ARTICLE IN BRIEF
CBS reporter Serene Branson's on-air dysphasia after the Grammy Awards prompts discussion about the factors that distinguish migraine from transient ischemic attacks.
Although transient ischemic attacks (TIAs) share a number of similar acute symptoms with complicated migraine, making a correct diagnosis remains difficult for a number of reasons.
Symptoms of both events dissipate rapidly, and emergency centers tend to exercise caution with such patients. Although fewer that 40 percent of these neurological episodes are in fact TIAs, there is a tendency to initially diagnose them as such because of the risk that they might presage a more serious stroke.
CBS reporter Serene Branson's on-air dysphasia is a case in point. Branson, who has no history of either migraine or cardiovascular disease, suddenly began speaking incoherently while covering the Feb. 13 Grammy Awards ceremony. Initially there was concern that she had suffered a TIA, but experts at the University of California Los Angeles Medical Center in Los Angeles concluded after several days of testing that it had been an initial episode of complicated migraine, not a TIA.
MIGRAINE CAN MIMIC TIA
Larry B. Goldstein, MD, professor of neurology at Duke University Medical Center, and director of the Duke Stroke Center in Durham, NC, told Neurology Today in a telephone interview that the two conditions are difficult to diagnose because migraine can mimic TIA symptoms. Regardless of the cause, he said, individuals with such symptoms must be evaluated as soon as possible.
Studies have shown that neurologists — even those with vascular training — often disagree on the diagnosis of TIA he noted, pointing to one study published in Stroke last year.
“The traditional diagnostic criteria for TIA has been focal symptoms of presumed ischemia, lasting 24 hours or less, but this 24-hour timeframe is now seen as being arbitrary,” Dr. Goldstein said.
Transient focal neurological deficits from TIA and migraine pose a problem for diagnosticians, and most err on the side of caution, he noted.
“Many doctors are reasonably reticent to make a diagnosis of complicated migraine in patients in the absence of prior migraine or associated headache, and that's where the problem comes in,” he said.
In 2010, the American Stroke Association issued revised diagnostic criteria for TIA. Patients with the same clinical presentation as TIA but with radiological evidence of acute brain tissue injury are now classified as having had a stroke.
“But in those without evidence of ischemic brain injury, the bugaboo is that symptoms tend to be presumed to be vascular until they are shown otherwise,” Dr. Goldstein said.
Patients with such symptoms are typically evaluated using CT scans, yet hospital admittance and emergency room procedures vary widely. TIAs are often harbingers of stroke and as such, patients are historically at high risk of suffering serious stroke in the first hours or days after an initial transient episode, so they need to be carefully monitored, he said.
In recent years, diagnostic and prognostic tools have become available that can help take some of the guesswork out of whether a patient has had a TIA and whether he will go on to have a stroke or not.
For example, there are evidence-based diagnostic algorithms that can be used to help identify low-risk patients, such as their ABCD2 score. First proposed in 2005 and further refined in 2007, the ABCD2 test is used to evaluate which TIA patients require emergency care. The scoring system predicts short-term stroke risk better than the two most common long-term risk prediction scales.
Based on age, blood pressure, clinical features, diabetes, and TIA duration, an ABCD2 score can predict with some accuracy stroke risk during the two-day window during which half of all sub-sequent strokes occur.
A SIMPLE SOLUTION?
Shyam K. Prabhakaran, MD, assistant professor of neurological sciences and head of the Cerebrovascular Disease and Neurocritical Care Section at Rush University Medical Center in Chicago, recently reported that three simple markers can help differentiate between TIA and TIA mimics such as migraine: prior history of unexplained transient neurological attacks, presence of nonspecific symptoms, and gradual symptom onset.
In a 2008 paper published in the journal Cerebrovascular Diseases, Dr. Prabhakaran and his colleagues examined records of 100 emergency room patients who had an initial diagnosis of TIA and were admitted for further evaluation. Only 40 percent of these were a TIA, and the three clinical features correctly identified 79 percent of the cases. The speed of onset of symptoms was an especially effective marker, they found.
“This is a very telling marker for differentiating between the two,” Dr. Prabhakaran told Neurology Today in a telephone interview. “With neurological problems like migraine and seizures that can mimic a TIA, the onset of symptoms is progressive. With migraine, symptoms march along the cerebral cortex over minutes, unlike TIA, which happens within seconds.”
With TIA mimics, patients often report other non-focal symptoms in addition to focal neurologic symptoms, such as feeling lightheaded, gastrointestinal problems, and tightness of the chest, he explained. TIA is also unlikely if a patient has had a history of similar episodes where a TIA was later ruled out.
The issue harkens back to the need for good bedside skills, and especially good history-taking after an event, he told Neurology Today. “You often have to tease out a patient's history, which can be difficult, especially in the immediate aftermath of an episode when they may not be thinking clearly. It's not as easy as it sounds — most patients don't remember what happened very well.”
Medication-related side effects are another area where symptoms of TIA can occur. Six out of 60 patients in the study who did not have a TIA had side effects from a medication they were taking at the time.
“Clearly, having experts like stroke neurologists involved early can often help decipher these nuances,” he said.
SPECIALIZED TESTING IS NECESSARY
“The problem is enormous, but evaluating these episodes is never a waste of resources,” commented Patrick D. Lyden, MD, chair of neurology at Cedars-Sinai Medical Center in Los Angeles.
“Many mimic episodes are really post-epileptic seizures and associated paralysis [or Todd's paresis, characterized by post-seizure localized weakness, often affecting speech and vision], as well as migraine, both of which can be dangerous conditions as well. Even if they have not experienced a true TIA, they need to be evaluated by a neurologist with vascular expertise,” he told Neurology Today in a telephone interview.
Cedars-Sinai is opening a new unit specifically dedicated to evaluating TIA patients in an effort to add to the current medical evidence base for decision-making. All patients seen at the new unit will be admitted overnight for evaluation, using imaging and other clinical tests.
“Many patients get a lot of redundant tests, but rarely have their history taken by experienced TIA neurologists,” he said. “Unfortunately, I think the trend is that fewer neurologists will get this training because we have bifurcated the profession into specialists in neurology and vascular neurology,” he noted.
“What we really need are better data on the diagnostic reliability of the tests that are being used,” Dr. Lyden said. “A lot of CT imaging used in the emergency phase of a possible TIA may not be necessary. After all, these patients are going to get an MRI anyway, and that will show whether there has been a vascular event.”