Multimodal Exploration of Patients With Multiple Sclerosis for an Early Detection of Subtle Progression

To assess the integrity of visual pathways through the optic nerves to the visual cortex, latencies and amplitudes of P100 will be measured after pattern-reversal stimuli.

To assess the integrity of sensitive pathways through the peripheral nerves and dorsal spinal cord to the somatosensory cortex. For the upper limbs, latencies and amplitudes of N9, N13, P14, N20 and P25 will be measured after median nerve stimulation. For the lower limbs, latency and amplitude of P40 will be measured after tibial nerve stimulation.

To measure the integrity of motor pathways, the central conduction times will be measured for upper and lower limbs through magnetic stimulations of the primary motor cortex and the spinal cord, at cervical and lumbar levels.

All patients will undergo a single brain MRI on a 3T scanner. The acquisition protocol will include high-resolution three-dimensional (3D) T2\*-weighted echo-planar imaging and 3D T2-FLAIR images acquired, respectively, during or after intravenous injection of a single dose (0.1mmol/kg) of gadolinium-based contrast material.

\- Neurofilament light chain (NfL) will be tested (Quanterix's Simoa® Technology) in the serum of patients. To evaluate their variation over time, 3 time-point tests will be obtained at 6 months apart (at baseline, at 6- and 12-month follow-up).

EBV serology will be assessed (VCA IgG) in the serum of patients to evaluate the variation of antibody titers over time (at baseline, at 6- and 12-month follow-up), and compare to titers at the time of diagnosis (when available in their medical record).