Unlike tumours, strokes have abrupt onset. They are caused by a pathological process of the blood vessels. Neuropsychological problems are the most common outcome.
As well as sudden onset, the other most important feature of vascular disease is that it produces warning symptoms that precede the attack. Confusion is common following attack and there is often amnesia, aphasia, and even denial. Strokes are one of the biggest killers in the Westernised world ranking about third as cause of death behind heart disease and cancer. The risk of stroke increases with age. The presence other physical health problems such as heart disease, diabetes, hypertension and vascular disease also increases risk.
Strokes may lead to infarcts where there is resultant dead tissue caused by obstruction of blood vessels supplying blood to a specific area. They can also involve anastomoses where the blood flow from two parallel blood vessels is mingled. Ischemia is the term used to describe an insufficient supply of blood to the brain.
The amount of brain damage caused by a stroke depends on a number of factors:
- The size of the blood vessels which have been blocked
- The health of the remaining blood vessels
- Whether there are any existing lesions of blood vessels
- The location
- Whether onset is rapid or slow
- The type of disorder
- Individual differences
During a stroke ischemia leads to either infarction or haemorrhage. Infarctions outnumber haemorrhage by three to one. Haemorrhage is more likely to result in death with only around a 20% survival rate. Of those who suffer infarction about 75% will survive, and so this type of stroke results in far more survivors with ongoing disabilities. A small percentage of strokes (less than 10%) are caused by aneurisms and angiomas.
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