This new definition has been endorsed and accepted by many cerebrovascular experts and incorporated into the study design of several major clinical trials. Others, however, have questioned the value of the new definition and raised multiple concerns. A common criticism involves the phrase "typically lasting less than one hour", as it is estimated that about 20% of TIAs last longer than 1 h. Another issue is that currently there is no well-accepted and widely available gold standard for documenting small brain infarctions. Some experts have suggested that episodes of brief duration (