Thoracic Outlet Syndrome on MRI & X-ray: Imaging Findings

Plain radiographs are the first-line study to identify cervical ribs or an elongated C7 transverse process compressing the brachial plexus or subclavian vessels. CT angiography or MR angiography with the arms in neutral and provocative elevated positions delineates arterial and venous compression dynamically. MRI of the brachial plexus using dedicated neurography sequences (coronal STIR and 3D FIESTA or SPACE) can demonstrate brachial plexus thickening, perineural edema, and muscle denervation changes in the hand and forearm. Axial T2-FS sequences assess the scalene muscles and any soft-tissue bands. Duplex ultrasound and venography evaluate venous thoracic outlet syndrome with subclavian vein thrombosis. Nerve conduction studies and electromyography confirm and localize neurogenic TOS.

Neurogenic TOS, accounting for over 95% of cases, results from compression of the brachial plexus between the scalene muscles, cervical rib or fibrous band, and first rib. Symptoms are predominantly sensory (paresthesias in C8-T1 distribution) with motor deficits in true neurogenic TOS (Gilliatt-Sumner hand with thenar and hypothenar wasting). Venous TOS (Paget-Schroetter syndrome) involves subclavian vein thrombosis from repetitive arm elevation compressing the vein between the first rib and subclavius and costoclavicular ligament, causing acute upper extremity swelling and cyanosis. Arterial TOS is the rarest form, caused by subclavian artery compression from a cervical rib, producing aneurysm formation, thromboembolism, and digital ischemia. Each type requires different diagnostic workup and treatment strategy.

Neurogenic TOS is initially managed conservatively with physical therapy emphasizing postural correction, scalene and pectoralis minor stretching, and shoulder girdle strengthening. Botulinum toxin injection into the anterior scalene can confirm the diagnosis and provide temporary relief. Surgical decompression via transaxillary or supraclavicular first rib resection, with scalenectomy and cervical rib removal when present, is reserved for patients who fail 3–6 months of conservative therapy. Venous TOS requires urgent catheter-directed thrombolysis for acute subclavian vein thrombosis followed by first rib resection to prevent recurrence. Arterial TOS necessitates surgical repair of the subclavian artery with aneurysm resection or bypass combined with first rib resection and cervical rib removal, with thromboembolectomy for acute ischemia.