Anomalous relationship of the spinal accessory nerve to the internal jugular vein.

A patient with an early cancer of the tongue and undergoing a staging neck dissection was noted to have an anomalous relationship of the internal jugular vein and spinal accessory nerve. At the upper end of the dissection (level II, Memorial Sloan-Kettering classification), the internal jugular vein was observed to divide above and reconstitute below the spinal accessory nerve. Although apparently not previously described in the literature, this finding may be encountered by other surgeons who operate in this area, and it is important that these anatomical variations are borne in mind to prevent inadvertent injury.