A watershed stroke is defined as a brain ischemia that is localized to the vulnerable border zones between the tissues supplied by the anterior, posterior and middle cerebral arteries.

[2] 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.

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.

There are several conditions that can predispose someone to watershed stroke by increasing the likelihood that insufficient blood supply will be able to reach the brain.

[6] People with many different cardiovascular diseases have a higher likelihood of experiencing a clot or a plaque that impedes flow through a blood vessel.

[3] Cardiovascular diseases that increase the risk of ischemia include: Although many imaging techniques are used to document watershed strokes, their pathogenesis remains controversial.

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.

On the other hand, they often detach, move into blood circulation, and eventually block smaller downstream branches of arteries causing a thromboembolism.

[2] The best supporting evidence is correlative; patients display subcortical abnormalities on CT scans and present more microembolic signals during a carotid endarterectomy.

The resulting watershed infarcts in carotid artery blockages have mostly been considered to be due to a reduced blood flow, similar to that of hypotension.

[2] Imaging studies in severe internal carotid artery (ICA) disease report an incidence of watershed stroke ranging from 19% to 64%.

The wall of internal carotid artery just distal to the bifurcation (split) is a common site of atherosclerosis because of the unique hemodynamic effects caused by the blood flow divider.

[2] Diagnosis of a cerebral vascular accident begins with a general neurological examination, used to identify specific areas of resulting injury.

Rather than using a balloon, a stent (metal mesh-like tube) is placed over the atherosclerotic plaque in the hopes of stabilizing it and allowing for increased blood flow to watershed portions of the brain.

Long-term care is focused around three areas: rehabilitative therapy, surgical interventions, and prevention of future watershed strokes.

[16] Occupational therapies can be provided to help to alleviate cognitive impairments that result from watershed stroke but its effectiveness remains unclear.

[15] Neuroscientists are currently researching stem cell transplantation therapies to improve recovery of cebreral tissue in affected areas of the brain post-stroke.

[21] Antiplatelet drugs, such as aspirin, as well as anticoagulants, are used to help prevent blood clots and therefore embolisms, which can cause watershed strokes.

Ischemic stroke is still a major health concern and studies are being conducted to determine the pathway in which brain damage occurs to identify targets for intervention.

It was observed that intraoperative decrease in blood pressure may lead to these strokes and patients who have undergone aortic procedures are more likely to have bilateral watershed infarcts.

Furthermore, bilateral watershed strokes are associated with poor short-term outcomes and are most reliably observed by diffusion-weighted imaging MRI.

[25] This new drug has been shown to home to ischemic stroke tissue as well as apoptotic neuronal cells of the penumbra region.

[10] 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.