PAINIn 1989, the orphan drug botulinum toxin batch 79-11 ("Oculinum") was approved by the Food and Drug Administration for the treatment of blepharospasm. 1 Within 5 years, the first paper appeared on the use of BT in headache. 2 In the years since, we have seen an incremental increase in publications and clinical trials, but as shown in the Figure, the number of publications of new randomized controlled trials (RCTs) since 2004 has been stable. 3 Many of the other publications and reviews cited the same datasets.From its first use, BT was used for the treatment of headache, temporomandibular dysfunction (TMD), myofascial face pain, and bruxism. 4-18 At that time, treating myofascial pain with injections was common and clinically driven by such authors as Janet Travell and David Simons whose Myofascial Pain and Dysfunction: The Trigger Point Manual was a mainstay of pain treatment. Their work was based upon the belief that pain could be reproduced with touch and that following pain with injections could lead to relief at some distance from the trigger point. 19 The evidence for treating myofascial pain of and outside of the face with BT was not forthcoming, 20-22 although correlating pain relief with weakening muscles with a presumed reduction in spasm may have found some credence in the treatment of TMD. 23-26 One author concluded that BT "appears both safe and efficacious in . . . chronic facial pain associated with masticatory hyperactivity," although he cautioned that one "RCT . . . is not enough to establish firm evidence." 27 Others had tried unsuccessfully to use BT in trigeminal neuralgia, 28-39 occipital neuralgia, 35,40,41 and, to date, no RCTs have ever been performed in cluster headache, 42-45 other trigeminal autonomic cephalalgias, or hemicrania continua. 15,46 Secondary headaches were never systematically studied, and even treating cervicogenic headache with BT yielded no firm evidence favoring its use. 47-49 Also, the well-established treatment of pain associated with cervical dystonia 50 did not translate to a treatment for headache associated with cervical dystonia. 15,[51][52][53][54][55] In their comprehensive review of pain treatment with BT, Rawicki et a...