Duplication of the lower third of the internal jugular vein--case report and surgical implications.

Duplication of the internal jugular vein is rare with a reported incidence of 0.4%. Most are located in the upper third and are almost always unilateral, duplication of the lower third is less common. In the case presented the vein divided above the omohyoid muscle with one branch passing superficial and the other deep to the muscle. Failure to recognise this anomaly could result in iatrogenic damage to the superficial branch in particular, with brisk and unexpected haemorrhage during neck dissection.