Dr Dalessio doubts that enough knowledge exists to determine whether migraine represents one or more entities. Dr Ziegler even questions whether migraine can be distin-guished reliably from other types of headache. Both authors stress the difficulties of defining neurologic symptoms, Dr Dalessio pointing out that a history of sensory experiences depends directly on the physician's assiduity. Dr Ziegler emphasizes that the diagnosis of migraine can range from 5% to 34% in different districts of the same country.1
Lacking identifiable biologic markers, migraine definitions rely on physiologic studies. Thus, on the basis of cerebral blood flow measurements, Lauritzen and Olesen argue that common and classic migraine differ. In patients with classic migraine, a wave of diminished perfusion flows cephalad across the territories of the major cerebral arteries, whereas patients with common migraine show no such changes.2 Since brain metabolism was not measured, we do not know whether a
Hachinski V. Common and Classic Migraine: One or Two Entities? Arch Neurol. 1985;42(3):277. doi:10.1001/archneur.1985.04060030095016
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