[Mechanisms involved in large subcortical infarcts].

Large subcortical infarcts(maximum diameter of infarct > or = 20 mm) result from various stroke patterns, including striatocapsular infarcts (SCI), corona radiata infarcts, centrum semiovale infarcts, and internal borderzone infarcts. A systematic investigation of stroke pathogenesis involved in large subcortical infarcts, however, has not been performed. This study attempted to clarify the stroke mechanisms involved in large subcortical infarcts, by examining 50 patients with large subcortical infarcts out of 430 ischemic stroke patients consecutively registered in our department. The subjects were divided into two groups according to the vascular territories involved on the MRI: 1) the lenticulostriate arteries group for 39 patients whose infarcts were restricted to within the vicinity of the lenticulostriate arteries; 2) the internal borderzone group for 11 patients whose infarcts mainly involved the internal borderzone (the upper part of the corona radiata and the centrum semiovale) between the territories of the deep perforating branches from the basal cerebral arteries and the medullary branches from the superficial pial arteries. Stroke pathogenesis were classified into the following 6 categories: A) cardiogenic embolism, 9 patients; B) artery-to-artery embolism, 6 patients; C) cryptogenic embolism, 2 patients; D) thrombotic MCA (M1) occlusion, 9 patients; E) thrombotic ICA occlusion, 10 patients; F) undetermined cause, 14 patients. The lenticulostriate arteries group consisted of 9 patients with cardiogenic embolism, 6 with artery-to-artery embolism, 2 with cryptogenic embolism, 8 with thrombotic M1 occlusion, and 14 with undetermined cause. The internal borderzone group consisted of 10 patients with thrombotic ICA occlusion and 1 patient with thrombotic M1 occlusion. The stroke pathogenesis of the undetermined cause is considered to be thrombotic occlusion at the orifice of the lateral lenticulostriate artery, a so-called "branch atheromatous disease (BAD)". The patients in this group experienced a gradual onset, and did not have a cardiac source of the embolism or proximal large artery disease. Among the patients reported as having SCI, BAD may play a role in some cases, especially in those whose the cause was classified as "undetermined". In conclusion, the lenticulostriate arteries group exhibited a higher frequency of cerebral embolisms (cardiogenic embolism, artery-to-artery embolism, and cryptogenic embolism) and thrombotic M1 occlusion, whereas the internal borderzone group had a higher frequency of thrombotic ICA occlusion.