Research Review By Dr. Robert Rodine©


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Date Posted:

November 2010

Study Title:

Thoracic Outlet Syndrome Part 1: Clinical manifestations, differentiation and treatment pathways


Watson LA, Pizzari T & Balster S

Author's Affiliations:

LifeCare Praham Sports Medicine Centre, Praham, Australia & the Musculoskeletal Research Centre, La Trobe University, Bundoora, Australia

Publication Information:

Manual Therapy 2009; 14: 586-595.

Background Information:

Thoracic outlet syndrome (TOS) represents a complex symptom pattern of pain, paresthesia, weakness and general discomfort of the upper limb that is primarily associated with arm elevation and/or specific head and neck movements.

TOS is highly controversial and poorly understood, both clinically and academically. There are numerous clinical conditions that can generate similar symptoms in the upper limb, which leads to the bulk of this misunderstanding. Predominantly however, the current understanding of this condition is vague, as its symptom set is diverse and difficult to pin-point with epidemiological research. It is important to consider that TOS is typically considered to be a diagnosis of exclusion, meaning that clinicians may utilize its label as a fallback diagnosis, rather than one of proactive direction (assess, don’t assume!).

Through their narrative review, Watson et al. attempt to clarify some misunderstandings regarding TOS and help guide clinicians in its diagnosis and management. In this first of a two part series, the authors address a brief overview of presentation, clinical manifestations, differential diagnoses and clinical examination. Part two will address a rehabilitative model once a diagnosis of TOS has been reached.

Clinical Relevance:

Anatomical Considerations:

Prior to furthering our understanding of TOS, we must review the relevant anatomy of the thoracic outlet. This includes the subclavian vasculature and the brachial plexus. Within this outlet, the vessels and nerves may be compromised and subject to compression and/or tension from surrounding structures.

Recall that the brachial plexus forms from the cervical nerve roots of C5-T1, transitions into 3 trunks, 6 divisions, 3 cords and eventually its terminal branches. The subclavian artery originates from the aortic arch (brachiocephalic trunk on the right) and is named the axillary artery once it travels distal to the clavicle (1).
Anterior View of Thoracic Outlet
The scalene musculature is also relevant to TOS, as the brachial plexus and the subclavian artery pass between the anterior and middle scalene muscles prior to descending into the upper limb. The subclavian vein travels anterior to the anterior scalene. This is considered to be the normal anatomy; however as always one must consider anatomical variants and potential congenital anomalies (1). With the relevant anatomy in mind, we may begin to consider compression sites involved in TOS.

Firstly, the brachial plexus (in particular the roots of the lower trunk) may be compromised via the 1st rib, the presence of a cervical rib, or the scalene musculature itself. Secondly, nerves and vessels may be compromised in the costoclavicular space, beneath the clavicle and exterior to the thoracic cage. Thirdly, nerves and vessels may be compromised within the sub-coracoid tunnel during abduction of the upper limb.

Additionally, we must also consider the ‘double-crush’ phenomenon, originally brought forth by Upton and McComas in the early 70s (2). This hypothesis refers to a situation where there are multiple sites of nerve compression, all producing sub-clinical symptoms in isolation, however acting synergistically to create pain and dysfunction. This is highly relevant to the TOS patient, and may help to explain the diversity of symptoms with most presentations.

As an example, your patient may present with neck, arm and hand symptoms with compression noted at the thoracic outlet and carpal tunnel in addition to cervical joint pathology – all of these areas can be simultaneously involved. Approach this hypothesis with caution however, as it is also controversial and lacks strong scientific support.

Sub-Types of TOS:

Upon evaluation, clinicians should primarily consider two sub-types of TOS, neurogenic (representing 98% of TOS presentations) and vascular.

The rarer sub-type – vascular TOS (vTOS) – can be differentiated into arterial and venous. Arterial compression results in symptoms of ischemic pain and paresthesia, as well as the possibility of eventual distal gangrene or irreversible tissue damage. Venous compression will present in a different manner – with pain and edema along with venous engorgement, distal swelling, and so on.

The more predominant sub-type of neurological TOS however needs to be further differentiated into true neurological TOS (tnTOS) and symptomatic TOS (sTOS):

The first sub-type, tnTOS, is caused by compression/irritation/traction upon the brachial plexus as a result of a bony or soft-tissue mass. Repetitive stress, acute trauma and postural alterations can be considered as inciting events leading to the development of symptoms. This sub-type will often present with radiological findings (such as a cervical rib) or with decreased function as identified through electro-physiological testing.

