Anatomic Alert: Spinal accessory nerve traversing a fenestrated internal jugular vein

High bilateral fenestration of the internal jugular vein

Duplications and fenestrations of the internal jugular vein (IJV) are rare anatomic variations. There were previously found mostly unilateral fenestrated internal jugular veins, either empty, or traversed by the spinal accessory nerves. It was documented the computed tomography angiogram of a 65 year-old female patient and bilateral high fenestrations of the IJVs were found. On both sides, the superior ends of the fenestrations were in the jugular foramina. On the right side the fenestration had 3.8 cm length and was located in front of the transverse processes of the first two cervical vertebrae. On the opposite side the fenestration had 1.5 cm length and was antero-lateral to the transverse process of the atlas vertebra. On both sides the antero-medial arms of the fenestrations received the inferior petrosal sinuses and anterior condylar veins. Such highly placed fenestrations of the IJVs should be carefully documented either preoperatively, or prior to central venous access.

Internal Jugular Vein Fenestration and Duplication: Anatomical Findings, Prevalence, and Literature Review

Background: Comprehensive knowledge of the internal jugular vein (IJV) regarding its anatomical variations and the pattern of its course is valuable for preventing unexpected injuries during surgical procedures or central venous access. IJV anatomical anomalies such as fenestration and duplication are rare, mainly represented by case reports, and intraoperative findings.

Objective: To present two additional cases of IJV anomalies and highlight its clinical presentation, anatomical characteristics, management, and prevalence through an extensive literature review.

Methods and Case Reports: From January 2017 to December 2018, we retrospectively collected data of 221 patients undergoing neck dissection (ND) procedures and identified two patients with IJV anomalies (fenestration and duplication) providing a clinical prevalence of ~0.9%. The IJV fenestration referred to an IJV bifurcation that reunites proximal to the subclavian vein, whereas in the IJV duplication both branches remain separated. In both of our cases, the spinal accessory nerve (SAN) crossed the window between the IJV branches.

Conclusion: Anatomical variations are more likely to be identified intraoperatively or incidentally, and due to the risk of SAN and vascular injury, special attention should be taken to identify them preoperatively in order to reduce the risk of iatrogenic injury and unexpected complications.