# Human vagus nerve fascicular anatomy and its implications for targeted cardiac stimulation: a microCT segmentation and histological pilot anatomical study

## TL;DR

This study explores the anatomy of the human vagus nerve to better understand how targeted cardiac stimulation could be achieved for treating heart conditions.

## Contribution

The study provides new insights into the organization of human vagus nerve fascicles using microCT and histology.

## Key findings

- Thoracic human vagus nerve fascicles show partial organization near branching points but merge further along the nerve.
- Right vagus nerves have larger diameters and more fascicles compared to left nerves.
- The superior cardiac branch remains distinct near typical stimulation sites, suggesting potential for targeted cardiac neuromodulation.

## Abstract

The functional anatomy of autonomic nerve fascicles has remained poorly understood. Building on prior evidence of organotopic organization in the pig cervical vagus nerve, this study examined the thoracic branches of the human vagus nerve using microcomputed tomography (microCT) and histological validation.

Left and right vagus nerves (n = 10) were dissected from human cadavers with cardiac, recurrent laryngeal, and pulmonary branches preserved. Fascicles were segmented and traced within 5 nerves from their branching points, and morphological features analyzed.

Cardiac, pulmonary, and recurrent laryngeal fascicles preserved partial organization near their entry points but merged further along the nerve. In left nerves, cardiac and pulmonary fascicles merged while recurrent laryngeal fascicles remained separate; in right nerves, cardiac fascicles merged with both pulmonary and recurrent laryngeal fascicles. Right nerves had a larger diameter and contained more fascicles, with counts varying along their length, indicative of the observed anastomoses.

Notably, the superior cardiac branch on both sides remained distinct near the typical vagus nerve stimulation cuff site, highlighting potential for targeted cardiac neuromodulation potentially relevant to conditions including myocardial infarction, heart failure, and atrial fibrillation. These findings advance understanding of human vagus nerve organization and support the design of selective stimulation strategies for precise autonomic regulation.