Magnetization transfer ratio evolution with demyelination and remyelination in multiple sclerosis lesions.
McConnell Brain Imaging Centre,
Montreal Neurological Institute and Hospital,
Montreal, Quebec.
OBJECTIVE:
To assess demyelination and remyelination in vivo (experimentation done in or on the living tissue) in acute gadolinium (Gd)-enhancing lesions of multiple sclerosis (MS).
METHODS:
We measured significant changes in magnetization transfer ratio (MTR) consistent with demyelination and remyelination of individual lesion voxels (a volume element, representing a value on a regular grid in three dimensional space), as well as the mean normalized MTR over all lesion voxels during and after contrast enhancement, in MS patients participating in a 3-year Canadian trial assessing immunoablation and autologous (a situation in which the donor and recipient are the same person) stem cell transplantation for treatment of MS.
RESULTS:
The average mean normalized lesion MTR over all lesions exhibited partial recovery over 2 to 4 months after Gd enhancement. Voxel-based analysis demonstrated that approximately 70% of the initially enhancing lesion volume (GdLV) was left with stably low MTR over 39 months of evaluation. The percentage of the GdLV undergoing significant increases in MTR consistent with remyelination increased for approximately 7 months after enhancement and then stabilized at 21 %GdLV.
Significant decreases in MTR consistent with demyelination were ongoing for approximately 33 months after enhancement, stabilizing at 9 %GdLV. The estimated error of these measurements, based on scan/rescan analysis, was less than 0.4 %GdLV.
INTERPRETATION:
We found significant changes in MTR consistent with demyelination and remyelination that followed different temporal evolutions and were ongoing in different lesion regions for at least 3 years after lesion formation