Time window and "tissue window": two approaches to assist decision-making in strokes.

Intravenous alteplase given in an appropriate time window has been recommended in guidelines and effects are on the decline over time. In general, the clinical decision is primarily based on whether ischemic stroke patients are sent to hospitals within the time window. However, some patients sent to the hospital over time limitations are eligible to receive intervention for recanalization due to good collateral circulation. In this dilemma, "tissue window" can be more reliable, which means using the penumbra as a major criterion for patient recruitment. Hence, we herein aim to address how could "tissue window" be a complementary approach when it does not conform to the time window's indication and affirming value of the later one. Some efforts obeying the time window are discussed first. In the later sections, we give the details of the definition of "tissue window", and then compare various neuroimaging techniques to determine the penumbra and summarize favorable patterns. Finally, we will focus on how the "tissue window" extends the therapeutic time window under specific circumstances.