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Thoracic outlet syndrome (TOS) is defined as symptomatic compression of the neurovascular structures at the thoracic outlet within an upper extremity.1–3 This group of conditions can take three forms including neurogenic, venous, and arterial. The majority of which is comprised of neurogenic symptoms, although vascular problems may be present. The incident of TOS is reported to be approximately 0.3% to 2% in the general population, affecting an age range from 25 to 40 years typically.4 Women are more commonly affected then men, with a ratio of 4:1.


The causes of TOS vary among the different forms. With neurogenic TOS, it is hypothesized to be a combination of osseous changes, soft tissue abnormalities, trauma, and inflammation.5 In addition to congenital predisposition of anatomic structures, acquired extrinsic factors may produce further compression. The causes of arterial TOS are usually a bony abnormality, such as a cervical rib or rudimentary first rib. Venous TOS is typically due to the costoclavicular ligament and subclavius muscle compression the subclavian vein.


Neurogenic TOS

The most common type of TOS is the neurogenic type constituting 94 to 97%.5 Symptoms are caused by compression of the brachial plexus. There are typically two patterns of brachial plexus compression: lower C8 and T1 plexus involvement and upper C5 and C6 involvement. The pictures can sometimes be mixed as well.

Lower plexus compression causes sensory disturbances to the ulnar nerve distribution. Complaints of pain and paresthesias in the medial aspect of the arm from axilla, through the brachial area and the forearm, down to hand in the fourth an fifth fingers are common. There can be weakness and even muscle wasting in extreme cases within the ulnar innervated muscles such as the hypothenar and interosseous. Pain in the anterior and posterior shoulder region as well as within the side or back of the neck can be present. Patients with upper plexus compression usually show symptoms within the upper and forearm, rather than the hand.6 This can also produce pain in the side of the neck that can radiate toward the ear, mandible, face, and temple. Typically will involve the median nerve distribution. Brachial plexus compression can cause subjective coldness of the hand and pallor. In very severe cases or in advanced cases, you may see muscle atrophy and weakness in the hand.

Venous TOS

Venous TOS accounts for 2% to 3% of patients.4 Usually will see signs of venous obstruction within the upper extremity that produces swelling, edema, cyanosis, and discomfort of the extremity that is aggravated with exertion. Patients can describe a sudden onset of symptoms from subclavian vein thrombosis. Over time, venous collateralization may develop and can be evident on exam with distension of superficial veins across the shoulder and ...

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