History of migraine with aura and cortical spreading depression from 1941 and onwards.

Several personal descriptions of migraine with aura from 1870 onwards reported a slow, gradual progression of symptoms. Lashley in 1941 meticulously chartered his own auras and concluded that the symptomatology reflected a cortical process progressing with a speed of 3 mm/min across the primary visual cortex. Leão described cortical spreading depression (CSD) in rabbits in 1944 and noticed its similarity to the migraine aura. Despite these scattered pieces of evidence, the prevailing theory was that the migraine aura was caused by a vasospasm and cortical ischaemia. The advent of a technique for measurements of regional cerebral blood flow (rCBF) in 1974 made it possible to detect spreading oligaemia during migraine aura. Between 1981 and 1990 a series of studies of rCBF during migraine attacks showed reduced brain blood flow posteriorly spreading slowly and contiguously anteriorly and crossing borders of supply of major cerebral arteries. These observations refuted the ischaemic hypothesis. The human studies showed initial hyperaemia followed by prolonged hypoperfusion. The relation between aura and CSD was known to cause short-lasting, and therefore not obvious vasodilation and it was considerably strengthened by the demonstration of a long-lasting oligaemia in rats in the wake of CSD. In the primates CSD is not easily elicited, but it has in recent years been clearly demonstrated in patients with brain trauma and stroke. Finally, mutations for familial hemiplegic migraine have been expressed in mice and lower the threshold for CSD. The seminal papers on rCBF and CSD published in the 1980s caused a dramatic shift in our concepts of migraine aura. They moved attention from ischaemia to CSD and thereby to the brain itself, and paved the way for subsequent discoveries of brainstem mechanisms.