Ischemic stroke (summary)

Last revised by Rohit Sharma on 25 Feb 2024
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.

  • anatomy

  • epidemiology

    • common, accounts for 80% of stroke overall 1

    • 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

    • 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)

    • secondary prevention

      • oral antiplatelet therapy

      • statin

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

  • 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

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