A cervical rib in humans is an extrarib which arises from the seventh cervical vertebra. Their presence is a congenital abnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2%[2] to 0.5%[3] (1 in 200 to 500) of the population.[4] People may have a cervical rib on the right, left or both sides.[5][6]
Most cases of cervical ribs are not clinically relevant and do not have symptoms;[7][8] cervical ribs are generally discovered incidentally, most often during x-rays and CT scans.[3][4][6] However, they vary widely in size and shape,[3] and in rare cases, they may cause problems such as contributing to thoracic outlet syndrome,[7] because of pressure on the nerves that may be caused by the presence of the rib.[7][9]
A cervical rib represents a persistent ossification of the C7 lateral costal element.[7][8] During early development, this ossified costal element typically becomes re-absorbed. Failure of this process results in a variably elongated transverse process or complete rib that can be anteriorly fused with the T1 first rib below.[10]
^Guttentag, Adam; Salwen, Julia (1999). "Keep Your Eyes on the Ribs: The Spectrum of Normal Variants and Diseases That Involve the Ribs". RadioGraphics. 19 (5): 1125–1142. doi:10.1148/radiographics.19.5.g99se011125. PMID10489169.