By comparison, sTOS is recognized as neurovascular compression due to repetitive stress, acute trauma and postural alterations that result in intermittent symptoms without the presence of a soft-tissue or bony mass. Therefore, this sub-type represents the ‘left-over’ group of patients who present with this diverse set of symptoms and normal radiological and electro-diagnostic testing results. It is also this group of patients who prove to be the most difficult to diagnose.

The authors additionally note that with TOS, in particular the sTOS sub-type, associated and causative factors may include the body’s adaptations to postural and/or occupational repetitive stress. This may include muscular hypertrophy or atrophy. Also, ‘poor posture’ alters the shape of the thoracic outlet as the head is carried in a forward position, the anterior chest wall is lowered and the shoulders move forward (3-7). These considerations are highly relevant to conservative management and should be components of any comprehensive treatment program.

Clinical Evaluation of TOS:

A systematic strategy should be employed during the process of evaluating the sTOS patient, as there are many conditions that can create comparable symptoms within the upper limb. Differential diagnoses could include carpal tunnel syndrome, deQuervain’s tenosynovitis, lateral epicondylitis/algia, complex regional pain syndrome, Horner’s syndrome, Raynaud’s disease, cervical radiculopathy, brachial plexus trauma, deep venous thrombosis, rotator-cuff pathology and glenohumeral joint pathology or instability.

Upon moving to clinical examination, several tests should be utilized specific to TOS. However, the authors caution that as TOS is a collection of symptoms, it is ‘unreasonable to assume that any one test or one investigation can always accurately examine the whole spectrum of pathology.’

Lindgren recommends retaining a clinical suspicion of TOS when at least three of the following are present:
  • A history of aggravation of symptoms with the arm in an elevated position
  • A history of paresthesia originating from the spinal segments C8/T1
  • Supraclavicular tenderness over the brachial plexus
  • A positive hands up abduction/external rotation or stress test
Physical examination should include inspection of postural alignment, digital palpation of the supra and infraclavicular fossae for the reproduction of the primary complaint, active and passive range of motion of the cervical spine, shoulder, elbow, wrist and hand, testing of the rotator-cuff and glenohumeral joint instability testing (see Related Reviews below).

Neurological examination is essential, as it may indicate true-neurological TOS, and peripheral nerve testing should be utilized to eliminate entrapment. Cervical nerve root pathology should also be excluded.

While the authors recommend that the Adson’s maneuver, Costoclavicular maneuver, Wright’s test and the Elevated arm stress test (EAST maneuver) be utilized in the clinical examination of TOS, no study to date has been published on the utility of these tests within the specific sub-types of TOS previously described. It is also cautioned that pulse obliteration is frequently found in healthy subjects, therefore tests are more valuable if they recreate the patients primary complaint and indicate a mechanical component to neurovascular compression.

Postural and scapular correction should also be utilized in an attempt to aggravate or relieve symptoms. This will help direct rehabilitative strategies…….which is an excellent place to leave and meet up again in Part 2 of this series.

Study Strengths / Weaknesses:

The most prominent limitation of this study is that it is a narrative review. Narrative reviews are subject to no objective scrutiny and present no details of a defined literature search strategy, search results, inclusion/exclusion criteria or quality assessment regarding reviewed papers. This being said, narrative reviews are helpful as they create discussion and help to generate new hypotheses. For reviewing clinical conditions they are often appropriate, however, as with the single-study case report, they exhibit minimal strength as scientific evidence.

This paper would be more valuable to the reader if more detailed information was presented on the known utility for physical examination regarding TOS, irrespective of sub-type.

Additional References:

  1. Moore KL and Dalley AF. Clinically oriented anatomy, 5th ed. 2006. Lippincott Williams & Wilkins.
  2. Upton AR, McComas AJ. The double crush in nerve entrapment syndromes. Lancet 1973; 2(7825): 359-62.
  3. Aligne C, Barral X. Rehabilitation of patients with thoracic outlet syndrome. Ann Vasc Surg 1927; 85(6): 839-57.
  4. Barkhordarian S. First rib resection in thoracic outlet syndrome. J Hand Surg 2007; 32(4): 565-70.
  5. Novak et al. Outcome following conservative management of thoracic outlet syndrome. J Hand Surg 1995; 20(4): 542-8.
  6. Ryan GM. Thoracic outlet syndrome. J Shoulder and Elbow Surg 1998; 7(4): 440-51.
  7. Ranney D. Thoracic outlet: an anatomical redefinition that makes clinical sense. Clin Anat 1996; 9(1): 50-2.
  8. Lindgren KA. Conservative treatment of thoracic outlet syndrome: a 2 year follow-up. Arch Phys Med Rehab 1997; 78(4): 373-8.