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Patients with low-risk suspected transient ischemic attack (TIA) and minor stroke had a higher-than-expected rate of true ischemia on MRI, suggesting neurologists' clinical assessment alone did not reliably produce the correct diagnosis, researchers for the prospective, observational DOUBT study reported.

In 1,028 patients with low-risk transient focal neurologic events, diffusion-weighted imaging (DWI) MRI scans found a 13.5% rate of acute ischemic stroke, reported Shelagh Coutts, MD, of the University of Calgary in Canada, and co-authors, in . In total, MRI helped revised the final diagnosis in 30.0% of these patients.

"Even experts are not always correct in the diagnosis of TIA mimics," Coutts told 番茄社区app.

"Many of the traditional teaching points regarding clinical symptoms can be incorrect, such as slow progression of symptoms from one body part to another," she added. "Classically, we think of that as being a migraine aura. But sometimes, it can be from ischemia."

More than receive a diagnosis of stroke or TIA in the U.S. each year, noted Margy McCullough-Hicks, MD, and Gregory Albers, MD, both of Stanford University, in an . These patients have an increased risk of stroke the first weeks after the event and need to be identified rapidly and correctly for secondary prevention to be effective. "Accurate diagnosis is important because some secondary preventive strategies carry risks of their own and are usually not appropriate for patients who did not have a TIA or stroke," they noted.

Definitive diagnosis can be elusive in some patients, especially those whose symptoms don't last long or who appear to have a low-risk event: "Patients with symptoms considered low risk often undergo less extensive evaluations, and differentiating between a cerebrovascular ischemic event vs another diagnosis (such as migraine, seizure, or peripheral vertigo) can be particularly difficult based solely on history and results of physical examination," McCullough-Hicks and Albers added.

" recommend performing magnetic resonance imaging (MRI) for patients with transient neurologic symptoms to help distinguish TIA from acute infarction," they continued. "However, despite the increasing use of MRI for such patients, current practice does not match the guideline recommendations to obtain an MRI scan as part of the routine evaluation of TIA."

In the multicenter, international DOUBT study, Coutts and colleagues looked at 1,028 patients without previous stroke history -- mostly from Canada -- showing low-risk transient or minor symptoms who were referred to neurology within 8 days of symptom onset from June 2010 to October 2016. Patients' mean age was 63. Symptoms included non-motor or non-speech minor focal neurologic events of any duration, or motor or speech symptoms that lasted 5 minutes or less.

Overall, 732 (71.2%) patients came from an outpatient clinic, the rest from the emergency department. All participants were examined by stroke neurologists. Participants were enrolled as soon as possible after their neurologic event, prior to undergoing MRI. Imaging was performed in a median of 102 hours. Symptoms had resolved by the time of assessment in 63.8% of patients, and median symptom duration was 120 minutes.

A total of 139 patients (13.5%) had acute stroke as defined by diffusion restriction detected on MRI. The final diagnosis was revised in 308 patients (30.0%) after undergoing MRI, and there were 7 (0.7%) recurrent strokes at 1 year.

Imaging also showed that a DWI-positive scan was associated with increased risk of recurrent stroke (RR 6.4; 95% CI 2.4-16.8) at 1 year. Absence of a DWI-positive lesion had a 99.8% negative predictive value for recurrent stroke.

In multivariable modeling, factors tied to MRI evidence of stroke were:

• Older age (OR 1.02; 95% CI 1.00-1.04)
• Male sex (OR 2.03; 95% CI 1.39-2.96)
• Motor or speech symptoms (OR 2.12; 95% CI 1.37-3.29)
• Ongoing symptoms at assessment (OR 1.97; 95% CI 1.29-3.02)
• No prior identical symptomatic event (OR 1.87; 95% CI 1.12-3.11)
• Abnormal results of initial neurologic examination (OR 1.71; 95% CI 1.11-2.65)

A detailed history and neurologic examination only were partially helpful and did not obviate the need for a brain MRI, Coutts and colleagues noted. "Because clinical features are not adequately discriminatory to obviate the need for MRI, a fast-head protocol MRI should be completed in similar patients within the first week after onset of symptoms," they concluded.

The results apply only to a study population of patients evaluated by a stroke neurologist with an initial suspicion of brain ischemia as a potential diagnosis who also had MRI within 8 days of symptom onset, not to patients assessed differently or at later time points, the researchers added. The study did not include vascular imaging, which might have identified more patients at risk for recurrent events.

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