Table 1.

Classification of TOS.

Classification	Neurogenic	Arterial	Venous	Traumatic
Subdivision/(alternative terminology)	True (Classic, cervical rib and band syndrome). Disputed (common, non-specific, assumed and symptomatic).		(Paget-Schroetter syndrome, effort thrombosis or McCleery syndrome)
Prevalence	90–95% or 70–80% of TOS cases. 2–3/100,000 population per year. True NTOS: 1% of the NTOS cases. Disputed NTOS: 99% of the NTOS cases.	1–2% of TOS cases. 0.2–0.7 /100,000 population per year.	5% or 20–30% of TOS cases. 0.5–1/100,000 population per year.	Rare, 1/106 population per year.
Pathophysiology	Compression of brachial plexus cause: 1) Stretch and Angulation of the Lower Brachial plexus. 2) Motor and Sensory Abnormalities of C8 and T1 roots.	Compression of Subclavian and Axillary artery cause: 1) Intima damage. 2) Turbulent flow. 3) Post-stenotic dilatation. 4) Creation of Thrombus. 5) Formation of Aneurysm.	Compression of Subclavian and Axillary vein cause: 1) Damage of the endothelium. 2) Turbulent flow. 3) Restricted vein flow. 4) Creation of Thrombus.	Clavicular trauma that leads to neurovascular bundle compression
Causes (most common)	1) Anterior and/or Middle Scalene Muscle Trauma and Fibrosis (27, 28). 2) Last cervical vertebra anomaly (29). 3) Trauma (whiplash or series of minor cervical injuries). 4) Poor body posture and habitus (long neck with droopy shoulders).	Cervical Rib.	1) Repetitive upper extremity movements (hyperabduction and extension in athletes). 2) Hypercoagulopathic conditions.	Clavicular trauma.
Symptoms	True NTOS Motor Abnormalities: Intrinsic hand muscle weakness and wasting (worse in thenar eminence), reduced hand dexterity, impaired fine motor skills. T1 root more affected than C8: Median nerve innervated muscle weakness and wasting. T1 and C8 equally affected: Ulnar nerve innervated muscle weakness and wasting. Sensory abnormalities: Pain, paraesthesia of C8 and T1 dermotome. Disputed NTOS Unclear and controversial. predominantly sensory abnormalities. Neck and supraclavicular pain that radiates to the upper limb following lower plexus (C8-T1) or Upper plexus (C5–C6).	Chronic upper limb ischaemia: Upper limb pain, claudication, coolness, pallor, decreased CRT, digital ulcers, painless pulsatile subclavian mass and audible bruit. Acute upper limb ischaemia from distal emboli	Acute occlusion: Diffuse upper extremity swelling, palpable thrombosed axillary veins, upper limb pain, digital cyanosis. Chronic occlusion: Dilated veins in the neck, upper chest and shoulder. McCleery syndrome Positional and intermittent swelling of the arm.	Acute trauma: Pain at the trauma site radiating to the upper extremity, upper extremity edema or loss of peripheral arterial pulse. Chronic trauma: Calus palpation on the clavicle at the level of previous injury. Medial cord injury: Sensory medial (1) part of arm, forearm, hand, ring and little finger. Motor (2) Any ulnar and median nerve innervated muscles, except flexor carpi radialis and pronator teres.
Diagnostic tests	1) Sensory and motor nerve conduction studies. 2) Needle EMG. 3) Plain radiography. 4) MRI chest without and with IV contrast (preferable imaging). 5) CT chest (can be considered for post-operative follow-up).	1) Plain radiography. 2) Duplex doppler subclavian artery and vein. 3) Catheter arteriography of the upper extremity. 4) CT angiogram of chest with IV contrast. 5) MRA without and with IV contrast of the chest.	1) Screen for thrombotic disorders. 2) Plain radiography. 3) Duplex doppler subclavian artery and vein. 4) Catheter venography upper extremity. 5) CT chest with IV contrast. 6) MR angiography (disagreement).	1) Plain radiography of chest and clavicle. 2) Sensory and motor nerve conduction studies. 3) CT chest with and without IV contrast. 4) MRI chest without and with IV contrast.

CRT, Capillary Refill Time; CT, Computer Tomography; EMG, Electromyography; IV, Intravenous; MRA, Magnetic Resonance Angiography; MRI, Magnetic Resonance Imaging; NTOS, Neurogenic Thoracic Outlet Syndrome; TOS, Thoracic Outlet Syndrome.