Bilateral subclavian arteries passing in front of the scalenus anterior muscles.

Herein, we present a very rare case of bilateral subclavian arteries passing in front of the scalenus anterior muscles in a cadaver. This abnormality was observed in a 73-year-old Japanese male cadaver during a dissection session for students in 2004 at Osaka Dental University. The bilateral scalenus anterior muscle originated from the anterior tubercle of the transverse processes of the fifth and sixth cervical vertebrae and inserted into the scalene tubercle of the first ribs. The right scalenus minimus muscle was observed, but no left scalenus minimus muscle was observed. The aortic arch was a type A according to Adachi's classification. The origin of the internal thoracic artery was distal to that of the thyrocervical trunk. The bilateral brachial plexuses was formed by the union of the ventral rami from the fifth cervical to the first thoracic nerves and passed between the scalenus anterior and the scalenus medius muscles. To our knowledge, such a case has not been reported previously.