An acute diffusion-weighted imaging (DWI) lesion may predict an increased long-term risk for recurrent ischemic stroke after transient ischemic attack (TIA) or minor stroke, according to the results of a large population-based study published in Neurology.1

The use of magnetic resonance DWI is recommended in the investigation of stroke and TIA and is the foundation for the tissue-based definition of TIA as opposed to the traditional time-based definition.2-4 It is unknown whether acute DWI lesions also predict longer-term outcome and whether they predict risk after minor stroke (National Institutes of Health Stroke Scale [NIHSS] ≤3) as well as after TIA.1 Thus, researchers compared the 10-year risk for recurrent ischemic stroke in individuals with a DWI lesion and without a DWI lesion who had a TIA or minor stroke (TIA: n=633; minor stroke: n=400) stratified according to cryptogenic and noncryptogenic etiology. Of these patients, 248 had acute lesions on DWI (13.9% of patients with TIAs; 40% of patients with minor strokes).

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Positive DWI was associated with an increased 10-year risk for recurrent ischemic stroke after an index TIA or a stroke with an NIHSS of 0-1 but not after a stroke with an NIHSS of 2-3. Ischemic stroke risk after DWI-positive TIA was at least equivalent to that after DWI-negative stroke, and among all patients, DWI positivity was most predictive of 10-year risk after cryptogenic events.

Despite the strengths of this study — namely the large population-based cohort, stroke specialist-confirmed TIA, and blinded radiologic review — the researchers point out limitations to consider. The lack of ethnic diversity in this study limits the generalizability of these findings, and further, a nonvascular cause for symptoms needs to be considered for patients with DWI-negative TIA/minor stroke. It is also important to consider that the predominately outpatient focus of this study makes it difficult to generalize the results to a hyperacute setting.

The investigators conclude that, “DWI positivity conveys useful, long-term prognostic information in patients with TIA and minor stroke, supporting the tissue-based definition of TIA, which could also be extended to include those with minor stroke.”1

References

1. Hurford R, Li L, Lovett N, et al. Prognostic value of “tissue-based” definitions of TIA and minor stroke: population-based study [published online April 17, 2019]. Neurology. doi:10.1212/WNL.0000000000007531

2. National Institute for Health and Care Excellence. Stroke and transient ischaemic attack in over 16s: diagnosis and initial management. NICE guideline [CG68]. London: NICE; 2008.

3. Kernan WN, Ovbiagele B, Black HR, et al. Guidelines for the prevention of stroke in patients with stroke and transient ischemic attack: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2014;45:2160-2236.

4. Albers GW, Caplan LR, Easton JD, et al. Transient ischemic attack — proposal for a new definition. N Engl J Med. 2002;347:1713-1716.