Cerebrovascular accident

Published on 03/03/2015 by admin

Filed under Neurology

Last modified 22/04/2025

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Chapter 1

Cerebrovascular accident

Definition

Cerebrovascular accident (CVA) is a clinical syndrome, of presumed vascular origin, typified by rapidly developing signs of focal or global disturbance of cerebral functions lasting more than 24 hours or leading to death (WHO 1978). If the symptoms of the lesion last less than 24 hours, the terms ‘transient ischaemic attack’ (TIA) or ‘mini stroke’ are used.

Epidemiology

Prevalence

The National UK Audit Office (DH 2006) reported that around 110 000 people suffer a stroke each year, at an overall cost to the economy of around £7 billion.

Age

Although stroke is often deemed an older person’s disease, one in four people are under 65; one in ten are under 55 and 1000 people under 30 have a stroke every year.

Gender

In the population of those aged under 75, men are at greater risk of a stroke than women.

Damage occurs as a result of a blockage of the arteries supplying the brain (S2.8). The most common causes are thrombosis formation or emboli. A thrombus is the formation of a blood clot inside an intact blood vessel which obstructs the flow of blood. This can occur in large vessels such as the internal carotid arteries, vertebral arteries and those that form the circle of Willis (S2.8) or in small deeper vessels when it is termed a lacunar stroke. An embolus occurs when an object (the embolus) migrates from one part of the body (through the circulation) and causes the blockage of a blood vessel in the brain. The main sources of an embolus are a thrombus, fat droplets (following a bone fracture) or air bubbles (cardiac artery bypass graft surgery (CABG), decompression sickness, or intravenous therapy).

Haemorrhage (20% of strokes)

Damage occurs as a result of a bleed from the circulatory system of the brain. Classification is made by location.

Intracranial haemorrhage

Intra-axial

This involves bleeding inside the brain but outside the tissue. For example, an intraventricular haemorrhage which occurs into the ventricles (S2.8) following moderate to severe traumatic brain injuries and is usually associated with other extensive trauma.

Extra-axial

This involves bleeding inside the skull but outside of the brain, that is between the meninges (S2.8). For example:

Epidural haematoma (EDH): A bleed between the dura mater and the skull usually caused by trauma (commonly acceleration–deceleration), although spontaneous haemorrhage is known to occur.

Subdural haematoma (SDH): A bleed within the subdural space often caused by head injury, when fast changing velocities within the skull may stretch and tear small bridging veins across the subdural space (S2.8).

Subarachnoid haemorrhage (SAH): A bleed into the subarachnoid space (S2.8), most often caused by the rupture of an intracranial aneurysm (85%) typically at the junctions or bifurcation of the major cerebral blood vessels. Other causes include non-aneurysmal mid-brain haemorrhage (10%) and vascular abnormalities (arteriovenous malformation and vasculitis) (5%).

Intracerebral haemorrhage

This is a bleed that occurs within the brain tissue itself and is the second most common cause of stroke. It may result from a ruptured aneurysm or arteriovenous malformation (AVM), invasive brain tumour, trauma or may be spontaneous.

Transient ischaemic attack (TIA)

This is thought to occur as a result of a brief interruption to the cerebral blood supply due to thrombosis, or embolism.

Pathology

Thrombosis formation

A thrombus is a pathological process resulting in a blood clot forming within an intact blood vessel (Fig. 1.1). The following conditions lead to thrombus formation. A change in the blood vessel wall following trauma due to hypertension or the formation of an atheroma which leads to alterations in blood flow through the vessel. Simultaneously, a condition needs to exist that causes a change in the blood composition, for example, hypercoagulability disorders, smoking, hyperlipidaemia (raised lipoprotein levels), hypercholesterolaemia or diabetes. This combination of factors leads to aggregation of platelets to produce a platelet plug and the activation of clotting factors, which facilitates thrombus formation.

Figure 1.1 Thrombus formation in an intact blood vessel.

Atheroma formation

An atheroma is an accumulation or swelling in the artery wall often referred to as an atheromatous plaque and the main causal factor in thrombus formation. The disease process which results in atheroma is termed atherosclerosis. The atheroma forms between the endothelium lining and the smooth muscle wall of the artery as a result of the accumulation of white blood cells. Over time, there is a build-up which produces a lipid core surrounded by an older calcified portion.

As previously mentioned, the atheromatous plaque may lead to formation of a thrombus but it is also associated with haemorrhage resulting from aneurysm formation or plaque rupture.

Aneurysm formation

An aneurysm is a localized, blood-filled dilation of a blood vessel (Fig. 1.2) caused by disease or weakening of the vessel wall. Aneurysms most commonly occur in arteries at the base of the brain, e.g. in the circle of Willis. Aneurysm formation is probably the result of multiple factors affecting the arterial wall, however the process is probably initiated by some weakness of the vessel wall and then compounded by the blood itself bombarding the inner surface. In effect, the aneurysm becomes self-perpetuating. Risk factors for an aneurysm include diabetes, obesity, hypertension, smoking, alcoholism, and copper deficiency (which affect the elastin component of the vessel wall).