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Erb-Duchenne syndrome or upper radicular syndrome involves injury to the C4, C5, and C6 nerve roots, or the upper trunk of the brachial plexus.1 This syndrome typically occurs following a hard blow to the neck or a birth injury. The signs consist of loss of arm abduction, elbow flexion, supination, and lateral arm rotation. The patient's arm assumes a "waiter's tip" arm position.
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The middle radicular syndrome occurs following an injury of the C7 nerve root or the middle trunk of the brachial plexus. There is typically loss of radially innervated muscles except brachioradialis and part of the triceps. This syndrome can occur with the inappropriate use of crutches (crutch paralysis).
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Klumpke syndrome or lower radicular syndrome occurs with an injury of the C8 and T1 nerve roots or the lower trunk of the brachial plexus.1,30 It appears clinically as a combined median and ulnar palsy. There is paralysis of the thenar muscles and flexors resulting in a flattened simian hand. The syndrome usually occurs after a sudden pull of the arm or during delivery.
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Thoracic Outlet Syndrome
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Thoracic outlet syndrome (TOS) occurs secondary to compression of the neurovascular bundle between the neck and axilla, causing variable hand and arm muscle weakness and wasting, pain, and vascular symptoms.
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Etiology/Pathogenesis
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Thoracic outlet syndrome can occur because of a number of disorders. An incomplete cervical rib with fibrous band passing from its tip to first rib is the most common cause. An elongated transverse process of C7 with fibrous bands passing to the first rib, a complete cervical rib that articulates with the first rib, and anomalies of position/insertion of the anterior and medial scalene muscles (neurovascular bundle passes between these), are other anatomic causes of TOS. Fractures of the clavicle and first rib, pseudoarthrosis of the clavicle, and traumatic injury to upper thorax can also result in TOS.
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Clinical Presentation
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Non-neurogenic TOS is usually seen in slender, "droop-shouldered" females with long necks, large breasts, and often poor muscle tone. This syndrome is usually accompanied by an ill-defined pain complex, with aching discomfort in shoulder, lower neck, pectoral region, upper arm, and sometimes hands, exacerbated by pulling down on and relieved by elevating the shoulder. In more severe cases, the patient may have signs of vascular compromise: subclavian vein compression—dusky color of the arm, venous distension, edema and thrombosis of vein after exercise (effort—thrombotic syndrome of Paget and Schroetter); or subclavian artery compression—digital gangrene, Raynaud phenomenon, brittle nails, or fingertip ulceration with or without supraclavicular bruit.
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Tests for vascular compression are not very sensitive or specific but may be of some diagnostic help. For the test to be considered positive, the patient's symptoms should be reproduced during the maneuver. The Adson test is performed with the patient seated with hands on the thighs; both radial pulses are palpated simultaneously, the breath is held after full and rapid inspiration, the neck is hyperextended, and the head is turned to the side. The test is positive if the radial pulse on the affected side is diminished or obliterated, with the unaffected side remaining normal.
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The shoulder hyperabduction test (Wright maneuver) is performed with the arm hyperabducted and externally rotated while the radial pulse is palpated; the pulse in normal subjects diminishes. The test is positive if the pulse diminishes asymmetrically in the presence of symptoms.
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In the shoulder bracing test, the shoulders are braced backwards in an "exaggerated military position." The pulse on the affected side decreases more markedly than normal in the presence of symptoms.
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Nerve conduction studies and EMG in non-neurogenic TOS are usually normal.
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Neurogenic TOS is extremely rare. The syndrome typically consists of weakness and wasting of hypothenar and thenar muscles (in severe cases, of other hand intrinsics as well as flexors of fourth and fifth digits). There is usually an aching pain and sensory loss in the C8/T1 dermatomes (lower trunk involvement). Sensory symptoms may be reproduced by applying firm supraclavicular pressure or downward traction on the arm. Reflexes are usually preserved.
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Nerve conduction studies and EMG show reduced amplitude of ulnar CNAP distally and across the thoracic outlet, prolonged ulnar F-wave latency, low CMAP in the median > ulnar nerve, and signs of chronic denervation in ulnar and median hand muscles.
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Evaluation for both types of TOS should include C-spine films (may show cervical rib, elongated C7 spinous process, or T2 vertebral body visible above shoulder), nerve conduction studies, EMG, and possibly somatosensory evoked potentials.