Diffusion-weighted MRI in patients with non-diagnostic CT in the post-acute phase of cerebral ischemia.

Background: Unenhanced computed tomography (CT) is the imaging technique used in acute stroke. In some cases it is unable to detect damage even 24-48 h after symptom onset. The aim of our work was to evaluate the diagnostic value of diffusion-weighted imaging (DWI) in the post-acute phase of cerebral ischemia in patients in whom CT did not yield a definitive diagnosis. Methods: We retrospectively evaluated DWI findings in 214 patients, out of a series of 1,680 patients admitted to our hospital following the acute onset of focal neurological symptoms, in whom non-contrast CT, performed within 30 h of symptom onset, was normal (123), incongruous, i.e. a marked hypodensity indicative of an old infarct or a slight hypodensity not consistent with the clinical findings (66), or leukoaraiotic, i.e. diffuse chronic hypodensities in the periventricular white matter (25). Results: DWI showed signs of recent brain ischemia in 125/214 (58%) patients: 64/123 (52%) with a normal CT, 41/66 (62%) with an incongruous CT, and 20/25 (80%) with leukoaraiosis (p = 0.027). Multiple lesions were detected in 16/125 (16%) patients, while single lesions were <= 2 cm in 83/109 (76%) cases. DWI showed signs of ischemia in 22/91 (24%) patients with TIA and in 103/123 (84%) patients with stroke (p = 0.0001). Conclusion: In a quite high proportion of patients with recent symptoms of transient ischemic attack/ischemic stroke and a repeat non-diagnostic CT, DWI may help in the diagnosis of ischemic stroke and in shedding light on the underlying pathogenic mechanism. Copyright (C) 2010 S. Karger AG, Basel