A new technique to stratify stroke risk in transient ischemic attack patients?

T ransient ischemic attack (TIA) presents a golden opportunity to prevent strokes. Many studies in recent years have demonstrated that 10 to 20% of patients will go on to an ischemic stroke, acute coronary event, or death in the ensuing days and weeks. Of all vascular outcomes that occur in the ensuing high-risk 90-day period, about half will occur in the first 2 days. In addition, it is clear that various features of the TIA itself are predictors of risk, so we can identify those patients at low versus high risk and base evaluation and treatment recommendations and urgency on this. The ADCD2 score has emerged as a useful predictor for early stroke, as have certain magnetic resonance imaging features. Patients with a very high ABCD2 score may have a 90-day stroke rate as high as 20 to 25%, whereas those with a very low score may have a rate of 0 to 3%. Clearly, a major goal of stratifying risk for vascular events in patients in the short term after TIA is to assess the need for urgency in identifying cause and the need for carotid endarterectomy or stenting, anticoagulation to prevent cardioembolism, or antiplatelet therapy. It is commonly believed that 5 to 10% of ischemic strokes in whites, and more in blacks, Asians, and Hispanics, are caused by intracranial atherosclerosis marked by stenoses of 50% or occlusions. Early studies have suggested both extracranial and intracranial stenoses are predictors of stroke. Amarenco and his colleagues studied a large cohort of patients presenting to their SOS-TIA clinic. They hypothesized that intracranial arterial stenoses and occlusions would be independent predictors of early stroke after TIA. In this issue, these investigators report the results of their study of transcranial Doppler (TCD) results to determine if TCD offers additional independent predicting information regarding future stroke. This study has several strengths. It is a large study conducted in a major center for acute assessment of TIA and was conducted over 5 years. TCD is an attractive technique that avoids the well-known risks and limitations of computed tomography and magnetic resonance angiography. Consequently, the conclusion that “Immediate TCD examination upon arrival at the TIA clinic is feasible and could help to identify patients at high risk of vascular events recurrence. This study supports a systematic intracranial vascular examination in the initial management of TIA” may be true. It is an appealing one. However, the study has limitations that prevent establishing this technique as routine. The origin of the diagnostic TCD criteria for stenosis/occlusion is not described. Were these criteria ever validated? What do the data regarding confirmatory testing with magnetic resonance angiography (MRA)/computed tomography angiography (CTA) reveal? Was MRA/CTA performance and interpretation blinded and standardized? These issues are important to clarify whether the approach used in this study—ultra early TCD to stratify the long-term risks in TIA patients—is to be generalized to other populations. For example, should other ultrasound laboratories use these TCD criteria or their own? Without data on confirmatory imaging, do we assume that all the TCD findings are accurate? Concluding that a lesion here was “symptomatic” required a correlation between lesion site and the vascular territory of symptoms, and confirmation by a second imaging test. The authors report that half of the intracranial lesions were deemed symptomatic. Did TCD fail to correlate with other imaging half of the time, or was this conclusion reached based on the vascular territory criterion? If TCD and other imaging failed to correlate a substantial portion of the time, how are we to interpret the overall finding that TCD abnormalities identify a TIA patient at high long-term risk? The accuracy of the TCD is important not only for identifying the high-risk patient but for pointing to specific needs for further evaluation and management. Data regarding the confirmatory imaging tests may provide further insight into the risk stratification of these patients. It is reported that 1,353 confirmatory imaging EDITORIAL