A dark side of subcortical diffusion-weighted lesions? Characteristics, cause, and outcome in large subcortical infarction: the Bergen Norwegian stroke cooperation study.

BACKGROUND AND PURPOSE Diffusion-weighted imaging (DWI) is highly accurate in identifying and locating ischemic stroke injury. Few studies using DWI have investigated large subcortical infarctions (LSIs). We aimed to study clinical characteristics, cause, and outcome in patients with ischemic stroke with LSI diagnosed on DWI and compare these with those who had lacunar DWI lesions or DWI lesions located elsewhere. METHODS Patients with stroke admitted between February 2006 and July 2013 were prospectively registered in a stroke database and examined with DWI. Patients with DWI lesions classified as LSI (subcortical, ≥15 mm) were compared with those with lacunar lesions (subcortical, <15 mm, lacunar infarction [LI]), cortical lesions (cortical infarction [CI]), or no LSI, which included LI, CI, mixed cortical-subcortical, cerebellar, brain stem, and combined lesion locations. RESULTS A total of 1886 patients with ischemic stroke were included, of which 128 patients (6.8%) had LSI, 317 (16.8%) LI, and 544 (28.8%) CI. The no LSI group included 1758 patients. Occlusive pathology in the proximal middle cerebral artery was more frequent in patients with acute stroke with LSI. Lacunar syndrome was associated with LSI when compared with CI and no LSI. Unknown cause was frequent in the LSI group (60.4%) and independently associated with LSI in the LSI versus LI (P<0.001), LSI versus CI (P=0.002), and LSI versus no LSI population (P<0.001). LSI was independently associated with unfavorable outcome, whether compared with LI (P=0.002), CI (P<0.001), or no LSI (P=0.002). CONCLUSIONS LSI is associated with distinct clinical characteristics, unknown cause, and unfavorable outcome, which separates this stroke entity from patients with lacunar subcortical DWI lesions or DWI lesions located elsewhere.