A reappraisal of the definition and pathophysiology of the transient ischemic attack

Recent data on the pathophysiology of brain ischemia obtained by neuroimaging methods and the new concept of transient ischemic attack (TIA) emergency have called for a redefinition of TIA. According to the new definition proposed by the TIA Working Group, TIA is a brief episode of neurological dysfunction caused by focal brain or retinal ischemia with clinical symptoms typically lasting less than one hour and without evidence of acute brain infarction. This new definition leads to a discussion on the duration of the neurological dysfunction and the availability of appropriate neuroimaging for all patients. It has been reported that the diffusion-weighted imaging abnormalities could be seen in TIA patients with durations of the neurological symptoms of less than 30 minutes, but they were not detected in 29% of patients with transient deficit lasting as much as 6 to 24 hours. Persisting perfusion abnormalities in TIA patients are also observed. Therefore, a cutoff period of any duration of TIA is inaccurate. From the pathophysiological viewpoint, TIA may be considered an ischemic penumbra of varied duration, which could proceed to cerebral infarction or reduce to benign oligemia. TIA, characterized as an ischemic penumbra, presents an ideal target for rapid reperfusion and neuroprotection. Follow-up perfusion imaging can guide and individualize its treatment.