Sensitivity of Diffusion- and Perfusion-Weighted Imaging for Diagnosing Acute Ischemic Stroke Is 97.5%

BACKGROUND AND PURPOSE: MRI using diffusion-weighted imaging (DWI) is the most sensitive diagnostic imaging modality for early detection of ischemia, but how accurate is it and how much does perfusion-weighted imaging (PWI) add to the sensitivity have to be known. METHODS: In this single-center study, we collected epidemiological, imaging, and outcome data on all patients with stroke undergoing MRI-based treatment with intravenous tissue-type plasminogen activator at our center from 2004 to 2010. The DWI negative patients were identified, and we calculated the sensitivity and specificity of DWI and additional PWI for diagnosing acute ischemic stroke. We compared DWI positive and negative patients to identify characteristics associated with DWI negativity. RESULTS: Five hundred sixty-nine consecutive patients were treated with intravenous tissue-type plasminogen activator on the basis of an acute MRI. A DWI lesion was evident in 518 patients. Forty-seven patients were DWI negative; however, a relevant PWI lesion was found in 33 of these patients. Four stroke mimics were treated with intravenous tissue-type plasminogen activator and 1 of these patients had a DWI lesion. Thus, 8% of all patients with stroke were DWI negative. The combination of DWI and PWI resulted in a sensitivity of 97.5% for the ischemic stroke diagnosis. DWI negativity was associated with less severe strokes, location in the posterior circulation, a longer time from onset to scan, and an improved 90-day outcome. The cause of small-vessel disease was more likely to be DWI negative. CONCLUSIONS: The combination of DWI and PWI before intravenous tissue-type plasminogen activator confirms the diagnosis in 97.5% of all ischemic strokes.