Thoracic Outlet Syndrome Types, Causes and Symptoms

Thoracic Outlet Syndrome, also known as TOS, is a compression of the brachial plexus and subclavian artery and vein. The brachial plexus supplies the upper limb with both sensory and motor nerve fibres, and the subclavian artery supplies the blood supply. There are four areas where the plexus and artery may be compressed and in each instance, the symptoms will present differently.

The part of the brachial plexus most likely to be affected is the medial cord, which originates from nerve roots C8 to T1.

Symptoms of Thoracic Outlet Syndrome:

Due to involvement of the medial cord of the brachial plexus, the ulnar nerve is most impacted by this compression syndrome. Muscles affected will be the Flexor Carpi Ulnaris, the ulnar aspect of the Flexor Digitorum Profundus, as well as most intrinsic (small) muscles of the hand. As a result, there will be some weakness or altered sensation on the ulnar aspect of the forearm, the hand and little finger. Signs and symptoms will vary, however, depending on the location of the compression and the structure involved.

Compression of a nerve will result in pain, loss of sensation and in chronic cases, muscle wasting or weakness. (This is known as denervation atrophy) Compression of blood vessels (subclavian or axillary arteries, depending on site of compression), will result in pain, paleness of the skin supplied by the artery, possible cyanosis (blue coloring) and decreased skin temperature. Prolonged decrease of blood supply can result in trophic skin changes, emboli (blood clots) and gangrene. Compression of a vein will result in edema, and the blood is unable to be carried back to the heart and lungs.

There are 4 main areas where compression may occur:

1) The anterior and middle scalene, aka the interscalene triangle. The brachial plexus and subclavian artery pass through here, but it is the medial cord of the plexus, arising from the C8-T1 nerve roots, which is most likely to be affected. (* Note: the scalenes are classified as secondary muscles of respiration because they attach to the ribs and contract during respiration)

2) Pectoralis minor – compression will occur between the pectoralis minor and its insertion on the coracoid process of the scapula. A person who presents with hyperkyphosis (rounded, slumped shoulders) may be more inclined to have compression here, especially when the muscle is stretched (for example, when they straighten up). The pectoralis minor, by attaching on ribs 1-8, may be affected by any respiratory disorder, leading to hypertonicity of the muscle and subsequent compression of the subclavian artery as it becomes the axillary artery when it passes deep to the clavicle.

3) Costoclavicular – compression occurs between the 1st rib and the clavicle. This is most likely to be a result of injury to the clavicle, such as a break or dislocation, and is prone to affect the vasculature (as the axillary vein becomes the subclavian vein)

4) Presence of a cervical rib – the presence of an extra rib is determined by an x-ray, and it interferes with the size of the interscalene triangle, therefore allowing less room for the plexus and vasculature.

The borders of the thoracic outlet are:

posteriorly (the back) the body of vertebrae T1 laterally the 1st rib bilaterally

anteriorly – manubrium of the sternum

Structures passing through the Thoracic Outlet

The brachial plexus, subclavian arteries and veins.The muscles involved in this syndrome are the anterior and middle scalenes, pectoralis minor and the subclavius.

Who is at risk for Thoracic Outlet Syndrome?

Thoracic Outlet Syndrome usually affects people whose posture tends to be very forward and slumping. Think of a person who sits at a desk all day, or who does a lot of work moving forward (or a massage therapist!). Others at risk may also have "military posture", extreme retraction of the shoulders which pulls the pectorialis minor tight over the plexus and artery, thus compressing it. Also at risk are people who have had a broken or dislocated clavicle, especially those with a more complicated or compounded break. Due to the attachment of the scalenes and pectoralis minor on the ribs, people who have a respiratory disorder and difficulty breathing often recruit these muscles, thus increasing the incidence of hypertonicity, and the presence of myofascial trigger points.

Thoracic Outlet Syndrome or Raynaud's Disease?

The therapist, during the course of performing orthopedic tests for TOS, will look for a positive test of a decreased or absent pulse, as well as numbness and tingling or fatigue in the ulnar distribution of the forearm and hand. Raynaud's Disease presents similarly, but is a peripheral vascular disorder which occurs due to vasospasm and results in decreased circulation. For Raynaud's disease to be diagnosed, it must be followed closely by a physician for 2 years and manifest as decreased circulation and increased sensitivity of the arms and hands.

How can massage therapy be used to treat Thoracic Outlet Syndrome?

Massage therapy can provide valuable assistance to someone suffering from TOS, either as a stand-alone treatment, or in conjunction with other modalities (ie physiotherapy or chiropractic).

Wherever the location of compression, the therapist will attempt to decrease hypertonicity and myofascial trigger points of the involved muscles as well as stretching. Manual lymph drainage can assist in the reduction of fluid build up post treatment. It will also be necessary to retrain the client concerning proper posture.After the treatment plan concludes, it would be wise to encourage the client to continue stretching, and also to schedule maintenance appointments to prevent a relapse.