Overview

Thoracic Outlet Syndrome

The term Thoracic Outlet Syndrome (TOS) encompasses three related syndromes that cause pain in the arm, shoulder, and neck:

• Neurogenic TOS (the pain is caused by compression of the brachial plexus)
• Vascular TOS (the pain is caused by compression of the subclavian artery or vein)
• Nonspecific TOS (the pain is from unexplained causes). 

Thoracic outlet syndrome is caused by compression of the brachial plexus or subclavian vessels as they pass through narrow passageways leading from the base of the neck to the armpit and arm. 

Sometimes making the diagnosis of thoracic outlet syndrome is difficult due to the similarity of its symptoms with rotator cuff injuries, cervical disc disorders, fibromyalgia, multiple sclerosis, complex regional pain syndrome, and tumors of the syrinx or spinal cord.