"Stroke versus TIA? s (TIA) occur in approximately 15% of patients before an eventual stroke, with the highest risk in the first days following an event ... While TIAs do not always come to medical attention, their presentation in the acute stroke setting ostensibly complicates the treatment decision in patients who may be exhibiting improvement. The majority of TIAs resolve in less than 60 minutes whereas the majority of true strokes reach peak deficit in the same time frame. A 2009 scientific statement from the / discourages the use of traditional time-based definitions of TIA in favor of a tissue-based definition (i.e. the presence or absence of lesions on diffusion-weighted ) ..."