Thoracic Outlet Syndrome, Subclavian Steal & Upper-Limb Ischemia
Where the arm's nerves and vessels get squeezed, stolen from, or blocked
Thoracic outlet syndrome
Anatomy. The brachial plexus and subclavian artery pass between the anterior and middle scalene muscles over the first rib, whereas the subclavian vein runs in front of the anterior scalene through the costoclavicular space. A cervical rib or anomalous first rib, scalene hypertrophy or post-traumatic scarring (e.g., after whiplash), and repetitive overhead activity narrow these spaces. Neurogenic compression accounts for about 95% of cases, venous for a few percent, and arterial for about 1%.
| Feature | Neurogenic | Venous (Paget-Schroetter) | Arterial |
|---|---|---|---|
| Structure | Lower trunk of brachial plexus (C8–T1) | Subclavian/axillary vein | Subclavian artery |
| Typical patient | Overhead workers, post-whiplash | Young athlete: swimmer, pitcher, weightlifter | Cervical or anomalous first rib |
| Presentation | Medial forearm and 4th–5th finger paresthesias, hand weakness or wasting | Sudden arm swelling, heaviness, cyanosis, dilated chest-wall veins | Pallor, coolness, arm claudication, digital emboli |
| Key test | Clinical; EMG/NCS to exclude mimics | Duplex ultrasound | Duplex, CTA |
| Treatment | Physical therapy → first-rib resection ± scalenectomy | Anticoagulation + catheter-directed thrombolysis → first-rib resection | Rib resection + arterial repair ± thrombectomy |
Neurogenic TOS. Pain and paresthesias follow the ulnar side of the forearm and hand and worsen with the arms overhead. Numbness of the medial forearm (medial antebrachial cutaneous nerve, C8–T1) places the lesion above the elbow, because isolated ulnar neuropathy spares it. The Adson maneuver (neck extended and rotated during deep inspiration, radial pulse diminishes) and the 3-minute elevated arm stress (Roos) test reproduce symptoms but are often positive in healthy people. Cervical spine or chest films look for a cervical rib, and EMG/nerve conduction studies exclude carpal tunnel syndrome, ulnar neuropathy, and C8 radiculopathy. Months of physical therapy (posture, scalene stretching, strengthening) come first; surgery, including excision of any cervical rib, is reserved for refractory cases.
Venous TOS. Paget-Schroetter syndrome is effort thrombosis of the axillosubclavian vein in a healthy young athlete. Duplex confirms it, and catheter-directed thrombolysis with anticoagulation works best within about 2 weeks of onset; first-rib resection then removes the compression to prevent rethrombosis. Untreated, it risks pulmonary embolism and post-thrombotic arm swelling. Contrast secondary upper-extremity DVT from central catheters or pacemaker leads, which is treated with anticoagulation alone.
Arterial TOS. A bony anomaly causes subclavian stenosis with poststenotic aneurysm whose mural thrombus embolizes to the hand; repair includes aneurysm resection and grafting.
Subclavian steal syndrome
Mechanism. A stenosis of the subclavian artery proximal to the vertebral origin, more often on the left, lowers pressure in the distal arm. When the arm exercises, the ipsilateral vertebral artery reverses direction and siphons blood from the basilar circulation. Atherosclerosis in older smokers is the usual cause; Takayasu arteritis (young women, "pulseless disease," elevated ESR, treated with glucocorticoids) is the classic cause in the young.
Findings. Arm fatigue or claudication and vertebrobasilar symptoms (vertigo, syncope, diplopia, ataxia) provoked by arm use; a weak, delayed radial pulse; a supraclavicular bruit; and a systolic gap >15–20 mmHg between arms. Duplex shows retrograde vertebral flow, and CTA or MRA defines the lesion.
Management. Reversed vertebral flow is often incidental and asymptomatic, needing only antiplatelet therapy, a statin, smoking cessation, and BP control based on the higher-reading arm. Disabling arm claudication or vertebrobasilar attacks warrant angioplasty and stenting or carotid-subclavian bypass/transposition.
Coronary-subclavian steal: in a patient with a LIMA-to-LAD graft, a proximal left subclavian stenosis steals flow from the graft, causing angina when the left arm works.
Acute embolic arm ischemia
Brachial embolus. Cardiac emboli from atrial fibrillation or post-MI mural thrombus usually lodge at the brachial bifurcation, producing sudden pain, pallor, pulselessness, paresthesia, and coolness. Give an immediate IV unfractionated heparin bolus and infusion, then perform brachial embolectomy with a Fogarty balloon catheter, often under local anesthesia. Obtain an echocardiogram and start long-term anticoagulation.
Digital ischemia and the palmar arch
| Feature | Primary Raynaud | Secondary Raynaud | Fixed digital ischemia |
|---|---|---|---|
| Pattern | Episodic white → blue → red; young women; symmetric | Episodic; later onset; asymmetric | Persistent pallor, ulcer, or gangrene |
| Clues | No ulcers, normal nailfold capillaries, negative ANA | Digital pits/ulcers, abnormal capillaries | Single digit or ulnar digits, embolic source |
| Causes | Idiopathic vasospasm | Systemic sclerosis, SLE, vibration tools, β-blockers | Emboli, hypothenar hammer, Buerger disease, vasculitis |
| Approach | Cold avoidance, smoking cessation, nifedipine or amlodipine | Same, plus treat the underlying disease | Duplex or angiography ± echocardiogram |
Hypothenar hammer syndrome. Using the heel of the hand as a hammer (mechanics, carpenters, machinists) injures the ulnar artery where it crosses the hook of the hamate. Thrombosis or aneurysm then embolizes to the 4th and 5th fingers, sparing the thumb. Angiography shows a tortuous "corkscrew" ulnar artery or occlusion. Treatment is stopping the trauma and tobacco, antithrombotic therapy, and resection with vein graft reconstruction for aneurysm or persistent ischemia. Buerger disease (young smokers) responds only to complete tobacco cessation.
Radial artery thrombosis. Occlusion after an arterial line or transradial catheterization is usually silent because the ulnar artery fills the palmar arch. An ischemic hand after cannulation requires removing the line, heparin, and urgent vascular surgery consultation.
- Compress both arteriesOcclude the radial and ulnar arteries at the wrist.
- Blanch the handThe patient clenches the fist until the palm is pale.
- Release the ulnar arteryBrisk return of color = adequate collateral; persistent pallor = choose another site.