Cortical spreading depression (CSD) is a wave of mass neuronal firing and neuronal and glial depolarisation which propagates through grey matter in the central nervous system in response to a pathologic stimulus, at a rate of between 1 and 5 mm per minute. First described by Leão in 1944 as a sudden depression of ECoG amplitude spreading across the cortex of the rabbit (Leao, A. A. P. 1944), CSD can be elicited in experimental animals by chemical, electrical, and mechanical stimuli, with varying degrees of ease. CSD provoked in healthy, normally perfused neural tissue does not induce persistent metabolic stress or cellular damage, and indeed such induction of CSD in animal experiments may confer protection against the adverse effects of a subsequent ischaemic insult (Kobayashi, S. et al. 1995).