Evaluation of the Impact of Lesions of the Motor and Proprioceptive Brain and Pan-medullary Pathways on Their Clinically and Electrophysiologically Assessed Function in Multiple Sclerosis

Multiple Sclerosis (MS) is the most common acquired neurological disease leading to disability, especially ambulatory, in young adults. To date, the correlation between the number or volume of white matter lesions seen on conventional MRI and the degree of disability of patients remains low to moderate. This phenomenon is known as the "clinical-radiological paradox". The impact of the precise localisation of focal MS lesions on certain circuits particularly involved in ambulation, such as pyramidal or proprioceptive beams, has however been little studied in imaging, mainly due to technical limitations. Indeed, such studies require the acquisition of brain and spinal cord MRI images of sufficient spatial resolution to allow the localisation of focal lesions and pathways. Several previous studies have shown encouraging results by separately studying damage to the brain or spinal cord portion of the corticospinal bundle and relating it to disability. To our knowledge, no studies have analysed the lesional involvement of the cortico-spinal bundle or the entire proprioceptive bundle from the motor cortex to the medullary cone in patients with MS. In a preliminary study, we studied the cerebral spinal cortex and cervical spinal cord bundle using data from the PHRC 2012 EMISEP and obtained encouraging results. In particular, we have shown that the cortico-spinal pathways are very frequently affected by focal lesions in the early years of the disease and that it is already correlated with the functional consequences in patients measured clinically and in electrophysiology. In this new project, we hypothesize that an evaluation of the corticospinal pathways including their thoracic medullary portion, as well as taking into account the severity of the lesions using quantitative MRI, will allow the investigators to refine the correlation with ambulatory disability in MS patients. We will complete the evaluation of motor pathways with those of the proprioceptive pathways also strongly involved in ambulation.