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Carlos A. Selmonosky, M.D. FACS, FACCP, FACC, AAFP.

Background; Lack of Accepted Diagnostic Criteria

The actual incidence of the Thoracic Outlet Syndrome (TOS) is unknown, it varies from 1 per million(1) to 100(2) to 3000 to 80,000(3) per million of population, these reports are not supported by valid epidemiological studies. The incidence depends upon the selected diagnostic criteria; the diagnostic criteria can be so restrictive that in some centers the incidence is reported to be 1 in a million(1), while thousands of TOS operations are performed worldwide in many reputable centers.

One of the difficulties in assessing the incidence of TOS in the general population is the lack of a reliable and reproducible set of signs and a common accepted diagnostic criteria or cost-effective laboratory tests(4-5-7-23-65).

TOS is an often misdiagnosed cause of chest(8-9-11-12-51-65), neck and shoulder pain(15-16-60) and it is also one of the frequent upper extremity neurovascular compression syndromes related to sport(17-18-19). TOS may be the most underrated, overlooked, misdiagnosed and most frequent peripheral nerve compression neuropathy(20-21-22-23-24). It is also the most common unrecognized cause of failed carpal or cubital tunnel surgery(25).

Anatomical Basis of TOS

Autopsy studies show a pattern of fibromuscular bands, similar in location to those found in operations for TOS(2-26-28). Clinical studies of selected populations suggest a high prevalence of TOS(29-30-31).

Symptoms; Not Only From the Upper Extremities

Symptoms of TOS are varied, but not all need to be present, therefore the physician should not expect a “typical” presentation of TOS. The symptoms are located not only in the upper extremities, chest pain caused by TOS can mimic anginal pain(8-11-12-51-65). Cardiac sympathetic nerves are the pathway for cardiac pain with ganglionic connections from C8 to T4; the compression of C8-T1 fibers occurring in TOS send impulses to the brain through pathways that are shared by the same dermatomal distribution in coronary ischemia producing chest pain. Positional compression of the vertebral artery also may cause temporary symptoms of vertebrobasilarly insufficiency(32-33-34-35-36-); shoulder and neck pain can be symptoms of TOS(15-16-60). A focused questionnaire and awareness of the numerous symptoms that can be present in TOS would help in clarifying the diagnosis.

PUB MED Search

In spite of more than 2,600 references about TOS quoted in PubMed and thousands of patients operated on yearly worldwide, there is a lack of common accepted diagnostic criteria(4-5-7-23-65). The diagnosis of TOS and the indications for surgery are seldom addressed in the major and most widely read medical journals.

Obstacles to the Diagnosis of TOS

One common obstacle to the understanding of the diagnosis of TOS is the mistaken belief that it is present only when there is atrophy of the hand muscles and positive neurological electrophysiological tests(1-37-38-39). A second obstacle to the understanding of TOS is the artificial division into neural or vascular forms. Many TOS patients have symptoms and signs of both neural and vascular compression(60-65-67-68) if the questioning is focused and the physical examination is pertinent and includes the Diagnostic Triad.

Obstacles Caused by the Misinterpretation of the Vascular Maneuvers

A third obstacle is the confusion surrounding the role of the vascular maneuvers in the diagnosis of TOS. Numerous vascular maneuvers have been described(40-41), all intended to support the diagnosis of TOS if they were positive. Positive means positional changes of the radial pulse amplitude, at one time they were thought to be pathognomonic of TOS(42).

A number of articles have stated that these maneuvers were positive in a large proportion of normal subjects(43-44-45-46-47-48). All of these reports do not define what a “normal” subject is. The documentation regarding the presence or absence of the Triad of Signs in these articles is lacking, or at least the mention of the presence or absence of weakness of the fifth finger. There has not been any long term study of what happens to those normal subjects whom had positive vascular maneuvers.

The real significance of the vascular maneuvers is to detect positional changes of pulse amplitude in the radial artery; the importance of the diagnostic utility of these maneuvers is to determine if they represent an abnormal response to positional changes. Positional compression of the subclavian artery is not a normal phenomenon; therefore a positive vascular maneuver is an abnormality. It is important to give a positive vascular maneuver an explanatory diagnostic or prognostic significance. A positive sign can be associated with absence of symptoms, but the absence of symptoms(49) does not diminish the diagnostic or prognostic significance of a positive test. Comparing vascular maneuvers can also cause confusion(50), all examiners should perform these maneuvers with the patient in the same position, and even a slight change in position may change the results. Therefore a detailed protocol should be used if the results of these vascular maneuvers are being compared in the medical literature.


Conflicting information about the incidence and diagnosis of TOS underscores the necessity for a clear definition and standardized, reliable, consistent set of diagnostic physical signs.

TOS is a group of symptoms arising not only from the upper extremities, but also from the chest, neck, shoulders and head. The symptoms are produced by a positional intermittent or continuous compression of the brachial plexus and/or subclavian artery and/or vein and the vertebral artery.

