12. Moskowitz MA, Bolay H, Dalkara T. Deciphering migraine mechanisms: Clues from familial hemiple- gic migraine genotypes. Ann Neurol. 2004;55:276- 280. 13. Magistretti PJ, Pellerin L. Cellular mechanisms of brain energy metabolism. Relevance to functional brain imaging and to neurodegenerative disorders. Ann N Y Acad Sci. 1996;777:380-387. 14. Barros LF, Porras OH, Bittner CX. Why glucose transport in the brain matters for PET. Trends Neurosci. 2005;28:117-119. Is Hemicrania Continua a Single Entity or the Association of Two Headache Forms? Considerations From a Case Report Marta Allena, MD; Christina Tassorelli, MD, PhD; Grazia Sances; Elena Guaschino, MD; Giorgio Sandrini, MD; Giuseppe Nappi, MD; Fabios Antonaci, MD, PhD Hemicrania continua (HC) belongs to the group of primary headaches and it is characterized by a strictly unilateral, continuous headache of moderate intensity, with superimposed exacerbations of severe intensity that are accompanied by trigeminal autonomic features. The syndrome is completely responsive to indomethacin. Here we report a case of a 49-year-old man with HC, which may be viewed as a combination of different types of headache, ie, chronic tension-type headache and trigeminal autonomic cephalalgia. The analysis of this case raises interesting issues regarding the proper place of HC among the primary headache forms. Key words: hemicrania continua, trigeminal autonomic cephalalgias, migraine, tension-type headache Two decades after its first description, hemicrania continua (HC) 1 remains – in terms of etiology and pathogenesis – an enigma in the field of primary headaches. HC is a strictly unilateral, continuous headache, completely responsive to indomethacin, which, in the 2nd Edition of the International Classi- fication of Headache Disorders (ICHD-II), 2 has been included in chapter IV “Other Primary Headaches.” However, HC shares several clinical similarities with trigeminal autonomic cephalalgias (TACs), for example, unilaterality of pain and its association with ipsilateral cranial autonomic phenomena, and some authors feel that it should more properly be classified among the TACs. 3 Here we report an intriguing case of HC that might shed some light on the debate regarding the proper place of this headache within ICHD-II. CASE REPORT A 49-year-old man presented with a 5-year history of episodic headache that had quickly increased in frequency during a particularly stressful period, becoming continuous in a couple of years. Since the beginning, the patient reported painful exacerbations whose frequency increased over a couple of years, until they became daily. The daily continuous pain was moderate, located in right occipital and temporal regions, as a sensation of stiffness and pressure, already present upon awak- ening and it was resistant to several symptomatic From the University Centre for the Study of Adaptive Disor- ders and Headache (UCADH), University of Pavia and Head- ache Centre, IRCCS ‘C. Mondino Institute of Neurology’ Foundation, Pavia, Italy (M. Allena, C. Tassorelli, G. Sances, E. Guaschino, G. Sandrini, G. Nappi, and F. Antonaci); Depart- ment of Clinical Neurology and Otorhinolaryngology, Univer- sity of Roma “La Sapienza” (G. Nappi); UCADH, Section of Varese (F. Antonaci). Address all correspondence to Marta Allena, MD, IRCCS ‘C. Mondino Institute of Neurology’ Foundation, Via Mondino 2, Pavia 27100, Italy. Accepted for publication July 28, 2008. Conflict of Interest: None Headache 877