Lacunar infarcts mainly occur in the basal ganglia, lenticular nucleus, and especially the putamen, thalamus, and white matter of the internal capsule, pons, and centrum semiovale. Lacunar infarcts occasionally occur in the cerebellum, cerebral gyri, and spinal cord, but they are rare in the gray matter of the cerebral surface, corpus callosum, and visual radiations.
Most lacunar infarcts occur in the territory of the deep penetrating arteries, mainly the lenticulostriate branches of the middle cerebral artery, but also in the anterior striate and Heubner arteries (ie, branches of anterior cerebral artery), anterior choroidal artery, paramedian branches of the basilar artery, and thalamoperforator branches of the posterior cerebral artery. The lenticulostriates and thalamoperforators have lumen diameters of 100-400 µm, whereas the diameter of the paramedian branches of the basilar artery ranges from 40-500 µm. These vessels directly arise from the larger vessels, without the gradual stepdown in size that occurs in the distal cortical vessels.