Introduction
Stroke is a sudden onset of brain dysfunction, caused by an alteration in cerebrovascular blood supply. It is characterised by:
- Rapid, acute onset – within a few minutes
- Focal neurological defect – almost always some sort of hemiplegia, with/without other focal neurological signs
- If these two instances are true, then there is a 95% chance there is a vascular cause. Be wary if the symptoms get worse over hours/days, as this points to another cause.
Stroke can be a clinical diagnosis – but it is easier to confirm with tests
Classification
- Haemorrhage – 10-20%
- Brain Ischaemia (Infarct) – 80-90%
- Thrombus
- Other type of embolism
- Systemic hypoperfusion
- TIA – Transient Ischaemic Attack
- This is essentially a ‘minor’ stroke. It may present with stroke like symptoms (limb weakness, dysphagia, visual defects), but the clinical effects will completely resolve within 24 hours. They are usually the result of micro emboli, (80%)but not always. Sometimes a mass lesion may mimic a TIA, and other times, they are the result of a temporary reduced blood flow – e.g. with massive postural hypotension, or decreased blood flow through a stenosed artery – which is later compensated for by autoregulation mechanisms.
- Completed Stroke
- The clinical effects have reached their maximum – usually within 6 hours of the onset.
- Stroke in evolution
- Describes the progress of a stroke in the first 24 hours.
- Cerebrovascular accident (CVA)– avoid using this term! Used to be synonymous with ‘Stroke’ but should be no longer used.
Prognosis
- Mortality – 20% in first 2 months, then roughly 10%/year
- <40% of stroke (not TIA) patients make a full recovery
- Drowsyness at presentation has a poor prognosis
Mechanisms of Stroke
- Arterial embolism – from a distant site; e.g. carotids, vertebral or basilar arteries. The embolus will occlude an artery of the brain resulting in infarction. May also come from heart valves in endocarditis.
- Haemorrhage – can be in the cerebrum itself, or also a subarachnoid haemorrhage may cause a similar effect
Uncommon causes
- Venous infarct
- Carotid/vertebral dissection
- Polycythemia
- Fat / air embolism – e.g. in divers
- MS – a demyelinating plaque may act as an embolus
- Mass lesions (e.g. tumour)
- Migraine
- Thrombocythaemia and thrombophilia
- Vasculitis
- Amyloidosis
- Drugs – particularly cocaine and OTC cold remedies that contain vasoconstrictors.