Cervical rib

Overview
A cervical rib is a supernumerary (extra) rib which arises from the seventh cervical vertebra. It is a congenital abnormality located above the normal first rib. A cervical rib is present in only about 1 in 200 (0.5%) of people; in even rarer cases, an individual may have not one but two cervical ribs. The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the brachial plexus or subclavian artery. Compression of the brachial plexus may be identified by weakness of the muscles around the muscles in the hand, near the base of the thumb. Compression of the subclavian artery is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder.

Anatomy Diagrams

 * Detailed diagrams of a cervical rib