People with migraines also may be suffering from some brain damage as brain cells swell and become starved of oxygen - a finding that may help explain why migraine sufferers have a higher risk of stroke, researchers reported on Sunday.

Similar brain damage can occur with concussions and after strokes, the researchers said in this week's issue of the journal Nature Neuroscience. They said their findings suggest that migraine sufferers should not simply get pain relief but should take drugs that prevent the migraine, which is often preceded by "aura" - a series of visual disturbances that can include flashes of light or black spots.

The research also suggests giving oxygen may help reduce the damage, said Takahiro Takano, Maiken Nedergaard and colleagues at the University of Rochester in New York.