• Dr. Brian Abelson DC., Dr Evangelos Mylonas DC.


Updated: Nov 1

A lot of patients complain about numbness or tingling in their hands when working at the computer, driving their vehicle, or even when waking up in the morning. Many of these same patients also experience tight and restricted neck muscles, have shoulder tension, feel chest tightness, and even pain that can radiate down their arms and hands. Although there are a number of conditions that can present with these same symptoms, one of the conditions is called Thoracic Outlet Syndrome (TOS). Several studies report an incidence of 3–80/1000 people who suffer from TOS.

TOS is an umbrella term that refers to conditions that involve compression of a neurovascular bundle. A neurovascular bundle is a structure that binds together nerves, veins, or arteries with connective tissues, allowing them to travel in tandem through the body. The neurovascular bundle involved in TOS contains the brachial plexus, the subclavian artery and subclavian vein.



In the neck and shoulder regions, the neurovascular bundle travels through the thoracic outlet space. The thoracic outlet space starts at the scalene triangle (a group of three muscles in the neck) and terminates at the pectoralis minor muscle. (1)

Some of the anatomical structures that can potentially cause compression of the neurovascular bundle include:

  • Scalene Muscles: Entrapment primarily occurs at the anterior and medial scalene, and not as much at the posterior scalene. (7)

  • Subclavian Muscle: In some cases this muscle can attach to the first rib and cause compression of the costoclavicular space. (6; 20)

  • Pectoralis Minor Muscle: Many cases of TOS can involve various muscles. In fact, some research is now showing that 75% of TOS cases involve the pectoralis minor muscle.(8) Because the brachial plexus is located just under the pectoralis minor, the compression it causes is primarily neurogenic. (8)

  • First Rib: The shape of the first rib can be a determining factor in whether or not it is involved in compression. (9)

  • Ulnar Nerve: The ulnar nerve is made up of the C8/T1 nerve roots. Since the C8/T1 nerve roots are located beside the first rib, they are more susceptible to compression. This is why 70-90% of TOS cases have an ulnar nerve distribution in the 4th and 5th fingers.(9)



TOS presents as one of three different syndromes, either Arterial, Venous or Neurogenic compression of an artery, vein or nerve. Over 90% of all TOS cases involve nerve compression (neurogenic TOS). (9; 19)

Common symptoms of Neurogenic TOS include:

  • Weakness: This could include weakness and fatigue in the upper extremity.

  • Neck Pain: Most commonly this involves lateral neck pain Trapezius (92%) and Scalenes. (21)

  • Headaches: Occipital headaches occur in 76% of patients with TOS. (10; 21)

  • Shoulder or Arm Pain: Shoulder pain could be a clue that the TOS is neurogenic since shoulder pain is uncommon in arterial or venous TOS. Shoulder and arm pain is seen in 88% of patients with TOS. (21)

  • Chest Pain: Approximately 72% of patients with TOS experience chest pain. (21)

  • Altered Sensation in the Hand: Approximately 58% of patients with TOS experience altered sensations (paresthesias) in their hands. (21)

  • Ulnar Nerve Distribution: Ulnar distribution is more common with TOS than involvement of the median or radial nerves. Over 90% of TOS cases are neurogenic, and 70% to 90% of TOS cases have an ulnar nerve distribution. (9) Distribution would include the medial arm and elbow, following a path to the 4th and 5th fingers. This would include weakness, numbness, and tingling (paresthesias).

Arterial TOS symptoms include decreased blood flow, coldness, and pain. With Venous TOS there may be swelling in the upper extremity, accompanied by increased pain or tingling with activity. In both cases of either Arterial or Venous TOS, shoulder and neck symptoms are uncommon. (11)



TOS can be a result of a previous trauma such as motor vehicle accident, a fall, sports injury, previous surgery, poor posture, repetitive arm and shoulder movements, and person-to-person anatomic variations. Many cases can be attributed to myofascial restrictions in the neck (scalene muscles) shoulder, and upper chest (subclavius, pectoralis minor), all of which can lead to nerve entrapment's, muscle imbalances, and dysfunction.

Poor posture is also a common contributing factor. In general, poor posture (anterior posture) often pulls the shoulder forward creating imbalances throughout the chest, upper back, and shoulder girdle. In addition, joint restrictions in the cervical and thoracic spine, between the collarbone (clavicle) and chest bone (sternum), and between the first rib and first thoracic vertebra can all lead to decreased mobility and compensatory movement patterns in the neck, shoulders, and chest-further adding to the development of the TOS syndrome.

The exact cause of TOS is often unknown, and often the symptoms come on slowly and may be of an unknown origin.



The videos below demonstrate some of the common procedures we use for evaluating a case of TOS.

Cervical Examination - Orthopaedic Testing

This video goes through inspection and observation, palpation, Active and Passive Ranges of motion, and orthopaedic examination of the cervical region.

Shoulder Examination - Orthopaedic Testing

This video teaches you some of the common causes of shoulder pain and how to diagnose them using orthopaedic examination procedures. This video is a summation of Parts 1 to 8 of the Shoulder Examination.

Upper Limb Neuro Exam

The upper limb neurological examination is part of the over all neurological examination process, and is used to assess the motor and sensory neurons which supply the upper limbs. This assessment helps to detect any impairment of the nervous system. It is used both as a screening and an investigative tool. (Note: This video will be available for the public on October 7/2022)

Cranial Nerve Examination - 12 Cranial Nerves

The Cranial Nerve examination is one of the ways that we assess sensory and motor dysfunction.

Peripheral Vascular Examination - Key Points

A peripheral vascular examination is a valuable tool used for ruling out signs of vascular-related pathology. The detection and subsequent treatment of PVD can potentially mitigate cardiovascular and cerebrovascular complications. In this video we go over some of the common procedures we perform in daily clinical practice. This video is available for the public on November 14/2022.


Orthopaedic Physical Assessment – David J. Magee https://amzn.to/3zgu0za

Dutton'sOrthopaedic: Examination, Evaluation and Intervention, Fifth Edition https://amzn.to/3st1AOv



It is important to remember that all diagnoses of TOS are a working diagnosis, it is not a diagnosis cast in stone. Especially when you consider that even with a comprehensive physical examination, a diagnosis of TOS often needs to be confirmed by the process of elimination.

Several other syndromes have similar symptoms to TOS and must always be considered. Some of these syndromes, though rare, could also co-exist with TOS. Some of these other conditions are:



Thoracic Outlet Syndrome can be an extremely painful and debilitating condition. Its resolution requires a thorough physical examination that includes a comprehensive history, orthopedic and neurological testing. It is important to rule out the multiple other syndromes that can have similar symptoms.

In part two of “Resolving Thoracic Outlet Syndrome,” I will discuss recommended treatments and exercise protocols. I will also include demonstration videos for soft-tissue and osseous treatments that we recommend along with examples of specific exercises that we often prescribe to our patients to support their TOS treatments.

Note: References are at the end of Part 2



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