"The incidence increases with age, with approximately 0.1 million new cases per year reported worldwide. Males predominate in the American population 10. The true incidence is probably underestimated because a large number of patients with TIA-related symptoms do not seek medical attention 11."
"In the past, transient ischaemic attack was arbitrarily distinguished from stroke by the duration of neurological symptoms of less than 24 hours 1. However, this definition allowed the risk of permanent infarction to be classified as a transient ischaemic attack; thus, the aforementioned tissue-based definition was favoured 1. It is well established nowadays that in most transient ischaemic attacks, symptoms resolve in less than one hour but occasionally prolonged episodes may occur 1,2."
"Uncertainty surrounds the radiographic features of transient ischaemic attacks given that there is currently no perfect radiographic corollary to the pathology, especially when even minute regions of infarction could differentiate a stroke from a transient ischaemic attack 1. While CT brain is often unremarkable, there is controversy regarding the significance of regions demonstrating high signal on DWI, a finding present in approximately half of all transient ischaemic attacks 5."