Examining the lacunar hypothesis with diffusion and perfusion magnetic resonance imaging.

BACKGROUND The clinical diagnosis of subcortical cerebral infarction is inaccurate for lesion location and pathogenesis. Clinically suspected small perforating artery occlusions may be embolic infarcts, with important implications for investigation and treatment. New MRI techniques may allow more accurate determination of the stroke mechanism soon after admission. METHODS In a prospective series of 106 patients evaluated with acute diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) within 24 hours of stroke, we enrolled 19 with a lacunar syndrome. On the basis of the topography, DWI and PWI findings, and outcome T2 MRI, we determined whether the mechanism of infarction was single perforating vessel occlusion or large artery embolism. RESULTS Thirteen patients had pure motor stroke, 2 had ataxic hemiparesis, and 4 had sensorimotor stroke. Six patients had lacunes on MRI, none with PWI lesions. Four patients had subcortical and distal cortical infarcts on DWI. Nine had solitary restricted striatocapsular infarcts. Seven of these 9 had PWI studies, 5 with PWI lesions. The presence of a PWI lesion reliably differentiated striatocapsular from lacunar infarction for solitary small subcortical infarcts (P=0.03). CONCLUSION DWI and PWI altered the final diagnosis of infarct pathogenesis from small perforating artery occlusion to large artery embolism in 13 of 19 patients presenting with lacunar syndromes. Lacunes cannot be reliably diagnosed on clinical grounds.