Thoracic outlet syndrome

Thoracic outlet syndrome is a generic diagnosis used to describe a collection of symptoms caused by compression on the nerves and in rare circumstances arteries or veins in an area known as the thoracic outlet.

The exact border of the thoracic outlet does not include the neck joints and nerve roots as they exit the neck joints. However, it does include the area above and between the shoulder blade (scapula) and collar bone (clavicle) as well as the soft tissue boundaries of the scalene and pectoral muscles. 

Symptoms of thoracic outlet syndrome are numerous and extremely varied according to the severity of the problem and the site of causality. Over ninety nine per cent of thoracic outlet syndrome cases are neurogenic with no vascular involvement. 

Primary symptoms of neurogenic thoracic outlet syndrome may include pain and sensory symptoms such as pins and needles, tingling or numbness in specific distributions throughout the affected upper limb or limbs. Often these symptoms will be related to a specific activity or movement depending on the underlying causes. Activities which cause thoracic outlet symptoms often involve repetitive or prolonged elevation of the upper limb above head height. Common examples can include swimming, certain sleeping positions, pc work and occupations such as electrician or plumber due to adopted arm positions.

Where there is any evidence of swelling, colour changes or weakness to the upper limb this is considered a medical emergency due to probable involvement of the vascular structures supplying the upper limb.

Scalene muscle compression

The scalene muscles attach to the first ribs and run towards the outer aspect of the middle neck joints with the brachial plexus running between the anterior and middle scalene. With significant postural adaptations, trauma to this area or with certain training adaptations which increase scalene muscle size (hypertrophy) of these muscles the brachial plexus may become pressured in this area. This hypertrophy will occur most commonly in certain athletes as well as patients with breathing conditions such as COPD.

Treatment of this form of thoracic outlet syndrome is treated with a progressive stretching program of the scalene muscles. This will normally be one part of a wider program designed to improve posture of the upper spine and neck. This may involve resistance training to strengthen the shoulder blades (scapulae) as well as the deep neck flexors. A comprehensive display screen equipment ergonomic review may also be conducted to identify and change any postural factors which may be contributing to the problem.

Costoclavicular syndrome & first rib syndrome

As the brachial plexus exits the scalene area it runs over the first rib and behind the clavicle towards the shoulder. In certain individuals, posture may adapt to have an elevated first rib and in others there may be an extra first rib or as it is commonly known an “accessory rib”. Other individuals who are at risk of this form of thoracic outlet syndrome include individuals with a very depressed or retracted shoulder position which leads to traction on the brachial plexus over the first rib or against the clavicle. 

Where there is evidence of a posturally elevated first rib physiotherapists may employ manual techniques to mobilise the first rib. This will often be complemented with an ongoing stretching program to the scalene muscles which attach to the first rib and when overactive can be a cause of this problem. 

In situations where x-rays or MRI scans have demonstrated an extra cervical rib or “accessory rib” surgery can be offered to remove the rib. Due to the thoracic outlet containing the brachial plexus as well as significant blood vessels this form of surgery should only be considered for individuals with severe symptoms due to the inherent risk. 

Pectoralis minor tendon compression

As the brachial plexus runs away from the first rib towards the axilla, the nerves run under the pectoralis minor tendon as it attaches to the coracoid process of the scapular. In some individuals with structural abnormalities or significant muscle and tendon stiffness to the pectoralis minor, when the arm is elevated this leads to traction of the nerve. 

For individuals with this form of thoracic outlet syndrome caused by a clear occupational or sporting activity there will often need to be a period of time modifying this activity to desensitise the neural tissue. There can then be a period of modifying the activity and gradual exposure to the system. A stretching program to the pectoral muscles and progressive mobilisation program to the middle spine and rib joints will also help this problem by allowing more spinal mobility. A complementary strengthening program designed to optimise the function of the spinal extensor muscles and scapular retractor muscles may also be of benefit.

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