Stroke for USMLE Step 3 / COMLEX-USA Level 3

• Ischemic Stroke: 85% of strokes. Caused by thrombosis or embolism, leading to a blockage of blood flow to the brain.
• Hemorrhagic Stroke: 15% of strokes. Caused by bleeding into or around the brain tissue.

• Mechanisms:
• Thrombotic: Artery blockage due to atherosclerosis and clot formation.
• Embolic: Clot formed elsewhere (commonly the heart) that travels and lodges in brain arteries.
• Risk Factors: Atrial fibrillation, hypertension, diabetes, smoking, dyslipidemia, prior stroke or TIA.

• Symptoms:
• Sudden onset of neurological deficits such as unilateral weakness, facial droop, speech disturbance, confusion, or severe headache.
• Use of the NIH Stroke Scale to assess severity.

For details regarding stroke patterns, see Stroke Syndromes

• Imaging:
• Non-contrast CT Head: Initial imaging to differentiate ischemic from hemorrhagic stroke.
• MRI Brain: More sensitive for early ischemia and small infarcts.
• Additional Studies:
• CTA or MRA of Head & Neck, or Carotid Ultrasound: To assess for carotid stenosis as a source of emboli.
• Echocardiography: To identify cardiac sources of emboli, such as atrial thrombus.

• Ischemic Stroke:
• Thrombolytic Therapy: IV alteplase (tPA) or IV tenecteplase (TNK) within 4.5 hours of onset, if no contraindications.
• Mechanical Thrombectomy: Considered for large vessel occlusion up to 24 hours from last known well, based on imaging and clinical criteria.
• Blood Pressure Management: Control aggressively only if specific criteria met (e.g., for thrombolytic eligibility or malignant hypertension).

• Antiplatelet Therapy: Aspirin, clopidogrel, or dual antiplatelet therapy for selected cases based on risk stratification.
• Anticoagulation: For atrial fibrillation or other hypercoagulable states.
• Statins: For all patients with ischemic stroke due to atherosclerosis.
• Lifestyle Changes: Smoking cessation, dietary modifications, regular exercise.

• Rehabilitation: Physical, occupational, and speech therapy as needed based on residual deficits.
• Complication Prevention: Manage risk factors for recurrent stroke, screen for depression, and address common post-stroke issues like spasticity and pain.

• Decision-Making in Acute Care: Timing and selection of interventions like tPA and thrombectomy.
• Interprofessional Care: Coordination with rehabilitation specialists, cardiologists, and primary care providers.
• Ethical Considerations: Decisions about life-sustaining treatments in severe stroke, discussion of prognosis and advanced directives.