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A watershed stroke or watershed infarct is defined as an ischemia, or blood flow blockage, that is localized to the border zones between the territories of two major arteries in the brain. Watershed locations are those border-zone regions in the brain supplied by the major cerebral arteries where blood supply is decreased. Watershed strokes are a concern because they comprise approximately 10% of all ischemic stroke cases.〔 Watershed strokes are localized to two primary regions of the brain, and are termed cortical watersheds (CWS) and internal watersheds (IWS). Patients with many different cardiovascular diseases have a higher likelihood of experiencing a blood clot or loss of blood flow in border-zone regions of the brain. The resulting symptoms differ based on the affected area of the brain. A CT scan and MRI are used for diagnosis, and afterward several treatment options are available, including the removal of atherosclerotic plaque and a physical widening of the clogged blood vessel. Long-term care is focused around three areas: rehabilitative therapy, surgical interventions, and prevention of future watershed strokes. Going forward, research to combat watershed strokes is focusing on various topics, such as stem cell research. ==Terminology and location== Watershed strokes are named because they affect the distal watershed areas of the brain. The original terminology came from the German literature, which used the analogy of an irrigation system. The German scholars compared the blood flow in distal arterial territories of the brain to the last field on a farm, which was the area with the least supply of water and therefore most vulnerable to any reduction in flow. In a medical context, the term “watershed” refers to those areas of the brain that receive dual blood supply from the branching ends of two large arteries.〔 These events are localized to two primary regions of the brain: # Cortical 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.〔 Nonetheless, within the literature itself, there exists confusion over the terminology used to describe cortical (outer brain) infarcts and subcortical (inner brain) infarcts. Besides watershed, border-zone is another common term used to refer to areas of the brain between the ends of two adjacent arteries. Other less used terms include: borderland, end zone, boundary zone, and terminal zone. These varying terms have arisen from the considerable anatomic variability both in the cerebral vascular structure and the territories of the brain that they supply.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Watershed stroke」の詳細全文を読む スポンサード リンク
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