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PH-NE01

Ischaemic stroke

How a blocked cerebral artery starves the brain of oxygen, why tissue dies in a core but can survive for a time in the penumbra, and why the deficit depends on which artery is blocked.

By the end, you can

  • Describe the arterial supply of the brain, the cerebral arterial circle and the territories of the anterior, middle and posterior cerebral arteries.
  • Distinguish thrombotic, embolic and small-vessel (lacunar) causes of ischaemic stroke.
  • Explain how energy failure leads to excitotoxic neuronal death, and the difference between the ischaemic core and the penumbra.
  • Relate the deficits of a stroke to the arterial territory affected.
  • Recognise how a cerebral infarct looks from hours to months, the TOAST and Bamford classifications and the imaging tests and time windows of stroke, and explain how thrombolysis, thrombectomy, antiplatelets, statins and anticoagulation act on the mechanism.

What it is

An ischaemic stroke is the sudden loss of brain function caused by blockage of an artery supplying the brain, with infarction (death) of the tissue it supplies. A transient ischaemic attack (TIA) causes similar symptoms that resolve without infarction. Ischaemic strokes make up most strokes; haemorrhagic stroke is a different process.

3 types to tell apart
Thrombotic (large artery)
A thrombus forms on an atherosclerotic plaque in a large artery, such as the internal carotid or basilar artery, and blocks it where it lies.
Embolic
A clot or fragment formed elsewhere (often the left atrium in atrial fibrillation, or a carotid plaque) travels and lodges in a cerebral artery.
Small-vessel (lacunar)
A small deep penetrating artery is blocked, usually after years of hypertension or diabetes, causing a small infarct (lacune) in deep structures such as the internal capsule.

US spelling: ischaemic → ischemic, haemorrhagic → hemorrhagic.

Normal function

How the brain is supplied with blood

The brain is about 2% of body weight but receives roughly 15% of the cardiac output and uses about a fifth of the body’s oxygen at rest. Neurones store almost no glucose or oxygen, so they depend on continuous flow from minute to minute.

Blood arrives through two in front and two behind, which join to form the . On the base of the brain these are linked by the and into the cerebral arterial circle (of Willis), which can redistribute flow if one supply narrows slowly. Its shape varies, and in many people it is incomplete.

Three pairs of arteries leave the circle. The supply the medial surface of the frontal and parietal lobes; the supply most of the lateral surface and, through small deep branches, the basal nuclei and internal capsule; the supply the occipital lobe and the underside of the temporal lobe.

Point to it on the model