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The thoracic outlet is the area at the base of the neck that is a passageway for 2 main arteries and 5 major nerves passing from the neck to the axilla (underarm). Thoracic outlet syndrome (TOS) occurs when these nerves and vessels become compressed. Compression can occur at a few different points within the thoracic outlet. The 3 areas are:

•    Costoclavicular syndrome – the space between the first rib and the clavicle (collar bone)
•    Anterior scalene muscle syndrome – between the anterior and middle scalene and the upper border of the first rib
•    Pectoralis minor muscle syndrome – between the coracoid process (bony process at the shoulder) and the pec minor muscle

(TOS) is caused by anything that narrows the space allowed for the nerves and vessels to pass.

Some causes of Thoracic outlet syndrome include:

•    Shortening/tightening of the scalene muscles
•    Shortening/tightening of the pectoralis minor muscle
•    Congenital abnormalities – e.g. extra rib
•    Trauma e.g. 1st rib, clavicle fractures, or arthritis
•    Decreased movement of the 1st rib
•    Poor posture and drooping shoulders

People especially at risk for developing TOS include people whose occupations involve repetitive actions with the arms extended, such as computer users, waiters and painters.


In most cases of (TOS) there is a mixture of neural and vascular symptoms that may include any of the following:

•    Pain in the neck or shoulder
•    Numbness, tingling of the arms and hand
•    Weakness and easily fatiguing arms and hands
•    A “dead arm” is common in the mornings upon waking
•    Swelling or coldness of the arm

(TOS) is often difficult to diagnose has its symptoms often mimic those of other conditions such as a herniated disc, or carpal tunnel.

Diagnosis and treatment

Your physiotherapist will be able to diagnose and treat this condition. Treatment would focus on the specific area of compromise. Treatment may consist of:

•    mobilizations to restore 1st rib and clavicle motion
•    soft tissue therapy, electrotherapeutic modalities and stretching of restricted tissues e.g. scalenes
•    mobilization of the shoulder, shoulder-shoulder blade joint
•    re-education of posture including specific strengthening and stretching exercises for muscles of the shoulder, neck and upper back region important to good posture

In some cases (TOS) does not respond to conservative management and thus surgery may be required.