The Wandering Nerve: Positional Variations of the Cervical Vagus Nerve and Neurosurgical Implications.

ABSTRACT

BACKGROUND: The vagus ("wandering") nerve is the longest cranial nerve with the largest territory of innervation in the human body. Injury during various operative procedures involving the anterior or lateral neck may lead to serious complications. Per "textbook" descriptions, the cervical vagus nerve (CVN) commonly locates within the carotid sheath, in between the common carotid artery (CCA) and internal jugular vein (IJV). However, anatomic variations in its positioning may occur more often than expected and intraoperative identification may anticipate potential surgical pitfalls. METHODS: A literature review was conducted per PRISMA guidelines for all studies describing positional variations of the CVN within the carotid sheath. A rare and potentially dangerous variation, occurring in only 0.7% of all reported cases, is illustrated with a cadaveric case. RESULTS: Overall, 10 anatomic CVN variations have been described across 971 specimens. The non-textbook variations (26.5%) consist of lateral (4.7%), anterolateral (8.7%), posteromedial (0.2%), posterior (5.8%), anterior (3.1%), medial (0.7%), and anteromedial (0.4%) to the CCA, as well as posterolateral (0.3%) and posterior (2.6%) to IJV. The "textbook" anatomic location is posterolateral to CCA (73.5%). Moreover, an increase in variability is reported on the left side (17.1%) compared with the right (11.3%). Our cadaveric dissection revealed a right-sided CVN directly medial to the CCA. CONCLUSIONS: Positional variations of the CVN occur in over 26% of patients and may add difficulty to an array of surgical procedures. Knowledge of these variations and their prevalence may aid the surgeon in conducting a more precise dissection possibly preventing significant potential adverse sequelae.