Regional white matter integrity differentiates between vascular dementia and Alzheimer disease.
OBJECTIVE
Considerable clinical and radiological overlap between vascular dementia (VaD) and Alzheimer disease (AD) often makes the diagnosis difficult. Diffusion-tensor imaging studies showed that fractional anisotropy (FA) could be a useful marker for white matter changes. This study aimed to identify regional FA changes to identify a biomarker that could be used to differentiate VaD from AD.


METHODS
T1-weighted and diffusion-tensor imaging scans were obtained in 13 VaD patients, 16 AD patients, and 22 healthy elderly controls. We used tract-based spatial statistics to study regional changes in fractional anisotropy in AD, VaD, and elderly controls. We then used probabilistic tractography to parcel the corpus callosum in 7 regions according to its connectivity with major cerebral cortices using diffusion-tensor imaging data set. We compared the volume and mean FA in each set of transcallosal fibers between groups using ANOVA and then applied a discriminant analysis based on FA and T2-weighted imaging measures.


RESULTS
FA reduction in forceps minor was the most significant area of difference between AD and VaD. Segmentation of the corpus callosum using tractography and comparison of FA changes of each segment confirmed the FA changes in transcallosal prefrontal tracts of patients with VaD when compared to AD. The best discriminant model was the combination of transcallosal prefrontal FA and Fazekas score with 87.5% accuracy, 100% specificity, and 93% sensitivity (P<0.0001).


CONCLUSIONS
Integrating mean FA in the forceps minor to the Fazekas score provides a useful quantitative marker for differentiating AD from VaD.
Zarei
Mojtaba
M
FMRIB Centre, University Oxford, Oxford, UK. mojtaba@fmrib.ox.ac.uk
Damoiseaux
Jeske S
JS
Morgese
Ciro
C
Beckmann
Christian F
CF
Smith
Steve M
SM
Matthews
Paul M
PM
Scheltens
Philip
P
Rombouts
Serge A R B
SA
Barkhof
Frederik
F
D000368:Aged; D000465:Algorithms; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000473:pathology*; D000704:Analysis of Variance; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D015331:Cohort Studies; D003337:Corpus Callosum / Q000473:pathology; D015140:Dementia, Vascular / Q000175:diagnosis* / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male