Ischemic stroke (summary)

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

Ischemic stroke is a clinical diagnosis where an acute neurological deficit follows brain infarction.

Reference article

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

Summary

• anatomy

  • cerebral vascular territories

• epidemiology

  • common, accounts for 80% of stroke overall ¹

    • the other 20% is hemorrhagic stroke

  • leading cause of disability

  • third highest cause of mortality in the UK ^2,3

• presentation

  • sudden focal neurological deficit whereby the exact clinical features depend on the specific vascular territory involved

  • time of onset is important when considering treatment

• pathophysiology

  • brain parenchyma is deprived of blood flow and therefore oxygen, usually due to an artery being occluded by thrombus or embolus

  • cell death results in edema and swelling

  • common causes include atrial fibrillation, carotid artery stenosis, and cervical artery dissection

• investigation

  • non-contrast CT head in the first instance

    • exclude hemorrhage or other cause

    • may show hyperdense vessel or evidence of infarction

  • CT angiography

    • used to identify the occluded artery

    • may identify the cause of the ischemic stroke, e.g. carotid stenosis, dissection, intracranial atherosclerotic disease

  • CT perfusion

    • used in some centers to identify infarcted brain ("core") and brain tissue at risk of infarcting ("penumbra")

  • MRI

    • less commonly used acutely in most centers, but is the best imaging modality for identifying infarcts (especially using the DWI sequence)

  • ultrasound

    • carotid Doppler ultrasound in the peri-stroke period to identify patients with carotid stenosis and then select patients who may benefit from endarterectomy

  • cardiac investigations are also performed to determine evidence of atrial fibrillation, which is an important cause of ischemic stroke

• treatment

  • all patients with stroke should be managed in a dedicated stroke unit where possible, with input from the local stroke service

  • acute treatment

    • intravenous thrombolysis

      • for ischemic strokes <4.5 hours old, but can be given up to 9 hours or in wake-up situations in certain circumstances

      • depends on the local protocol

    • endovascular clot retrieval (mechanical thrombectomy)

      • for ischemic stroke due to large vessel occlusion

  • secondary prevention

    • oral antiplatelet therapy

    • statin

    • medical management of hypertension, diabetes mellitus, and other risk factors

Imaging

• role of imaging

  • is there evidence of ischemic stroke?

  • what is the distribution and severity of the stroke?

  • is there hemorrhagic transformation?

  • is a cause visible, e.g. in situ thrombus?

  • are there contraindications to intravenous thrombolysis?

  • are there indications for endovascular clot retrieval?

  • is there significant carotid stenosis?

• radiographic features

  • CT

    • parenchymal infarction may not be visible in the acute setting

    • with time, cytotoxic edema causes reduced density on CT

    • clot within a vessel may be seen as hyperdensity

    • acute hemorrhage will appear dense

  • MRI

    • the most important sequence is the DWI (diffusion sequence)

    • diffusion restriction in this context is highly sensitive for ischemia

  • angiography (CTA/MRA/DSA)

    • assessment of arterial supply to confirm whether a clot is present

  • perfusion (CT/MRI)

    • assessment of core and penumbra

  • carotid Doppler

    • not in the acute setting but usually within two weeks following stroke

    • assessment of the neck vessels looking for carotid stenosis

    • if >70% stenosis on affected side, surgery may be offered