A cervical rib is the result of over-development of the costal element of the seventh cervical vertebra. It occurs in 1 in 200 people. The cervical rib may be bony and attached to the first normal rib, its cartilage or the sternum. Also, it may project freely with no anterior attachment. Alternatively, it may be a thin, fibrous strand which paradoxically may produce more symptoms than a complete rib. In half the cases, it is unilateral, usually on the right side.
The subclavian artery and first thoracic nerve may be affected as they pass over the cervical rib to gain access to the upper limb. The artery may be narrowed, with post-stenotic dilatation. Thrombus may collect in this aneurysm, predisposing to emboli and acute ischaemia. The nerve may be damaged by direct pressure.
A cervical rib is a common cause of the thoracic outlet syndrome.
Last reviewed 01/2018