IV Thrombolysis Linked to Better Mild Stroke Outcomes
Key Takeaways
- In a propensity-matched Norwegian registry cohort of 3,472 patients with acute ischemic stroke and admission NIHSS scores of 5 or lower, intravenous thrombolysis was associated with a higher rate of excellent 90-day functional outcome than no thrombolysis, with 68.4% versus 61.2% achieving mRS 0–1.
- The association with better 90-day outcome was seen in the NIHSS 2–3 and 4–5 subgroups.
- Favorable secondary functional findings were also reported, overall mortality did not significantly differ, and symptomatic intracerebral hemorrhage occurred in treated patients.
After those exclusions, 1:1 propensity score matching yielded 1,736 intravenous thrombolysis (IVT)-treated patients and 1,736 controls. The primary endpoint was excellent 90-day function, defined as mRS 0–1, and secondary endpoints were mRS 0–2, ordinal mRS shift, and death at 28 and 90 days. Outcome models were adjusted for age and sex, sensitivity analyses also accounted for atrial fibrillation and diabetes, and subgroup analyses by NIHSS 0–1, 2–3, and 4–5 were exploratory.
In matched analyses, 90-day functional outcomes in mild ischemic stroke favored IVT for excellent recovery, with OR 1.39 (95% CI 1.20–1.60) for mRS 0–1 at 90 days. Secondary functional measures moved in the same direction, including better odds of mRS 0–2 at 90 days with OR 1.57 (95% CI 1.29–1.91), and the full modified Rankin Scale distribution also shifted favorably. Baseline NIHSS modified the primary association (p for interaction = 0.03), with significant associations in NIHSS 2–3, OR 1.64 (95% CI 1.32–2.03), and NIHSS 4–5, OR 1.53 (95% CI 1.06–2.21), but not in NIHSS 0–1, OR 1.14 (95% CI 0.89–1.44). Overall mortality did not significantly differ, and the apparent association concentrated toward the upper end of the mild-stroke NIHSS range.
Even after matching, the registry design leaves room for residual confounding and confounding by indication, so the findings describe association rather than causation. The registry also lacked enough clinical detail to sort deficits into disabling and nondisabling categories used in recent trials, and it did not capture early dual antiplatelet therapy. Symptomatic intracerebral hemorrhage (sICH) occurred in 3.7% of IVT-treated patients, but that outcome was recorded only for treated patients, preventing a direct hemorrhage comparison with controls. A 21% loss to follow-up among otherwise eligible patients further bounds interpretation, and these registry data reflect Norwegian practice patterns rather than a direct statement about U.S. care.
Within this matched registry analysis, intravenous thrombolysis was associated with better functional outcomes overall in mild acute ischemic stroke, with the pattern appearing strongest among patients with baseline NIHSS scores of 2–5 rather than 0–1. =
Clinician Questions
Which patients with mild acute ischemic stroke were included in the Norwegian registry analysis of IV thrombolysis?
The analysis covered hospitalized patients in Norway with acute ischemic stroke coded as ICD-10 I63, an admission NIHSS score of 5 or lower, and treatment eligibility within the study’s thrombolysis framework after exclusions. The findings do not directly cover patients who arrived more than 4.5 hours after onset, were using anticoagulants at stroke onset, had wake-up or unknown-onset stroke, underwent thrombectomy, had a pre-stroke mRS score of 3 or higher, or lacked timely follow-up data.
How did the Norwegian registry study define excellent functional outcome after IV thrombolysis for mild stroke?
Excellent functional outcome was defined as a modified Rankin Scale score of 0–1 at 90 days. Secondary functional measures were mRS 0–2 and shift across the full mRS 0–6 range, with follow-up obtained by telephone interview, letter, or in-person outpatient assessment, while vital status came from linkage to the Norwegian Causes of Death Registry.
Why can’t this mild-stroke thrombolysis study compare hemorrhage risk directly between treated and untreated patients?
Symptomatic intracerebral hemorrhage within 36 hours was recorded only for patients who received intravenous thrombolysis, so the analysis cannot provide a direct between-group comparison of hemorrhage risk. In this registry, symptomatic intracerebral hemorrhage meant hemorrhage accompanied by neurologic worsening or death, documented by computed tomography imaging or autopsy.