White matter pathology in Parkinson’s disease: the effect of imaging protocol differences and relevance to executive function.
NeuroImage. 2012-09-01; 62(3): 1675-1684
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1. Neuroimage. 2012 Sep;62(3):1675-84. doi: 10.1016/j.neuroimage.2012.06.012. Epub
2012 Jun 17.
White matter pathology in Parkinson’s disease: the effect of imaging protocol
differences and relevance to executive function.
Rae CL(1), Correia MM, Altena E, Hughes LE, Barker RA, Rowe JB.
(1)MRC Cognition and Brain Sciences Unit, Cambridge, CB2 7EF, UK.
Diffusion magnetic resonance imaging is increasingly used as a non-invasive
method to investigate white matter structure in neurological and neuropsychiatric
disease. However, many options are available for the acquisition sequence and
analysis method. Here we used Parkinson’s disease as a model neurodegenerative
disorder to compare imaging protocols and analysis options. We investigated
fractional anisotropy and mean diffusivity of white matter in patients and
age-matched controls, comparing two datasets acquired with different imaging
protocols. One protocol prioritised the number of b value acquisitions, whilst
the other prioritised the number of gradient directions. The dataset with more
gradient directions was more sensitive to reductions in fractional anisotropy in
Parkinson’s disease, whilst the dataset with more b values was more sensitive to
increases in mean diffusivity. Moreover, the areas of reduced fractional
anisotropy were highly similar to areas of increased mean diffusivity in PD
patients. Next, we compared two widely used analysis methods: tract-based spatial
statistics identified reduced fractional anisotropy and increased mean
diffusivity in Parkinson’s disease in many of the major white matter tracts in
the frontal and parietal lobes. Voxel-based analyses were less sensitive, with
similar patterns of white matter pathology observed only at liberal statistical
thresholds. We also used tract-based spatial statistics to identify correlations
between a test of executive function (phonemic fluency), fractional anisotropy
and mean diffusivity in prefrontal white matter in both Parkinson’s disease
patients and controls. These findings suggest that in Parkinson’s disease there
is widespread pathology of cerebral white matter, and furthermore, pathological
white matter in the frontal lobe may be associated with executive dysfunction.
Diffusion imaging protocols that prioritised the number of directions versus the
number of b values were differentially sensitive to alternative markers of white
matter pathology, such as fractional anisotropy and mean diffusivity.
Copyright © 2012 Elsevier Inc. All rights reserved.
PMID: 22713671 [Indexed for MEDLINE]