Gross and MicroCT Characterization of the Carotid Sinus Nerve and Intercarotid Plexus

Introduction: The carotid sinus nerve (CSN) is a branch of cranial nerve IX with communications from CN X. It contributes to the intercarotid plexus (IP) and receives input from the carotid sinus and body. Given CSN’s role in the baroreflex, electrostimulation of the CSN has become a non-pharmacologic treatment for hypertension. Our team is the first to correlate the gross structure of the CSN and IP with microCT imaging to facilitate more precise CSN stimulation while also providing insight into the anatomic diversity that surgeons may encounter when locating the CSN.

Methods: Eighteen CSNs were dissected from 13 cadavers with 5 nerves imaged via microCT. Distance from major anatomic landmarks, general anatomic course, and branching pattern were recorded while preserving the in situ position of the distal CSN within the carotid sheath.

Results: The mean distance of the CSN’s origin (from CN IX) from key landmarks were: 9.48 ±4.66mm to the jugular foramen, 13.47 ±5.88mm to the distal styloid process, and 51.23 ±0.73mm to the anterior margin of the tragus. The CSN most commonly descended along the anterolateral (6 of 11) surface of the right internal carotid artery (ICA) and the posterolateral (4 of 7) surface of the left ICA. A novel CSN branching schema was developed based on published literature and applied to assess the frequency of branching patterns in our cohort. The first microCT scans of the CSN and IP at a resolution of 11.4μm demonstrate highly variable contributions from nearby nerves and distal branch patterns.

Conclusion : Our CSN and IP images support earlier attempts to employ organization to the IP. Along with distances from major anatomic landmarks and our novel classification system, these insights may inform surgical approaches to the CSN and provide a basis for improved precision of CSN stimulation.