Visualizing anatomical variability of the vagus nerve

The SPARC Phase-2 REVA project is producing high resolution images and segmentations of vagus nerves from many subjects, all of which will be publicly available on the SPARC Portal following FAIR guidelines. As part of this effort each vagus nerve is being mapped onto an anatomical scaffold which provides a common 3-D coordinate system for the vagus trunk independently of the scale of the subject, plus variable per-subject branching. Datasets will also include fascicle networks and histological data to embed in the scaffolds. This work presents techniques using scaffolds for visualizing the anatomical variability found across the REVA datasets, informing the design and placement of vagal nerve stimulation devices. A key result is presenting the numbers and positions of branches innervating each organ. As each subject may have variable numbers of branches innervating a given organ, a single mean across subjects is overly simplistic, but visualizing all branches at their mapped locations and directions colored according to the target organ gives confidence that all fibres from an organ are present at certain levels. Similarly, branches to an organ can be colored by subject to view inter-subject variability. The subject-specific vagus scaffolds are built from ex-vivo specimens imaged in segments and stitched, so the geometry is not of any in-body configuration. Visualizations can be made on idealized common vagus material coordinates consisting of a straight trunk with branches radiating from it and marked with landmark points and regions such as the cervical and thoracic trunk. Some datasets include traces of the vagus and branches in the cadaver which can be used to fit realistic geometry for the trunk, and branches for that subject only. From this a population study of trunk geometry can be made to produce an average vagus on which branch directions can be shown in the body configuration. Imaging can also be remapped into per-subject and average body geometric configurations. We will describe future work that can take advantage of these FAIR datasets, and free and open-source software for doing this. Embedded fascicle networks allow estimation of distributions of where fibres from branch fascicles end up at distances up the trunk, further informing stimulation device design and placement. Interfaces can be built for bringing up data and visualizations across the study at fixed anatomical locations on the nerves. Some of these will become available on the SPARC portal. This work is supported by the NIH SPARC program under award number OT3OD025347. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.