title: FDG PET and MRI in logopenic primary progressive aphasia versus dementia of the Alzheimer's type.
abstract: OBJECTIVE
  The logopenic variant of primary progressive aphasia is an atypical clinical variant of Alzheimer's disease which is typically characterized by left temporoparietal atrophy on magnetic resonance imaging and hypometabolism on F-18 fluorodeoxyglucose positron emission tomography. We aimed to characterize and compare patterns of atrophy and hypometabolism in logopenic primary progressive aphasia, and determine which brain regions and imaging modality best differentiates logopenic primary progressive aphasia from typical dementia of the Alzheimer's type.
  
  
  METHODS
  A total of 27 logopenic primary progressive aphasia subjects underwent fluorodeoxyglucose positron emission tomography and volumetric magnetic resonance imaging. These subjects were matched to 27 controls and 27 subjects with dementia of the Alzheimer's type. Patterns of atrophy and hypometabolism were assessed at the voxel and region-level using Statistical Parametric Mapping. Penalized logistic regression analysis was used to determine what combinations of regions best discriminate between groups.
  
  
  RESULTS
  Atrophy and hypometabolism was observed in lateral temporoparietal and medial parietal lobes, left greater than right, and left frontal lobe in the logopenic group. The logopenic group showed greater left inferior, middle and superior lateral temporal atrophy (inferior p = 0.02; middle p = 0.007, superior p = 0.002) and hypometabolism (inferior p = 0.006, middle p = 0.002, superior p = 0.001), and less right medial temporal atrophy (p = 0.02) and hypometabolism (p<0.001), and right posterior cingulate hypometabolism (p<0.001) than dementia of the Alzheimer's type. An age-adjusted penalized logistic model incorporating atrophy and hypometabolism achieved excellent discrimination (area under the receiver operator characteristic curve = 0.89) between logopenic and dementia of the Alzheimer's type subjects, with optimal discrimination achieved using right medial temporal and posterior cingulate hypometabolism, left inferior, middle and superior temporal hypometabolism, and left superior temporal volume.
  
  
  CONCLUSIONS
  Patterns of atrophy and hypometabolism both differ between logopenic primary progressive aphasia and dementia of the Alzheimer's type and both modalities provide excellent discrimination between groups.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Ajay
authors.initials: A
authors.lastname: Madhavan
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Whitwell
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Weigand
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Duffy
authors.forename: Edythe A
authors.initials: EA
authors.lastname: Strand
authors.forename: Mary M
authors.initials: MM
authors.lastname: Machulda
authors.forename: Nirubol
authors.initials: N
authors.lastname: Tosakulwong
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Senjem
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Gunter
authors.forename: Val J
authors.initials: VJ
authors.lastname: Lowe
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Petersen
authors.forename: Clifford R
authors.initials: CR
authors.lastname: Jack
authors.forename: Keith A
authors.initials: KA
authors.lastname: Josephs
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis*; D018888:Aphasia, Primary Progressive / Q000175:diagnosis*; D001921:Brain / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography
chemical_list: D019788:Fluorodeoxyglucose F18