Transient ischemic attack: the rules have changed.

Bob: If you thought you knew what a transient ischemic attack (TIA) is, and how to evaluate for it, think again. This scientific statement snuck past a lot of us and its implications are far-reaching. The guideline includes three game changers for all physicians: • It revises the definition of TIA • It recommends that magnetic resonance imaging (MRI) be performed within 24 hours in patients presenting with TIA • It recommends that the ABCD2 (age, blood pressure, clinical features, duration, diabetes mellitus) score be used in the evaluation of TIA Let’s start with the change in definition. Many of us learned the classic 24-hour definition: if neurologic symptoms resolve within 24 hours of onset, it is considered a TIA. In 2002, the TIA Working Group recognized that an ischemic episode that improves at 23 hours is not biologically different from one that improves at 25 hours. Simply put, there was nothing magical about the 24-hour cutoff. The TIA Working Group recommended changing the definition to the following: a brief episode of neurologic dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than one hour and without evidence of acute infarction.1 The big change in the current guideline is the elimination of reference to duration of symptoms. In other words, the “less than one hour” is gone. This is because one-third of patients whose symptoms abate within one hour have evidence of acute stroke on diffusion-weighted MRI. The new definition of TIA also states that there must be no evidence of acute infarction. This leads into the second recommendation, that patients with suspected TIA should preferably undergo diffusion-weighted MRI as a means of ruling out infarction within 24 hours of symptom onset. Lastly, the guideline recommends that the ABCD2 score (Table 12) be used to determine which patients should be hospitalized: patients with a score of 3 or greater and patients with lower scores who may not follow up within two days.