15.5
Posterior Circulation
a
275
b
c
Fig. 15.21 Acute “top of the basilar� syndrome. On the angiogram normal filling of the basilar artery. There is, however, irregularity of the right P1 segment (arrow) and there is no injection of the posterior thalamoperforating arteries (a). After selective pharmacological thrombolysis
normalization of the P1 segment and reappearance of the perforators (b). The comatose patient recovered completely. On the routine MR (c) 3 days later performed in an asymptomatic patient, small ischemic lesions in the medial right midbrain was recognizable
As in other parts of the brain, lacunar infarcts can also occur owing to involvement of the perforators by lipohyalinosis. The association of these lesions with similar microinfarct in the anterior circulation is frequent. They often occur in hypertensive and diabetic patients (Fisher and Caplan 1971; Caplan 1996; Bradac et al. 2008b). The prognosis of these lacunar lesions are quoad vitam better than those due to occlusion of the branches by microatheromas.
15.5.4 Cerebellar Arteries The cerebellar arteries (PICA, AICA, SCA) are involved in different degrees in acute occlusion of the intracranial VA and/or BA. Selective occlusion can occur because of atheroma at the origin of the arteries. Artery-to-artery or cardiac embolism is another cause of ischemia (Amarenco et al. 1990; Amarenco and Caplan 1993). Finally, involvement of these arteries can occur in the