Normal diffusion-weighted MRI during stroke-like deficits

Background Diffusion-weighted MRI (DWI) represents a major advance in the early diagnosis of acute ischemic,stroke. When abnormal in patients with stroke-like deficit, DWI usually establishes the presence and location of ischemic: brain. injury. However, this: is not always the case. Objective: To investigate patients with stroke-like deficits occurring without DWI abnormalities in brain regions clinically suspected to be responsible. Methods: We identified 27 of 782 consecutive patients scanned when stroke-like neurologic deficits were still present and who had normal DWI in the brain region(s) clinically implicated.. Based on all the clinical and radiologic data, we attempted to arrive at a pathophysiologic diagnosis in each. Results: Best final diagnosis was a stroke mimic in 37% and a cerebral ischemic event in 63%. Stroke mimics (10 patients) included migraine, seizures, functional disorder, transient global amnesia, and brain tumor. The remaining patients were considered to have had cerebral ischemic events: lacunar syndrome (7 patients; 3 with infarcts demonstrated subsequently) and hemispheric cortical syndrome (10 patients; 5 with TLA, 2 with prolonged reversible deficits, 3 with infarction on follow-up imaging). In each of the latter three patients, the regions destined to infarct showed decreased perfusion on the initial hemodynamically weighted MRI (HWI). Conclusions: Normal DWI in patients with stroke-like deficits should stimulate a search for nonischemic cause of symptoms. However, more than one-half of such patients have an ischemic cause as the best clinical diagnosis. Small brainstem lacunar infarctions may escape detection. Concomitant HWI can identify some-patients with brain ischemia that is symptomatic but not yet to the stage of causing DWI abnormality.