Discussion:

TOS is usually caused by extrinsic compression and subsequent stenosis of the neurovascular structure. An anatomical abnormality is the typically fundamental prerequisite, including a cervical rib, anomalous first rib, or anomalous scalene muscle [6]. Additionally, injuries such as hyperextension/flexion injury of neck and bony fracture have been described [7, 8]. Thrombosis and tumor are also potential etiologies. The vTOS composed of 3-5% cases of TOS. It is more common in younger (aged 14-45), able-bodies individuals, and most often affects the dominant upper extremity [9]. The vTOS is also grouped into 3 categories: intermittent positional stenosis/obstruction, secondary subclavian vein thrombosis due to catheter placement, and effort thrombosis [3].
The symptoms of nTOS include pain, dysesthesia, numbness, and weakness involving the distribution area of C5 through T1 brachial plexus nerves. The aTOS can present with hand ischemic symptoms like pain, pallor, paresthesia, and coldness. The vTOS presents with upper extremity edema, accompanied by pain and cyanosis. Symptoms may be atypical and elusive, as illustrated in our patient with recurrent chest pressure, masquerading as angina pectoris. A clue to diagnosis was the precipitant of symptoms triggered by arm movement. As such, he was referred for an upper extremity venous duplex with examination maneuvers to temporarily occlude the neurovascular structure. Electrodiagnostic testing via nerve conduction and electromyography (EMG) are indicated for suspected nTOS. For vTOS and aTOS, Doppler ultrasound is the primary test of choice due to real-time assessment of dynamic Doppler signals associated with compressive maneuvers, yielding a high sensitivity and specificity[10]. Secondary tests include CT or MRI to define anatomical defects, such as prominent cervical rib or compressive tumors and their anatomical relationship to the thoracic outlet[10].
Treatment strategy of TOS depends on the underlying etiology, and can involve conservative or surgical measures. Cervical rib or anomalous rib without symptoms only need observation. Therapeutic strategies for nTOS include physical therapy with option for interscalene injection, corticosteroids, and botulinum toxin type A. Anticoagulation can be given for thrombosis complicating VTOS or aTOS. Surgical intervention such as thoracic outlet decompression remains the final method conservative management fails. Surgical intervention is often the initial approach for vTOS and aTOS in current practice, with the first rib being resected to decompress the brachial plexus. The procedure is usually performed by transaxillary, supraclavicular, or infraclavicular techniques. Blocking the scalene muscle or pectoralis minor may be done to predict the effect of surgery.