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.
Aetiology
Ischaemia (80% of strokes)
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).
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.
