False-negative and False-positive Diffusion-weighted MR Findings in Acute Ischemic Stroke and Stroke-like Episodes / Journal of Rural Medicine

ABSTRACT

Background: Diffusion-weighted magnetic resonance (MR) imaging (DWI) is an excellent examination for detecting acute ischemic stroke, but false-negative cases have been reported recently.Patients and Methods: Since the present MR scanner (1.5-T, Siemens Symphony) was introduced to our hospital, a prospective study was designed in the Departments of Neurology and Radiology to evaluate the DWI findings in patients tentatively diagnosed to have an acute infarction and in those with stroke-like episodes. During the 31 months between June 2000 and December 2002, 572 consecutive patients with acute cerebral infarction or presenting conditions mimicking ischemic stroke, including transient ischemic attack (TIA), sudden-onset isolated vertigo, and loss of consciousness (LOC) with or without seizure, underwent DWI.Results: Four of 366 patients with a cerebral infarction (1.1%) had false-negative DWI in the acute stage, and 10 of 206 patients with conditions mimicking ischemic stroke (4.9%) had false-positive DWI in the acute stage. Of these 10 patients, there were five cases with TIA, four with sudden-onset isolated vertigo, and 1 with LOC with seizure. Sensitivity and specificity values were 98.9% and 97.6%, respectively, when DWIs were performed to diagnose acute cerebral infarction.Conclusion: DWI rarely fails to detect an acute-stage cerebral infarction, but further confirmatory measures may be necessary when there is a negative examination using a clinical or computed tomographic diagnosis to the contrary.