Background and Purpose Significant 24 h improvement is the strongest indicator of functional recovery following thrombolytic treatment for acute ischemic stroke. This study sought to analyze factors contributing to rapid neurological improvement (RNI) following intra-arterial thrombolytic treatment (IATT).

Methods Angiograms and clinical information derived from consecutive patients receiving treatment initiated within 6 h of stroke onset were retrospectively reviewed. RNI was defined as at least 50% 24 h improvement on the National Institutes of Health Stroke Scale score. Logistic regression analysis identified factors associated with RNI. Variables tested included: age, gender, serum glucose, platelet count, pial collateral formation, presenting National Institutes of Health Stroke Scale score, time to treatment, extent of reperfusion, site and location of occlusion, treatment agent and systolic blood pressure.

Results Greater than 50% reperfusion of the involved territory, time to treatment within 270 min and good pial collateral formation (large penumbra zone) significantly predicted RNI. RNI occurred in 31% of the 112 patients studied. RNI occurred in 21/26 (80.8%) patients exhibiting all three favorable variables whereas patients with only one favorable variable had a 6.5% chance of RNI. 94% of patients displaying RNI had a modified Rankin Scale score of 2 or less at 3 months compared with 28.6% without RNI.

Conclusions RNI following IATT for stroke is more likely when at least two of the following are present: good reperfusion, good pial collateral formation and treatment within 4.5 h of symptom onset, and is strongly predictive of 3 month outcomes. Important to clinical management, IATT may need to be reconsidered in patients with poor pial collateral formation if time to treatment exceeds 4.5 h.