MRI acquisition and analysis
BLIND
Anatomical MRI was available for a subset of participants (n = 26). Images were acquired with a Siemens 3 T MAGNETOM Skyra scanner (Siemens, Erlangen, Germany) with a 64-channel head coil. The scan protocol was: T1-weighted image MPRAGE (voxel 1 mm x 1 mm x 1 mm, repetition time (TR) = 2300 ms, echo time (TE) = 2.98 ms, flip angle = 9°); T2-weighted fluid-attenuated inversion recovery (FLAIR; voxel 1 mm × 0.5 mm × 0.5 mm, TR = 5000 ms, TE = 393 ms). Image processing was carried out using FSL (FMRIB Software Library, Oxford, UK). Non-brain tissue was removed using BET. T1 and T2 images were then registered using FLIRT and lesion masks manually traced by an experienced investigator blind to allocation. Lesion masks were used to obtain lesion volume. A weighted lesion load was also obtained as a measure of injury to the ipsilesional descending motor pathways