this condition is a common cause of death and disability, especially in older people. Predisposing factors elude: hypertension atheroma cigarette smoking diabetes mellitus.
It occurs when blood flow to the brain is suddenly interrupted, causing hypoxia. The effects include paralysis of a limb or one side of the body and disturbances of speech and vision. The nature and extent of damage depend on the size and location of the affected blood vessels. The main causes are cerebral infarction (approx. 85%) and spontaneous intracranial haemorrhage (15%).
Cerebral infarction
This is caused by atheroma complicated by thrombosis or blockage of an artery by an embolus from e.g infective endocarditis. The cerebral hemispheres are usually affected. When complete recovery occurs within 24 hours, the event is called a transient ischaemic attack (TIA). Recurrence or completed stroke associated with permanent damage may follow.
spontaneous intracranial haemorrhages
the haemorrhage may be into the subarachnoid space or intracerebral . It is commonly associated with an aeurysm or hypertension. In each case the escaped blood may cause arterial spasm, leading to ischaemia, infarction, fibrosis (gliosis) and hypoxic brain damage.
A severe haemorrhage may be instantly fatal while repeated small haemorrhages have a cumulative effect in extending brain damage (multi-infarct dementia).
Intracerebral haemorrhage
Prolonged hypertension leads to the formation of multi-ple microaneurysms in the walls of very small arteries in the brain. Rupture of one or more of these, due to continuing rise in blood pressure, is usually the cause of intracerebral haemorrhage. The most common sites are branches of the middle cerebral artery in the region of the internal capsule and the basal ganglia. Severe haemorrhage. This causes compression and destruction of tissue, a sudden increase in ICP and dis-tortion and herniation of the brain. Death follows when the vital centres in the medulla oblongata are dam-aged by haemorrhage or if there is coning due to increased ICP.
Less severe haemorrhage. This causes paralysis and loss of sensation of varying severity, affecting the side of the body opposite the haemorrhage. If the bleeding stops and does not recur a fluid-filled cyst develops, i.e. the haematoma is walled off by gliosis, the blood clot is gradually absorbed and the cavity filled with tissue exudate. When the ICP returns to normal some function may be restored, e.g. speech and movement of limbs.
Subarachnoid haemorrhage This is usually due to rupture of a berry aneurysm on one of the major cerebral arteries, or bleeding from a congenitally malformed blood vessel . The blood may remain localised but usually spreads in the subarachnoid space round the brain and spinal cord, causing a general increase in ICI' without distortion of the brain . The irritant effect of the blood may cause arterial spasm, leading to ischaemia, infarc-tion, gliosis and the effects of localised brain damage. It occurs most commonly in middle life, but occasionally in young people owing to rupture of a malformed blood vessel. This condition is often fatal or results in perma-nent disability.
Intracerebral haemorrhage
Prolonged hypertension leads to the formation of multi-ple microaneurysms in the walls of very small arteries in the brain. Rupture of one or more of these, due to continuing rise in blood pressure, is usually the cause of intracerebral haemorrhage. The most common sites are branches of the middle cerebral artery in the region of the internal capsule and the basal ganglia. Severe haemorrhage. This causes compression and destruction of tissue, a sudden increase in ICP and dis-tortion and herniation of the brain. Death follows when the vital centres in the medulla oblongata are dam-aged by haemorrhage or if there is coning due to increased ICP.
Less severe haemorrhage. This causes paralysis and loss of sensation of varying severity, affecting the side of the body opposite the haemorrhage. If the bleeding stops and does not recur a fluid-filled cyst develops, i.e. the haematoma is walled off by gliosis, the blood clot is gradually absorbed and the cavity filled with tissue exudate. When the ICP returns to normal some function may be restored, e.g. speech and movement of limbs.
Subarachnoid haemorrhage This is usually due to rupture of a berry aneurysm on one of the major cerebral arteries, or bleeding from a congenitally malformed blood vessel . The blood may remain localised but usually spreads in the subarachnoid space round the brain and spinal cord, causing a general increase in ICI' without distortion of the brain . The irritant effect of the blood may cause arterial spasm, leading to ischaemia, infarc-tion, gliosis and the effects of localised brain damage. It occurs most commonly in middle life, but occasionally in young people owing to rupture of a malformed blood vessel. This condition is often fatal or results in perma-nent disability.
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