Ischemic Stroke Summary

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Ischemic Stroke Summary

Ischemic Stroke Summary

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Definition

A stroke is the sudden onset focal or global neurological deficit of presumed vascular etiology. Ischemic stroke occurs when blood flow to the brain is blocked.

Epidemiology

Ischemic stroke accounts for approximately 85-90% of all strokes.

Main Types/Causes

Ischemic strokes result from Cerebral infarction. The main mechanisms are:

  • Embolism
  • Thrombosis
  • Other causes: small vessel occlusion and systemic hypoperfusion.

Common Causes (Etiology)

  • Embolic Strokes:
    • Often from cardiac emboli (e.g., in Atrial Fibrillation (AF), Atrial or ventricular thrombi, Rheumatic heart disease, Ventricular aneurysms).
    • Atherosclerotic emboli (Internal carotid artery, Aortic arch).
    • Infectious emboli (bacterial endocarditis).
    • Paradoxical embolism (right-to-left cardiac shunt).
  • Thrombotic Strokes:
    • Related to atherosclerosis.

Major Risk Factors

  • Old Age (>65 y)
  • Hypertension
  • Diabetes mellitus
  • Atrial Fibrillation (AF)
  • Dyslipidemia
  • Smoking
  • Carotid artery stenosis
  • Family history of ischemic stroke
  • Previous stroke/TIA/MI

Typical Clinical Presentation

  • Typically, new symptoms develop over seconds to minutes, or may be present on waking from sleep.
  • Characterized by sudden onset of focal neurologic deficits.
  • Headache, confusion, and nausea may occur.
  • Thrombotic strokes: Usually occurs during sleep, may have "stuttering," intermittent progression.
  • Embolic strokes: Immediate onset of neurologic deficits, usually occurs during waking hours.

Initial Diagnostic Test

Non contrast CT Brain is the most used. It is performed immediately to exclude mimics such as Intracerebral hemorrhage (ICH), Subarachnoid Hemorrhage (SAH) or masses.

Acute Treatment

  • Thrombolysis with recombinant tissue plasminogen activator (rt-PA):
    • Alteplase® is the only FDA-approved medication.
    • Must be given within 3-4.5 hours (golden time window) from the onset of symptoms.
  • Key Contraindications for Thrombolysis:
    • Intracranial hemorrhage (history or presence on imaging).
    • Brain CT demonstrates large infarction.
    • Elevated Blood pressure > 185/110 mm Hg.
    • Recent severe head trauma or neurosurgery (within 3 months).
    • INR >1.7, thrombocytopenia.
    • Recent use of heparin or direct oral anticoagulants.
    • Intracranial neoplasm or aneurysm.
    • Active internal bleeding.
  • Intra-Arterial Mechanical Thrombectomy:
    • Useful in achieving recanalization for large artery occlusion in the anterior cerebral circulation in carefully selected patients.

Secondary Prevention

Aspirin or clopidogrel.

Important Concepts to Understand

  • Stroke is a leading cause of severe neurologic disability in adults.
  • The specific presentation and localization of hemiplegia or other neurological deficits varies according to the site of the lesion and the etiology. Neurologic deficit varies according to cerebral territory affected.

Pathophysiology

Ischemic stroke is caused by focal cerebral ischemia, a localized reduction in blood flow. If ischemia is not reversed, irreversible cellular injury results in cerebral infarction.

Penumbra Concept

An area called a PENUMBRA is tissue at risk of infarction but is still salvageable if re-perfused. The infarct core is tissue that has already infarfected or will infarct regardless of reperfusion. The primary aim of acute intervention is to prevent the penumbra from progressing to established infarct.

Other Imaging

While CT is the initial test to exclude hemorrhage, other imaging studies like MRI brain, CTA/MRA are used for diagnosis and evaluating vessels.

Laboratory Investigations

  • Cardiac biomarkers
  • Fasting lipid profile
  • Uric acid serum level
  • Coagulation parameters (INR, PT, aPTT)
  • Thrombophilia workup is indicated for unexplained stroke in young patients (< 50 y) or with suspicion of a hypercoagulable state.

General Treatment Principles

Include:

  • Stabilizing the patient's general condition (ABC).
  • Giving therapy directed at specific aspects of stroke pathogenesis (recanalization, preventing neuronal death).
  • Treating complications (secondary hemorrhage, edema, seizures, aspiration, infection, DVT, PE).
  • Initiating early secondary prevention.
  • Beginning rehabilitation.

Potential Complications of Thrombolysis

Include bleeding (intracranial and extracranial) and angioedema.

Differential Diagnoses

Include other conditions that can mimic stroke, such as hemorrhage.

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