An unusual foramen in the transverse process of first thoracic vertebra.

The presence of foramina in the transverse processes of thoracic vertebrae is not a common feature while they are the characteristic feature of cervical vertebrae. Foramina present in the transverse process of cervical vertebrae give passage to the vertebral artery-an important artery supplying the brain and spinal cord. Thoracic vertebrae typically bear facets on the body and the transverse processes for articulation with ribs. We report the presence of a complete foramen in the left transverse process of first thoracic vertebra, which is a very rare finding. The foramen was present near the root of the transverse process in alignment with the foramina transversaria of the cervical vertebrae of the same side. This variation is explained embryologically in relation to the branches of dorsal aortae in post-branchial stage of development. Knowledge of such a variation may be of great relevance for accurate interpretation of radiological pictures and for CT and MR angiographies as well as for the management of surgical procedures.