Which Types of Strokes Are the Most Severe?

Brainstem Strokes, Bilateral Watershed Strokes, Hemorrhagic Strokes and More

All types of stroke are dangerous, but some may cause more severe disability or a rapid progression to death. Below we describe the most common strokes which are known for having the potential to cause severe disability and even death.

Brainstem Strokes:

All of the nerve impulses from the brain that go to the body must go through the brainstem, which is why brainstem strokes can be even more devastating than a spinal cord injury.

The brainstem also controls many of our most important functions, such as breathing, blood pressure, and heart rate, and contains the brain's awareness center, which allows us to stay conscious of the world around us. Therefore depending on the severity of a brainstem stroke, a person may become hemiplegic, paralyzed, or permanently unconscious.

Bilateral Watershed Strokes

Watershed strokes inherit their name from their effect on brain areas commonly referred to as the "watershed areas." These areas receive their blood supply from the farthest end branches of two adjacent vascular territories and require adequate blood pressure to ensure that enough blood is pumped into them at all times. Because of this, watershed areas on both sides of the brain are at high risk of developing ischemia, or lack of blood flow, during times of extremely low blood pressure, which can be caused by extreme dehydration, heart attacks, and sepsis (widespread infections), among others.

Watershed strokes cause severe disability because they affect large muscle groups on both sides of the body (e.g., shoulders and hips). People with advanced carotid stenosis (clogging of the neck arteries) on both sides of the neck are particularly vulnerable to suffering this type of stroke.

Hemorrhagic Strokes

Hemorrhagic strokes are caused by bleeding in the brain.

There are multiple reasons why people develop bleeding inside the brain, but some of the most dangerous ones include:

Hemorrhagic strokes are extremely dangerous because blood in the brain can sometimes lead to dangerous conditions such as hydrocephalus, increased intracranial pressure, and dangerous blood vessel spasms. If not treated aggressively, these conditions can lead to severe brain damage, brain herniation, and even death. This is why even minor episodes of bleeding inside the brain require emergency evaluation by a neurosurgeon.

Large Thrombotic Strokes

Thrombotic strokes are caused by large blood clots which either form inside of, or migrate into, one of the main blood vessels of the brain. These large blood clots are especially dangerous because they can completely stop blood from flowing through the largest, and thus most important, blood vessels in the brain.

The so-called “malignant middle cerebral artery (MCA) syndrome” is an example of such as stroke. Here, the MCA is blocked by a large blood clot causing the massive infarction (i.e., death) of almost one entire side of the brain.

The potent swelling that ensues as a result of such a massive event causes a rapid increase in brain pressure throughout the entire brain. In turn, this high pressure leads to global brain dysfunction, impaired consciousness and very often, to brain herniation and death.

Large thrombotic strokes are commonly the result of medical conditions in which people have a tendency to form blood clots inside the blood vessels of the brain, inside the heart or inside blood vessels that that bring blood into the brain. Such conditions include carotid, vertebral, or basilar artery dissection, and atrial fibrillation.

Brain Death

Sometimes severe strokes cause a condition called brain death


Unfortunately, the symptoms of large strokes can be deceiving, and can originally seem like a simple episode of dizziness or headache. However, certain strokes have a tendency to cause very specific symptoms. For instance, a classic symptom of hemorrhagic strokes (bleeding inside the brain) is the sudden onset of a headache which is typically described by people as the "worst headache of my life."

Large brainstem strokes typically cause double or blurry vision, vertigo, unsteadiness of gait, and/or severe nausea and vomiting. Depending on the part of the brain they affect, large thrombotic strokes can cause a sudden onset of weakness and or numbness on one entire side of the body. Large strokes can also cause sudden loss of consciousness. Needless to say, should you, or someone you know, ever be affected by these symptoms act quickly and call 911 without delay.


J. P. Mohr, Dennis W. Choi, James C. Grotta, Bryce Weir, Phillip A. Wolf Stroke: Pathophysiology, Diagnosis, and Management Churchill Livingstone; 4th edition (2004)

Continue Reading