Dementia with Lewy bodies and Alzheimer disease: neurodegenerative patterns characterized by DTI.
OBJECTIVE
To identify the patterns of diffusivity changes in patients with dementia with Lewy bodies (DLB) and Alzheimer disease (AD) and to determine whether diffusion tensor MRI (DTI) is complementary to structural MRI in depicting the tissue abnormalities characteristic of DLB and AD.


METHODS
We studied clinically diagnosed age-, gender-, and education-matched subjects with DLB (n = 30), subjects with AD (n = 30), and cognitively normal (CN) subjects (n = 60) in a case-control study. DTI was performed at 3T with a fluid-attenuated inversion recovery-based DTI sequence that enabled cortical diffusion measurements. Mean diffusivity (MD) and gray matter (GM) density were measured from segmented cortical regions. Tract-based diffusivity was measured using color-coded fractional anisotropy (FA) maps.


RESULTS
Patients with DLB were characterized by elevated MD in the amygdala and decreased FA in the inferior longitudinal fasciculus (ILF). ILF diffusivity was associated with the presence of visual hallucinations (p = 0.007), and amygdala diffusivity was associated with Unified Parkinson's Disease Rating Scale (r = 0.50; p = 0.005) in DLB. In contrast, patients with AD were characterized by elevated MD in the medial temporal, temporal, and parietal lobe association cortices and decreased FA in the fornix, cingulum, and ILF. Amygdala diffusivity was complementary to GM density in discriminating DLB from CN; hippocampal and parahippocampal diffusivity was complementary to GM density in discriminating AD from CN.


CONCLUSIONS
Increased amygdalar diffusivity in the absence of tissue loss in dementia with Lewy bodies (DLB) may be related to microvacuolation, a common pathology associated with Lewy body disease in the amygdala. Diffusivity measurements were complementary to structural MRI, demonstrating that measures of diffusivity on diffusion tensor MRI are valuable tools for characterizing the tissue abnormalities characteristic of Alzheimer disease and DLB.
Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. kantarci.kejal@mayo.edu
K
K
Kantarci
R
R
Avula
M L
ML
Senjem
A R
AR
Samikoglu
B
B
Zhang
S D
SD
Weigand
S A
SA
Przybelski
H A
HA
Edmonson
P
P
Vemuri
D S
DS
Knopman
T J
TJ
Ferman
B F
BF
Boeve
R C
RC
Petersen
C R
CR
Jack
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology*; D016880:Anisotropy; D001931:Brain Mapping; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D001330:Electronic Data Processing; D005260:Female; D006801:Humans; D020961:Lewy Body Disease / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways; D009483:Neuropsychological Tests