Occup Med (Lond) 2003 Cooke 331 6

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Thoracic outlet syndromeaspects of

diagnosis in the differential diagnosis of

handarm vibration syndromeR. A. Cooke

Background Thoracic outlet syndrome (TOS) is a cause of vascular and neurological co

promise to the arm and hand, and may manifest as Raynauds phenomenon. It m

be under-diagnosed.

Aim This review was undertaken in order to clarify the diagnostic and investigat

features of TOS that may differentiate it from handarm vibration syndrome.

Methods A tiered review of the world literature was undertaken using Medline and Embase

the primary search engines.Conclusion Thoracic outlet syndrome most commonly presents with neurological symptoms

the arm. Vascular symptoms, including Raynauds phenomenon, may occur in ~10

of cases. Careful clinical assessment by history and examination may reveal t

elements of forearm and upper arm symptoms with postural exacerbation, wh

distinguish this condition from handarm vibration syndrome. The usefulness

investigation is unclear, but Doppler and neuroelectric studies may be valuab

Magnetic resonance imaging scan is the investigation of choice.

Key words Raynauds phenomenon; thoracic outlet syndrome.

Received 6 June 2003

Accepted 10 June 2003

Introduction

Thoracic outlet syndrome (TOS) refers to abnormal

compression of nerve, arterial and, less frequently, venous

structures at the base of the neck or thoracic outlet. It

has also been referred to as scalenus anticus syndrome,

cervical rib syndrome, costo-clavicular syndrome, hyper-

abduction syndrome and TOS [1]. It is recognized as a

cause of Raynauds phenomenon, as well as of neuro-

logical symptoms affecting the upper limb. It follows that

TOS must be considered as a possible cause of symptoms

comparable with those of handarm vibration syndrome.

Potential causes of TOS are a cervical rib, abnormalligamentous tissue and hypertrophy of the scalenus

anterior muscle, as well as postural effects that interfere

with the normal relationship between the first rib and

those structures overlying it.

It has been suggested that TOS may be the most und

rated, overlooked and misdiagnosed peripheral ner

compression in the upper extremity [2], as well as t

most important and difficult to manage. A retrospect

study of cases of TOS presenting to an emergency depa

ment during a 29 year period concluded that a lack

thorough evaluation resulted in under-diagnosis of TO

[3]. Ouriel [4] suggested that the relative rarity of vascu

disorders of the arm accounts for even experienc

vascular clinicians being unfamiliar with upper extrem

diagnostic testing.

Anatomy

The thoracic outlet is bounded by the first thorac

vertebra, the superior border of the manubrium ster

anteriorly, and the first rib and costal cartilage lateral

The structures passing through this area and into t

upper limb are the subclavian artery and vein, and t

nervous structures of the brachial plexus (see Figure 1)

Correspondence to: Dr R. A. Cooke,Summers Place,Whitbourne,Worcester

WR6 5ST, UK. Tel: +44 1886 821644; fax: +44 1886 821944;

e-mail: [email protected]

Occupational Medicine2003;53:331

DOI: 10.1093/occmed/kqg

Occupational Medicine, Vol. 53 No. 5,

Society of Occupational Medicine; all rights reserved 331


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Incidence

The normal frequency of cervical anomalies in the

population is 0.121%.However,Boleset al.[5] reported

15 members of a single family (the two parents and their

13 children) affected with a TOS secondary to a cervical

rib and or an apophysomegaly of the seventh cervical

vertebra. Sallstrom and Thulesius [6] reported that the

prevalence of TOS was almost twice as common in

women as in men (ratio 1.76:1).

Risk factors

In many cases, an anatomical abnormality will be present

and be the underlying reason for the development of

symptoms of TOS.There may be occupational influences

to provoke or exacerbate symptoms, such as working

repeatedly with the arms at or above shoulder height.

The throwing athlete is at risk for neurovascular

injuries of the shoulder because of the demands placed

upon the shoulder by repetitive throwing motions. The

most commonly recognized neurovascular compression

syndromes are axillary artery occlusion, effort throm-

bosis, quadrilateral space syndrome and TOS [7]. After

studying 167 patients exposed to handarm vibration,Kakosky [8] suggested that such exposure may play a part

in the development of TOS,and conversely that TOS may

contribute to Raynauds phenomenon of occupational

origin.

Clinical presentation

Blanchardet al.[9] described five syndromes involving

the thoracic outlet, namely:

1. Arterial, due to a well formed cervical rib or to an

abnormal first rib.

