A watershed infarct, also known as a border zone infarct or watershed stroke, is a type of ischemic stroke that occurs in the vulnerable areas of the brain where blood supply from two major arteries converges. These areas are often referred to as “watershed zones” or “border zones” because they are at the borders or boundaries between different arterial territories. Watershed infarcts typically result from reduced blood flow, which can be caused by conditions such as hypotension (low blood pressure) or emboli (clots).

There are several watershed zones in the brain, and these are susceptible to ischemia because they receive blood from the end branches of two major arteries. The three main watershed areas are:

Cortical Watershed Area (CWS): Located at the junctions between the anterior, middle, and posterior cerebral arteries, these areas are particularly vulnerable to ischemia.

Caudate Watershed Area (Caudate Nucleus): Found at the junction of the anterior and middle cerebral arteries.

Subcortical Watershed Area (Subcortical White Matter): Situated at the junction of the anterior and middle cerebral arteries.

The term “watershed” reflects the fact that these areas are like the meeting points or borders between the territories supplied by different arteries, making them more susceptible to insufficient blood flow.

Causes of watershed infarcts include:

Hypoperfusion: Reduced blood flow to the brain due to systemic hypotension, cardiac failure, or other conditions affecting blood supply.

Embolism: Blood clots or emboli that travel to the brain and block blood vessels.

Vasospasm: Constriction of blood vessels, reducing blood flow to vulnerable areas.

Clinical manifestations of watershed infarcts can vary depending on the specific areas affected, but common symptoms may include weakness, sensory disturbances, and visual deficits. The clinical presentation may resemble other types of strokes.

Diagnosis involves imaging studies such as CT scans or MRI to visualize the infarcted areas and identify the underlying cause. Treatment aims to address the cause of reduced blood flow and may involve blood pressure management, anticoagulation therapy, and other measures depending on the specific circumstances.

The prognosis for individuals with watershed infarcts depends on the extent of the damage, the rapidity of medical intervention, and the underlying cause. Early recognition and management are crucial for optimizing outcomes in these cases.