The thoracic outlet is an anatomic region containing the first rib, the subclavian artery and vein, the brachial plexus, the clavicle, and the lung apex. Injury to these structures may result in posture or task-related pain around the shoulder and supraclavicular region. There are at least three subtypes of thoracic outlet syndrome (TOS). True neurogenic TOS results from compression of the lower trunk of the brachial plexus by an anomalous band of tissue connecting an elongate transverse process at C7 with the first rib. Neurologic deficits include weakness of intrinsic muscles of the hand and diminished sensation on the palmar aspect of the fourth and fifth digits. EMG and nerve conduction studies confirm the diagnosis. Definitive treatment consists of surgical division of the anomalous band compressing either the lower trunk of the brachial plexus or ventral rami of the C8 or T1 nerve roots. The weakness and wasting of intrinsic hand muscles typically does not improve, but surgery halts the insidious progression of weakness. .
The arterial TOS results from compression of the subclavian artery by a cervical rib; the compression results in poststenotic dilatation of the artery and thrombus formation. Blood pressure is reduced in the affected limb, and signs of emboli may be present in the hand; neurologic signs are absent. Noninvasive ultrasound techniques confirm the diagnosis. Treatment is with thrombolysis or anticoagulation (with or without embolectomy) and surgical excision of the cervical rib compressing the subclavian artery or vein. The disputed TOS includes a large number of patients with chronic arm and shoulder pain of unclear cause. The lack of sensitive and specific findings on physical examination or laboratory markers for this condition frequently results in diagnostic uncertainty. The role of surgery in disputed TOS
is controversial; conservative approaches often include
multidisciplinary pain management. Treatment is often unsuccessful
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Brachial Plexus and Nerves