Thoracic outlet syndrome is a term used to describe the compression of nerves and/or blood vessels which travel from the neck to the armpit. These important vessels are situated in an area in the lower neck and are surrounded by both bony and soft tissue neighbours. This compression can cause pain, tingling, numbness, and weakness from the neck throughout the arm.

What causes this compression differs between individuals. It is usually caused by the first rib and the clavicle, or collar bone, coming together and pinching the vessels between them. This space is called the Thoracic Outlet and contains large vessels including the Brachial Plexus and the subclavian artery and vein. The Brachial Plexus is a large network of nerves that originates in the neck and travels through the Thoracic Outlet, through the armpit where it splits to become different nerves that are responsible for us feeling and moving our arm. (Bayot et al., 2021)

According to a 2019 study, the most common type of TOS is neurogenic, or nervy in nature – in which the Brachial Plexus is the main structure being compressed. In fact, these cases make up 90% of patients presenting with TOS. Compression of the subclavian artery and vein are seen less then that of the nerves, however, tend to occur more in congenital TOS. Venous TOS is also possible following repetitive motion and can be sometimes referred to as Paget–Schroetter disease (PSS). PSS is more commonly seen in younger patients -in their 20s and 30s -with a male to female ratio of 2:1. Often athletes are effected by PSS, specifically, those engaging in the repetitive over-the-head motion of their arms, including baseball or softball pitchers, swimmers, rowers, or weightlifters.

Causes of TOS include traumatic injuries such as whiplash, sports impact injuries or falls. In rare cases, a birth defect in which people can have an extra rib (Cervical Rib) can cause the compression of both the nerves and blood vessels. TOS can also occur from repetitive functional, sporting or occupational activities such as overhead throwing, excessive pushing activities, and can be worsened with poor postural awareness around the shoulder, neck and upper back.

TOS can be easily confused with other neurological issues in the arms. Physiotherapists must differentiate TOS from other issues such as cervical radiculopathy, painful and inflexible trapezius or shoulder muscles, rotator cuff irritations or tears, shoulder bursitis etc.

It is worth mentioning that many referrals for TOS seen in physiotherapy clinics in modern day, may not have direct compression of the structures causing the patients symptoms. We call this presentation pseudo-Thoracic outlet syndrome. Similar to Piriformis Syndrome of the leg, tight or weak muscles may mimic the same symptoms as with TOS, but can be treated with exercise and manual work to reduce the irritation of the muscles and nerves in the upper arm and lower neck.

A true case of TOS can be diagnosed by the clinician’s detailed assessment of the neck and shoulder. Physios can rule in or out a nerve injury by certain neural tests, and can even hypothesize where the issue is stemming from by these tests. X-ray and medical/birth history will help diagnose cases of congenital TOS.

When TOS is caused by muscular imbalances physiotherapy plays a large role. In recent years, physio has in fact jumped to the forefront of TOS treatment, with referrals for surgery becoming rarer and rarer.

Common muscles that can contribute to the symptoms of TOS include the pectoralis muscles group, in particular pec minor, as it allows the nerves and vascular structures to travel underneath it. Scalene muscles in the neck can be particularly nasty to release but gives great symptomatic relief as these muscles can irritate the nerves as they appear just above the Thoracic Outlet. Upper fiber traps and rotator cuff muscles should be considered when treating TOS and they affect the postural position of the upper quadrant, and are sometimes responsible for occupational causes of the syndrome.

Nerve gliders or “flossing” exercises can reduce nerve irritation and improve blood flow to the neural structures from the neck to the fingers. They are used widely in physiotherapy, not only in the treatment of TOS.

For sports-people, reduction of repetitive overhead activities can relieve the stress on the structures within the Thoracic Outlet, and a gradual re-introduction of these exercises should be used in conjunction with a strengthening and stretching program for the athlete.

Thoracic Outlet Syndrome and pseudo-TOS are irritating and debilitating issues for athletes and lay-people alike. Physiotherapy plays a large role in improving symptoms and preventing ongoing issues from this injury in modern day medicine. TOS treatment is a relative slow-burner, and guidelines state that a trial for 4-6 months should be given to conservative management before further referral, so patience and perseverance is the key to overcoming this issue.

Written by:

Angela Crowley (Physiotherapist)

M.R.S Physiotherapy, 122 Remuera Road. Auckland.

References:

Bayot ML, Nassereddin A, Varacallo M. Anatomy, Shoulder and Upper Limb, Brachial Plexus. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500016/

Hidlay DT, Graham RS, Isaacs JE. Anomalous first thoracic rib as a cause of thoracic outlet syndrome with upper trunk symptoms: a case report. Hand (N Y). 2014;9(4):484-487. doi:10.1007/s11552-014-9621-2

Jones MR, Prabhakar A, Viswanath O, et al. Thoracic Outlet Syndrome: A Comprehensive Review of Pathophysiology, Diagnosis, and Treatment. Pain Ther. 2019;8(1):5-18. doi:10.1007/s40122-019-0124-2

Saleem T, Baril DT. Paget Schroetter Syndrome. [Updated 2021 Jun 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482416/