Cerebral Stroke

Cerebral stroke is an acute episode of neurological dysfunction caused by focal injury to the brain, spinal cord, or retina from a vascular cause - either blockage of blood flow (ischaemic stroke) or bleeding (haemorrhagic stroke). It is a defining example of cerebrovascular pathology, in which interruption of the cerebral circulation produces rapidly evolving, region-specific loss of function.

Definition

Stroke is an episode of acute neurological dysfunction caused by focal infarction or haemorrhage of the central nervous system of vascular origin; ischaemic stroke results from occlusion of a supplying artery, and haemorrhagic stroke from rupture of a blood vessel into or around brain tissue, as formalised in the updated 21st-century definition of stroke.

Scope

The entry covers the pathological basis of stroke as a cerebrovascular disease: the distinction between ischaemic and haemorrhagic mechanisms, the concept of infarction and the ischaemic penumbra, and the morphological evolution of a cerebral infarct. It is a reference and educational overview and does not provide acute management or treatment instructions.

Core questions

• What distinguishes ischaemic from haemorrhagic stroke at the level of mechanism and tissue injury?
• What is the ischaemic penumbra, and why does it matter for the extent of irreversible damage?
• How does a cerebral infarct evolve morphologically over time?

Key concepts

• Ischaemic stroke (infarction)
• Haemorrhagic stroke (intracerebral and subarachnoid haemorrhage)
• Ischaemic penumbra
• Cerebral infarction and liquefactive necrosis
• Focal neurological deficit
• Cerebral atherosclerosis and cardioembolism
• Vascular territory and selective vulnerability

Mechanisms

In ischaemic stroke, occlusion of a cerebral artery - by local thrombosis, often on an atherosclerotic plaque, or by an embolus, frequently of cardiac origin - deprives the supplied territory of oxygen and glucose. A densely ischaemic core undergoes rapid infarction, surrounded by a penumbra of hypoperfused but still-viable tissue that may be salvaged or progress to infarction depending on the duration and severity of ischaemia. The infarcted brain undergoes liquefactive necrosis, with subsequent removal of dead tissue by macrophages and reactive gliosis at the margins, leaving a cystic cavity. In haemorrhagic stroke, rupture of a vessel - for example from hypertensive small-vessel disease, a ruptured aneurysm, or vascular malformation - allows blood to enter brain parenchyma or the subarachnoid space, causing injury through mass effect, raised intracranial pressure, and the toxic effects of extravasated blood.

Clinical relevance

Stroke produces sudden, focal neurological deficits whose pattern reflects the vascular territory affected, and the underlying pathology is central to understanding cerebrovascular disease. This entry describes the disease process for reference and education; it is not a guide to acute diagnosis or treatment, which are addressed in clinical guidelines.

Epidemiology

Stroke is among the leading causes of death and of acquired adult disability worldwide and is one of the largest contributors to the global burden of neurological disease. Ischaemic stroke accounts for the majority of cases, with intracerebral and subarachnoid haemorrhage making up the remainder, and incidence rises steeply with age.

Evidence & guidelines

The contemporary definition of stroke is set out in an American Heart Association/American Stroke Association statement, and the early management of acute ischaemic stroke is governed by consensus clinical guidelines. Burden estimates derive from the Global Burden of Disease neurological-disorders analyses.

History

The clinical phenomenon was long described under the term apoplexy, and the vascular basis of stroke - distinguishing infarction from haemorrhage - was clarified through pathological correlation over the nineteenth and twentieth centuries. The concept of a salvageable ischaemic penumbra and the modern tissue-based definition of stroke reflect later integration of pathology with imaging.

Debates

Should stroke be defined by clinical deficit duration or by tissue injury?

Traditional definitions relied on the persistence of clinical deficits for more than 24 hours, but the updated 21st-century definition shifts emphasis to evidence of central nervous system infarction or haemorrhage, recognising that imaging can demonstrate tissue injury even when symptoms are transient.

Seminal works

• sacco-2013
• donnan-2008

Frequently asked questions

What is the difference between ischaemic and haemorrhagic stroke?

Ischaemic stroke is caused by blockage of a cerebral artery that cuts off blood supply and leads to infarction, whereas haemorrhagic stroke results from rupture of a blood vessel with bleeding into or around the brain. They share the feature of a vascular cause but differ in mechanism and tissue injury.

What is the ischaemic penumbra?

The penumbra is the rim of hypoperfused but still-viable brain tissue surrounding the densely ischaemic infarct core; whether it survives or progresses to infarction depends on the severity and duration of reduced blood flow. This is a descriptive concept, not treatment advice.