External jugular vein passing through triangle formed by tendon of cleido-occipitalis cervicalis muscle, trapezius muscle and clavicle – a case report

A rare case of variation was found in a South Indian female cadaver of about 40 year of age, during routine dissection of neck region for undergraduate students at Melaka-Manipal Medical College, Manipal University, Manipal. Trapezius muscle on right side of neck presented a rare variation called cleido-occipitalis cervicalis. The variant muscle was a separate part of trapezius and was inserted on the posterior surface of clavicle at the junction of its medial one third with the lateral two thirds. The right external jugular vein was bifid and reunited, then passed between the tendon of cleido-occipitalis cervicalis muscle and clavicle, finally draining into the right suprascapular vein. This unique anatomical position of external jugular vein may lead to its impingement during certain actions of trapezius muscle. Trapezius muscle and external jugular vein of left side did not show any unusual presentation except that the left external jugular vein drained into left internal jugular vein. These variations are important as the external jugular vein is routinely used in catheterization for diagnostic or therapeutic purposes, as well as in port implantation and transjugular intrahepatic porto-systemic shunts or selective venous sampling. Probable embryological cause of the variation has also been explained.