PATHOPHYSIOLOGY OF THE MIGRAINE AURA - THE SPREADING DEPRESSION THEORY

The characteristic form and development of sensory disturbances during migraine auras suggests that the underlying mechanism is a disturbanc e of the cerebral cortex, probably the cortical spreading depression ( CSD) of Leao. The demonstration of unique changes of brain bloodflow d uring attacks of migraine with aura, which have been replicated in ani mal experiments during CSD, constitutes another important line of supp ort for the 'spreading depression' theory, which may be a key to an un derstanding of the migraine attack. Cortical spreading depression is a short-lasting depolarization wave that moves across the cortex at a r ate of 3-5 mm/min. A brief phase of excitation heralds the reaction wh ich is immediately followed by prolonged nerve cell depression synchro nously with a dramatic failure of brain ion homeostasis, efflux of exc itatory amino acids from nerve cells and enhanced energy metabolism. R ecent experimental work has shown that CSD in the neocortex of a varie ty of species including man is dependent on activation of a single rec eptor, the N-methyl-D-aspartate receptor, one of the three subtypes of glutamate receptors. The combined experimental and clinical studies p oint to fruitful areas in which to look for migraine treatments of the future and provide a framework within which important aspects of the migraine attack can be modelled.