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 more rare 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. This is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in one arm is lost during abduction and external rotation of the shoulder.

Anatomy Diagrams

• Detailed diagrams of a cervical rib

Supernumerary body parts