Thoracic outlet syndrome (TOS) is a condition presenting with arm symptoms of pain, numbness, tingling and weakness. The cause is pressure in the neck against the nerves and blood vessels that go to the arm. The origin of the problem originates in the neck: especially the scalene muscles, but the symptoms manifest in the arm: usually on one side. The acupuncture treatment for TOS is to alleviate pressure, tension, pain and numbness in the arm by restoring and normalizing the flow of blood and energy in the muscles of the neck. Acupuncture can be a very effective treatment for TOS in just a few treatments, often when nothing else has helped the TOS symptoms.