• Diffusion MRI (tractography) Tractography is performed on the basis of a diffusion MRI sequence which, after computer processing, will result in a map of the apparent diffusion coefficient and a diffusion tensor beam reconstruction (DTI tractography) performed with the Sisyphus software.
• Multi-shell diffusion MRI (NODDI-tract)

Compared to their usual management, the participation of the patient in this study implies an additional visit during which an MRI examination without contrast injection will be performed, lasting approximately 40 minutes (including installation and deinstallation).

The operative time, surgical procedures and postoperative follow-up are not modified in this study.

Response to electrical stimulation, which determines the presence or absence of an essential bundle, is the primary end point.

The ability of the NODDI-tract method to reconstruct essential bundles in vasogenic edema will be assessed by estimating the correspondence between the response to intraoperative direct electrical stimulation (DES) and the presence of an MRI reconstructed bundle.

Based on the response to electrical stimulation, the NODDI-tract data will be classified into one of four groups:

• True positive = response to stimulation and presence of an MRI beam
• True negative = no response to stimulation and no beam on MRI
• False positive = no response to stimulation and presence of a beam on MRI
• False-negative = response to stimulation and absence of beam in MRI. The distance between the reconstructed beam and the stimulation point (whether or not the stimulation was effective) will also be measured.

Reconstructions obtained using the NODDI protocol or tractography will be compared on the total number of fibers reconstructed by both methods.

The comparison will be made on the total number of reconstructed fibers and on the number of reconstructed fibers crossing the edema.