Recovering From A Watershed Stroke: Is It Possible?

A watershed stroke is a medical emergency that occurs when the blood flow to the border zones of the brain is severely reduced, leading to brain tissue death. These border zones are the areas of the brain that are furthest away from the three major arteries that service it. While rarely fatal, watershed strokes can lead to severe disability, including the loss of motor function, dementia, and other neurological problems. However, with quick and effective treatment, it is possible to recover from a watershed stroke.

What is a watershed stroke?

A watershed stroke is a type of ischemic stroke that occurs when the blood flow to parts of the brain, known as border zones, is severely reduced, leading to brain tissue death. These border zones are situated in the areas of the brain that are farthest from the three major arteries that service the brain. This means that they are highly vulnerable to reductions in perfusion.

Watershed strokes are localized to two primary regions of the brain and are termed cortical watersheds (CWS) and internal watersheds (IWS). CWSs are located between the cortical territories of the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA). IWSs 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.

Watershed strokes are caused by ischemia or a lack of blood flow to the brain. This can be due to a blockage or restriction in the blood vessels supplying the brain. The symptoms of a watershed stroke are similar to those of other types of strokes but are often milder and can come and go, making them easy to miss or overlook. They can include:

• Tilting of the head to one side
• Weakness or paralysis of one leg (and sometimes the arm on the same side of the body)
• Vision loss in half of the field of vision
• Seizures
• Mood disturbances (such as uncontrollable and inappropriate laughing or crying)
• Numbness, paralysis, or weakness on one side of the body or face
• Drooping of the face
• Confusion, forgetfulness, or other changes in mental status
• Changes in consciousness, awareness, or responsiveness
• Difficulty speaking or understanding speech
• Difficulty breathing
• Difficulty walking, loss of balance, or dizziness
• Vision problems, such as difficulty seeing or decreased pupil size

Watershed strokes are a medical emergency and require immediate attention to prevent irreparable brain injury. Treatment options include blood thinners, tissue plasminogen activator (TPA), carotid endarterectomy, percutaneous angioplasty, oxygen therapy, intravenous (IV) fluids, and compression therapy.

What are the symptoms?

A watershed stroke is a medical emergency and requires immediate attention. It is characterised by severely reduced blood flow to the brain, specifically the border zones, which are situated far away from the three major arteries that service the brain. The symptoms of a watershed stroke are often milder and more difficult to identify than those of other types of stroke, but they can still lead to severe disability and even death if not treated promptly.

The symptoms of a watershed stroke are due to reduced blood flow to the brain, which can lead to brain damage. The initial symptoms, as promoted by the American Stroke Association, can be remembered with the acronym FAST:

• Facial weakness (droop)
• Arm weakness (drift)
• Speech difficulty (slur)
• Time to act (priority of intervention)

Any one of these symptoms, whether alone or in combination, should be treated as a stroke until proven otherwise. Other symptoms of a watershed stroke include:

• Tilting of the head to one side
• Weakness or paralysis, especially of one leg, and sometimes the arm on the same side of the body
• Vision loss in half of the field of vision
• Seizures (more common with watershed strokes)
• Mood disturbances (e.g. uncontrollable and inappropriate laughing or crying)
• Numbness, paralysis, or weakness on one side of the body or face
• Drooping of the face
• Confusion, forgetfulness, or other changes in mental status
• Changes in consciousness, awareness, or responsiveness
• Difficulty speaking or understanding speech
• Difficulty breathing
• Difficulty walking, loss of balance, or dizziness
• Vision problems, such as decreased pupil size
• Altered breathing
• Problems with balance
• Decreased sensation in the face
• Aphasia or confusion
• Lack of motor movement
• Bilateral visual loss
• Stupor
• Weakness of the proximal limbs, sparing the face, hands and feet

What are the causes?

A watershed stroke is a medical emergency caused by a reduction in blood flow to the brain. It is a type of ischemic stroke, whereby blood clots impair blood flow in the brain. This can be caused by a blockage or restriction in the blood supply to the brain, which is usually located far away from the infarcts.

Watershed strokes are caused by two main factors:

Reduced Blood Flow to the Brain

This can be caused by a heart attack, which affects the heart's ability to pump an adequate blood supply to the brain. This is especially true in people with carotid artery stenosis, which is the narrowing of the main blood vessel that delivers blood from the heart to the brain.

