Acute ischemic stroke

Acute Ischemic Stroke (AIS) is a condition characterized by the sudden loss of blood circulation to an area of the brain, resulting in a corresponding loss of neurologic function. This medical emergency is caused primarily by blockages (such as blood clots) in arteries leading to the brain, leading to ischemia - the reduction of blood flow that can cause damage or death to brain cells.

Etiology

The primary cause of an acute ischemic stroke is the obstruction of blood flow to the brain due to a clot. These clots can form in situ (within the brain's arteries) or travel from elsewhere in the body, a process known as embolism. Major risk factors include Atherosclerosis, Atrial Fibrillation, high blood pressure, smoking, diabetes, obesity, and high cholesterol levels.

Pathophysiology

During an AIS, the sudden reduction in blood flow results in deprivation of oxygen and nutrients to brain tissue. This ischemia can lead to the death of neurons and other cells within minutes. The area directly affected by the lack of blood flow undergoes necrosis, forming the core of the infarct. Surrounding this core is the ischemic penumbra, a zone of potentially salvageable tissue that is at risk of further damage without prompt treatment.

Symptoms

Symptoms of an acute ischemic stroke can vary but often include sudden numbness or weakness, especially on one side of the body, confusion, trouble speaking or understanding speech, visual disturbances, difficulty walking, dizziness, and loss of balance or coordination. The severity of symptoms depends on the location and extent of the brain affected.

Diagnosis

Diagnosis of AIS involves a combination of clinical assessment and imaging. The National Institutes of Health Stroke Scale (NIHSS) is commonly used to evaluate the severity of the stroke. Imaging tests such as Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI) are crucial for confirming the presence of a stroke and for distinguishing between ischemic and hemorrhagic stroke.

Treatment

Immediate treatment for AIS focuses on restoring blood flow to the affected area of the brain. This can be achieved through the use of thrombolytic agents, which dissolve the blood clot causing the stroke. Intravenous tissue plasminogen activator (tPA) is the most commonly used thrombolytic medication and is most effective when administered within a 4.5-hour window from the onset of symptoms. In some cases, mechanical thrombectomy, a procedure to physically remove the clot, may be performed.

Prevention

Preventive measures for acute ischemic stroke include controlling high blood pressure, managing diabetes, quitting smoking, maintaining a healthy weight, and regular physical activity. For individuals with atrial fibrillation, anticoagulant medications may be prescribed to reduce the risk of clot formation.

Prognosis

The prognosis for individuals with AIS varies widely and depends on the stroke's size, location, and the timeliness of treatment. Early intervention can significantly improve outcomes, reducing the extent of brain damage and enhancing recovery prospects.

See Also

• Stroke
• Cerebrovascular Accident
• Thrombolysis
• Brain Ischemia

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