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July 2001
Vol. 4, No. 7, p 13.
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Migraine and MRI

Classic migraine headaches start with a visual aura, which begins centrally and expands to the peripheral vision over a period of 5–20 min. Following scintillations, blind regions progress similarly. Researchers have suggested that migraine aura is related to cortical spreading depression (CSD), a wave of neuronal and glial depolarization or neutralization. This unique, slow spread of electrophysiological events is followed by suppression of neural activity.

Several imaging studies have suggested that CSD and migraine are related, but none have shown any relation between aura and spreading hypofusion or blood oxygen-level-dependent (BOLD) signal changes. BOLD signals reflect the balance between oxygen delivery and consumption and have been detected during CSD in experimental animals.

Nouchine Hadjikhani and colleagues at Massachusetts General Hospital (Boston) investigated the relationship between CSD and migraine aura using functional magnetic resonance imaging (MRI) (Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 4687–4692). The team studied five migraine attacks in three men. One subject played basketball continuously for 80 min, an activity that had previously triggered migraines, and was taken to the MRI facility for BOLD imaging before visual symptoms started. The two other participants worked in the building where the experiments took place and reported to the test site at first indication of the aura.

The team noted that increases in visual activity or scintillations coincide with increases in mean BOLD levels. Team members observed a slowly spreading area of abnormal blood flow in the occipital lobe during the migraine aura. The data suggested that an electrophysiological event such as CSD generates the aura in the human visual cortex.

“We conclude that migraine aura is not evoked by ischemia,” said Hadjikhani. “More likely, it is evoked by aberrant firing of neurons and related cellular elements characteristic of CSD, and vascular changes develop due to fluctuation in neuronal activity during the visual aura.”

These results open the door to novel treatments for migraine aura and drugs that inhibit the development and propagation of CSD. The researchers suggest that similar techniques can clarify the relationship between BOLD, headache, and onset of pain.


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