Shape and volume of lacunar infarcts: a 3D MRI study in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.

BACKGROUND AND PURPOSE The shape and exact size of lacunar infarcts have been investigated only postmortem. Recent imaging techniques based on triangulation and connectivity can now be used for 3D segmentation of cerebral lesions. The shape and size of lacunar infarcts was investigated using these techniques in 10 cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) patients. METHODS We segmented 102 lacunar infarcts on T1-weighted images. The surface of the corresponding set of voxels was computed as a mesh of triangles. Thereafter, the shape of each lesion in 3D was visually analyzed by 2 investigators. RESULTS The volume of lesions ranged from 10.5 to 1146 mm, with 93% of them having a volume <500 mm; 83% lacunar infarcts had a spheroid or ovoid shape, but 17% presented as sticks, slabs, or with a complex shape. Lesions with multiple components appeared larger than the others, and a tail extension was noticed in 13 of 102 lesions. CONCLUSIONS These results suggest the following: (1) most lacunar infarcts in CADASIL have a volume far below one third of that of a sphere of 15 mm in diameter, the upper limit currently used for their identification on 2D imaging; (2) a significant proportion of lacunar infarcts have a shape distinct from the spheroid-ovoid morphology; and (3) lesions with a complex shape may result from the involvement of the largest small arteries, confluence of ischemic lesions, or secondary tissue degeneration. The segmentation of lacunar infarcts appears promising to better understand the pathophysiology of tissue lesions secondary to small vessel diseases.