A watershed stroke or watershed infarct is defined as ischemia that is localized to the vulnerable border zones between the tissues supplied via the Anterior, Posterior and Middle Cerebral arteries.(Note that the actual blood stream blockage/restriction site can be located far away from the infarcts. See “Pathogenesis” followed.) 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. The watershed zones themselves are particularly susceptible to infarction from global ischemia as the distal nature of the vasculature predisposes these areas to be most sensitive to profound hypoperfusion
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.