EM@3AM: Thoracic Outlet Syndrome

Authors: Kerrigan Samons, MD (EM Resident Physician, UK- Lexington, KY); Blake Davidson, MD (Assistant Program Director of EM/Attending Physician, UK- Lexington, KY) // Reviewed by: Sophia Görgens, MD (EM Physician, Yale University, CT); Cassandra Mackey, MD (Assistant Professor of Emergency Medicine, UMass Chan Medical School)

Welcome to EM@3AM, an emDOCs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

A 35-year-old female presents to the ED with intermittent right arm pain and numbness that has been worsening for the last month. She endorses symptoms are worsened by lifting her arm above her head, especially when styling her hair. She has also noticed new hand swelling and a “cold” sensation in her fingertips. She denies any trauma.

Vitals are as follows HR 72, RR 16, 99% on RA, BP 117/79, afebrile. On exam, she has diminished sensation in the 4^th and 5^th digit with noticeable hand swelling. She does have a palpable radial pulse.

What should be considered in your differential diagnosis?

Answer: Thoracic Outlet Syndrome (TOS)^1-7

Background:

• Thoracic outlet syndrome (TOS) refers to a group of conditions caused by compression of the neurovascular structures (brachial plexus, subclavian artery, or vein) as they pass through the thoracic outlet located between the clavicle and first rib⁷.

Etiology:

• Most commonly due to anatomical variations (such as a cervical first rib or anomalous scalene muscles), repetitive overhead activity, or trauma, all that can lead to narrowing of the thoracic outlet space, compression and inflammation⁷.
• Congenital abnormalities that are present at birth are often not symptomatic until adolescence or adulthood, often delayed secondary to development, posture changes, or increased physical activity⁸.
• Repetitive overhead motions- seen in athletes, laborers, or occupations requiring arm elevation- lead to gradual symptoms that can lead to chronic complications like neurovascular injury⁸.
• Traumatic causes can include clavicle fractures or whiplash injuries and can have immediate symptoms of thoracic outlet syndrome.

Epidemiology:

• Incidence is unclear- there is one study indicating 2-3 cases per 100,000 from a recent prospective database from a vascular surgery clinic¹.
• More common in women (ages 20-50)¹¹, believed to be due to structural differences (narrower thoracic outlet, smaller muscle mass) and reported jobs more at risk for developing symptoms.
• 3 subtypes: Neurogenic (90-95%), venous (3-5%), arterial (<1%)⁹
  • Subtypes are named based on the primary structure being compressed: neurogenic involves brachial plexus compression (paresthesias, pain, weakness), venous is compression of subclavian vein (swelling and cyanosis), and arterial is compression of subclavian artery (distal ischemia, coolness, pain)
• It is believed soft tissue and repetitive use mechanisms cause the majority of symptomatic cases (~70%), with bony/congenital abnormalities leading to other cases (~30%)¹¹.

Anatomy:

• The thoracic outlet is the space bordered by the first rib, clavicle, and surrounding musculature (anterior and middle scalene muscles, pectoralis minor), forming three potential compression sites: the interscalene triangle, costoclavicular space, and subpectoral (retropectoralis minor) space.
• Key structures traversing this region include the brachial plexus, subclavian artery, and subclavian vein, with the specific structure compressed determining whether symptoms are neurogenic, arterial, or venous.²

Clinical Presentation⁷:

• Neurogenic TOS (most common):
  • arm/shoulder pain
  • paresthesias (often ulnar distribution)
  • weakness
  • symptoms worsened with overhead activity or prolonged use.
• Venous TOS:
  • acute arm swelling
  • cyanosis
  • heaviness
  • prominent superficial veins (effort thrombosis)
  • Does NOT always cause a clot, but can mimic DVT symptoms when provoked⁴
  • Also known as Paget-Schroetter Syndrome, upper extremity DVTs are very uncommon and typically only seen in setting of TOS, cancer or indwelling lines⁴.
• Arterial TOS (rare):
  • limb ischemia
  • pallor
  • coolness
  • diminished pulses
  • can mimic distal embolic disease with digital pain and ischemia.

