title: Microinfarct disruption of white matter structure: a longitudinal diffusion tensor analysis.
abstract: OBJECTIVE
  To evaluate the local effect of small asymptomatic infarctions detected by diffusion-weighted imaging (DWI) on white matter microstructure using longitudinal structural and diffusion tensor imaging (DTI).
  
  
  METHODS
  Nine acute to subacute DWI lesions were identified in 6 subjects with probable cerebral amyloid angiopathy who had undergone high-resolution MRI both before and after DWI lesion detection. Regions of interest (ROIs) corresponding to the site of the DWI lesion (lesion ROI) and corresponding site in the nonlesioned contralateral hemisphere (control ROI) were coregistered to the pre- and postlesional scans. DTI tractography was additionally performed to reconstruct the white matter tracts containing the ROIs. DTI parameters (fractional anisotropy [FA], mean diffusivity [MD]) were quantified within each ROI, the 6-mm lesion-containing tract segments, and the entire lesion-containing tract bundle. Lesion/control FA and MD ratios were compared across time points.
  
  
  RESULTS
  The postlesional scans (performed a mean 7.1 ± 4.7 months after DWI lesion detection) demonstrated a decrease in median FA lesion/control ROI ratio (1.08 to 0.93, p = 0.038) and increase in median MD lesion/control ROI ratio (0.97 to 1.17, p = 0.015) relative to the prelesional scans. There were no visible changes on postlesional high-resolution T1-weighted and fluid-attenuated inversion recovery images in 4 of 9 lesion ROIs and small (2-5 mm) T1 hypointensities in the remaining 5. No postlesional changes in FA or MD ratios were detected in the 6-mm lesion-containing tract segments or full tract bundles.
  
  
  CONCLUSIONS
  Asymptomatic DWI lesions produce chronic local microstructural injury. The cumulative effects of these widely distributed lesions may directly contribute to small-vessel-related vascular cognitive impairment.
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Eitan
authors.initials: E
authors.lastname: Auriel
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Edlow
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Yael D
authors.initials: YD
authors.lastname: Reijmer
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Fotiadis
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Sergi
authors.initials: S
authors.lastname: Ramirez-Martinez
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Jun
authors.initials: J
authors.lastname: Ni
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Reed
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Vashkevich
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Kristin
authors.initials: K
authors.lastname: Schwab
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rosand
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Anand
authors.initials: A
authors.lastname: Viswanathan
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Ona
authors.initials: O
authors.lastname: Wu
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: M Edip
authors.initials: ME
authors.lastname: Gurol
authors.affiliation: From the J. Philip Kistler Stroke Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA. sgreenberg@partners.org.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Greenberg
mesh_terms: D000368:Aged; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D002544:Cerebral Infarction / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging / Q000379:methods; D018450:Disease Progression; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology