Thoracic Outlet Syndrome
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- This syndrome consists of a constellation of symptoms that affect the head, neck, shoulders, and upper extremities caused by compression of the neurovascular structures (brachial plexus and subclavian vessels) at the thoracic outlet, specifically in the area superior to the 1st rib and posterior to the clavicle.
- Three forms of thoracic outlet syndrome (TOS) have been described: neurogenic, vascular (with venous and arterial symptoms), and nonspecific (includes traumatic and secondary to certain provocative movements).
- Synonym(s): scalenus anticus syndrome; cervical rib syndrome; costoclavicular syndrome
Generalized tissue fluid accumulations and postural changes may aggravate symptoms.
- Predominant age
- Neurogenic type (95%): 20 to 60 years
- Venous type (4%): 20 to 35 years
- Arterial type (1%; atherosclerosis): young adult or >50 years
- Predominant sex
- Neurogenic type: female > male (3.5:1)
- Venous type: male > female
- Arterial type: male = female
- No objective confirmatory tests available to measure true incidence
- Estimated 3 to 8/1,000 cases for neurogenic type
- Incidence of other TOS types is unclear.
Etiology and Pathophysiology
The interscalene triangle area is reduced in TOS and may become smaller during certain shoulder and arm movements. Fibrotic bands, cervical ribs, and muscle variations may further narrow the triangle. Trauma or provocative movements affecting the lower brachial plexus have strong implications in TOS pathogenesis.
- Three known causes of TOS: anatomic, traumatic/repetitive movement activities, and neurovascular entrapment
- Anatomic: Variations in the anatomy of the neck scalene muscles may be responsible for presentations of the neurologic type of TOS and may involve the superior border of the 1st rib. Cervical ribs also have been implicated as a cause of neurologic TOS, with subsequent neuronal fibrosing and degeneration associated with arterial hyalinization in the lower trunk of the brachial plexus. Fibrous bands to cervical ribs are often congenital.
- Trauma or repetitive movement activities: Motor vehicle accidents with hyperextension injury and resulting fibrosis, including fibrous bands to the clavicle; musicians who maintain prolonged positions of shoulder abduction or extension may be at increased risk.
- Neurovascular entrapment: occurring in the costoclavicular space between the 1st rib and the head of the clavicle
- Trauma, especially to the shoulder girdle
- Presence of a cervical rib
- Posttraumatic, exostosis of clavicle or 1st rib, postural abnormalities (e.g., drooping of shoulders, scoliosis), body building with increased muscular bulk in thoracic outlet area, rapid weight loss with vigorous physical exertion and/or exercise, pendulous breasts
- Occupational exposure: computer users; musicians; repetitive work involving shoulders, arms, hands
- Young, thin females with long necks and drooping shoulders
Consider workplace evaluation for proper occupational ergonomics.
Commonly Associated Conditions
- Paget–von Schrötter syndrome: thrombosis of subclavian vein
- Gilliatt-Sumner hand: neurogenic atrophy of abductor pollicis brevis