Thoracic outlet syndrome (TOS) refers to a group of conditions that produce varying neurologic or vascular symptoms depending on the etiology. Etiologies include compression of neurologic or vascular structures at various anatomical sites in the upper extremity with neurologic involvement being far more common. The diagnosis of thoracic outlet syndrome is largely clinical, with clinical history and physical exam findings being the most sensitive and specific. The majority of cases can be treated successfully with nonoperative management. Surgery, which aims to decompress sites of anatomic compression, may be helpful in patients with symptoms refractory to nonoperative treatment.
21 Thoracic Outlet Syndrome
I. General overview
Two separates entities:
Neurogenic thoracic outlet syndrome (nTOS)
Vascular thoracic outlet syndrome (vTOS).
Caused by anatomical sites of compression of nervous structures/brachial plexus (nTOS) or shoulder girdle vessels (vTOS)
Incidence is 1 to 2% of general population:
nTOS is more common (19:1).
More common in women than men (3.5:1):
Theoretical risk factors are long neck and drooping shoulders.
Clinical symptoms include upper extremity pain, paresthesias, numbness, weakness, fatigability, heaviness, swelling, discoloration, and Raynaud phenomenon:
Pain and paresthesias most common.
Operative versus nonoperative management depending on cause.
Five roots: C5, C6, C7, C8, T1
Three trunks: Superior, middle, and inferior
Six divisions: Anterior and posterior divisions of three trunks
Three cords: Posterior, lateral, and medial
Five branches: Median, axillary, radial, musculocutaneous, and ulnar nerves
Lower trunk (C8–T1) > upper trunk (C5–C7) involvement in nTOS.
Runs anterior to interscalene triangle proximally
Becomes axillary vein after crossing first rib
Joins artery and brachial plexus in costoclavicular and retropectoralis minor space.
Branches off brachiocephalic trunk
Becomes axillary artery after crossing first rib.
Axillary artery (▶ Fig. 21.1 ):
Sites of compression from proximal to distal (▶ Fig. 21.2 ):
Anterior scalene muscle: Anterior border
Middle scalene muscle: Posterior border
First rib: Inferior border.
Clavicle: Anterior border
First rib: Posteromedial border
Costoclavicular ligament/scapula: Posterolateral border.
Retropectoralis minor space:
Pectoralis minor: Anterior border
Ribs 2 to 4: Posterior border
Coracoid: Superior border.
Anatomical anomalies causing TOS:
i. Variation in scalene muscle origin or insertion
ii. Presence of scalenus minimus
iii. Fibromuscular bands constricting inlet spaces.
i. Presence of cervical ribs
ii. Prominent C7 vertebrae transverse processes
iii. First rib anomalies
iv. Vertebral anomalies.
i. Atypical vessel course and branching.
i. Osteochondroma of first rib/clavicle
ii. Malunion after fracture of first rib/clavicle
iv. Posterior sternoclavicular dislocation.
i. Repetitive overhead activity produces cumulative effects of micro trauma.
i. Hypertrophic scalene muscles.