Tactile-associated recruitment of the cervical cord is altered in patients with multiple sclerosis

Abstract

Functional magnetic resonance imaging (fMRI) studies of the brain have shown that cortical reorganization might contribute to a more favourable clinical outcome of multiple sclerosis (MS). In order to assess whether fMRI changes can also be detected in the spinal cord from patients with MS, and to investigate their nature and extent, twenty-five patients and 12 matched healthy controls were scanned during a tactile stimulation of the palm of the right hand. The task-related mean signal change was computed for all activated voxels within the cervical cord and, separately, in the right and left anterior, right and left posterior, and middle cervical cord from C5 to C8. Cord lesion number, brain T2-weighted lesion load, gray matter mean diffusivity (MD), and normal appearing white matter MD and fractional anisotropy were also measured. One control and one patient were excluded prior to fMRI analysis due to motion artifacts. The task-related signal change of all cord activated voxels was 3.2% (SD=0.8) for controls and 3.9% (SD=0.9) for MS patients (p=0.02). Compared with controls, MS patients showed a higher signal change in the following cord sections: right anterior at C5 (p=0.05), right anterior (p=0.04) and posterior (p=0.04) at C6, and middle at C6 (p=0.03) and C7/C8 (p=0.01). MS patients showed a more frequent cord activity in the left posterior cervical cord at C5/C6 than controls (p=0.02). No significant correlation was found between cord fMRI changes and brain structural MRI metrics. In MS patients, the over-recruitment of the ipsilateral posterior cervical cord associated to a reduced functional lateralization suggests an abnormal function of the spinal relay interneurons.