The diagnosis of TOS should be made by the physician’s awareness of the symptoms and by the use of a Triad of Signs(51-52) during the physical examination.

Selmonosky Diagnostic Triad

The Triad of Signs consists of the following:

  1. Weakness of abduction and adduction of the 5th finger, and weakness of the pinch strength between the thumb and 5th finger as compared with the pinch strength between the thumb and the index finger.

  2. Tiredness and/or paresthesias, numbness of the upper extremity and hand on elevation; associated or not with paleness of the hand.

  3. Tenderness on thumb pressure over the ipsilateral supraclavicular area, lateral to the sternocleidomastoid muscle just above the clavicle. The patient’s nonverbal response, particularly facial grimaces and withdrawal should be observed.

Elevation of the Hand Maneuver

In the elevation of the hands maneuver, the patient sits comfortably elevating the hands above the shoulder girdle with the fingers pointing towards the ceiling and with the palms facing the observer,the thumbs should be close to each other as possible. The axis of the upper extremities should be parallel to the axis of the body. The duration of this maneuver is three minutes or until the patient became symptomatic. This is a test to assess the positional compression of the brachial plexus as manifested by complaints of paresthesias, tiredness and/or numbness of the upper extremity and hand.

The White Hand Sign

It is also important to assess the positional subclavian artery compression at the thoracic outlet by observing the presence of absence of paleness of the hands. The presence of marked paleness is called the White Hand Sign(51-52), and indicates severe positional vascular compression.

The absence of color changes of the hands should not be interpreted as the absence of TOS, since severe nerve compression can be present without severe vascular compression (53-54).

Read more about the White Hand Sign here.

Weakness of the Fifth Finger

Weakness of the fifth finger is a component of the diagnostic triad. It represents the results of the compression of the lower trunk of the branchial plexus, C8 and T1 root fibers by fibromuscular bands or osseous structures. The strength of the fifth finger is never or seldom assessed in the physical examination by Primary Care of Emergency Department Physicians. The simple examination of the pinch strength of the fifth finger as compared to the pinch strength of the second finger can be a clue to the diagnosis of symptoms arising from the upper extremity, chest, neck and shoulder.

Weakness of the fifth finger (pinch strength, abduction, adduction), excluding generalized neuropathies or myopathies, is only found in four compression neuropathies of the upper extremity. The order of frequency as searched in Google, Yahoo and Bing is:

  1. Thoracic Outlet Syndrome

  2. Ulnar Entrapment at the Elbow

  3. Ulnar Entrapment at the Wrist

  4. Isolated C8 or T1 Root Compression

The assessment of the degree of weakness can be done qualitatively: none, mild, moderate, severe; or objectively demonstrated with digital pinch dynamometry.

Physical Examination, Splinting, Posture, Swelling, Sweating and Coldness

The diagnostic triad should be complemented in the physical examination by observation of the posture of the patient, and the presence in the upper extremity of:

  • Splinting

  • Swelling of the Fingers and/or Hands

  • Coolness or Sweating of the Hands

The sweating of the hands is produced by increased sympathetic tone secondary to mechanical irritation of the sympathetic fibers of the brachial plexus, which may also produce coldness of the hands(12-55-57).

Swelling of the fingers and or hands may occur because of subclavian vein compression at the thoracic outlet being present without thrombosis(58-59-60); the most serious form of venous compression is caused by thrombosis of the subclavian vein and is called: Paget-Schroetter syndrome or effort thrombosis(19-61-62).

Many of the TOS patients have a slouched posture that may reflect depression(62-63-64-65), some with severe pain present with splinting of the upper extremity.

Imaging Needed to Reinforce the Diagnosis

Chest and cervical spine plain x-rays are the only imaging needed ; to rule out intrathoracic pathology, cervical spine pathology, first rib and clavicular abnormalities and cervical ribs. The abnormalities of the transverse process of seventh cervical vertebra, lengthening, enlargement and downwards peaking deformity, should be reported by the radiologist because they are very frequently found in patients with TOS.

Validity of the Diagnostic Triad

A new diagnostic test, “The Diagnostic Triad”, should consider the simplicity, intra and inter observer variability, and perhaps most importantly, the practical clinical value(66).

The validity of this triad rest in the following facts:

  1. It is not present in any other disease or syndrome than TOS

  2. Intra and inter observer variability are very low because of the simplicity of the maneuvers needed to elicit the signs.

Clinical Implications

The practical clinical value could be immense if this triad of signs is routinely performed in patients with upper extremity pain, neck and shoulder pain and/or paresthesias, noncoronary chest pains, vertebrobasilarly insufficiency symptoms and whiplash injury.

If this Triad of Signs, associated or not with the White Hand Sign, is found to be present, the diagnosis of TOS should be considered, it will be partially or totally responsible for the symptoms attributed to a different pathology.


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