Thoracic outlet: an anatomical redefinition that makes clinical sense.

The diagnosis of thoracic outlet syndrome (TOS) is intrinsically difficult, and the literature about it is full of confusing terminology. Symptoms may arise due to compression of neural and/or vascular elements in one or more of three different locations. A number of tests were developed during the early part of this century, and a variety of syndromes have been described that relate to these tests, all of which are now considered to be subtypes of the thoracic outlet syndrome. Yet anatomists and clinicians fail to agree on even the definition of the thoracic outlet. It is proposed that anatomists not use the term thoracic inlet as a synonym for the superior thoracic aperture, nor thoracic outlet for the inferior thoracic aperture. What many clinicians call the thoracic outlet should be called the scalene triangle by both anatomists and clinicians, divisible into a lower portion to be called the thoracic outlet (for subclavian vessels and nerve roots C.8 and T.1) and an upper portion, the cervical outlet (for nerve roots C.5, C.6, and normally C.7). What is currently called thoracic outlet syndrome should be renamed the cervicoaxillary syndrome (CAS), divisible into three subtypes: thoracic outlet, costoclavicular, and pectoralis minor syndromes. Compression of the upper roots of the brachial plexus between the anterior and middle scalene muscles should be recognized as cervical outlet syndrome, and all terms containing the word scalenus should be discarded.