Stroke Quiz: Mechanisms and Types

Stroke (Cerebrovascular Accident)

• Stroke is an acute neurological deficit caused by a vascular disorder that injures brain tissue.
• It's a leading cause of mortality and morbidity in the United States.

Cerebral Circulation

• Blood flow to the brain is supplied by two internal carotid arteries (anteriorly) and vertebral arteries (posteriorly).
• The internal carotid artery branches into smaller arteries including ophthalmic, posterior communicating, choroidal, anterior cerebral, and middle cerebral arteries.
• The two vertebral arteries join to form the basilar artery, supplying the medulla, pons, cerebellum, midbrain, and caudal diencephalon.
• The Circle of Willis, an anastomosis of arteries, allows continued circulation if a main vessel is blocked.

Types of Stroke

• Two main types: ischemic and hemorrhagic stroke.
• Ischemic stroke (70-80% of all strokes): Caused by an interruption of blood flow in a cerebral vessel, usually due to thrombosis or emboli.
• Hemorrhagic stroke: Caused by bleeding into brain tissue, often from a ruptured blood vessel. It usually results from hypertension, aneurysms, or head trauma, and has a higher fatality rate than ischemic strokes.

Atherosclerosis Stroke

• A type of ischemic stroke where cholesterol plaque buildup blocks blood flow in an artery.

Hemorrhagic Stroke

• Spontaneously occurring hemorrhage into the brain tissue results in edema, compression of brain contents, and adjacent blood vessel spasm.
• Advancing age and hypertension are common causes. Others include aneurysms, trauma, and drugs.
• Symptoms commonly include sudden onset, vomiting, headache, and contralateral hemiplegia (paralysis on opposite side of the body).
• The hemorrhage, along with edema, exerts great pressure on brain substance causing a rapid progression to coma and often death.

Risk Factors for Stroke

• Age
• Sex
• Race
• Heart disease
• Hypertension
• High cholesterol levels
• Cigarette smoking
• Prior stroke
• Diabetes mellitus
• Excess alcohol use
• Sedentary lifestyle

Ischemic Stroke

• Caused by cerebrovascular obstruction due to thrombosis or emboli.
• Common classification system identifies five subtypes, including large artery atherosclerotic disease (both thrombosis & emboli), small vessel/penetrating artery disease (lacunar stroke), cardiogenic embolism, cryptogenic stroke (undetermined cause), and unusual causes.
• Example causes are 20% large artery atherosclerotic disease (both thrombosis and arterial embolus), 25% small vessel or penetrating artery disease (lacunar stroke), 20% cardiogenic embolism and 30% cryptogenic stroke. A further 5% may be due to unusual causes such as migraine.

Ischemic Penumbra

• During a stroke, a central core of dead/dying cells is surrounded by an ischemic area of minimally perfused cells (penumbra, or halo).
• Cell survival in the penumbra depends on the return of adequate circulation and the volume of toxic products released by neighboring dying cells.
• Oligemia (hypo-perfused parenchyma) with cerebral blood flow (CBF) between 22-60 mL/100 g/min is above the ischemic threshold of 22 mL/100 g/min.
• The core represents irreversibly injured tissue; diffusion abnormality reflects irreversibly injured tissue; perfusion abnormality represents viable threatened brain tissue surrounded by benign oligemia.

Transient Ischemic Attack (TIA)

• Ischemic cerebral neurologic deficits lasting less than 24 hours.
• A temporary disturbance in cerebral blood flow.
• A TIA is analogous to angina in relation to heart attack.
• TIAs are important because they may provide a warning or signal of impending stroke.
• Often the risk of stroke after a TIA is maximal immediately after the event.

Signs of Stroke (in Men and Women)

• Numbness/weakness (face, arm, leg), especially on one side of the body.
• Confusion/trouble speaking or understanding speech.
• Trouble seeing in one or both eyes.
• Trouble walking, dizziness, or balance problems.
• Severe headache with no known cause.

FAST Assessment for Stroke

• Face: Ask the person to smile. Does one side of the face droop?
• Arms: Ask the person to raise both arms. Does one arm drift downward?
• Speech: Ask the person to repeat a simple phrase. Is the speech slurred or strange?
• Time: If you see any of these signs, call 9-1-1 right away.