Diffusion-weighted lesions in stroke patients with transient symptoms--where are they located?

MR diffusion-weighted imaging (DWI) has revolutionized neuroimaging and contributed to a tissue-based redefinition of transient ischemic attack (TIA). Stroke patients with DWI lesions may have neurological symptoms that resolve completely within 24 h, suggesting successful vessel recanalization. Prior studies of stroke patients with transient symptoms have not found any predilection for DWI lesions in any specific territory. Other studies have, however, reported an association between higher brain dysfunction and presence of DWI lesions in patients with transient ischemic symptoms, suggesting a high rate of cortical affection in these patients. We sought to see whether DWI location in stroke patients with transient symptoms <24 h differed from those with persistent symptoms ≥ 24 h. We hypothesized an association between transient symptoms <24 h and cortical DWI lesion localization due to a possible higher rate of vessel recanalization in patients with transient symptoms causing distal cortical infarctions.

Ischemic stroke patients examined with DWI and admitted within 24 h after symptom onset between February 2006 and November 2013 were prospectively registered in a database (The Bergen NORSTROKE Registry). Based on neurological examination 24 h after admission, patients were classified as having either transient symptoms <24 h (DWI <24) or persistent symptoms ≥ 24 h (DWI ≥ 24). DWI lesions were classified into different groups depending on lesion location: cortical lesions, confined to the supratentorial cortex; large subcortical lesions, located in the hemispheric white matter, basal ganglia, internal capsule, thalamus or corona radiate with a diameter ≥ 15 mm; lacunar lesions, located in the same territory as large subcortical lesions with a diameter <15 mm; mixed cortical-subcortical lesions, located in both supratentorial cortex and subcortex; cerebellar lesions, confined to the cerebellum; brain stem lesions, confined to the brain stem; multiple locations, located in more than one of the above defined areas.

A total of 142 ischemic stroke patients had DWI <24 and 830 DWI ≥ 24. Cortical DWI location was more frequent in patients with DWI <24 (54.2% vs. 29.5%, p < 0.001), while proportions of mixed cortical-subcortical lesions (13.4% vs. 26.5%, p = 0.001) and lesions with multiple locations (5.6% vs. 11.1%, p = 0.048) were less frequent as compared to DWI ≥ 24. Cortical DWI location was independently associated with DWI <24 when adjusted for confounders in multiple regression analyses (OR 1.89, 95% CI 1.28-2.81, p = 0.001).

Cortical DWI location was independently associated with transient stroke symptoms <24 h. This may be explained by vessel recanalization, resulting in upstream transportation of remaining particles and distal cortical lesions.