Thoracic Outlet Syndrome: What is it?

Jan 12

Reading time: 4 minutes

As a clinically-based chiropractor, it's essential to understand the diagnosis of thoracic outlet syndrome (TOS). TOS is upper extremity pain or paresthesia due to occlusion, compression, injury, or irritation of the neurovascular structures within the thoracic outlet.

What is Neurogenic Thoracic Outlet Syndrome

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

Pain, paresthesia, and possible motor weakness in the affected arm
Aggravation of symptoms 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

The 3 specific sites of compression leading to 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

New Research Alert

In a study by Tremblais (2022), nerve adhesion at the thoracic outlet significantly affected the mobility of the ulnar nerve, causing it to undergo greater deformation than usual and potentially leading to traumatic deformation exceeding 8%. (1)

The ability of a nerve to lengthen or shorten can cause damage to the nerve if excessively stretched. Nerves do not tolerate elongation well. After 8% stretch deformation, there may be reversible damage to the vascularization and axonal transport of the nerve. However, if the deformation exceeds 15%, there can be severe ischemia and irreversible damage to the axonal transport throughout the entire nerve tract.

Thoracic Outlet Syndrome Tests

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

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.

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 and then passively elevates their shoulder girdles. Hold this position for up to 3 minutes. A positive result includes either symptom reproduction or paresthesia secondary to a neurovascular release phenomenon.

The clinician monitors the patient's radial pulse while the seated patient's arm moves into hyperabduction and external rotation—a positive test results in the diminution of pulse intensity and reproduction of distal symptoms. Reproduction of TOS complaints implicates pectoral involvement. Aka stress hyperabduction test.

The clinician monitors radial pulse while the patient is seated with the shoulder in extension and chest in an exaggerated military posture—a positive test results in the diminution of pulse intensity and reproduction of distal symptoms.

Thoracic Outlet Syndrome Treatment

A combination of postural advice, manipulation, mobilization, soft tissue therapy, and at-home rehabilitation is the best recipe for these cases.
Joint manipulation may be indicated for restrictions in the cervical spine, first rib, cervicothoracic junction, shoulder, elbow, hand, and wrist.
Stretching and myofascial release techniques should address problems in the cervical spine, scalenes, pectoral muscles, and distal sites of potential "double crush" involvement, i.e., cubital tunnel, carpal tunnel, wrist flexors, etc.
Nerve mobilization, particularly for the ulnar nerve, will likely play a role in recovery. (3)
Lifestyle modifications may include avoidance of repetitive postural stress and workstation modification.
Patients should avoid carrying heavy loads, especially on their shoulders. Bra straps may need additional padding or consideration of replacement with a sports bra.

Types Of Thoracic Outlet Syndrome

In most cases, TOS is relatively benign, responding well to conservative care. However, a small percentage of cases (about 5%) may have more serious underlying causes. Recognizing the signs of these ominous presentations and knowing the best practices for evaluating and treating TOS is essential.

Arterial TOS (A-TOS)

Arterial pathology, including (A-TOS) is a vascular problem but may be due to repetitive mechanical trauma and (is sometimes) misdiagnosed as musculoskeletal injury. (4)

Arterial occlusion of the subclavian artery may occur secondary to stenosis, aneurysm, embolus, or compression from a cervical rib or abnormal 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)

Management: Urgently refer to emergency management if you suspect A-TOS

Venous TOS (V-TOS)

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 shoulder
Constant symptoms that worsen with activity
Swelling and cyanotic discoloration of the upper extremity

Management: Refer to a vascular specialist if you suspect V-TOS.

Thoracic Outlet Syndrome Surgery

Patients with progressive motor deficits require advanced diagnostic workup and referral. (5)
The surgical treatment of TOS remains controversial. (6)
Studies have shown that candidates who undergo surgical resection of a rib do not have functional improvements matching those who choose conservative care. (7)
Other studies have shown good surgical outcomes (90%) when conservative measures have failed for neurogenic TOS patients. (8)

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.

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1. Tremblais L, Rutka V, Cievet-Bonfils M, Gazarian A. The consequences of a thoracic outlet syndrome's entrapment model on the biomechanics of the ulnar nerve-Cadaveric study. Journal of Hand Therapy. 2022 Oct 23.
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.
3. Mackinnon SE, Novak CB. Thoracic outlet syndrome. Current problems in surgery. 2002 Nov 1;39(11):1070-145.
4. 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.
5. Kim SW, Jeong JS, Kim BJ, Choe YH, Yoon YC, Sung DH. Clinical, electrodiagnostic and imaging features of true neurogenic thoracic outlet syndrome: Experience at a tertiary referral center. J Neurol Sci. 2019 Sep 15;404:115-123.
6. Degeorges R, Reynaud C, Becquemin JP. Thoracic outlet syndrome surgery: long-term functional results. Annals of vascular surgery. 2004 Sep 1;18(5):558-65.
7. Landry GJ, Moneta GL, Taylor Jr LM, Edwards JM, Porter JM. Long-term functional outcome of neurogenic thoracic outlet syndrome in surgically and conservatively treated patients. Journal of vascular surgery. 2001 Feb 1;33(2):312-9.
8. Balderman J, Abuirqeba AA, Eichaker L, Pate C, Earley JA, Bottros MM, Jayarajan SN, Thompson RW. Physical therapy management, surgical treatment, and patient-reported outcomes measures in a prospective observational cohort of patients with neurogenic thoracic outlet syndrome. Journal of vascular surgery. 2019 Mar 7.

Brandon Steele

Dr. Steele is currently in private practice at Premier Rehab in the greater St. Louis area. He began his career with a post-graduate residency at The Central Institute for Human Performance. During this unique opportunity, he was able to create and implement rehabilitation programs for members of the St. Louis Cardinals, Rams, and Blues. Dr. Steele currently lectures extensively on evidence-based treatment of musculoskeletal disorders for the University of Bridgeport’s diplomate in orthopedics program. He serves on the executive board of the Illinois Chiropractic Society. He is also a Diplomate and Fellow of the Academy of Chiropractic Orthopedists (FACO).