Curr Pain Headache. Rep 2002 Feb;6(1):52-56
The design and execution of clinical trials poses special problems for cluster headache. Although there is less inter-individual and intra-individual variability of attacks than seen with migraine, the brevity of attacks, spontaneous remissions unrelated to treatment, and the relative rarity of cluster headaches challenge investigators. The International Headache Society has developed guidelines that represent a compromise between scientific rigor and practicality. Only injectable sumatriptan for acute attacks and verapamil for prophylaxis have demonstrated a robust therapeutic effect in controlled clinical trials.
Comment: Kenneth Moore raises important methodological considerations. It is possible to undertake crossover trials comparing different active treatments? He is correct in his assertion that few agents show robust efficacy. A major issue relates to the proportion of patients with episodic versus chronic cluster headache where efficacy of active treatments can vary. For example, oral zolmitriptan was effective against placebo only in those patients with episodic disease (Bahra A, Gawel MJ, Hardebo JE, Millson DS, Breen SA, Goadsby PJ. Oral zolmitriptan is effective in the acute treatment of cluster headache. Neurology. 2000;54:1832-1839). And a set of small studies on melatonin and cluster demonstrate the problems Dr. Moore describes. In one study (Leone M, D'Amico D, Moschiano F, Fraschini F, Busonne G. Metalonin versus placebo in the prophylaxis of cluster headache: a double-blind pilot study with parallel groups. Cephalalgia. 1996;16:494-496), the melatonin worked only in episodic, not chronic cluster patients. In the second study (Prinsheim T, Magnoux E, Dobson CF, Hamel E, Aube M. Melatonin as adjuctive therapy in the prophylaxis of cluster headache: a pilot study. Headache. 2002;42:787-792), melatonin did not work better than placebo in either episodic or chronic cluster patients. Furthermore, the paper abstracted above by Torelli and Manzoni suggests that episodic cluster may progress to chronic cluster as a result of extrinsic factors such as smoking. Finally, there are ethical issues in placebo-controlled cluster studies, given the severity of the pain and the availability of effective acute and chronic treatments. As noted above, Dr. Peter Goadsby points out the need to persevere with these studies to find nonvasoactive treatments for patients with cluster headache. DSM and SJT