Tractography of the cranial nerves: state of the art, development and application in surgery of skull base tumorsl. ; Tractographie des nerfs crâniens : état de l’art, développement et application en chirurgie des tumeurs de la base du crâne.

Tractography is a recent imaging tool that uses the diffusion signal from the magnetic resonance imaging to detect the preferential orientation of water molecules within the tissues and particularly along white fibers of the brain. This technique has caught the attention of the scientific community describing non-invasively the in vivo white matter architecture. Nonetheless, its application to fiber crossing areas or small-scale structures, such as cranial nerves, remains inaccurate. New methods are being developed for both the acquisition and post-processing steps, but the angular and spatial resolution is still insufficient. The objective of this work is the application of the technique of tractography to cranial nerves and in the clinical setting for the detection of their trajectory in case of skull base tumors. After reminding the basics to understand each step involved in tractography, I present the current state-ofthe- art for application to cranial nerves. From 21 selected studies, I report all parameters of acquisition and tracking, the algorithms of reconstruction, the design of the regions of interest, and filtering methods. I then develop a dedicated tractography pipeline and show its value for surgical management through a 62 case series of various skull base tumors and two clinical images. Finally, I propose a new full-tractography approach that can reconstruct cranial nerves in their whole anatomical environment with or without tumor, which could be used in the clinical routine, notably for presurgical planning, aiming to improve the functional outcome of patients. ; Apparue à la fin des années 1990, la tractographie utilise le signal diffusion de l’imagerie par résonance magnétique (IRM) pour détecter l’orientation préférentielle des molécules d’eau et reconstruire l’architecture des tissus biologiques, notamment celle des fibres blanches intra cérébrales. Cette technique a suscité l’engouement de la communauté scientifique en permettant, pour la première fois, l’étude in vivo non invasive des ...