MRI-based intravenous thrombolysis in stroke patients with unknown time of symptom onset

Background: Currently, stroke patients with unknown time of symptom onset (UTOS) are excluded from therapy with intravenous tissue Plasminogen Activator. We hypothesized that MRI-based intravenous thrombolysis is safe in UTOS. Methods: We analyzed radiological and clinical data as well as outcomes of stroke patients (including UTOS) who received intravenous thrombolytic therapy after MRI. Results: Compared to patients with known time of symptom onset (n = 131), UTOS (n = 17) were older (81, 71-88 vs. 75 years, 66-82, P = 0.03), had a longer median time between last-seen-well and thrombolysis (12.3 h, IQR 11.5-15.2 h vs. 2.1 h, 1.8-2.8 h, P < 0.01), had a longer median door-to-needle time (86 min, 49-112 vs. 60 min, 49-76, P = 0.02), and a higher rate of arterial obstruction on MR-angiography (82.4% vs. 56.5%, P = 0.04). No symptomatic intracerebral hemorrhage occurred in UTOS. After 3 months, there was no significant difference between groups concerning good functional outcome (modified Rankin Scale 0-2; 35.3% vs. 49.6%, P = 0.26) or mortality (0% vs. 15.3%, P = 0.08). In multivariate analyses including age, gender, baseline NIHSS, and atrial fibrillation UTOS did not have an independent effect on good functional outcome after 3 months (OR 1.16; 0.32-4.12, P = 0.81). Conclusions: Thrombolysis after MRI seems safe and effective in UTOS. This observation may encourage those who plan prospective placebo-controlled trials of thrombolytics in this subgroup of stroke patients.