Four cases of spinal accessory nerve passing through the fenestrated internal jugular vein

Neck dissection (ND) is an important technique for the treatment of cervical lymph node metastasis in patients with head and neck cancer. Since the introduction of functional ND (FND), various modifications have been made to reduce the adverse effects of radical ND. Recently, many investigators have documented cases of FND with preservation of the spinal accessory nerve (SAN) and/or the sternocleidomastoid muscle, which have contributed to improve the quality of life following ND. For this type of ND, special attention must be paid to identify the SAN and the internal jugular vein (IJV). We performed 123 NDs over 2 years at the Department of Otolaryngology, Head and Neck Surgery, Kobe University Hospital. We collected data of all patients who underwent NDs by retrospectively reviewing the relevant hospital medical records and operative notes. In 4 out of 123 NDs (3.3%), an anomaly of the SAN passing through the fenestrated IJV was observed. Although this anomaly is rare, head and neck surgeons should be aware of this anomalous relationship between the SAN and the IJV in order to avoid accidental injury to these structures during ND.