Approximately 10% of patients with transient ischemic attack (TIA; including all underlying mechanisms) have an ischemic stroke within 5 years of the first attack. Approximately 50% of all strokes after TIA or minor ischemic stroke occur within 1 year, irrespective of the territory involved (carotid or vertebrobasilar system). The causes of death after carotid or vertebrobasilar TIA are similar (˜45% cardiac and 30% hemorrhagic or ischemic stroke). Survival is nearly 90% at 1 year after the first TIA and approximately 70% at 5 years, 50% at 8 years, and 40% at 10 years.

A registry of 4,789 patients with recent TIA or minor cerebral infarction reported by Amarenco and others in the New England Journal of Medicine indicated that the stroke rates were 1.5% at 2 days, 2.1% at 7 days, 2.8% at 30 days, 3.7% at 90 days, and 5.1% at 365 days. At 5 years, the risk of stroke was 9.5%. Factors associated with an increased risk of subsequent stroke included ipsilateral large-artery atherosclerosis, cardioembolism, and a baseline ABCD2 score (see below) of 4 or more. In a large multihospital study with a single health maintenance organization in California, the risk for stroke after TIA was 11% at 3 months, with half of the strokes occurring within the first 2 days. An increased risk for subsequent stroke was predicted by the following factors: age greater than 60 years (odds ratio [OR] 1.8), diabetes mellitus (OR 2.0), symptom duration more than 10 minutes (OR 2.3), and weakness (OR 1.9) or speech impairment (OR 1.5) as a symptom of the TIA.