The extension of time window until 4.5 hours and development of MRI in t-PA patients

In Japan, time window of IV-t-PA therapy for acute stroke is within 3 hours of stroke onset. Recently, ECASS III study revealed that time window of 3-4.5 hours of stroke onset is effective for acute stroke. Thus, now US, Australia, and many countries in Europe and Asia are available for time window of 4.5 hours. The extension of time window until 4.5 hours is expected in Japan. The target of treatment in acute stroke is penumbra. MRI can estimate the area of penumbra using perfusion MRI and diffusion MRI. IV-t-PA study using MRI was conducted in acute stroke patients with over 3-4.5 hours of onset, but did not reach satisfied results. We reported that M1 susceptibility vessel sign (SVS) on T(2)(*) can predict no early recanalization after t-PA infusion. Next, FLAIR can estimate the onset time of stroke in acute stroke patients within 24h of onset. Our study demonstrated that acute stroke patients with unknown onset time may be able to safely receive intravenous thrombolysis using FLAIR. Extension of time window and development of t-PA therapy using the MRI is expected in future.