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Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) refers to a symptom complex of upper extremity pain and paresthesias involving compression neurovascular structures (90,91). It has been subdivided into:

(a) vascular (arterial and venous),

(b) true neurological, and

(c) nonspecific or “disputed” neurological categories.

The exact incidences of these categories are unclear. The true neurological TOS is rare and involves compression of the brachial plexus, typically involving the lower trunk and/or C8 to T1 anterior primary rami, by a cervical rib or a fibrous band from the tip of the transverse process .

Neurogenic TOS may present with atrophy in the abductor pollicis brevis, whereas the vascular TOS is the result of compression of the subclavian blood vessels as they emerge from the thorax and enter the upper limb. The disputed, nonspecific entity is the most common presentation. The physician must have a suspicion for this diagnosis clinically, because investigations often are nondiagnostic and the diagnosis is made by exclusion.

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