MRI in acute stroke

When considering IV tissue plasminogen activator (tPA) for ischemic stroke, acute imaging must ensure neurologic deficits are not due to intracerebral hemorrhage and ascertain the presence of early ischemic changes in the 3- to 4.5-hour window. The National Institute of Neurological Disorders and Stroke IV tPA study required a CT for this purpose, but the European Cooperative Acute Stroke Study (ECASS) III trial allowed both CT and MRI for screening for treatment in the 3- to 4.5-hour window.^1,2 However, of the 821 patients enrolled in ECASS III, only 50 (6%) were screened with MRI before randomization.¹ Thus, our success with IV tPA has occurred in the setting of a simple, noncontrast CT. Furthermore, the pooled IV tPA data, including more than 6,000 patients, demonstrate the convincing positive consequences of early treatment to enable a good functional outcome.² Every 15 minutes earlier that tPA is given provides an additional 1 month of disability-free life—indicating real-world public health implications of early treatment.³ Therefore, using MRI as a screening tool for IV tPA decision-making, which, at present, comes at the expense of time and brain, should be approached with utmost caution.