title: Anatomical mapping of white matter hyperintensities (WMH): exploring the relationships between periventricular WMH, deep WMH, and total WMH burden.
abstract: OBJECTIVE
  MRI segmentation and mapping techniques were used to assess evidence in support of categorical distinctions between periventricular white matter hyperintensities (PVWMH) and deep WMH (DWMH). Qualitative MRI studies generally identify 2 categories of WMH on the basis of anatomical localization. Separate pathophysiologies and behavioral consequences are often attributed to these 2 classes of WMH. However, evidence to support these empirical distinctions has not been rigorously sought.
  
  
  METHODS
  MRI analysis of 55 subjects included quantification of WMH volume, mapping onto a common anatomical image, and spatial localization of each WMH voxel. WMH locations were then divided into PVWMH and DWMH on the basis of distance from the lateral ventricles and correlations, with total WMH volume determined. Periventricular distance histograms of WMH voxels were also calculated.
  
  
  RESULTS
  PVWMH and DWMH were highly correlated with total WMH (R2>0.95) and with each other (R2>0.87). Mapping of all WMH revealed smooth expansion from around central cerebrospinal fluid spaces into more distal cerebral white matter with increasing WMH volume.
  
  
  CONCLUSIONS
  PVWMH, DWMH, and total WMH are highly correlated with each other. Moreover, spatial analysis failed to identify distinct subpopulations for PVWMH and DWMH. These results suggest that categorical distinctions between PVWMH and DWMH may be arbitrary, and conclusions regarding individual relationships between causal factors or behavior for PVWMH and DWMH may more accurately reflect total WMH volume relationships.
authors.affiliation: Department of Neurology, University of California at Davis, Davis, Calif, USA. cdecarli@ucdavis.edu
authors.forename: Charles
authors.initials: C
authors.lastname: DeCarli
authors.forename: Evan
authors.initials: E
authors.lastname: Fletcher
authors.forename: Vincent
authors.initials: V
authors.lastname: Ramey
authors.forename: Danielle
authors.initials: D
authors.lastname: Harvey
authors.forename: William J
authors.initials: WJ
authors.lastname: Jagust
mesh_terms: D000368:Aged; D001921:Brain / Q000473:pathology*; D002540:Cerebral Cortex / Q000473:pathology; D002552:Cerebral Ventricles / Q000473:pathology; D002561:Cerebrovascular Disorders / Q000473:pathology*; D003072:Cognition Disorders / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male