Evaluation:

• Initial priority is to rule out life-threatening causes in the ED, these include: DVT, arterial occlusion, or pulmonary embolism (PE).
• Imaging:
  • Ultrasound: first line for venous TOS (DVT)
  • CT Angiography (CTA): evaluate for arterial TOS or other cause of arterial occlusion
  • MRI: first line imaging to assess soft tissue/brachial plexus compromise, however, likely unable to obtain in ED
  • XR: not as useful, but sometimes able to evaluate for cervical rib or other bony abnormalities.

Treatment⁶:

• Neurogenic TOS: discharge with outpatient follow up with PM&R/physical therapy for initial management, NSAIDs, if refractory to first line can require surgical decompression with Vascular Surgery⁶.
• Venous TOS: anticoagulation alone typically not sufficient, requires admission for anticoagulation with heparin, thrombolysis and possible surgical decompression with Vascular Surgery.
• Arterial TOS: requires emergent Vascular Surgery consultation and admission, initiation of heparin and possible thrombectomy, arterial repair or decompression.

Complications:

• Untreated TOS:
  • Chronic pain, functional upper extremity weakness
  • Progression to DVT with VTOS
  • Limb ischemia, tissue damage with ATOS
• Treated TOS:
  • Surgical risks: bleeding, infection, nerve injury
  • Continued symptoms despite surgical decompression
  • Vascular injury from intervention
  • Bleeding risk if started on anticoagulation

Pearls:

• Neurogenic TOS accounts for 90-95% of cases and is often a diagnosis of exclusion
• Initial management of neurogenic TOS is conservative (physical therapy, posture correction), if refractory, consider outpatient surgical decompression⁶.
• Arterial and Venous TOS often require anticoagulation and possible surgical decompression urgently. Be prompt and start treatment in the ED.

What is the typical presentation of a patient with thoracic outlet syndrome?

A) Burning pain and paresthesias limited to the thumb, index finger, and middle finger that worsen at night

B) Neck pain radiating down the arm in a dermatomal distribution with diminished deep tendon reflexes

C) Paresthesias isolated to the fourth and fifth digits that worsen with prolonged elbow flexion

D) Shoulder pain with weakness during abduction and external rotation without distal sensory symptoms

E) Upper extremity pain, paresthesias, and heaviness that worsens with arm elevation

Answer: E

Thoracic outlet syndrome results from compression of the brachial plexus, subclavian vein, subclavian artery, or a combination of these structures as they pass through the thoracic outlet. Neurogenic thoracic outlet syndrome is the most common form and typically causes upper extremity pain, paresthesias, numbness, weakness, heaviness, or fatigue.

Symptoms are often positional and are characteristically exacerbated by elevation of the affected arm or repetitive overhead activity. Neurologic symptoms may involve the shoulder, arm, forearm, or hand and do not always conform to a single peripheral nerve or dermatomal distribution. Patients may have a normal neurologic examination when the arm is at rest.

The diagnosis of neurogenic thoracic outlet syndrome is primarily clinical and is supported by a compatible history and physical examination after excluding more common causes of upper extremity symptoms such as cervical radiculopathy and peripheral nerve entrapment. Provocative maneuvers, including the elevated arm stress test and Tinel sign over the brachial plexus, may reproduce symptoms but are not independently diagnostic. Chest or cervical spine radiography can identify anatomic abnormalities such as a cervical rib.

Initial treatment generally consists of conservative management with physical therapy, postural correction, and modification of activities that provoke symptoms. Surgical decompression may be considered when symptoms persist despite appropriate conservative therapy or when significant muscle weakness or atrophy is present.

Burning pain and paresthesias limited to the thumb, index finger, and middle finger that worsen at night (A) is more consistent with carpal tunnel syndrome, which results from compression of the median nerve at the wrist. Sensory symptoms typically involve the thumb, index finger, middle finger, and radial aspect of the ring finger. Symptoms are often worse at night or with repetitive wrist activity. Thoracic outlet syndrome more commonly causes broader upper extremity symptoms provoked by arm elevation.

Neck pain radiating down the arm in a dermatomal distribution with diminished deep tendon reflexes (B) is more suggestive of cervical radiculopathy. Cervical nerve root compression typically causes pain or paresthesias in a dermatomal distribution and may be accompanied by focal weakness or reduced reflexes corresponding to the affected nerve root. Neck movement may reproduce symptoms. Thoracic outlet syndrome is more strongly associated with symptoms provoked by overhead arm positioning and may not follow a single dermatome.