2. Neurological, related to the fibrous band associated

with a rudimentary cervical rib or a giant transverse

process of C7. In 1980, Roos [10] reported the

results of 1120 operations for TOS, indicating that

most TOS patients have anomalous fibro-muscular

bands near the brachial plexus and subclavian vessels.He identified nine different types of these soft tissue

anomalies not visible radiographically, describing

them as often multiple, and sometimes associated

with bone abnormalities as well.

3. Venouseffort thrombosis.

4. Late post-traumatic, secondary to a fracture of the

clavicle.

5. The syndrome previously called scalenus anticus

syndrome, being due to either trauma, typically a

whiplash type of injury, or hypotonic shoulder

muscles, occurring mostly in women, and responding

well to specific and simple exercises.

TOS can present with symptoms and signs of any of

these, namely arterial insufficiency, venous obstruction,

painless wasting of intrinsic hand muscles and pain [2].

More than 90% of the patients present with neurolog-

ical symptomspain, paraesthesiae, or arm and hand

weaknessand 10% also have vascular problems [11]. In

the 10% of patients who have vascular involvement,

urgent investigation and early surgery may be necessary

if ischaemic complications are to be avoided [12].

Branchereau et al. [13] reported that among 10 cases

of cervical ribs operated upon in seven patients, the

predominantly neurological symptoms and signs were

associated with vascular problems in three cases, withintermittent compression of the subclavian vessels.

Dangerous vascular complications are the embolization

of a subclavian aneurysm and the acute thrombosis of the

subclavian vein [14]. Desai and Robbs [15] reported a

series of 26 patients, among whom 17 presented with a

fixed pulse deficit, 13 had a palpable aneurysm and 12

had distal embolization. Durhamet al.[16] reviewed 34

patients treated for upper extremity symptoms of TOS

from 1983 to 1993. They reported that 22 patients (27

arms) had subclavian artery injury, which was most com-

monly caused by compression by a bony abnormality

(cervical rib, 16; anomalous first rib, 2; cervical rib and

anomalous first rib, 2). Fourteen of the 27 arms had

distal embolization. Twelve additional patients (nine

athletes) had axillary artery involvement, all from arterial

compression by the head of the humerus during ab-

duction manoeuvres; all had concomitant compression

of the posterior circumflex humeral artery. Axillary

arterial injury included thrombosis (one), aneurysm

(two) and symptomatic extrinsic compression only

(nine). They concluded that most patients with TOS who

have arterial involvement have a bony anomaly causing

Figure 1. Anatomy.

332 OCCUPATIONAL MEDICINE


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subclavian artery compression. They demonstrated that

humeral head compression of the axillary artery and its

circumflex branches is a surprisingly common pathologic

mechanism.

Neurological presentation

Initial symptoms are pain and paraesthesiae in the

affected area, followed by sensory and motor deficits in

advanced cases. Complaints of paraesthesiae and numb-

ness will relate to the nerve compression component of

TOS, whereas the pain associated with this syndrome

is largely caused by muscle imbalance in the neck,

shoulders and upper back [17]. Rayan [18] reported two

patients with TOS secondary to cervical rib, both of

whom had vague shoulder pain as well as neurological

manifestations due to compression neuropathy of the

lower trunk of the brachial plexus. One of the patients

had been suspected initially to have carpal tunnel

syndrome. Typically, it is the lower trunk of the brachialplexus that is affected, so that TOS manifests as symp-

toms of lower cervical nerve involvementsC8 and

T1with hypoaesthesia and paraesthesia [19]. This is

likely to result in pain, sometimes accompanied by

paraesthesiae, along the lateral (ulnar) border of the

forearm, and into the corresponding area of the hand and

fingers. Although rare, upper plexus TOS may manifest

with symptoms due to the involvement of the C5C7

nerve roots [19], which may then result in pain or

paraesthesiae along the medial aspect of the arm and

forearm, and into the hands and fingers. In either case,

the pain or paraesthesiae may be aggravated by elevation

of the arm or by carrying heavy weights.Muscles supplied by the median or ulnar nerves

derived from these trunks may be weak and wasted.

Novaket al.[23] found that two-point discrimination was

normal in 98% of cases.

Vascular presentation

The most frequent vascular presentation of TOS may be

that of Raynauds phenomenon [20], or may be the less

clearly defined symptoms of coldness, cyanosis and

swelling of the hands, possibly resulting from irritation of

sympathetic fibres in the subclavian bundle. Upper limbpulses may be diminished, with bruits heard over the

subclavian artery.

