Research Article

Changes in mild cognitive impairment and its subtypes as seen on diffusion tensor imaging

Senthil Thillainadesan^a1, Wei Wen^a1, Lin Zhuang^a1, John Crawford^a1, Nicole Kochan^a1, Simone Reppermund^a1, Melissa Slavin^a1a2, Julian Trollor^a3, Henry Brodaty^a2a4 and Perminder Sachdev^a1a5 c1

^a1 Brain and Ageing Research Program, School of Psychiatry, University of New South Wales, Sydney, Australia

^a2 Dementia Collaborative Research Centre, School of Psychiatry, University of New South Wales, Sydney, Australia

^a3 Department of Developmental Disability Neuropsychiatry, School of Psychiatry, University of New South Wales, Sydney, Australia

^a4 Academic Department for Old Age Psychiatry, The Prince of Wales Hospital, Randwick, New South Wales, Australia

^a5 Neuropsychiatric Institute, The Prince of Wales Hospital, Randwick, New South Wales, Australia

ABSTRACT

Background: Previous studies using diffusion tensor imaging (DTI) have observed microstructural abnormalities in white matter regions in both Alzheimer's disease and mild cognitive impairment (MCI). The aim of this work was to examine the abnormalities in white matter and subcortical regions of MCI and its subtypes in a large, community-dwelling older aged cohort

Methods: A community-based sample of 396 individuals without dementia underwent medical assessment, neuropsychiatric testing, and neuroimaging. Of these, 158 subjects were classified as MCI and 238 as cognitively normal (controls) based on international MCI consensus criteria. Regional fractional anisotropy (FA) and mean diffusivity (MD) measures were calculated from the DTI and compared between groups. The false discovery rate correction was applied for multiple testing.

Results: Subjects with MCI did not have significant differences in FA compared with controls after correction for multiple testing, but had increased MD in the right putamen, right anterior limb of the internal capsule, genu and splenium of the corpus callosum, right posterior cingulate gyrus, left superior frontal gyrus, and right and left corona radiata. When compared with controls, changes in left anterior cingulate, left superior frontal gyrus, and right corona radiata were associated with amnestic MCI (aMCI), whereas changes in the right putamen, right anterior limb of the internal capsule, and the right corona radiata were associated with non-amnestic MCI (naMCI). On logistic regression, the FA values in the left superior gyrus and MD values in the anterior cingulate distinguished aMCI from naMCI.

Conclusions: MCI is associated with changes in white matter and subcortical regions as seen on DTI. Changes in some anterior brain regions distinguish aMCI from naMCI.

(Received May 24 2011)

(Revised September 18 2011)

(Revised February 07 2012)

(Accepted February 07 2012)

(Online publication March 27 2012)

Key words:

• dementia;
• MRI;
• fractional anisotropy;
• mean diffusivity

Correspondence:

^c1 Correspondence should be addressed to: Professor Perminder Sachdev, Neuropsychiatric Institute, The Prince of Wales Hospital, Randwick, NSW 2031, Australia. Phone: +61 2 9382 3763; Fax: +61 2 93823774. Email: p.sachdev@unsw.edu.au.