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Thoracic outlet syndrome (TOS) is a common diagnosis for evidence-based chiropractors. The condition is characterized by upper extremity pain and paresthesia secondary to occlusion, compression, injury, or irritation to the neurovascular structures traversing the thoracic outlet.

The majority of TOS cases are relatively benign and will respond favorably to conservative care, however, approximately 5% of TOS presentations arise from more threatening origins. This video blog will give you tools to spot ominous presentations and review current best practice evaluations for the remainder.

Learn more 👇


This blog provides a simple synopsis on how to quickly differentiate:

  • Neurogenic TOS
  • Arterial TOS
  • Venous TOS

Let’s break it down:

Arterial TOS (A-TOS) (blood can’t get in)

Arterial pathology, including (A-TOS) is a vascular problem, but may be due to repetitive mechanical trauma and (is sometimes) misdiagnosed as musculoskeletal injury. (1)

Arterial occlusion of the subclavian artery may occur secondary to stenosis, aneurysm, embolus, or compression from a cervical rib or anomalous first rib. It is the most threatening cause of TOS, accounting for less than 1% of all cases. Signs and symptoms include:


  • Non-radicular pain of the upper extremity
  • Pain rarely involves the shoulder or neck
  • Pain may be present at rest but worsened by elevating the arms above the head.
  • Possible Raynaud’s phenomenon
  • Signs of vascular claudication (5 P’s: pain, paralysis, pallor, paresthesia, & pulselessness)


Urgently refer for emergency management if you suspect A-TOS

Arterial TOS (A-TOS)

Venous TOS (V-TOS) (blood gets in, but can’t get out)

Subclavian vein obstruction (V-TOS) is the causative mechanism for less than 5% of all cases of TOS. Findings include:


  • “Deep” pain in the upper extremity, chest, and/or shoulder
  • Constant symptoms that worsen with activity
  • Swelling and cyanotic discoloration of the upper extremity


Refer for emergency management if you suspect V-TOS.

Venous TOS (V-TOS)

Neurogenic TOS (N-TOS) (irritation to the brachial plexus)

Neurogenic TOS is the most common cause of TOS, accounting for over 95% of all cases. N-TOS results from compression or irritation to the lower trunk or medial cord of the brachial plexus. Symptoms typically include:


  • Pain, paresthesia, and possible motor weakness in the affected arm
  • Symptoms are aggravated by elevation of the arms or excessive head and neck movement
  • Symptoms predominately involve the C8/T1 segmental level and follow an ulnar nerve distribution in 90% of cases

There are three potential sites of compression for N-TOS:


  • “Scalene” induced TOS occurs from the compression of the neurovascular bundle between the anterior and middle scalene muscles
  • “Pectoral” compression occurs beneath the pectoralis minor tendon “Costoclavicular” compression happens between the first rib and clavicle

The current evidence-based clinical evaluation of TOS includes (2):

Brachial Plexus Compression Test (General Screening):

This test is positive when deeper palpation of the supraclavicular fossa elicits distal symptoms. Positive in up to 68% of TOS patients. aka Morley test

Cyriax Release Maneuver (General Screening):

The clinician stands behind the seated patient and grasps beneath both forearms, holding the elbows at 80 degrees of flexion with the forearms and wrists neutral. The clinician leans the patient’s trunk posteriorly then passively elevates their shoulder girdles. This position is held for up to 3 minutes. A positive result includes either symptom reproduction or paresthesia secondary to a neurovascular release phenomenon.

Wright’s Test (Pectoral Involvement):

The clinician monitors the patient’s radial pulse while the seated patient’s arm is taken into in hyperabduction and external rotation. A positive test results in diminution of pulse intensity and reproduction of distal symptoms. Reproduction of TOS complaints implicates pectoral involvement. aka stress hyperabduction test.

Costoclavicular Test (Costoclavicular Involvement):

The clinician monitors radial pulse while the patient is seated with shoulder in extension, chest in exaggerated military posture. This maneuver is believed to compress the costoclavicular space. A positive test results in diminution of pulse intensity and reproduction of distal symptoms.


Evidence-based chiropractors provide care to effectively treat N-TOS. A combination of postural advice, manipulation, mobilization, soft tissue therapy, and at home rehabilitation is the best recipe for these cases. Check out the ChiroUp Condition Reference for a more complete synopsis of the most up-to-date information on how to diagnose and treat N-TOS. 

TOS Clinical Pearls

  • Weakness, coldness, fatigability, and diffuse arm pain may be arterial TOS and should be referred out (<1%)
  • Repetitive arm abduction creating edema, cyanosis, and venous dilation may be a sign of venous TOS (<5%)
  • Symptoms follow an ulnar distribution 90% of the time
  • TOS is more common in women with some estimates as high as 9:1
  • Clinicians should assess for potential double crush partners. i.e. cubital tunnel, carpal tunnel, etc.
  • Up to 23% of cervical soft tissue injuries (whiplash) may include a TOS component

Wouldn’t it be awesome if there were an online library that held all of these best practices for TOS and other common conditions? 

Well, guess what… There is.

ChiroUp gives you access to evaluation & rehab for 96 conditions in a matter of seconds.

This means no more time spent researching and determining what test is the best, because we do that part for you – it’s your job to apply them. 

Do yourself a favor & get started with an account today.

(We’ll do you a favor & give you your first 14-days for free 🙂)

  1. Menon D, Onida S, Davies AH. Overview of arterial pathology related to repetitive trauma in athletes. J Vasc Surg. 2019 May 18. pii: S0741-5214(19)30202-2.
  2. Horris HB et al. The Diagnostic Accuracy of Clinical Diagnostic Tests for Thoracic Outlet Syndrome. Journal of Sport Rehabilitation, 2017, vol. 26, issue 5, p 459

About the Author

Dr. Brandon Steele

Dr. Brandon Steele


Dr. Steele began his career at The Central Institute for Human Performance. Dr. Steele has trained with experts including Pavel Kolar, Stuart McGill, Brett Winchester, and Clayton Skaggs. He has been certified in Motion Palpation, DNS, ART, and McKenzie Therapy. Dr. Steele lectures extensively on clinical excellence and evidence-based musculoskeletal management. He currently practices in Swansea, IL and serves on the executive board of the ICS.

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