Subcortical White Matter Infarcts: Comparison of Superficial Perforating Artery and Internal Border-Zone Infarcts Using Diffusion-Weighted Magnetic Resonance Imaging

Background and Purpose - Because of difficulty in distinguishing between superficial perforator (SP) and internal border-zone (IB) infarcts, some studies lumped SP and IB infarcts together as so-called subcortical white matter infarcts, which might complicate the classification of infarct type and its pathogenesis. Using diffusion-weighted MRI (DWI), we made comparative analyses of clinical and neuroradiological characteristics between IB and SP infarcts to clarify the difference in underlying pathogenesis. Methods - We selected SP and IB infarcts on DWI using templates for the identification of subcortical vascular territories. Sex, age, neurological symptoms, clinical course, risk factors, concomitant cortical spotty lesions, and degree and location of arterial occlusive disease were compared between the 2 groups. Results - Among the 720 consecutive patients, 54 and 29 patients met the criteria for SP and IB infarcts, respectively. The SP group had lower initial National Institutes of Health Stroke Scale scores (2.4±2.1 versus 4.4±3.1; P=0.001), favorable clinical outcomes (P=0.001), and more frequent potential cardioembolic sources (14.8% versus 0%; P=0.046) than the IB group. Cortical spotty lesions were more frequently accompanied by SP than IB infarcts (72.2% versus 24.1%; P<0.001). IB infarcts were larger (24.2±10.2 versus 11.4±8.5 mm; P<0.001), appeared in a chainlike fashion (72.4% versus 33.3%; P=0.001), and had a higher degree of stenosis or occlusion (86.2% versus 46.3%; P=0.001) compared with SP infarcts. Conclusions - Our present study suggests that embolic pathogenesis makes a greater contribution to SP infarcts than IB infarcts. This finding may explain the difference in clinical and neuroradiological characteristics between the 2 groups.