Thoracic Outlet Syndrome Thoracic outlet syndrome is actually a collection of syndromes brought about by abnormal compression of the neurovascular bundle by bony, ligamentous or muscular obstacles between the cervical spine and the lower border of the axilla. This injury usually consists of the neurovascular bundle, the brachial plexus, and the subclavian artery and vein. The bony ligamentous and muscular obstacles all define the cervicoaxillary canal or the thoracic outlet and its course from the base of the neck to the axilla or armpit. Thoracic outlet syndrome is characterized by pain, numbness, tingling, and/or