Abstract & Commentary
Commentary by John J. Caronna, Vice-Chairman, Department of Neurology, Cornell University Medical Center, Professor of Clinical Neurology, New York Hospital, and Associate Editor of Neurology Alert.
Synopsis: The therapeutic response to indomethacin is the most reliable differential diagnostic criterion for PH vs CH.
Sources: Zidverc-Trajkovic J, et al. Cluster Headache and Paroxysmal Hemicrania. Cephalalgia. 2005;25:244-248; Boes C. Differentiating Paroxysmal Hemicrania From Cluster Headaches. Cephalalgia. 2005;25:241-243.
Beginning in 1974, Sjaastad and Dale1,2 described a new treatable headache entity which they named chronic paroxysmal hemicrania (PH). They insisted that the absolute effectiveness of indomethacin was the diagnostic criterion that distinguished PH from cluster headache (CH). Subsequently, Goadsby and Lipton3 proposed the term "trigeminal autonomic cephalgias" (TAC) to encompass several short-lasting primary headache syndromes, including CH, PA, short-lasting unilateral neuralgiform pain with conjunctional injection and tearing syndrome (SUNCT), and painful exacerbation of hemicrania continua.
Zidverc-Trajkovic and colleagues sought to further define the clinical characteristics that distinguish CH from PH. It is clinically important to distinguish between PH and CH because treatments for one generally are not effective for the other. In genera, the clinical features that distinguish PH from CH include female preponderance, higher frequency and shorter duration of attacks, and complete response to indomethacin. Nevertheless, there is considerable overlap of these characteristics in the syndromes as encountered in clinical practice. Therefore, Zidverc-Trajkovic et al compared the clinical features of 54 CH patients with 8 PH patients. The diagnosis of headache types was made on the basis of a clinical history and neurological examination according to the International Headache Society Criteria4, including indomethacin response in the PH group. All PH patients responded to indomethecin in daily doses of 75-150mg. Other differences between the 2 types of headaches included maximal pain localization (extraocular in PH), mean attack duration (shorter in PH), mean attack frequency (higher in PH), and clinical course (more often chronic in PH). There was, however, no clinical characteristic that belonged exclusively to either type of headache (see Table 1). The response to verapamil did not differ between CH and PH groups. In the end, Zidverc-Trajkovic et al concluded that the therapeutic response to indomethacin is the most reliable differential diagnostic criterion for PH vs CH.
Table 1: Features of attacks*
Commentary
Although it is generally agreed that indomethacin response is the only sure way to identify PH, the mechanism by which indomethacin works is not established. Various theories of action are discussed by Boes in his editorial. His opinion is that indomethacin may exert its effect on PH by antagonizing one or more steps in the nitric oxide pathway and thereby prevent activation of the cranial parasympathetic system that characterizes PH.
The clinical value of this paper is that it suggests that a patient with paroxysmal hemicranial headaches who fails an adequate trial of indomethacin, should be tried next on medications that are useful for CH rather than other medications reported useful in PH.
References
1. Sjaastad O, et al. Evidence for a New, Treatable Headache Entity. Headache. 1974;14:105-108.
2. Sjaastad O, et al. A New, Clinical Headache Entity "Chronic Paroxysmal Hemicrania". Acta Neurological Scand. 1976;54:140-159.
3. Goadsby PJ, et al. Brain. 1997;20:193-209.
4. Headache Classification Committee of the International Headache Society. Cephalalgia. 1988;8(supp1.7):1-96.
The therapeutic response to indomethacin is the most reliable differential diagnostic criterion for PH vs CH.
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