title: Diffusion and perfusion characteristics of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode) in thirteen patients.
abstract: OBJECTIVE
  We analyzed the diffusion and perfusion characteristics of acute MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode) lesions in a large series to investigate the controversial changes of the apparent diffusion coefficient (ADC) that were reported in prior studies.
  
  
  METHODS
  We analyzed 44 newly appearing lesions during 28 stroke-like episodes in 13 patients with MELAS. We performed a visual assessment of the MR images including the ADC and perfusion maps, comparison of the ADC between the normal and abnormal areas, comparison of % ADC between the 44 MELAS lesions and the 30 acute ischemic infarcts. In addition, the patterns of evolution on follow-up MR images were analyzed.
  
  
  RESULTS
  Decreased, increased, and normal ADCs were noted in 16 (36%), 16 (36%), and 12 (27%) lesions, respectively. The mean % ADC was 102 ± 40.9% in the MELAS and 64 ± 17.8% in the acute vascular infarcts (p < 0.001), while perfusion imaging demonstrated hyper-perfusion in six acute MELAS lesions. On follow-up images, resolution, progression, and tissue loss were noted in 10, 4, and 17 lesions, respectively.
  
  
  CONCLUSIONS
  The cytotoxic edema gradually evolves following an acute stroke-like episode in patients with MELAS, and this may overlap with hyper-perfusion and vasogenic edema. The edematous swelling may be reversible or it may evolve to encephalomalacia, suggesting irreversible damage.
authors.affiliation: Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul 135-710, Korea.
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Kim
authors.forename: Myung Kwan
authors.initials: MK
authors.lastname: Lim
authors.forename: Tae Yeon
authors.initials: TY
authors.lastname: Jeon
authors.forename: Joung Ho
authors.initials: JH
authors.lastname: Rha
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Rha
authors.forename: Hong
authors.initials: H
authors.lastname: Eo
authors.forename: So-Young
authors.initials: SY
authors.lastname: Yoo
authors.forename: Chang Hae
authors.initials: CH
authors.lastname: Shu
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000473:pathology*; D001929:Brain Edema / Q000473:pathology; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D017241:MELAS Syndrome / Q000473:pathology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000473:pathology; D055815:Young Adult