DISTINGUISHING SILENT LACUNAR INFARCTION FROM ENLARGED VIRCHOW-ROBIN SPACES - A MAGNETIC-RESONANCE-IMAGING AND PATHOLOGICAL-STUDY

We studied clinicopathological correlations between magnetic resonance imaging (MRI) appearances of postmortem brains and pathological findi ngs in 12 patients to identify simple criteria with which to distingui sh lacunar infarctions from enlarged Virchow-Robin spaces. In vivo MRI was also available for 6 of the 12 patients. We focused on small, sil ent, focal lesions including lacunar infarctions and enlarged Virchow- Robin spaces that were confirmed pathologically. From a total of 114 l esions, enlarged Virchow-Robin spaces were most often found in the bas al ganglia and had a round or linear shape. Lacunar infarctions also w ere most frequent in the basal ganglia, but 47% of these were wedge-sh aped. In the pathological studies, excluding lesions from the lower ba sal ganglia region, enlarged Virchow-Robin spaces were usually smaller than 2 x 1 mm. The shapes and sizes of the lesions determined by MRI (in vivo and postmortem) concurred with the pathological findings, exc ept that on MRI the lesions appeared to be about 1 mm larger than foun d in the pathological study. When lesions from the lower basal ganglia and the brain stem regions are excluded, the sensitivity and specific ity for discriminating enlarged Virchow-Robin spaces from lacunar infa rctions are optimal when their size is 2 x 1 mm or less in the patholo gical study (79%/75%, respectively), 2 x 2 mm or less in both of the M RI studies: postmortem (81%/90%), and in vivo (86%/91%). In conclusion . we were able to differentiate most lacunar infarctions from enlarged Virchow-Robin spaces on MRI on the basis of their location, shape and size. We stress that size is the most important factor used to discri minate these lesions on MRI.