Cerebral ischemia

 

Cerebral ischemia or brain ischemia, is a condition that occurs when there isn’t enough blood flow to the brain to meet metabolic demand. This leads to limited oxygen supply or cerebral hypoxia and leads to the death of brain tissue, cerebral infarction, or ischemic stroke. It is a sub-type of stroke along with subarachnoid hemorrhage and intracerebral hemorrhage.

There are two kinds of ischemia:

• focal ischemia: confined to a specific region of the brain
• global ischemia: encompasses wide areas of brain tissue.

Symptoms:

The main symptoms of ischemia include:

• impairments in vision, body movement, and speaking
• unconsciousness
• blindness
• problems with coordination
• weakness in the body

Other conditions that may result from brain ischemia are stroke, cardiorespiratory arrest, and irreversible brain damage. The causes of brain ischemia can vary from sickle cell anemia to congenital heart defects.

The term “stroke” can be divided into three categories: brain ischemia, subarachnoid hemorrhage and intracerebral hemorrhage. Brain ischemia can be further sectioned into thrombotic, embolic, and hypoperfusion. Thrombotic and embolic are focal or multifocal in nature while hypoperfusion affects the brain altogether.

Focal cerebral ischemia

Focal cerebral (or brain) ischemia occurs when a blood clot has blocked a cerebral vessel. Focal cerebral ischemia reduces blood flow to the particular brain region, increasing the risk of cell death to that area. It can be either caused by thrombosis or embolism.

Global cerebral ischemia

Global cerebral ischemia occurs when blood flow to the brain is stopped or reduced. This is usually triggered by cardiac arrest. If adequate circulation is restored within a short period of time, symptoms may be brief. However, if a large amount of time passes before restoration, brain damage can be permanent. While reperfusion may be essential to protecting as much brain tissue as possible, it may also lead to reperfusion injury or damage that results from the restoration of blood supply to ischemic tissue.

The symptoms of cerebral ischemia include:

• blindness in one eye
• weakness in one arm or leg
• weakness in one entire side of the body
• dizziness, vertigo, double vision
• weakness on both sides of the body
• difficulty speaking
• slurred speech
• loss of coordination

The symptoms of cerebral ischemia range from mild to severe. Symptoms can last from a few seconds to a few minutes or for extended periods of time. If the brain becomes damaged irreversibly and tissue death occurs, the symptoms may be permanent

Cerebral ischemia is linked to many diseases or irregularities. Patients with compressed blood vessels, plaque buildup in the arteries, blood clots, very low blood pressure as a result of heart attack, congenital heart defects and even sickle cell anemia have a higher tendency to cerebral ischemia in comparison to their healthy counterparts.

Sickle cell anemia may cause cerebral ischemia linked with the irregularly shaped blood cells. Sickle shaped blood cells clot more easily than normal blood cells, obstructing blood flow to the brain.

Compression of blood vessels may also lead to cerebral ischemia, by obstructing the arteries that bring oxygen to the brain. Tumors can be a cause of blood vessel compression.

Plaque buildup in the arteries may also result in ischemia. Even the slightest amount of plaque buildup can cause the narrowing of passageways, affecting that area to become more prone to blood clots. Bigger blood clots can also cause ischemia by blocking blood flow.

A heart attack can also lead to cerebral ischemia due to the association that exists between heart attack and low blood pressure. Extremely low blood pressure usually characterizes the insufficient oxygenation of tissues. Untreated heart attacks slow blood flow enough that blood may start to clot and stop the flow of blood to the brain or other major organs. Cerebral ischemia can result from events other than heart attacks.

Congenital heart defects  can result in cerebral ischemia due to the lack of proper artery formation and connection. Patients with congenital heart defects may also be predisposed to blood clots.

In order to treat cerebral ischemia, doctors may prescribe medications for ischemic stroke. Alteplase is an medication used to acute ischemic stroke. If this medication is administered within four and a half hours, the treatment with tpa improves the probability for a promising outcome over a placebo treatment. Systemic blood pressure should be maintained to restore blood flow to the cerebrum. Anticonvulsants are usually prescribed to avoid seizures as well.

 

Sources : columbianeurosurgery.org