Paresthesias isolated to the fourth and fifth digits that worsen with prolonged elbow flexion (C) suggests ulnar neuropathy, particularly compression of the ulnar nerve at the elbow. Patients usually report numbness or tingling in the fifth digit and ulnar half of the fourth digit, and symptoms may worsen with prolonged elbow flexion.

Shoulder pain with weakness during abduction and external rotation without distal sensory symptoms (D) is more consistent with rotator cuff pathology. Rotator cuff disease commonly produces shoulder pain and weakness with specific shoulder movements, particularly abduction or external rotation.

Rosh Review Website Link

Further Reading:

1. https://www.aliem.com/splinter-series-venous-thoracic-outlet-syndrome/
2. https://www.emdocs.net/em3am-upper-extremity-dvt/

References:

1. Illig KA, Rodriguez-Zoppi E, Bland T, Muftah M, Jospitre E. The Incidence of Thoracic Outlet Syndrome. Ann Vasc Surg. 2021 Jan;70:263-272. doi: 10.1016/j.avsg.2020.07.029. Epub 2020 Aug 6. PMID: 32771464.
2. “Thoracic Outlet Syndrome (TOS).” Physiopedia. 1 Apr 2025, 08:06 UTC. 23 Apr 2026, 17:30<https://www.physiopedia.com/index.php?title=Thoracic_Outlet_Syndrome_(TOS)&oldid=367513>.
3. Rizzo S, Talei Franzesi C, Cara A, Cassina EM, Libretti L, Pirondini E, Raveglia F, Tuoro A, Vaquer S, Degiovanni S, et al. Diagnostic and Therapeutic Approach to Thoracic Outlet Syndrome. Tomography. 2024; 10(9):1365-1378. https://doi.org/10.3390/tomography10090103
4. Hangge P, Rotellini-Coltvet L, Deipolyi AR, Albadawi H, Oklu R. Paget-Schroetter syndrome: treatment of venous thrombosis and outcomes. Cardiovasc Diagn Ther. 2017 Dec;7(Suppl 3):S285-S290. doi: 10.21037/cdt.2017.08.15. PMID: 29399532; PMCID: PMC5778512.
5. https://www.radiologymasterclass.co.uk/gallery/chest/variants/cervical_rib
6. Chang DC, Rotellini-Coltvet LA, Mukherjee D, De Leon R, Freischlag JA. Surgical intervention for thoracic outlet syndrome improves patient’s quality of life. J Vasc Surg. 2009 Mar;49(3):630-5; discussion 635-7. doi: 10.1016/j.jvs.2008.10.023. Epub 2009 Jan 14. PMID: 19147319.
7. Sanders RJ, Hammond SL, Rao NM. Diagnosis of thoracic outlet syndrome. J Vasc Surg. 2007 Sep;46(3):601-4. doi: 10.1016/j.jvs.2007.04.050. PMID: 17826254.
8. Maślanka K, Zielinska N, Karauda P, Balcerzak A, Georgiev G, Borowski A, Drobniewski M, Olewnik Ł. Congenital, Acquired, and Trauma-Related Risk Factors for Thoracic Outlet Syndrome-Review of the Literature. J Clin Med. 2023 Oct 27;12(21):6811. doi: 10.3390/jcm12216811. PMID: 37959276; PMCID: PMC10648912.
9. Jones MR, Prabhakar A, Viswanath O, Urits I, Green JB, Kendrick JB, Brunk AJ, Eng MR, Orhurhu V, Cornett EM, Kaye AD. Thoracic Outlet Syndrome: A Comprehensive Review of Pathophysiology, Diagnosis, and Treatment. Pain Ther. 2019 Jun;8(1):5-18. doi: 10.1007/s40122-019-0124-2. Epub 2019 Apr 29. PMID: 31037504; PMCID: PMC6514035.
10. Li N, Dierks G, Vervaeke HE, Jumonville A, Kaye AD, Myrcik D, Paladini A, Varrassi G, Viswanath O, Urits I. Thoracic Outlet Syndrome: A Narrative Review. Journal of Clinical Medicine. 2021; 10(5):962. https://doi.org/10.3390/jcm10050962
11. Kaplan J, Kanwal A. Thoracic Outlet Syndrome. [Updated 2023 Apr 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/sites/books/NBK557450/?utm_source=chatgpt.com