Administer IV Alteplase
For a patient with NIHSS 5 and mild left-sided weakness presenting within 4.5 hours, IV alteplase (0.9 mg/kg, max 90 mg) should be administered. This patient meets eligibility criteria and the benefit of treatment outweighs risks, particularly given the time-dependent nature of stroke therapy 1.
Rationale for Treatment
The 2018 AHA/ASA guidelines explicitly recommend IV alteplase for patients within the 3-4.5 hour window, and there is no lower NIHSS threshold that excludes treatment 1. The guideline states treatment should be "initiated as quickly as possible" because "benefit of therapy is time dependent" 1.
Key Eligibility Considerations
Your patient qualifies based on:
- Time window: Within 4.5 hours (Class I, LOE B-R) 1
- NIHSS score: No upper limit restriction for 3-4.5 hour window (only applies if NIHSS >25) 1
- Age: No age restriction for 3-4.5 hour window if ≤80 years 1
The "Mild Stroke" Evidence
While some clinicians hesitate with low NIHSS scores, recent evidence supports treatment:
- Meta-analysis of 5,846 patients with mild stroke (NIHSS ≤5) showed alteplase improved functional outcomes (mRS 0-1: OR 1.12,95% CI 1.02-1.23) 2
- Symptomatic ICH risk was 4.46 times higher but absolute rates remained low 2
- No mortality difference between treated and untreated groups 2
- Subgroup analysis demonstrated best outcomes when treated within 3-4.5 hours 2
A 2025 study specifically addressing patients with NIHSS ≤5 and severe vessel stenosis found alteplase associated with significantly better 90-day outcomes (79.9% vs 56.9% mRS 0-1, adjusted OR 3.17) without increased hemorrhagic complications 3.
Critical Pitfalls to Avoid
Do not withhold treatment based solely on "mild" symptoms. The term "mild" is subjective—left-sided weakness can be functionally devastating even at NIHSS 5. The pooled analysis of major trials shows benefit extends throughout the 0-270 minute window, with adjusted OR for favorable outcome of 1.34 (95% CI 1.06-1.68) at 181-270 minutes 4.
Do not delay for "wait and see." Every 15-minute delay reduces the probability of good outcome. The relationship between onset-to-treatment time and benefit is continuous, with odds of favorable outcome decreasing as time increases (p=0.0269) 4.
Safety Profile
Expected hemorrhagic transformation rates:
- Symptomatic ICH: ~2.2% in the 3-4.5 hour window 5
- Any ICH: ~5.2% (vs 1.0% in controls) 4
- Mortality: No significant increase when treated appropriately 2, 4
Contraindications to Verify
Before administering, confirm:
- Blood pressure: Can be safely lowered to <185/110 mmHg 1
- Blood glucose: >50 mg/dL 1
- CT scan: No hemorrhage, no extensive early ischemic changes (>1/3 MCA territory) 1
- No history of both diabetes AND prior stroke (specific exclusion for 3-4.5 hour window) 1
- Not taking oral anticoagulants (or if taking, INR must be appropriate) 1
Dosing
Administer 0.9 mg/kg (maximum 90 mg) over 60 minutes with 10% as initial bolus over 1 minute 1. Treatment should begin immediately upon eligibility confirmation—every minute counts.