Watershed Stroke Symptoms, Causes, and Treatment

A watershed stroke describes a stroke that affects one or more of the watershed regions of the brain. The watershed regions of the brain are located at the farthest end branches of two adjacent vascular territories (areas supplied by arteries). This means that two separate sets of arteries supply blood to the watershed regions.

A watershed stroke can occur if the blood supply is decreased, either by blockage of the vessel or restriction of blood flow.

Symptoms and Diagnosis

Symptoms of a watershed stroke might include weakness or paralysis, especially of the legs, and mood disturbances. Some individuals experience vision loss in half of their field of vision. Watershed strokes cause seizures more often than do other types of stroke.

A watershed stroke can often be diagnosed through a neurological history and physical examination and can often be identified on a brain CT or MRI.

Causes

Ischemic Stroke

A blood clot interrupting the blood supply can cause an ischemic stroke in any location of the brain, including the watershed regions. Ischemia causes an area of the brain to "starve" because blood provides vital nutrients and oxygen, which results in a stroke.

Because the watershed region of the brain relies on both sets of arteries to provide adequate blood supply, an interruption in supply through either artery could ultimately cause an ischemic stroke in the watershed region.

Low Fluid Volume/Low Blood Pressure

Because the watershed areas are the farthest regions supplied by arterial systems, adequate blood flow and blood pressure must be maintained to ensure that enough blood is pumped into these areas. Watershed areas are at high risk during extreme drops of blood pressure.

Common triggers for watershed strokes include events that affect the blood supply to the brain. Heart attacks, which affect the pumping ability of the heart, can significantly weaken the blood flow to the brain. Watershed areas may also be vulnerable to low blood pressure in people who have advanced carotid stenosis, which is narrowing of the blood vessels in the neck that carry blood to the brain.

The conditions that can cause sudden or severely low blood pressure include severe dehydration, which results in an overall low volume of fluid in the whole body. Severe infections, such as sepsis, an infection that has spread throughout the bloodstream, may cause the blood pressure to drop dramatically, potentially causing a watershed stroke. Profuse bleeding, which may result from major injury and trauma, can cause such a significant amount of blood loss that the brain does not receive enough blood supply to the watershed regions.

Treatment

Like all strokes, watershed strokes require urgent medical attention. The management of watershed strokes includes close observation and careful medical management.

If you have had an ischemic watershed stroke caused by a blood clot, then you should expect to receive stroke treatments focused on blood thinners and medical stabilization. If you get medical treatment quickly, you might be a candidate for tissue plasminogen activator treatment, which is given intravenously to dissolve the clot. Sometimes procedures can be carried out to remove the clot via stenting or suctioning.

If you have had a watershed stroke as a result of severe blood loss or low blood pressure, then your treatment is more likely to be focused on maintaining adequate fluid and blood pressure.

A Word From Verywell

A stroke is a major event that changes your life. As you recover from your stroke, you will most likely get a medical workup that identifies whether you have stroke risk factors. If you learn that you have any of the stroke risk factors, you can take steps to prevent another stroke from happening.