Musculoskeletal · Vascular and Neurological Compression Syndromes
The facts most likely to be tested
Thoracic outlet syndrome results from the compression of the neurovascular bundle (brachial plexus, subclavian artery, or subclavian vein) as it exits the thoracic outlet.
The most common form is neurogenic thoracic outlet syndrome, which typically presents with paresthesias and atrophy of the intrinsic hand muscles (specifically the thenar eminence).
Vascular thoracic outlet syndrome involving the subclavian vein presents with upper extremity edema, cyanosis, and venous distension.
Subclavian artery compression manifests as exertional arm fatigue, pallor, coolness, and a diminished radial pulse.
The Adson test (loss of radial pulse during neck extension and head rotation toward the affected side) is a classic, though non-specific, physical exam maneuver.
Cervical ribs or fibrous bands extending from the C7 transverse process are the most common anatomical anomalies associated with the condition.
First-line management for neurogenic cases is physical therapy focusing on postural correction and strengthening of the shoulder girdle.
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A 32-year-old female weightlifter presents with a 3-month history of intermittent numbness and tingling in her right 4th and 5th digits. She reports that her symptoms worsen when she performs overhead presses. Physical examination reveals atrophy of the thenar eminence and a diminished radial pulse when the patient extends her neck and rotates her head toward the right. A chest X-ray reveals an elongated C7 transverse process.
What is the most likely diagnosis?
Thoracic outlet syndrome
The patient's presentation of neurovascular compression symptoms exacerbated by overhead activity, combined with the presence of a cervical rib (elongated C7 transverse process), is classic for thoracic outlet syndrome.
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Etiology / Epidemiology
Compression of the brachial plexus, subclavian artery, or subclavian vein in the thoracic outlet. Common in repetitive overhead activity or cervical rib presence.
Clinical Manifestations
Ulnar-sided paresthesias, hand atrophy, and vascular compromise. Adson's test is the classic, though non-specific, physical exam maneuver.
Diagnosis
MRI/CT angiography is the gold standard for vascular involvement; electromyography (EMG) confirms neurogenic TOS.
Treatment
Physical therapy is the first-line treatment for all patients. Avoid surgical intervention until conservative measures fail.
Prognosis
Most improve with conservative therapy; surgical decompression is reserved for refractory cases or vascular complications.
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Epidemiology & Etiology
Most common in patients aged 20–50 years with occupations requiring repetitive overhead arm motion. Anatomical variants such as a cervical rib or an elongated C7 transverse process predispose patients to compression. Trauma, such as a clavicle fracture, can also narrow the thoracic outlet space.
Pertinent Anatomy
The thoracic outlet is bounded by the first rib, the clavicle, and the scalenus anticus muscle. Compression occurs at the interscalene triangle, costoclavicular space, or subcoracoid space.
Pathophysiology
Neurogenic TOS (95% of cases) involves compression of the brachial plexus (usually C8-T1). Venous TOS involves subclavian vein compression, leading to Paget-Schroetter syndrome (effort thrombosis). Arterial TOS is the rarest, involving subclavian artery stenosis or aneurysm formation.
Clinical Manifestations
Patients present with ulnar nerve distribution paresthesias and pain. Look for thenar/hypothenar atrophy in chronic cases. Vascular red flags include arm swelling, cyanosis, or absent radial pulse with provocation. Adson's test, Roos test, and Wright's test are classic maneuvers used to reproduce symptoms.
Diagnosis
Diagnosis is primarily clinical. Electromyography (EMG) and nerve conduction studies are essential to confirm neurogenic TOS. CT angiography or MRI is the gold standard for identifying anatomical obstructions or vascular compromise.
Treatment
Initial management is physical therapy focusing on posture and strengthening the shoulder girdle. Avoid heavy lifting and overhead activities during the acute phase. If vascular compromise or severe neurological deficit exists, surgical decompression (first rib resection) is indicated.
Prognosis
The majority of patients achieve symptom resolution with conservative management. Key complications include permanent nerve damage or thromboembolic events in vascular TOS cases.
Differential Diagnosis
Cervical radiculopathy: pain reproduced by neck movement/Spurling test
Carpal tunnel syndrome: median nerve distribution, not ulnar
Pancoast tumor: apical lung mass causing Horner's syndrome
Ulnar neuropathy: symptoms isolated to the elbow/wrist
Complex regional pain syndrome: associated with autonomic skin changes