A randomised trial, some of it conducted in New Zealand, evaluated the benefit of thrombolysis within 4.5 and 9 hours of stroke onset (or if within 9 hours of the midpoint of sleep for those who awake with stroke symptoms).1
The outcome was a 0 or 1 on the Rankin score (0 = no symptoms and 6 = death). At 90 days this was achieved in 40/113 (35.4%) in the thrombolysis group, and 33/112 (29.5%) in the placebo group. This is a number needed to treat of 17.
The take-home message is that patients with symptoms of stroke (FAST = face, arms, speech and time) should still go to a hospital (even after the 4.5-hour window) for a perfusion CT scan where they can be assessed for viable brain and, where relevant, offered thrombolysis.
This Gem has been checked by Professor Alan Barber from The University of Auckland, one of the study investigators.