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SCOTTSDALE, Ariz. -- Migraine with aura is one of the three most common conditions, along with seizures and psychiatric disorders, that mimic stroke and can lead to inappropriate thrombolytic treatment, a researcher said here.

"There are other forms of stroke mimics, but these are the big three," said R. Allan Purdy, MD, of Dalhousie University in Halifax, Nova Scotia, Canada, at a plenary session at the American Headache Society Scottsdale Headache Symposium.

"There can't be a neurologist or healthcare professional who hasn't thought about what might happen if tissue plasminogen activator (tPA) is given to a patient with migraine," Purdy noted. "Since 1995 when tPA came out, there's been a concern that, at some point, we might be giving it to a patient with a stroke mimic."

Earlier this year, a found that migraine with aura was responsible for 1.79% of all emergency stroke unit evaluations, possibly due to efforts to reduce door-to-needle time for tPA (alteplase) stroke treatment. Migraine with aura was the third most common mimic.

Nearly 7% of tPA administrations were for non-stroke events, with migraine making up about 18% of these. Despite a lack of strong supporting data, thrombolysis in migraine with aura appeared to carry an extremely low risk of adverse events (0.01%), the authors concluded.

"This review was important because of what came out almost at the same time, which were the ," said Purdy. Those guidelines stated that "the risk of symptomatic intracranial hemorrhage in the stroke mimic population is quite low; thus, starting IV alteplase is probably recommended in preference over delaying treatment to pursue additional diagnostic studies."

"The key word here is 'probably' -- and this is important to recognize," Purdy said. "On balance, a lot of patients with stroke mimics have been given tPA, and although the untoward event percentage is extremely low, it's never going to be zero."

The aura is the thing to focus on, Purdy pointed out. "It's not the headache that you can analyze and determine whether it's a stroke mimic, because a lot of patients with transient ischemic attack (TIA) and stroke have headache. You have to look at the aura." The secret to distinguishing migraine from stroke may be in cases with a "slow march of a migraine aura over 20 minutes," in contrast to the abrupt onset of aura symptoms in strokes, he said. Unlike stroke, , he added.

In the systematic review, migraine patients tended to arrive quickly at the hospital, often within 1 hour of clinical onset. Overall, stroke mimic patients often were younger, more frequently women, had fewer cardiovascular risk factors, and showed psychiatric disorders as the most common comorbidity. The presence of neurological aura in young women, particularly if it involves speech or vision without hemiplegia, could signify a stroke mimic, Purdy noted. While that group also is risk for stroke, especially women who smoke and use oral contraception medication, "this would be a group you would look at very carefully before giving tPA," he said.

"The neurological differential diagnosis is still important in the emergency department," Purdy observed. "One still has to differentiate what's actually going on. This is important; the therapy is not without risk."

It's important to bear in mind that reaching a correct treatment decision requires knowledge of neurovascular anatomy, clinical stroke syndromes, and common mimics -- all while remembering time is brain, Purdy noted. "A quick assessment of patients takes away the opportunity for a reflective assessment, which we were all trained to think about," he said.