title: [Conventional and diffusion-weighted magnetic resonance imaging and proton spectroscopy in MELAS].
abstract: BACKGROUND
  MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) is a mitochondrial hereditary dysfunction in which the physiopathological mechanism of cerebral lesions is not totally understood as yet. Typically, these lesions are described as having normal to increased apparent diffusion coefficient (ADC), and this has been used to distinguish stroke-like lesions from ischemic lesions. Notwithstanding this, within the last few years, there have been reports of diffusion restriction in stroke-like episodes.
  
  
  OBJECTIVE
  Analysis of the diffusion characteristics on serial magnetic resonance imaging (MRI) over a 16 month period, on a patient with MELAS and stroke-like lesions, to investigate the controversial changes of the ADC, reported in the last years. Evaluation of the proton spectroscopy changes in stroke-like lesions and apparently spared brain.
  
  
  METHODS
  We performed four serial magnetic resonance imaging (MRI), including two stroke-like episodes, in a 28-year-old man with MELAS (mitochondrial DNA mutation A3243G). Qualitative analysis of the magnetic resonance images, including the single voxel spectroscopy and ADC maps, with analysis of evolution patterns of the last ones.
  
  
  RESULTS
  Both MRI that were performed during those episodes of stroke-like lesion revealed areas of diffusion restriction, coexisting areas of high ADC. During the chronic phase, there was a regression of those changes. Proton spectroscopy showed the presence of lactate and reduction of N-acetyl aspartate peak in stroke-like lesion and the presence of lactate in apparently spared brain.
  
  
  CONCLUSIONS
  All alterations that were recorded strengthen the view that cytotoxic oedema can occur in stroke-like lesions. Thus, their presence should not weaken the possibility of MELAS, especially if those lesions affect the temporal, parietal and/or occipital lobes, or if they predominantly involve the cortical gray matter, spanning vascular borders and if proton spectroscopy reveals lactate peak in the apparently spared brain.
authors.affiliation: Serviço de Imagiologia dos Hospitais da Universidade de Coimbra, Coimbra, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Casimiro
authors.forename: Joana
authors.initials: J
authors.lastname: Martins
authors.forename: César
authors.initials: C
authors.lastname: Nunes
authors.forename: Tiago
authors.initials: T
authors.lastname: Parreira
authors.forename: Sónia
authors.initials: S
authors.lastname: Batista
authors.forename: Miguel
authors.initials: M
authors.lastname: Cordeiro
authors.forename: Fernando
authors.initials: F
authors.lastname: Matias
authors.forename: Olinda
authors.initials: O
authors.lastname: Rebelo
authors.forename: Pedro
authors.initials: P
authors.lastname: Freitas
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D017241:MELAS Syndrome / Q000175:diagnosis*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011522:Protons
chemical_list: D011522:Protons