Surgical anatomy of the carotid sympathetic plexus in endoscopic endonasal approaches: strategies for preventing Horner syndrome

Objective: Endoscopic endonasal approaches (EEAs) specifically for procedures involving manipulation of the internal carotid artery (ICA), such as the transcavernous and translacerum approaches, confer a potential risk of carotid sympathetic plexus injury, potentially leading to postganglionic Horner syndrome. The primary aim of this study was to delineate the surgical anatomy of the carotid sympathetic plexus from an endoscopic endonasal perspective, offering insights to facilitate intraoperative anatomical identification and injury prevention.

Methods: A comprehensive dissection was conducted on 20 silicone-injected, lightly embalmed postmortem human heads. The segments, patterns, and surgical landmarks of the carotid sympathetic plexus were investigated in a stepwise manner. In addition, 3 illustrative cases highlighting the involvement of the carotid sympathetic plexus in EEAs are included to contextualize the anatomical findings.

Results: The carotid sympathetic plexus can be categorized into 3 segments: 1) the cavernous sinus (CS) segment, beginning at the upper surface of the petrolingual ligament and ascending anterosuperiorly along the inferior compartment of the CS (mean ± SD length 5 ± 0.5 mm); 2) the lacerum segment, starting at the exit of the petrous carotid canal and ascending laterally and vertically to the upper surface of the petrolingual ligament (mean ± SD length 10 ± 1 mm); and 3) the petrous segment, originating at the external opening of the carotid canal and terminating at the foramen lacerum (mean ± SD length 18 ± 1 mm). Two primary morphological patterns of the sympathetic plexus at the CS and lacerum segments were identified: a plexus-like pattern in 12 (30%) hemispheres, and a nerve-like pattern that was subcategorized as double (18 [45%] hemispheres) or single (10 [25%] hemispheres) trunks. Surgical strategies emphasize the importance of recognizing key landmarks when approaching the carotid sympathetic plexus, including the pterygosphenoidal triangle, lingual process, petrolingual ligament, lateral parasellar ligament, and abducens nerve.

Conclusions: This article provides a comprehensive anatomical description of the carotid sympathetic plexus in EEAs, highlighting key anatomical segments and patterns for intraoperative identification. A better understanding of anatomical landmarks for the carotid sympathetic plexus could help reduce the incidence of postganglionic Horner syndrome, augmenting the safety and efficacy of endoscopic endonasal transcavernous surgery.