title: Mechanisms of bihemispheric brain infarctions in the anterior circulation on diffusion-weighted images.
abstract: OBJECTIVE
  Multiple acute brain infarctions in both cerebral hemispheres usually suggest an embolic mechanism, particularly one of aortic or cardiac origin. The purpose of this study was to clarify the etiologic mechanisms and topographic features of bihemispheric infarctions depicted on diffusion-weighted imaging (DWI).
  
  
  METHODS
  Among 411 consecutive patients with ischemic stroke who underwent MR imaging in the acute phase, DWI showed bilateral infarctions in 19 (4.6%). In these patients, we analyzed the presence of carotid, aortic or cardiac embolic sources by using ultrasonography, cerebral angiography, and/or transesophageal echocardiography and evaluated the size and topographic distribution of the lesions. We assessed intracranial cross-flow through the anterior communicating artery, mainly on the basis of the anatomic information obtained from angiography or MR angiography.
  
  
  RESULTS
  Bilateral lesions were derived from cardiac and/or aortic embolic sources in 16 (84%) of 19 patients and appeared to originate from unilateral carotid diseases in three (16%). In nine (82%) of 11 patients with cardiac embolic sources, at least one large territorial or subcortical lesion was found in either hemisphere, whereas in all eight patients without a cardiac embolic source, the lesions were small and disseminated bilaterally.
  
  
  CONCLUSIONS
  Unilateral carotid lesions can cause bihemispheric infarctions through cross-flow in the anterior communicating artery. On DWI, small bihemispheric, disseminated lesions strongly suggest an artery-to-artery embolism. In such cases, aortic and carotid lesions should be assessed as potential embolic sources.
authors.affiliation: Department of Medicine, Cerebrovascular Division, Nara Medical University, Osaka, Japan. ksaito@naramed-u.ac.jp
authors.forename: Kozue
authors.initials: K
authors.lastname: Saito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moriwaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Oe
authors.forename: Kotaro
authors.initials: K
authors.lastname: Miyashita
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Nagatsuka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ueno
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Naritomi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D020520:Brain Infarction / Q000175:diagnosis* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged