Transient Ischemic Attack Vs Stroke

Transient ischemic attack (TIA) and acute ischemic stroke are often difficult to differentiate in the emergency room if patients are seen acutely within minutes or hours of symptom onset. In fact, TIA and stroke may represent a spectrum of ischemic stroke. Recent evidence suggests that TIA is a medical emergency. When focal cerebral ischemic symptoms completely resolve within 24 hours, the event has been considered a TIA, not a stroke. However, the majority of TIAs resolve within minutes, and advanced neuroimaging studies demonstrate that events with longer-lasting symptoms are likely to be strokes (3). TIAs have a more serious prognostic implication than previously appreciated. After a TIA occurs, approximately 10% of patients will have a stroke in the next three months, and almost half of these strokes will develop within the first two days of the initial symptoms (4). Simple symptom duration/risk factor scales (4,5) can be used with imaging to identify patients at high risk for TIA. Patients with TIAs that have persistent arterial occlusion on ultrasound or brain lesion(s) on diffusion-weighted MRI are at particularly high risk of early stroke recurrence (6,7). Because TIA is a serious risk factor that is highly predictive of stroke, patients suspected of having TIA must be evaluated in a timely and comprehensive manner. Clinical history, knowledge of neurologic symptoms, and timely performance of brain imaging tests are essential in the workup of these patients.

Data from the National Institutes of Neurological Disorders and Stroke (NINDS) recombinant tissue plasminogen activator (rtPA) study demonstrate that, in most cases, symptoms of ischemia, which persist for at least one hour, progress to permanent deficits. In this pivotal trial of thrombolytic therapy for ischemic stroke, half of the patients with ischemic symptoms persistent at 1 hour received placebo. Unfortunately, at 24 hours after symptom onset, only 2.6% of patients who received placebo had complete recovery of neurologic function (8 ) . Therefore, from a clinical perspective, patients who have symptoms that last for at least 1 hour have a 97% chance of having a stroke and should be evaluated emergently. The current time window for the only approved therapy with systemic rtPA is 3 hours after symptom onset. However, the majority of patients who suffer stroke arrive at the hospital outside this strict time window. Despite this, diagnostic testing of patients with symptoms that last longer than 3 hours should still be prioritized and accomplished in a timely manner, as effective measures to prevent stroke recurrence exist and depend on a stroke pathogenic mechanism (9).

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