Primary Raynauds phenomenon in patients with signs

of TOS has been shown to be indistinguishable from that

in those without signs of TOS in respect of family history,

gender, thumb involvement or asymmetry of Raynauds

phenomenon [21].

In a study of 167 workers exposed to handarm

vibration, all of whom had Raynauds phenomenon, with

or without numbness and muscle weakness, Kakosky

found that a brachial plexus nerve lesion was the mo

commonly electrophysiologically demonstrated lesion.

16.2% of patients compression of the subclavian arte

was also demonstrated. It was concluded that handar

vibration exposure may play a part in the development

TOS, and conversely that TOS may contribute

Raynauds phenomenon of occupational origin [8].

A number of provocative tests have been describebased on the concept that change in shoulder/ne

position may produce symptoms, including Adsons a

Roos tests. Pulse obliteration indicates some element

anatomic tightness,but it has been suggested that witho

symptom reproduction, pulse change has no diagnos

relationship to TOS [22]. Novaket al.[23] reported th

94% had positive provocative position and compressi

test results, and suggested that clinical assessment

TOS is best achieved by reproduction of symptoms w

compression and positional provocative testing.

In a study of TOS shoulder manoeuvres in 53 healt

subjects, the outcomes of pulse alteration or paraestheswere unreliable in general. However, TOS shoulder ma

oeuvres have reasonably low false-positive rates when

positive outcome is defined as pain after Adsons te

costo-clavicular manoeuvre or supraclavicular pressu

discontinuation of the elevated arm stress test seconda

to pain; pain in the same arm with two or more ma

oeuvres; or any symptom in the same arm with three

more manoeuvres [24]. Warrens and Heaton [2

assessed manoeuvres advocated for the assessment

thoracic outlet compression on 64 randomly chos

volunteers. Although only 17% had any symptoms

thoracic outlet compression, 58% had a positive result

at least one of the manoeuvres. Only 2% were positive

more than two manoeuvres. They concluded by sugge

ing that the low specificity devalues these tests in clinic

practice. Gillardet al.[26] found that provocative te

had mean sensitivity and specificity values of 72 and 53

respectively, with better values for the Adson test [posit

predictive value (PPV) = 85%] and the hyperabducti

test (PPV = 92%).

Kitamura et al. [27] assessed the influence of de

breathing on Adsons test by using laser Doppler flo

metry to quantitatively assess changes in blood fl

measured at the arm during Adsons test, the rever

Adson test and deep breathing in the sitting position.

10 patients who were found during surgery to ha

anatomical abnormalities in the thoracic outlet are

preoperative administration of Adsons test had n

indicated any compression that caused cardiac wa

disappearance and continued blood flow reduction. Th

concluded that Adsons test, which involves compressi

by the scalene muscles, is greatly affected by de

breathing during the test, and that the results of this te

do not faithfully reflect vascular compression.

R. A. COOKE: THORACIC OUTLET SYNDROME 3


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Clinical investigation

The diagnosis of thoracic outlet compression syndrome is

usually made on the basis of an adequate history and

physical examination. Diagnosis is largely one of exclu-

sion,but it may be aided in some patients by angiography,

assessment of the conduction velocity of the ulnar nerve

and other objective tests [28]. It has been suggested that

electromyograms, arteriograms and venograms are not

helpful for the neurological type of TOS [11]. Stanton

et al.[29] suggested that nerve conduction velocities and

directional Doppler studies are the most useful adjuncts

in diagnosis.

Plain radiology

Plain X-ray of the chest or thoracic outlet may demon-

strate a supplementary rib, usually arising from the

seventh cervical vertebra, but sometimes from the sixth

and rarely from the fifth. Thirty-one patients with TOSwere studied by Lascelleset al.[30], who found that the

majority of patients had radiological abnormalities and all

had structural lesions in the superior thoracic aperture

seen at operation.

Computerized tomography (CT) scan

Where a cervical rib is present, CT may demonstrate not

only the bony abnormality but also the relationship of any

bony deformity with arterial compression [31], Novak

et al.[23] reported that 32% of the patients studied had acompressive anatomical abnormality identified by CT

scan.Three-dimensional CT imaging is effective for iden-

tifying the structures in the thoracic outlet [32]. A helical

CT arterial and/or venous angiogram with postural

manoeuvres has been shown to be useful in providing

accurate information on the location and mechanism of

vascular compression [26,33].

