[临床医学]脑梗塞的特殊类型--分水岭区梗死.ppt

Cortica watershed strokes (CWS), or outer brain infarcts, are located between the cortical territories of the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA). Internal watershed strokes (IWS), or subcortical brain infarcts, are located in the white matter,along and slightly above the lateral ventricle,between the deep and the superficial arterial systems of the MCA, or between the superficial systems of the MCA and ACA. Watersheds or border zones are areas that lie at the junction of two different drainage areas. The vascular supply of the cerebral parenchyma can be envisioned in a similar manner, with defined boundaries between different arterial systems. Cerebral infarcts in border zones were first discussed in 1883 and were defined as ischemic lesions in an area between two neighboring vascular territories . These territories can be further classified in two broad categories as (a) external (cortical) or (b) internal (subcortical) border zones. Border zone infarcts constitute approximately 10% of all cerebral infarcts . Various theories have been proposed to explain their pathogenesis. It is believed that repeated episodes of severe systemic hypotension are the most frequent cause . Susceptibility of border zones to ischemia was proved in an autopsy study of patients with border zone infarcts . Various neuropathologic studies have shown neuronal necrosis from hypotension in these regions and have advanced our understanding of the preferential distribution of border zone infarcts . The appearances of border zone infarcts depicted by standard imaging modalities are well described. Advanced imaging techniques can help identify areas of misery perfusion associated with these infarcts. Misery perfusion(低灌注) represents a chronic failure of cerebral autoregulation associated with decreased cerebral perfusion pressures in the presence of extracranial and intracranial atheromatous disease. The important info