White matter myelin profiles linked to clinical subtypes of Parkinson's disease.
BACKGROUND
White matter (WM) microstructural integrity is important for effective brain functioning and alterations have been shown in many neurodegenerative diseases.


PURPOSE
To investigate WM myelin profiles and their relation to clinical features of Parkinson's disease (PD).


STUDY TYPE
Retrospective cross-sectional.


POPULATION
In all, 29 PD subjects and 15 healthy controls.


FIELD STRENGTH/SEQUENCE
Multiecho GRASE with 10 msec echo spacing and echo planar imaging (EPI) diffusion-weighted (b-value = 700 with 32 gradient directions) on a 3T scanner.


ASSESSMENT
Myelin water fraction (MWF) and fractional anisotropy (FA) across 20 WM regions of interest (ROIs) were compared between groups. Partial least squares (PLS) was used to associate MWF and FA with clinical and behavioral measures.


STATISTICAL TESTS
Group comparisons were done using two-sample t-tests. PLS was assessed with permutation tests. Bootstrapping was used to investigate the robustness of imaging features.


RESULTS
No group differences in myelin content could be detected with univariate tests. A three-component PLS model linked MWF profiles to clinical phenotypes but no FA profiles. The three components appeared to follow along broad motor/nonmotor subtypes of "akinetic-rigid," "tremor-predominant," and "depression/apathy" subtypes, respectively. The first component showed associations between overall motor scores (r = -0.43, P = 0.0196) and cognitive performance (r = 0.44, P = 0.0171) with interhemispheric and long-range association fibers. A second component linked overall motor scores (r = -0.58, P = 0.0009) and tremor scores (r = -0.48, P = 0.0091) to predominantly projection fibers. The last component related depression (r = -0.60, P = 0.0006) and apathy scores (r = -0.66, P = 0.0001 and r = -49, P = 0.0072) to a mixture of association and projection fibers.


DATA CONCLUSION
MWF was robustly linked to distinct clinical subtypes of PD and may serve as an additional tool to characterize the disease.


LEVEL OF EVIDENCE
4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:164-174.
['Baumeister|Tobias R|TR|', 'Kim|Jowon L|JL|', 'Zhu|Maria|M|', 'McKeown|Martin J|MJ|']
D000368:Aged D016880:Anisotropy D016022:Case-Control Studies D016000:Cluster Analysis D005260:Female D006801:Humans D016018:Least-Squares Analysis D008297:Male D008875:Middle Aged D015233:Models, Statistical D009186:Myelin Sheath D010300:Parkinson Disease D010641:Phenotype D012189:Retrospective Studies D014867:Water D066127:White Matter
white matter Parkinson's disease brain myelin water fraction multivariate analysis