Normal diffusion-weighted MRI during stroke-like deficits

Background Diffusion-weighted MRI (DWI) represents a major advance in the e arly diagnosis of acute ischemic,stroke. When abnormal in patients with str oke-like deficit, DWI usually establishes the presence and location of isch emic: brain. injury. However, this: is not always the case. Objective: To i nvestigate patients with stroke-like deficits occurring without DWI abnorma lities in brain regions clinically suspected to be responsible. Methods: We identified 27 of 782 consecutive patients scanned when stroke-like neurolo gic deficits were still present and who had normal DWI in the brain region( s) clinically implicated.. Based on all the clinical and radiologic data, w e attempted to arrive at a pathophysiologic diagnosis in each. Results: Bes t final diagnosis was a stroke mimic in 37% and a cerebral ischemic event i n 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 cortic al syndrome (10 patients; 5 with TLA, 2 with prolonged reversible deficits, 3 with infarction on follow-up imaging). In each of the latter three patie nts, the regions destined to infarct showed decreased perfusion on the init ial 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 m ay escape detection. Concomitant HWI can identify some-patients with brain ischemia that is symptomatic but not yet to the stage of causing DWI abnorm ality.