Mechanisms of migraine aura revealed by functional MRI in human visual cortex

Cortical spreading depression (CSD) may cause migraine visual aura. Testing this in humans has been difficult. Researchers used high-field functional MRI to study three subjects. They recorded changes in blood oxygenation level-dependent (BOLD) signals. These signals showed at least eight characteristics of CSD. Changes were time-locked to the onset of aura perception. Initially, there was a focal increase in BOLD signal, possibly due to vasodilation. This increase occurred within the extrastriate cortex, specifically area V3A. The BOLD change then progressed slowly, moving at about 3.5 mm/min. It spread over the occipital cortex, aligning with the visual percept's retinotopy. Following this progression, the BOLD signal diminished, possibly indicating vasoconstriction. This occurred after the initial increase. During scintillation periods, BOLD signals still followed the retinotopic progression. These findings strongly suggest that CSD generates the aura in human visual cortex. Clinical relevance: This research highlights potential mechanisms behind migraine aura, guiding future therapeutic strategies.