Thoracic Outlet Syndrome (TOS) is an umbrella term to describe a few different conditions whereby the brachial plexus (a network of nerves formed from the lower levels of the neck) becomes compressed at specific sites between the neck and the armpit. Common sites of compression are between the scalene muscles of the neck and under the pectoralis minor muscle Thoracic outlet syndromes are often misdiagnosed as neck or shoulder problems, and they frequently cause pain in this a