Magnetic resonance imaging (MRI) scan

MRI scan is the imaging method of choice for evaluatingthe anatomy and pathology of the brachial plexus [34].

However, this may require elevation of the arm or

hyperabduction manoeuvres to demonstrate compression

of vascular or neurological structures [35,36]. Gado-

linium enhancement angiography allows rapid evaluation

and comparison of the vascular structures in both the

neutral and abducted positions [37]. Since conventional

MRI scanners may not allow investigation with the arm

in abduction, an open magnet scanner may be seen as

essential for this [38].

Nerve conduction and electromyograph

(EMG) studies

Novaket al.[23] found that only one patient out of 50

with TOS had a positive nerve conduction study/EMG at

the brachial plexus level. However,others have concluded

that neuroelectric studies are inconsistently helpful, but

may be useful in ruling out other, more distal nerve en-

trapments [22]. Gruss [14] suggested that a neurological

examination with measuring of the proximal ulnar and

median nerve conduction times is mandatory.

Doppler studies

Hachullaet al.[39] reviewed 95 healthy subjects examined

regarding the presence of TOS by clinical examination

and by Doppler flowmetry during performance of Adson,

hyperabduction and abductionexternal rotation man-

oeuvres. The response was considered positive when the

radial pulse disappeared for the clinical test, and when theflow was totally arrested for the Doppler flowmetry. They

concluded that Doppler flowmetry is useful for the TOS

diagnosis only when the clinical evaluation is abnormal,

that total arrest of flow is sometimes temporary, that

arterial flow must be examined for at least 20 s, and that

total arrest of flow is never seen during Adson manoeuvre

or hyperabduction at 45 or 90 in healthy subjects.

Novakovic et al. [40] examined 34 patients and 30

asymptomatic volunteers, and studied the retroscalenal

part of the subclavian artery using real-time (B-mode)

duplex imaging. They found significant reduction of

lumen diameter of the subclavian artery during Adsons

manoeuvre in 51% of cases. During Adsons costo-

clavicular and hyperabduction manoeuvre, they found

significant changes in linear blood velocity, reduction of

blood flow and turbulence in 91% of cases. Adsons

manoeuvre was positive in 52%, costo-clavicular in 29%

and hyperabduction (to 90) in 19% of cases.

Wadhwaniet al.[41] concluded that colour Doppler

sonography is a non-invasive, effective method compared

with digital subtraction angiography in the diagnosis of

TOS.

Sallstrom and Thulesius [6] found a significant correla-

tion between arterial compression measured by Doppler

flowmetry and the presence of compression of the plexus,but the validity of this method was not satisfactory, giving

both false-positive and -negative results. They also

reported a very good correlation between arterial com-

pression assessed clinically and by Doppler flowmetry.

They concluded that the Doppler technique added very

little with significant vascular compression being easily

detected by clinical assessment. Gillard et al. [26] re-

ported that Doppler ultrasonography visualized vascular

parietal abnormalities and confirmed the diagnosis in

some patients.



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Angiography

Angiography is an effective method of vascular inves-

tigation, but is highly invasive. In TOS, it may be used to

demonstrate compression of the subclavian artery.

Ostheium and Schmitt [42] showed that half a series of

18 patients so investigated had occlusion of the digital

arteries on the side of the compressed subclavian artery.

Conclusion

Careful assessment is required of the patient who

presents with neurological and/or vascular symptoms

in the upper limb, including Raynauds phenomenon.

Thoracic outlet syndrome should be considered with

particular consideration to the following

pain as a primary feature of the presentation; neurological symptoms or findings suggestive of a

dermatomal distribution, particularly C8 or T1, but

also less commonly at higher levels;

exacerbation of symptoms with elevation of the armeither given as a part of the history or on examination.

Careful clinical assessment is likely to indicate the

diagnosis. Although there is variable evidence regarding

the usefulness of postural/ provocative tests, the com-

bination of pulse obliteration and reproduction of

symptoms by such manoeuvres must be useful.

Clinical investigations also appear to have mixed

reviews. Nerve conduction studies are likely to be useful,

if only to exclude other neurological lesions. Plain X-ray

may demonstrate a cervical rib. CT scan is likely to

demonstrate the presence of non-bony lesions. Dopplerstudies may be useful, although some studies suggest that

their value is no greater than that of good clinical

assessment. MRI is the investigation of choice.

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Occup Med (Lond) 2003 Cooke 331 6