Other causes of reduced blood flow include:

• Hypovolemia, which is a condition that causes a sudden or severe drop in blood pressure due to the loss of body fluids or blood, including severe dehydration and profuse bleeding.
• Sepsis, a severe infection that spreads into the bloodstream and triggers an extreme inflammatory reaction that causes a dramatic drop in blood pressure.

Atherosclerosis

This is a buildup of fats and other debris in the arteries, causing them to narrow and harden. This increases the risk of blood clots forming, which can block blood flow to the brain. Atherosclerosis is associated with the following risk factors:

• High cholesterol
• High blood pressure
• Close biological relatives with cardiovascular disease

Other conditions that can increase the likelihood of blood clots include:

• Being overweight or obese
• Long periods of bed rest or inactivity
• Hormone replacement therapy

Watershed strokes are a concern because they comprise approximately 10% of all ischemic stroke cases. They are rarely fatal but can lead to severe disabilities such as dementia and loss of motor function if not treated promptly.

How is it diagnosed?

A watershed stroke is a medical emergency and requires immediate attention. To diagnose a watershed stroke, doctors will typically start by reviewing the patient's symptoms and medical history. This is followed by physical examinations and imaging tests to determine the cause of the stroke.

Imaging studies used to diagnose a watershed stroke include:

• Computed Tomography (CT) scan: This technology uses multiple X-ray images to create three-dimensional "slices" of the brain. CT scans are particularly effective at identifying hemorrhagic strokes.
• Magnetic Resonance Imaging (MRI) scan: This technology uses magnetic and radio waves to create detailed images of soft tissues. When used with a contrast dye, an MRI can locate areas of blockage or reduced blood flow in the vessels servicing the brain.
• Diffusion-Weighted Imaging (DWI) MRI: This technique is very sensitive for locating areas of ischemic stroke, such as a watershed stroke.
• Doppler ultrasound: This technology uses reflected sound waves to create images of blood vessels and soft tissues. It can detect strokes caused by blood clots and narrowed vessels.

Blood tests may also be ordered to check for risk factors associated with ischemic stroke, such as cholesterol and triglyceride levels, and blood coagulation tests.

What are the treatment options?

Treatment options for a watershed stroke depend on the underlying cause and the severity of the stroke. Here are some of the treatment options available:

• Medications: Tissue plasminogen activator (tPA) is a medication that can be given through a vein to break up blood clots and improve blood flow. It is most effective when administered within 3 hours of the onset of symptoms, but it can be given up to 4.5 hours if deemed beneficial. If tPA is not suitable, blood-thinning medications such as aspirin or clopidogrel (Plavix) can be used to prevent new clots from forming or existing clots from getting bigger.
• Angioplasty or stenting: This procedure involves inserting a thin tube with a balloon or mesh stent to help keep the clogged blood vessel open and improve blood flow.
• Carotid endarterectomy: A surgical procedure to remove atherosclerotic plaque and physically widen the clogged blood vessel, thereby increasing blood flow.
• Percutaneous angioplasty: A less invasive procedure than carotid endarterectomy, where a balloon catheter is inserted and inflated to widen the narrowed blood vessel.
• Intravenous (IV) fluids: If the watershed stroke is caused by severe blood loss or low blood pressure, treatment may focus on maintaining adequate fluid levels and blood pressure with IV fluids and/or a blood transfusion.
• Oxygen therapy: Administering oxygen through a mask or ventilator to support breathing.
• Compression therapy: Using an air-filled sleeve to reduce the risk of blood clots in the legs.
• Rehabilitative therapy: Long-term rehabilitative therapy may include physical, occupational, and speech and language therapies to improve motor function, cognitive impairments, fine motor skills, and speech production.
• Surgical interventions: Endovascular interventions, such as surgical revascularization, can increase blood flow in the affected area, reducing the likelihood of subsequent strokes.
• Nutritional interventions and drug use: Nutritional interventions, such as increased consumption of certain amino acids, antioxidants, B-group vitamins, and zinc, can enhance the recovery of neurocognitive function. Additionally, antiplatelet drugs, anticoagulants, and statin drugs can help prevent blood clots, embolisms, and control risk factors like hyperlipidemia.

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