A stroke describes a sudden onset focal neurological deficit of vascular aetiology, with symptoms lasting >24 hours (or with evidence of infarction on imaging)
Aetiology
Stroke can be categorized into two types: ischaemic, accounting for about 85% of all strokes, and haemorrhagic, accounting for the remaining 15%
Strong risk factors include: older age, male sex, family history of haemorrhagic stroke, haemophilia, cerebral amyloid angiopathy/hypertension, anticoagulation therapy, iliccit sympathomimetic drugs (such as cocaine and amphetamines), vascular malformations (especially in younger patients)
Weaker risk factors: NSAIDs, heavy alcohol use, thrombocytopenia
Pathophysiology
Ischaemic stroke (80-85%)
Ischaemic stroke occurs when blood supply in a cerebral vascular territory is reduced secondary to stenosis or complete occlusion of a cerebral artery
Thrombotic - clot blocking artery at site of occlusion
The clot can be in a small inter-cranial vessel, or a larger vessel e.g. carotid artery stenosis
Embolic - clot blocking artery has travelled from elsewhere
Atheroembolism - platelet rich embolism which formed on an atherosclerotic plaque
Cardioembolism - clotting factor rich embolism which formed in the heart, usually left atrium
Rare causes of ischaemic stroke include primary vascular causes (such as vasculitis and arterial dissection) and haematological causes (prothrombotic states)
Haemorrhagic stroke (15-20%)
Bleeding occurs inside or around brain tissue due to rupture of a blood vessel
Most commonly caused by hypertension
Can also be caused by a weakened blood vessel wall e.g. aneurysm, vasculitis, Moya Moya disease