We know that earlier treatment of ischemic stroke with IV thrombolysis results in better clinical outcomes for patients, even when looking at parameters such as intracranial hemorrhage and in-hospital mortality. Strbian et al looked at ultra-early intravenous thrombolysis (delivery of tPA within 90 minutes of symptom onset) and reported that patients benefited differently based on their NIHSS. Outcomes were measured at three months with an excellent outcome defined as a modified Rankin Scale of 0-1. They found that patients with an NIHSS of 7-12 had an excellent outcome when they received ultra-early IV tPA, but that patients with an NIHSS of 0-6 or greater than 12 did not show the same benefit.

Why didn’t patients with an NIHSS greater than 12 show an excellent outcome with ultra-early tPA? Patients with higher stroke scale symptoms probably have larger stroke syndromes with proximal vessel occlusions and in these situations, tPA is not as effective. But, also likely is that these patients did improve with ultra-early tPA, but not to the degree of reaching an mRS of 0-1. 

The patients with an NIHSS of 0-6 did not have an excellent outcome from ultra-early thrombolysis when the outcome was measured as mRS 0-1. However, when the 3 month outcome was set to an mRS 0, these patients did indeed benefit from ultra-early thrombolysis. 
So perhaps the take-home message from this paper should be that our clinical measurement tools are limited in their ability to grade improvement, rather than the suggestion that ultra-early tPA only helps patients with a certain stroke severity. The authors’ conclusions seem to be an artifact of their analysis – had they looked at any improvement in the mRS, rather than exclusively 0-1, they probably would have demonstrated benefit across all NIHSS groups.