Ischemic stroke (summary)

This is a basic article for medical students and other non-radiologists

Stroke is a clinical diagnosis where an acute neurological deficit follows a cerebrovascular insult. There are two main groups of stroke: ischaemic (>80%) or haemorrhagic (<20%) ¹.

Reference article

This is a summary article; read more in our article on stroke.

Summary

• anatomy
  • cerebral vascular territories
• epidemiology
  • common
  • leading cause of disability
  • third highest cause of mortality in the UK ^2,3
• presentation
  • sudden neurological deficit
  • manifest symptoms depend on the vascular territories involved
  • time of onset is important when considering treatment
• pathophysiology
  • brain parenchyma is deprived of blood flow and therefore oxygen
  • ischaemic
    • arteries occluded by thrombus or embolus
    • temporary loss of blood flow may occur (TIA)
  • cell death results in oedema and swelling
• investigation
  • non-contrast CT head in the first instance
    • exclude haemorrhage or other cause
    • may show hyperdense vessel or evidence of infarction
  • CT angiography
    • some centres use this to identify blockages and assess collaterals when planning clot retrieval
  • MRI
    • less commonly used for acute events, but good for identifying infarcts (especially using DWI sequences)
  • ultrasound
    • carotid Doppler ultrasound in the peri-stroke period to select patients who may benefit from endarterectomy
• treatment
  • thrombolysis or thrombectomy
    • ischaemic strokes less than 4<4.5 hours old
    • depends on the local protocol
    • should be discussed with an acute stroke service
  • stroke patients should be managed in a stroke centre
  • oral antiplatelet therapy
  • medical management of hypertension and risk factor reduction

Imaging

• role of imaging
  • is there evidence of stroke?
  • what is the distribution and severity of the stroke?
  • is there haemorrhagic transformation?
  • is a cause visible, e.g. in situ thrombus?
  • are there contraindications to IV thrombolysis?
  • are there indications for clot-retrieval?
  • is there significant carotid stenosis?
• radiographic features
  • CT
    • parenchymal infarction may not be visible in the acute setting
    • with time, cytotoxic oedema causes reduced density on CT
    • clot within a vessel may be seen as hyperdensity
    • acute haemorrhage will appear dense
  • MRI
    • the most important sequence is the DWI (diffusion sequence)
    • diffusion restriction in this context is highly sensitive for ischaemia
  • angiography (CTA/MRA/DSA)
    • assessment of arterial supply to confirm whether a clot is present
  • perfusion (CT/MRI)
    • assessment of ischaemic/infarcted areas
    • ischaemia may be reversible
  • carotid dopplerDoppler
    • not in the acute setting but usually within two weeks following onset
    • assessment of the neck vessels looking for carotid stenosis
    • if >70% stenosis on affected side, surgery may be offered