Types of Stroke

A stroke can affect any part of the brain.

There are many different types and categories of stroke. Types of stroke are described by two main criteria- their location and by the cause of tissue damage in the brain.

Cause of Tissue Damage

Strokes can be caused by a variety of factors. Often the causes can help determine the prognosis as well as the best method of treatment. A stroke may result from a blood clot interrupting blood flow in the brain, by a bleeding blood vessel in the brain, or by low blood flow to a region of the brain.

Blood Clot- Ischemia

A stroke caused by a blood clot is called an ischemic stroke due to the lack of blood supply, and thus oxygen and vital nutrients, to a region of brain tissue. An ischemic stroke may be caused by an embolus, which is a blood clot traveling from another part of the body. It may be caused by a thrombus, usually as a result of cerebrovascular disease. Or, it may be the result of vasospasm, the sudden severe narrowing of a blood vessel in the brain.

Hemorrhagic 

Bleeding of a blood vessel in the brain causes a hemorrhagic stroke. Sometimes the rupture of a brain aneurysm causes bleeding. Extreme changes in blood pressure may trigger the rupture of a brain aneurysm. Sometimes a region of the brain that has been damaged by ischemia can bleed within the first few days after a stroke, causing a secondary hemorrhage.

Watershed stroke 

A watershed stroke is caused by low blood pressure or low blood flow that compromises blood supply to susceptible areas of the brain.

A watershed stroke may occur in regions of the brain that are supplied by tiny arteries.

Location

Strokes are also described by their location because the affected part of the brain corresponds to specific neurological or behavioral deficits.

Cortical stroke

A cortical stroke affects the cerebral cortex, which controls high level processing.

Different parts of the cerebral cortex control different functions. 

Frontal Cortex

A frontal lobe stroke often causes muscle weakness on the opposite side of the body and trouble with decision-making. People with a stroke involving the frontal cortex may display socially inappropriate behavior, paranoia or may regress in maturity. Occasionally, loss of bladder or bowel control may result.

Parietal Cortex

The parietal cortex is involved with integration of sensation and language. People with a parietal stroke often display impaired sensation or trouble with the production of speech.

Occipital cortex

The occipital cortex integrates vision. A stroke in this region may cause complete or partial loss of vision on the opposite side of the occipital region affected.

Temporal cortex

The temporal cortex is involved with hearing and language. People who have had a temporal lobe stroke often have trouble understanding written or spoken language.

Subcortical

A subcortical stroke affects the deeper regions of the brain.

Thalamic

A thalamic stroke usually causes significant sensory deficits on the opposite side of one or more parts of body, even when the stroke affects a relatively small region of the brain.

Internal capsule

A stroke affecting the internal capsule may affect motor or sensory function of one or more parts of the opposite side of the body.

Brainstem

A brainstem stroke can cause a wide variety of signs and symptoms. It may cause weakness, sensory changes, or trouble speaking. A brainstem stroke can affect the movement of the opposite side or the same side of the face or mouth.  People who experience a brainstem stroke may have trouble with eye movements, which often manifests as double vision or blurred vision. Additionally, the brainstem controls breathing and regulates the heart rate. A brainstem stroke may affect vital functions, even when a relatively small area is affected.

Blood Vessel

Some strokes are named after the blood vessel that was blocked or bleeding.The most commonly identified blood vessel in a stroke is the middle cerebral artery, which often causes a large cortical stroke affecting the temporal and parietal lobes.

Sources

Walter G. Bradley DM FRCP, Robert B. Daroff MD, Gerald M Fenichel MD, Joseph Jankovic MD, Neurology in Clinical Practice, 4th Edition, Butterworth-Heinemann, 2003

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