Acute or chronic arterial hypertension accounts for 40-50% of cases of spontaneous ICH. Rupture of Charcot-Bouchard aneurysms is the usual mechanism in chronic hypertensives.
However:
- arterial rupture may occur in the absence of aneurysm
- 50% of patients with spontaneous ICH have no history or clinical evidence of hypertension
- acute rises in blood pressure may precipitate ICH in situations typically associated with hypertension. For example, drugs such as amphetamines and cocaine; exposure to extreme cold; trigeminal nerve stimulation; following carotid endarterectomy, correction of congenital heart lesions or heart transplantation
Other causes of spontaneous ICH include:
- amyloid angiopathy - accounts for one third of cases in the elderly. Infiltration of amyloid into the arterial walls is associated with weakening of the small vessels in cerebral white matter and the subarachnoid space
- vascular malformations - usually, arteriovascular malformations and cavernous angiomas; common in young normotensives
- bleeding diastheses - thrombocytopenia, leukaemia, haemophilia; anticoagulant therapy, e.g. warfarin
- head injury
Rare associations are:
- systemic administration of fibrinolytics
- reperfusion after brain infarction