The Cerebrovascular System and Cerebral Vascular Accidents

Core Concepts

The brain's blood supply and why it is fragile

The anterior (front) circulation via the internal carotid arteries feeds the large frontal, parietal, and temporal lobes. The posterior (back) circulation via the vertebral and basilar arteries feeds the brainstem, cerebellum, and occipital lobes. The circle of Willis ties the systems together, so a blockage in one vessel may be partially compensated by flow from another — but the compensation has limits, and many people have incomplete or variant circles. The brain consumes oxygen and glucose at a high, constant rate, has tiny energy reserves, and is enclosed in the rigid skull. If flow stops, the affected neurons run out of fuel within minutes and begin to die; if a vessel ruptures, the accumulating blood raises pressure inside the skull and compresses tissue. These two failures — too little blood, or blood where it should not be — account for nearly all stroke mechanisms.

What happens when flow is interrupted

When a vessel is blocked, the brain region it serves is starved of oxygen and glucose (ischemia). The most severely affected center of the territory dies quickly and becomes an infarct (dead tissue). Around it lies the penumbra — tissue that is not getting enough blood to function normally but is not yet dead. The penumbra is the target of emergency treatment: if flow is restored in time, much of it can be saved; if not, it joins the infarct. This is why every minute matters and why rapid recognition and transport are the first steps of stroke care.

Ischemic versus hemorrhagic stroke

Ischemic stroke — a blocked vessel — accounts for the majority of strokes. Blockages arise when a clot forms on a diseased vessel wall (thrombosis), when a clot or other material travels from elsewhere in the body (embolism, commonly from the heart in people with atrial fibrillation), or when blood pressure falls so low that flow is inadequate. Hemorrhagic stroke — a ruptured vessel — occurs when a weakened vessel (often from long-standing high blood pressure) bursts within the brain (intracerebral hemorrhage) or when blood collects between the brain and its coverings (subarachnoid hemorrhage, often from a ruptured aneurysm). The two types can present similarly, which is why imaging is essential before any treatment decisions are made — the correct response to a blockage is not the correct response to a bleed. This distinction is covered in depth in the related topics.

Risk factors: modifiable and non-modifiable

Some stroke risk cannot be changed: increasing age, sex, family history, and ethnicity-related predisposition. Many risk factors, however, are modifiable and are the focus of prevention teaching: high blood pressure (the single most important modifiable risk factor), diabetes, high cholesterol, smoking, physical inactivity, unhealthy diet, obesity, atrial fibrillation and other heart disease, and heavy alcohol use. Prevention is a major nursing role — teaching people to manage blood pressure, stop smoking, stay active, and take prescribed medications as ordered can prevent strokes that would otherwise occur years later.

Recognizing stroke: FAST

Public and professional education uses the FAST mnemonic to recognize a probable stroke quickly:

• F — Face: does one side of the face droop when the person smiles?
• A — Arms: does one arm drift down when both are raised?
• S — Speech: is speech slurred or strange, or is the person unable to speak?
• T — Time: if any of these is present, time is critical — activate the emergency response immediately and note when the person was last seen well.

FAST captures the most common signs but not all of them: sudden severe headache, sudden vision loss, sudden dizziness or loss of balance, and sudden confusion can also be stroke symptoms. Any sudden neurologic change should be treated as an emergency until proven otherwise.

The nursing role

The nurse's contributions span the whole journey: prevention teaching in every encounter; recognizing possible stroke and activating the response pathway per institutional protocol; documenting the time the person was last known well; performing standardized neurologic assessments (such as the NIH Stroke Scale) as trained and directed; monitoring the person through the acute phase; and supporting rehabilitation and secondary prevention afterward. Specific treatments, imaging decisions, and medications are directed by the care team under current guidelines; scope of practice varies by setting and license.

Common Confusions