9.1 Cerebrovascular Disease & Stroke

Cerebrovascular Disease and Stroke

Acute cerebrovascular syndromes require rapid clinical differentiation and immediate triage. Ischemic strokes constitute 85% of cases, with the remainder arising from primary intracerebral hemorrhage (ICH) or subarachnoid hemorrhage (SAH). The initial diagnostic workup must begin with an emergent non-contrast head CT to rule out hemorrhage before administering antithrombotic or thrombolytic therapy.

Intravenous Thrombolysis: Windows and Criteria

Intravenous thrombolysis using recombinant tissue plasminogen activator (tPA), such as alteplase or tenecteplase, is the cornerstone of acute ischemic stroke therapy. The standard therapeutic window is within 3 hours of symptom onset (defined as the last known well time). An extended window of 3 to 4.5 hours is approved for select patients, but excludes individuals older than 80 years, those with severe stroke (NIHSS score > 25), patients taking oral anticoagulants regardless of INR, or those with a combined history of diabetes and prior ischemic stroke.

To safely administer tPA, clinicians must screen for contraindications.

Contraindications to Intravenous tPA Administration

Absolute Contraindications:

• Active internal bleeding
• History of previous intracranial hemorrhage
• Recent intracranial or intraspinal surgery or serious head trauma within 3 months
• Intracranial neoplasm, arteriovenous malformation, or aneurysm
• Bleeding diathesis (platelet count < 100,000/mm³, heparin use within 48 hours with elevated aPTT, or warfarin use with INR > 1.7 or PT > 15 seconds)
• Use of direct thrombin inhibitors or factor Xa inhibitors within 48 hours
• Severe uncontrolled hypertension (systolic BP > 185 mmHg or diastolic BP > 110 mmHg despite antihypertensive therapy)
• Severe hypoglycemia (< 50 mg/dL) that mimics stroke

Relative Contraindications:

• Pregnancy
• Major surgery or severe trauma within 14 days
• Gastrointestinal or urinary tract hemorrhage within 21 days
• Myocardial infarction within 3 months
• Seizure at the onset of stroke symptoms

Blood Pressure Management

Blood pressure targets diverge based on reperfusion eligibility. For patients eligible for intravenous thrombolysis, blood pressure must be reduced to < 185/110 mmHg before drug administration. This is achieved with titratable IV agents like labetalol, nicardipine, or clevidipine. During tPA infusion and for the subsequent 24 hours, blood pressure must remain below 180/105 mmHg to minimize the risk of hemorrhagic transformation. In patients with acute ischemic stroke who are not candidates for thrombolysis, blood pressure should not be treated unless it exceeds 220 mmHg systolic or 120 mmHg diastolic (permissive hypertension). The goal is to lower blood pressure by 15% within the first 24 hours if these thresholds are exceeded, preserving collateral perfusion to the ischemic penumbra.

Mechanical Thrombectomy

For patients with a documented large vessel occlusion (LVO) in the anterior circulation (e.g., internal carotid or middle cerebral artery M1 segment), mechanical thrombectomy is indicated. The standard window is within 6 hours of symptom onset. However, endovascular therapy is approved up to 24 hours for patients showing a mismatch between clinical deficit and infarct volume or between perfusion deficit and ischemic core on advanced imaging (CT perfusion or diffusion-weighted MRI) per DAWN and DEFUSE-3 trials. Mechanical thrombectomy is performed in addition to thrombolysis if the patient is within the tPA window.

Hemorrhagic Stroke

Hemorrhagic stroke requires immediate stabilization and coagulopathy reversal. Intracerebral hemorrhage (ICH) is caused by chronic hypertension or amyloid angiopathy. Management focuses on strict blood pressure control (targeting a systolic pressure of 140 mmHg) and reversing anticoagulation. Warfarin is reversed with IV vitamin K and four-factor prothrombin complex concentrate (PCC). Heparin is reversed with protamine. Dabigatran is reversed with idarucizumab, and factor Xa inhibitors are reversed with andexanet alfa. Neurosurgical intervention is indicated for cerebellar hemorrhages > 3 cm, mass effect, or acute hydrocephalus.

Subarachnoid hemorrhage (SAH) presents as a sudden-onset, 'worst headache of life,' often with meningismus and vomiting, primarily due to rupture of a saccular (berry) aneurysm. A non-contrast head CT is highly sensitive in the first 24 hours. If CT is negative but suspicion remains high, a lumbar puncture must be performed to check for xanthochromia. Once confirmed, the aneurysm must be secured by endovascular coiling or surgical clipping within 24 to 48 hours. Maintain systolic pressure below 160 mmHg to prevent rebleeding, and initiate oral nimodipine (60 mg every 4 hours for 21 days) within 96 hours to prevent delayed cerebral ischemia from vasospasm.

Transient Ischemic Attack & Secondary Prevention

A transient ischemic attack is defined as a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction on neuroimaging. The ABCD² score stratifies 2-day stroke risk: Age >= 60 (1 point), Blood pressure >= 140/90 (1 point), Clinical features (unilateral weakness [2], speech impairment [1]), Duration (>= 60 minutes [2], 10-59 minutes [1]), and Diabetes (1). A score of 4 or higher indicates moderate-to-high risk.

For high-risk TIA (ABCD² >= 4) or minor acute ischemic stroke (NIHSS <= 3), dual antiplatelet therapy (DAPT) with aspirin and clopidogrel is initiated within 24 hours and continued for 21 days. After 21 days, patients transition to single antiplatelet therapy. Secondary prevention also requires initiating high-intensity statin therapy (e.g., atorvastatin 80 mg) targeting an LDL cholesterol < 70 mg/dL, blood pressure optimization, and screening for atrial fibrillation. If atrial fibrillation is detected, oral anticoagulation is indicated. Symptomatic carotid artery stenosis of 70% to 99% warrants carotid endarterectomy (CEA) within 2 weeks of the index event. For asymptomatic patients, CEA is considered for stenosis of 60% to 99% if life expectancy is at least 5 years and the perioperative risk is low.