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Abstract
Objective: To develop a composite MRI-based measure of motor network integrity, and determine if it explains disability better than conventional MRI measures in patients with multiple sclerosis (MS).
Methods: Tract density imaging and constrained spherical deconvolution tractography were used to identify motor network connections in 22 controls. Fractional anisotropy (FA), magnetization transfer ratio (MTR), and normalized volume were computed in each tract in 71 people with relapse onset MS. Principal component analysis was used to distill the FA, MTR, and tract volume data into a single metric for each tract, which in turn was used to compute a composite measure of motor network efficiency (composite NE) using graph theory. Associations were investigated between the Expanded Disability Status Scale (EDSS) and the following MRI measures: composite motor NE, NE calculated using FA alone, FA averaged in the combined motor network tracts, brain T2 lesion volume, brain parenchymal fraction, normal-appearing white matter MTR, and cervical cord cross-sectional area.
Results: In univariable analysis, composite motor NE explained 58% of the variation in EDSS in the whole MS group, more than twice that of the other MRI measures investigated. In a multivariable regression model, only composite NE and disease duration were independently associated with EDSS.
Conclusions: A composite MRI measure of motor NE was able to predict disability substantially better than conventional non-network-based MRI measures.
GLOSSARY
- AC-PC=
- anterior commissure–posterior commissure;
- BPF=
- brain parenchymal fraction;
- EDSS=
- Expanded Disability Status Scale;
- FA=
- fractional anisotropy;
- GM=
- gray matter;
- GT=
- graph theory;
- MS=
- multiple sclerosis;
- MTI=
- magnetization transfer imaging;
- MTR=
- magnetization transfer ratio;
- NAWM=
- normal-appearing white matter;
- NE=
- network efficiency;
- PASAT=
- Paced Auditory Serial Addition Test;
- PCA=
- principal component analysis;
- PD=
- proton density;
- ROI=
- region of interest;
- RRMS=
- relapsing-remitting multiple sclerosis;
- SPMS=
- secondary progressive multiple sclerosis;
- TE=
- echo time;
- TOI=
- tract of interest;
- TR=
- repetition time;
- WM=
- white matter
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Supplemental data at Neurology.org
Editorial, page 1096
- Received January 12, 2015.
- Accepted in final form April 24, 2015.
- © 2015 American Academy of Neurology
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