Clinical Correlates of Infarct Shape and Volume in Lacunar Strokes

The volume of acute ischemic infarcts has been shown to correlate with stroke severity and functional outcomes in all subtypes of ischemic stroke. In patients with lacunar stroke, infarct size in conjunction with infarct location has been proposed to distinguish this subtype from other forms of subcortical ischemic stroke. Most lacunar infarcts are caused by occlusion of the penetrating small vessels and classically have a maximum diameter <15 mm in the chronic phase. Infarct size is typically reported only by maximum lesion diameter on axial imaging, which may inadequately characterize actual volume. Moreover, lesion shape may be an indicator of mechanism. Recent 3-dimensional (3D) volumetric imaging analyses of chronic lacunar infarcts show that a significant proportion of these lesions does not have spheroid–ovoid morphology and may have more complex shapes. Previous imaging studies have suggested that both lacunar infarct volume and shape may be predictive of early neurological deterioration in this population. The relationship between lacunar infarct shape and volume with functional outcome has not been confirmed in a large-scale study of recent lacunar stroke patients, and the predictive value of infarct shape and volume for recurrent ischemic events is unknown. We studied the relationships between infarct shape and volume with vascular risk factors, functional outcome, and recurrent stroke in patients enrolled in the Secondary Prevention of Small Subcortical Strokes (SPS3) trial, a well-defined cohort in which cardioembolic and carotid stroke causes were excluded. We sought to determine whether a small acute subcortical infarct associated with a clinical lacunar syndrome could still have different patterns Background and Purpose—Infarct size and location are thought to correlate with different mechanisms of lacunar infarcts. We examined the relationship between the size and shape of lacunar infarcts and vascular risk factors and outcomes. Methods—We studied 1679 participants in the Secondary Prevention of Small Subcortical Stroke trial with a lacunar infarct visualized on diffusion-weighted imaging. Infarct volume was measured planimetrically, and shape was classified based on visual analysis after 3-dimensional reconstruction of axial MRI slices. Results—Infarct shape was ovoid/spheroid in 63%, slab in 12%, stick in 7%, and multicomponent in 17%. Median infarct volume was smallest in ovoid/spheroid relative to other shapes: 0.46, 0.65, 0.54, and 0.90 mL, respectively (P<0.001). Distributions of vascular risk factors were similar across the 4 groups except that patients in the ovoid/spheroid and stick groups were more often diabetic and those with multicomponent had significantly higher blood pressure at study entry. Intracranial stenosis did not differ among groups (P=0.2). Infarct volume was not associated with vascular risk factors. Increased volume was associated with worse functional status at baseline and 3 months. Overall, 162 recurrent strokes occurred during an average of 3.4 years of follow-up with no difference in recurrent ischemic stroke rate by shape or volume. Conclusions—In patients with recent lacunar stroke, vascular risk factor profile was similar among the different infarct shapes and sizes. Infarct size correlated with worse short-term functional outcome. Neither shape nor volume was predictive of stroke recurrence. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00059306. (Stroke. 2014;45:2952-2958.)