Surgical and radiological perspectives for the Spinal Accessory Nerve passing through a fenestrated Internal Jugular Vein: case series and literature review

Abstract

Rationale The preservation of the spinal accessory nerve (SAN) represents a key goal in head and neck oncologic surgery during selective neck dissection. This study aims to illustrate the anatomical variants of the XI cranial nerve, delving into the relationship between the spinal nerve and the internal jugular vein (IJV), as well as the surgical implications. Materials and Methods Two cases of patients who underwent oncologic surgery with neck dissection are described. Both cases found the SAN passing through the fenestration of the internal jugular vein. An independent literature review was conducted alongside the case report using the Medline and PubMed databases. Articles were selected by searching for the following key words: "spinal accessory nerve," "cranial nerve XI," "shoulder syndrome," "fenestrated jugular vein," "anatomy," "surgical anatomy," and "anatomical variant." This review aims to describe: the incidence of the anatomical variants of the accessory nerve, its resulting surgical implications, the imaging techniques useful in their identification and the underlying embryology. Results According to the literature, in the majority of cases (67–96%), the SAN traces a lateral course to the IJV. Less frequently, the XI cranial nerve courses medial to the IJV. A rarer anatomical variant, as described in the case report of this article, sees the nerve crossing through the fenestration of the vein (incidence: 0.48–3.3%). One report also indicates the nerve splitting around the internal jugular vein. Conclusions Anatomic variants of the spinal nerve are less frequent but their knowledge is of paramount importance to the head and neck surgeon in order to avoid iatrogenic damage to the SAN and the IJV.