Causes and mechanisms of territorial and nonterritorial cerebellar infarcts in 115 consecutive patients.

BACKGROUND AND PURPOSE: Territorial cerebellar infarcts have mainly a thromboembolic mechanism. Cerebellar infarcts less than 2 cm in diameter have recently been reported as nonterritorial infarcts, but it is not clear whether they are low-flow or embolic infarcts. The aim of the present study was to compare the characteristics and causes of territorial and nonterritorial infarcts in a prospective series of 115 patients. METHODS: We collected data from 115 consecutive patients with cerebellar infarcts (79 territorial and 36 nonterritorial ie, less than 2 cm), using magnetic resonance imaging (88 patients) and computed tomography. RESULTS: Patients with territorial infarcts and those with nonterritorial infarcts had similar vascular risk factors and clinical presentations and an equal frequency of cardiac source of embolism (32% versus 42%; P = NS) and of large artery occlusive disease (23% versus 19%; P = NS). Occlusive lesions of large arteries at angiography occurred at the level of one cerebellar artery (5% versus 0%; P = NS) and proximal to the ostia of the cerebellar arteries (18% versus 19%; P = NS). Infarcts distal to occlusive lesions were subdivided into unilateral vertebral artery occlusive disease (presumed artery-to-artery embolic mechanism; 18% versus 5%; P = NS) and low-flow state distal to bilateral vertebral or basilar artery occlusion (presumed hemodynamic mechanism; 0% versus 14%; P = .004). Patients with nonterritorial infarcts had more frequent hypercoagulable state (17% versus 1.25%; odds ratio, 15.6 95% confidence interval, 1.8 to 135). For the remaining patients, the mechanism of the infarct was unknown (34% versus 22%; P = NS). CONCLUSIONS: Cerebellar infarcts less than 2 cm in diameter (ie, nonterritorial) have the same high rate of embolic mechanism as territorial infarcts (47% versus 49%; P = NS), have more frequent hypercoagulable state, and sometimes have a hemodynamic mechanism.