Functional MRI of the Spinal Cord

Evidence to date shows that fMRI of the spinal cord (spinal fMRI) can reliably demonstrate regions involved with sensation of tactile, thermal, and painful stimuli, and with motor tasks. The spin-echo-based spinal fMRI method with “signal enhancement by extravascular protons” contrast has been developed more extensively than the BOLD (blood oxygen level dependent)-based method. Results have demonstrated good localization to areas of activity within the spinal cord cross-section and to the spinal cord segmental level, in both the cervical and lumbar spinal cord, with a range of thermal stimuli as well as tactile, vibration, and motor stimuli. The method has also demonstrated the first results in the injured spinal cord with thermal and motor stimuli, and in people with multiple sclerosis with proprioceptive and tactile stimuli. The image quality obtained with this method has also resulted in the ability to obtain 3D data in thin sagittal slices spanning 20 cm, to spatially normalize the results, and thereby apply group analysis methods of partial least-squares, analysis of effective connectivity, and automatic determination of voxel-by-voxel repeatability across studies or volunteers. The availability of essentially automated analysis, large extent coverage of the spinal cord, and spatial normalization to permit comparisons with reference results and labelling of active regions are essential elements for developing the method into a practical clinical assessment tool.