1.10 Acute Insults to the CNS: Stroke/TIA Flashcards
How long does neurological dysfunction have to persist to be considered a stroke?
At least 24 hours
List some non-modifiable risk factors for stroke
- Age
- Race
- Gender
- History of TIA/other conditions
- Genetics
List some modifiable risk factors for stroke
- Things that cause clots (diabetes, heart disease like AF, hypertension)
- Lifestyle factors (diet, exercise, alcohol, smoking)
Which is more common: haemorrhagic or ischaemic stroke?
Ischaemic (~85%)
What are the two kinds of ischaemic stroke?
Thrombotic and embolic
Where in blood vessels is it most common for atherosclerotic plaques to form that cause strokes?
Branches and curves in circulation
What is the most common cause of cerebral infarction?
Cerebral atherosclerosis
What are some common upstream causes of embolic stroke?
- Atrial fibrillation
- Infective endocarditis
- Recent MI
Which tends to have faster onset: thrombotic or embolic stroke?
Embolic
Compare and contrast large vessel disease and small vessel disease
- Usually multiple sites of infarction in SVD
- SVD occurs in smaller vessels (“end of the road”)
- SVD entails much smaller infarct(s)
What structures is small vessel disease most likely to affect?
Deep non-cortical structures: internal capsule, basal ganglia, brain stem
What is the most common risk factor for lacunar strokes in small vessel disease?
Chronic hypertension
Why are the resulting infarctions from small vessel disease called “lacunar” infarctions?
Because the process of healing results in small lake-like cavities
What syndromes can small vessel disease cause?
Think about the origin:
- Pure motor hemiplegia
- Pure sensory hemiplegia
- Dysarthria
What are some factors that influence the size of a cerebral infarction?
- Availability of collateral circulation
- Duration of ischaemia
- Magnitude of reduction in cerebral blood flow
Describe red infarcts. What causes them, and are they haemorrhagic or ischaemic?
- Often caused by embolic events (ischaemic, not haemorrhagic)
- After tissue is reperfused, tiny amounts of blood leak out of damaged vessels, resulting in petechial pattern
Describe pale infarcts. What underlying events are they usually associated with?
- Usually associated with thrombosis (non-haemorrhagic)
- Typical thrombosis -> loss of oxygen to tissue -> infarction
True or false: penumbra tissue can survive for many hours using collateral blood supply
True
Under what circumstances would it not be useful to reperfuse brain tissue with thrombolysis/thrombectomy?
If there is no penumbra, then reperfusion injury may cause more harm than good.
List some factors that can cause secondary injury following stroke
- Inflammation
- Excitotoxicity
- Loss of ion homeostasis
- Mitochondrial damage
- Disruption of blood brain barrier
Give two examples of conditions where reperfusion injury is more likely to occur?
- Embolic stroke
- Long-lasting ischaemic event
Describe the mechanism of reperfusion injury following embolic stroke
- During embolic stroke, the endothelial lining of the vessels may be damaged
- Upon reperfusion, this causes leakage of blood components into brain parenchyma (red infarct)
- Damaged endothelial cells release inflammatory mediators and generate free radicals, both of which lead to increased neuronal death
What is the typical duration of a TIA?
Less than 1hr
In terms of types of tissue damage, what is occurring in a TIA?
Penumbra without infarction
What pathologies can TIAs mimic?
- Migraine
- Hypoglycaemia
- Brain tumours
- Multiple Sclerosis (demyelinating)
Describe the basic difference in pathology between TIA and stroke
Same mechanism, different duration of arterial occlusion
Describe haemorrhagic transformation of ischaemic stroke
- Re-delivery of blood into ischaemic tissue
- Vessels damaged/leaky from ischaemia
- Blood moves into brain parenchyma
What is the most common underlying cause of intracerebral haemorrhage? What about non-spontaneous causes?
Most common: Long-standing hypertension
Non spontaneous: traumatic brain injury
Describe cerebral amyloid angiopathy and its role in haemorrhagic stroke
- Amyloid (protein) deposition in walls of arterioles
- Leads to weakening of walls and potential haemorrhage
Where doe intracerebral haemorrhages occur (be specific)?
Arterioles. Typically in deep non-cortical structures
Describe charcot-bouchard aneurysms
Deposition of lipid-hyaline into walls of small branching arterioles, weakening vessel wall, leading to aneurysms
Aside from typical clinical signs (e.g. hemiparesis/hemiplegia) of stroke, what are some clinical features specific to haemorrhagic strokes?
- Severe headache
- Vomiting
- Rapid loss of consciousness
What is the most common cause of subarachnoid haemorrhage?
Berry aneurysms
What causes berry aneurysms, and where do they occur?
- They occur at branch points in the circle of Willis
- Developmental defects in elastic lamina causes decreased elasticity, leading to aneurysm
How can hypertension worsen berry aneurysms?
By exacerbating deficits in arterial elastic laminae, increasing chance of rupture (like a bursting balloon)
What is the most common consequence of a ruptured berry aneurysm? What is a less common consequence?
Most common: Subarachnoid Haemorrhage
Less common: Intracerebral haemorrhage
What percentage of patients die immediately after a ruptured berry aneurysm?
30%
What are some common clinical features of subarachnoid haemorrhage (SAH)?
- Sudden onset of severe headache (nociceptors in meninges)
- Nausea and vomiting (increased ICP)
- Stiff neck (meningeal irritation)
- Photophobia
- Loss of consciousness
What factors influence the outcome of subarachnoid haemorrhage?
- Haeomorrhage severity
- Age
- Gender
- Time to treatment
Describe 2 mechanisms by which SAH causes hydrocephalus
- Scarring of arachnoid granulations
- Blocking flow of CSF
How is hydrocephalus treated?
Extraventricular drain
True or false: vasospasm occurs most commonly immediately after a SAH
- False
- Takes 4-14 days, most commonly 7 days
Describe the mechanism of vasospasm post SAH
- Blood products released due to haemorrhage
- These products are toxic to the brain, causing them to constrict
- Decreased blood flow to distal parts of brain
List three common complications of haemorrhagic stroke
- Hydrocephalus
- Peri-haematomal oedema
- Vasospasm
Why is it better to administer antithrombolytics (e.g. alteplase) sooner in a stroke patient? (2 reasons)
- Faster medication leads to higher rates of clot removal (and therefore reperfusion)
- As time passes, the clot becomes more resistant to fibrinolysis
True or false: endovascular thrombectomy works when tPA cannot
True; results in improved patient outcomes
What investigations are used to make the diagnosis of stroke?
- CT scan
- MRI
Describe the acute treatment of ICH
- Reduce BP to around 140
- Reverse coagulopathy
What is a hemicraniectomy?
Removal of a part of the skull to allow the brain to bulge out, thus reducing some pressure.
Describe a subacute ischaemic stroke CT presentation
- Hypodensity (darkness) around vascualr territory
- Oedema
- Common haemorrhagic transformation
What characterises chronic brain infarct on CT?
Encephalomalacia (liquefactive necrosis)
Greek word “Malakos” = “soft” ≈ “malaka”
Risk factors for venous sinus thrombosis
- Female
- Hormonal factors (pregnancy, steroids, hyperthyroidism)
- Infection
- Trauma
