A rare unreported bilateral thoracic muscle on the inferior and posteromedial aspect of the rib cage: case report and literature review.

Thoracic wall muscles are essential for respiration. Few anatomical variations in thoracic wall muscles have been reported. Such variants must be considered during surgical procedures that involve the thorax muscles. During routine dissection of a 65-year-old male cadaver as part of a fourth-year clinical anatomy elective, additional muscle strips were found in the inner and inferior aspect of the rib cage closer to the posteromedial body wall. The muscle consisted of two strips of narrow muscle fibres originating from the inferior borders of ribs 11 and 12 that radiated to insert on the transverse processes of the T11 and T12 vertebrae. The case report describes an unusual, novel medial thoracic wall muscle that has not been previously described in the literature. Variations in thoracic muscles can affect respiratory function and surgical interventions like chest tube placement and needle therapy for local anaesthesia, therefore, it is important for clinicians to be aware of such variants.

Bilateral vertebral arteries entering the C4 foramen transversarium with the left vertebral artery originating from the aortic arch.

Vertebral arteries (VAs) serve as major blood vessels to the central nervous system. VAs typically arise from the subclavian arteries and ascend separately within the transverse foramina of the cervical vertebrae (C6-C1) before entering the skull at the foramen magnum and joining at the base of the pons to form the basilar artery of the vertebrobasilar circulation. Therefore, variations in the origin and anatomic course of the VAs have implications for invasive medical procedures involving the superior thoracic/cervical regions or the cervical vertebrae. The current case report describes variation in the entry point of both VAs and the site of origin of the left vertebral artery. The variation was revealed during routine dissection of a 72-year-old female cadaver. It was found that the left vertebral artery originated directly from the aortic arch to abnormally enter the transverse foramen of C4 instead of the transverse foramen of C6. The right vertebral artery arose as usual from the right subclavian artery. However, the right vertebral artery also directly entered the transverse foramen of C4 instead of the transverse foramen of C6.