Anatomy of the Thoracic Outlet and Related Structures

Knowledge of anatomy is the key to understanding the thoracic outlet syndrome (TOS). By definition, TOS is hand and arm symptoms of pain, paresthesia, and weakness due to compression of the neurovascular bundle in the thoracic outlet area. While initially the scalene triangle was the focus of pathology in TOS, recent studies indicate that more than half of the patients thought to have TOS also have associated pectoralis minor compression, and in some patients this is the only diagnosis. Finally, it is important to recognize that the large majority of patients with anatomic abnormalities are asymptomatic unless neck trauma is also present – in other words, the mere presence of an abnormality does not mean it must be treated. Like many medical conditions, both an anatomic predisposition plus an environmental stressor are usually necessary for pathology to exist.