BERLIN—Gray matter–white matter (GM/WM) contrast ratio on T1 magnetization prepared rapid gradient echo (MPRAGE) is sensitive to multiple sclerosis (MS), but not to migraine pathology, according to research presented at ECTRIMS 2018. The diagnostic and prognostic value of this MRI marker could be subjects for future investigations, said the study authors.
Researchers have suggested that MRI brain T1 GM/WM contrast may be a marker of neurodegeneration in Alzheimer’s disease. Whether this contrast has diagnostic value in MS remains unknown, however. Tina Mitrovic, a research assistant at the University of Basel in Switzerland, and colleagues conducted a study to compare the T1 GM/WM contrast in patients with MS, migraineurs, and healthy controls. They also investigated whether the contrast was associated with disability outcomes in MS.
Ms. Mitrovic and colleagues analyzed precontrast 3D MPRAGE data from two independent cohorts. Cohort A was examined with 1.5-T MRI and included 124 patients with MS (65% relapsing-remitting MS; 66% female; mean disease duration, 13 years; median Expanded Disability Status Scale [EDSS] score, 2.5) and 20 healthy controls. Cohort B was examined with 3-T MRI and included 43 patients with relapsing-remitting MS (56% female; mean disease duration, three years; median EDSS score, 1.5), 19 migraineurs (47% with aura and 54% with WM abnormalities on T2-weighted scans), and 37 healthy controls.
WM lesions were segmented manually on T1- and T2-weighted images. GM and WM were segmented using Statistical Parametric Mapping 12. The researchers calculated GM and WM fractions and thresholded GM and WM masks by 95%. T1 GM/WM contrast ratio was calculated as [mean T1 intensity of WM minus mean T1 intensity of GM] divided by [mean T1 intensity of WM plus mean T1 intensity of GM]. Clinical outcomes included EDSS and Multiple Sclerosis Functional Composite (MSFC) scores. Associations between variables were investigated using univariate and multivariate general linear models. Results were bootstrapped.
Mean T1 GM/WM contrast ratio was lower in patients with MS than healthy controls in both cohorts. Furthermore, T1 GM/WM contrast ratio was lower in patients with MS than migraineurs, but the researchers observed no difference between migraine and healthy controls. Mean T1 GM/WM contrast was lowest in patients with progressive MS (11.7%), followed by those with relapsing-remitting MS or clinically isolated syndrome (12.2%) and healthy controls (12.8%). In MS, T1 GM/WM contrast was associated with WM lesion volume, disease duration, EDSS, and MSFC. A multivariable analysis with T1 GM/WM contrast as a dependent variable and age, disease duration, T1 and T2 WM lesion volume, and GM and WM fraction as independent variables, indicated that GM fraction and T2 lesion volume were independently associated with T1 GM/WM contrast ratio.