Triggers linked to migraines with aura remain nebulous

By Peter Sergo, medwireNews Reporter

Only a small fraction of patients who suffer from migraine with aura (MA) experience an attack when they are exposed to self-reported natural triggers in an experimental setting, research shows.

Researchers from the University of Copenhagen in Denmark studied 27 MA patients who blamed their migraine attacks on exposure to bright or flickering light or strenuous exercise. To examine a causal relation between the specific trigger and resulting attacks, patients in the Neurology study reported aura or other migraine-related symptoms during and following experimental exposure to various types of photo stimulation, strenuous exercise, or a combination of the two.

The stimulus provocation elicited three (11%) reported attacks of MA; one from exercise alone (out of 12 patients) and two stemming from a combination of exercise and light exposure (out of seven patients). None of the 11 patients exposed to photostimulation alone experienced MA. Another three patients experienced a migraine without an aura attack after exercise.

"This outcome suggests that MA can be triggered by strenuous physical activity, at least in a subgroup of patients," writes primary author Jes Olesen and colleagues who cite previous findings that have associated physical activity with MA yet come up short in elucidating the underlying physiologic mechanisms.

Hougaard and his team note that migraine research has largely been based on retrospective surveys that are vulnerable to recall bias and lack confirmation through controlled exposure to trigger factors. In the current study, for example, patients claimed light-induced auras yet have repeatedly been exposed to bright sunlight without incident.

"[I]n addition to identification, prospective confirmation of trigger factors is also necessary," say the study authors, who reason that avoidance of a suspected trigger should cease if no effect is seen after numerous exposures. They recommend patients should expose themselves two to three times to properly "challenge the suspicion."

Describing Olesen et al's results as "less than spectacular" in an accompanying editorial, Peter Goadsby (University of California, San Francisco) and Stephen Silberstein (Thomas Jefferson University, Philadelphia) point out the complexity of replicating MA triggers.

Aside from the likelihood that patients are wrong about their suspected triggers, they comment, it is also unclear whether the triggers - such as exercise or consuming chocolate - are, instead, responses to an attack that has already begun. "The response to a trigger," the authors conclude, "depends on expectation to the response, prior conditioning, learning, memory, motivation, and meaning."

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