Gray and white matter water diffusion in the syndromic variants of frontotemporal dementia.
OBJECTIVE
To use diffusion tensor imaging (DTI) to assess gray matter and white matter tract diffusion in behavioral variant frontotemporal dementia (bvFTD), semantic dementia (SMD), and progressive nonfluent aphasia (PNFA).


METHODS
This was a case-control study where 16 subjects with bvFTD, 7 with PNFA, and 4 with SMD were identified and matched by age and gender to 19 controls. All subjects had 3-T head MRI with a DTI sequence with diffusion encoding in 21 directions. Gray matter mean diffusivity (MD) was assessed using a region-of-interest (ROI) and voxel-level approach, and voxel-based morphometry was used to assess patterns of gray matter loss. White matter tract diffusivity (fractional anisotropy and radial diffusivity) was assessed by placing ROIs on tracts of interest.


RESULTS
In bvFTD, increased gray matter MD and gray matter loss were identified bilaterally throughout frontal and temporal lobes, with abnormal diffusivity observed in white matter tracts that connect to these regions. In SMD, gray matter loss and increased MD were identified predominantly in the left temporal lobe, with tract abnormalities observed in the inferior longitudinal fasciculus and uncinate fasciculus. In PNFA, gray matter loss and increased MD were observed in left inferior frontal lobe, insula, and supplemental motor area, with tract abnormalities observed in the superior longitudinal fasciculus.


CONCLUSIONS
The diffusivity of gray matter is increased in regions that are atrophic in frontotemporal dementia, suggesting disruption of the cytoarchitecture of remaining tissue. Furthermore, damage was identified in white matter tracts that interconnect these regions, supporting the hypothesis that these diseases involve different and specific brain networks.
Whitwell
J L
JL
Department of Radiology, Mayo Clinic, Rochester MN 55905, USA. whitwell.jennifer@mayo.edu
Avula
R
R
Senjem
M L
ML
Kantarci
K
K
Weigand
S D
SD
Samikoglu
A
A
Edmonson
H A
HA
Vemuri
P
P
Knopman
D S
DS
Boeve
B F
BF
Petersen
R C
RC
Josephs
K A
KA
Jack
C R
CR
D000368:Aged; D016880:Anisotropy; D001284:Atrophy / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping; D016022:Case-Control Studies; D004058:Diffusion; D056324:Diffusion Tensor Imaging; D018450:Disease Progression; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D057180:Frontotemporal Dementia / Q000473:pathology* / Q000503:physiopathology; D057174:Frontotemporal Lobar Degeneration / Q000473:pathology* / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology* / Q000503:physiopathology; D057178:Primary Progressive Nonfluent Aphasia / Q000473:pathology* / Q000503:physiopathology; D012720:Severity of Illness Index; D013702:Temporal Lobe / Q000473:pathology / Q000503:physiopathology
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