Poster Session P2 - Diagnosis and Disease Progression - Neuroimaging

Monday, July 19, 2004

Abstract: P2-204

Citation: NeuroBiology of Aging, Volume 25, Number S2 , July 2004, Page 288


White Matter Correlates of Cognitive Impairments in Early Alzheimer's Disease

Voyko Kavcic, Charles J. Duffy, Sven Ekholm, Jianhui Zhong

University of Rochester Medical Center, Rochester, NY, USA. Contact e-mail: voyko_kavcic@urmc.rochester.edu

Background: Based on our previous research on perceptual and attentional impairments in AD, we have developed a two-stage concurrent inhibition model which predicts that AD patients lack proper connectivity between perceptual and mnemonic modules. Objectives: We tested this prediction by using MR diffusion tensor imaging (DTI) to measure integrity of white matter (WM) fibers, known to be part of the mnemonic and attentional networks at the prefrontal, posterior parietal, cingular, and medial temporal regions. In addition, we also assessed WM in the corpus callosum (CC), fiber connecting the two hemispheres Methods: After initial diagnostic evaluation at AD Clinic of University of Rochester Medical Center, 15 mildly impaired AD patients (MMSE > 20) and 15 age-matched controls underwent extensive neuropsychological testing, including: 1) The Mini-Mental Status Examination; 2) The Road Map test; 3) Two subtests from the Wechsler Memory scale were used: the Verbal Paired Associates and the Figural Memory tests; 4) The Category Name Retrieval test; 5) The Judgement of Line Orientation test; 6) The Facial Recognition test. All participants also underwent perceptual testing for determining motion perception thresholds. MRI examinations were performed on a GE Signa 1.5 T MR scanner with a single-shot pulsed-gradient spin-echo (PGSE) EPI. Diffusion weighting were applied in 20 different orientations with b value = 0 and 1000 s/mm2. Results: Behaviorally, AD showed lower scores in all neuropsychological tests, except the Facial Recognition test. AD patients also showed higher motion perceptual thresholds than controls. Neuroanatomically, in a subgroup of AD patients studied to date, we found significantly decreased fractional anisotropy (FA) values in WM in the anterior (genu) and posterior (splenium) CC and posterior cingulum. We also found significant correlations between FA values from different regions and performance on neuropsychological tests: better performance on the tests was correlated with higher integrity of WM. Conclusions: Overall, the results indicate a strong link of perceptual and attentional impairments to WM changes in early AD. Our initial pilot results are, thus, encouraging and promising in that with combining neuroanatomical and behavioral methods we may be able to reliably distinguish AD from normal aging at a relatively early stage.