Ischemic stroke

Background

• Acute ischemia of brain parenchyma due to arterial occlusion
• Most common type of stroke (~87% of all strokes)
• 5th leading cause of death in the US; leading cause of long-term disability
• "Time is brain": ~1.9 million neurons lost per minute of untreated large vessel occlusion
• IV tPA window: up to 4.5 hours from last known well
• Thrombectomy window: up to 24 hours in select patients with large vessel occlusion (LVO) and favorable imaging

Etiology

• Large artery atherosclerosis (~25%): carotid stenosis, intracranial atherosclerosis
• Cardioembolism (~25%): atrial fibrillation (most common), valvular disease, LV thrombus
• Small vessel disease (lacunar, ~20%): lipohyalinosis of penetrating arteries (hypertension)
• Other determined (~5%): dissection, hypercoagulable state, vasculitis, sickle cell
• Cryptogenic/undetermined (~25%)

Clinical Features

• Sudden onset focal neurologic deficit (maximal at onset or rapidly progressive)
• Last known well (LKW) time is the most critical historical datapoint

Anterior Circulation (Carotid Territory)

• MCA stroke (most common): contralateral face/arm > leg weakness, hemisensory loss, aphasia (dominant hemisphere) or neglect (nondominant), gaze deviation toward lesion
• ACA stroke: contralateral leg > arm weakness, urinary incontinence, abulia
• ICA occlusion: entire MCA territory ± ACA territory

Posterior Circulation (Vertebrobasilar)

• PCA stroke: homonymous hemianopia, memory deficits, alexia without agraphia
• Basilar occlusion (emergency): bilateral motor/sensory deficits, cranial nerve palsies, coma, locked-in syndrome
• Cerebellar stroke: ataxia, vertigo, nystagmus, headache → can cause brainstem compression (surgical emergency)
• HINTS exam to distinguish cerebellar/brainstem stroke from peripheral vertigo

Mimics (Important to Recognize)

• Hypoglycemia (always check glucose), seizure with Todd paralysis, Bell palsy, migraine with aura, conversion disorder, intracranial mass

Differential Diagnosis

• Hemorrhagic stroke (cannot distinguish clinically — MUST image)
• Hypoglycemia
• Postictal (Todd) paralysis
• Complicated migraine
• Bell palsy
• Intracranial mass/abscess
• Psychogenic/conversion
• Drug toxicity

Evaluation

Critical First Steps

• Blood glucose (POC STAT — hypoglycemia mimics stroke and must be corrected)
• Non-contrast CT head (rule out hemorrhage — ONLY test required before tPA)
• CT angiography (CTA) head and neck: identify large vessel occlusion (LVO) for thrombectomy candidacy
• CT perfusion (CTP): ischemic penumbra assessment for extended-window cases

NIHSS Score

• Standardized neurologic exam scoring (0-42)
• Correlates with stroke severity and helps guide treatment decisions
• NIHSS ≥6: consider LVO until proven otherwise; higher scores = worse prognosis
• Use the NIHSS calculator for scoring

Additional Studies

• ECG: atrial fibrillation, MI
• CBC, BMP, coagulation studies (PT/INR, PTT)
• Troponin (concurrent cardiac events)
• A1c, lipid panel (risk factor assessment, not urgent)
• Echocardiography (identify cardioembolic source)

Do NOT Delay tPA for:

• Labs (except glucose)
• CTA/CTP
• Complete history
• Only glucose and NCCT are needed before tPA

Management

IV Alteplase (tPA)

• Indicated within 4.5 hours of last known well (LKW)
• Dose: 0.9 mg/kg IV (max 90 mg):
  • 10% as bolus over 1 minute
  • Remaining 90% infused over 60 minutes
• Extended window (3-4.5 hours): additional exclusions apply (age >80, NIHSS >25, oral anticoagulant use, history of DM + prior stroke)
• Key contraindications:
  • Active internal bleeding, recent intracranial surgery/trauma (3 months)
  • Intracranial hemorrhage on CT
  • SBP >185 or DBP >110 (lower BP first)
  • Platelets <100,000, INR >1.7, aPTT elevated
  • Blood glucose <50 mg/dL
• Tenecteplase (0.25 mg/kg IV bolus, max 25 mg): emerging alternative, single-bolus dosing, favorable in LVO

Endovascular Thrombectomy

• Standard window: within 6 hours of LKW for anterior LVO
• Extended window: up to 24 hours with favorable perfusion imaging (DAWN and DEFUSE 3 trials)
• Target vessels: ICA, M1, and sometimes M2 MCA, basilar artery
• NNT = ~2.6 for reduced disability (one of the most effective treatments in medicine)
• Thrombectomy is ADDITIVE to IV tPA — give tPA first, do not delay for thrombectomy

Blood Pressure Management

• If tPA candidate: lower BP to <185/110 before tPA; maintain <180/105 for 24h after
• If NOT receiving tPA: permissive hypertension up to 220/120 (avoid aggressive lowering)
• Post-thrombectomy with successful recanalization: target SBP <140 (BP-TARGET trial)
• Preferred agents: labetalol, nicardipine

General Management

• NPO until swallow assessment (aspiration risk)
• Aspirin 325 mg PO/PR within 24-48 hours (if no tPA in past 24h)
• DVT prophylaxis (SCDs immediately; chemical prophylaxis after 24-48h)
• Glucose management: target 140-180 mg/dL; treat hypoglycemia; avoid hyperglycemia
• Avoid fever (antipyretics for temp >38°C)
• Avoid hypotension (maintain adequate cerebral perfusion)

Disposition

• All acute stroke patients: admit to stroke unit/neuro ICU
• Transfer to comprehensive stroke center if LVO identified and thrombectomy capability unavailable
• Do NOT delay tPA for transfer — give tPA at presenting hospital then transfer ("drip and ship")
• Neurology and neurointerventional consultation
• Start workup for stroke etiology (echo, prolonged cardiac monitoring, vascular imaging)

See Also

• Hemorrhagic stroke
• Subarachnoid hemorrhage
• Transient ischemic attack
• NIHSS calculator
• Atrial fibrillation
• Stroke mimics

References

• Goyal M, et al. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis. Lancet. 2016;387(10029):1723-1731. PMID 26898852
• Hacke W, et al. Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke (ECASS III). N Engl J Med. 2008;359(13):1317-1329. PMID 18815396