THORACIC OUTLET

SYNDROME 

                                                                  Dr.Anil Haripriya

  

Historically Sir Astley Cooper described the symptoms of

Thoracic outlet syndrome in 1821. In 1861, Coote reported the

excision of a cervical rib. In 1903, Bramwell suggested the

relationship of possible brachial plexus Compression and a

normal first rib. The phrase Thoracic out let syndrome was first

used by Peet in 1956 and was popularized by Rob and

Standeven in 1958.In late 1960s and 1970s, the dominant

operative trend centered around the transaxillary resection of the

first rib empirically to relieve the symptoms of thoracic outlet

syndrome. In recent years however the trend is towards exact

location of the compression. The syndrome should be considered

in all patients with neurological and vascular complaints of the

arm. Basic understanding of the anatomy is absolutely vital in all

diagnostic and operative considerations in thoracic outlet

syndrome1. 

SURGICAL ANATOMY

At the superior aperture of the thorax, the subclavian vessels and

the brachial plexus traverse the cervicoaxillary canal to reach the

upper extremity. The cervicoaxillary canal is divided by the first

rib into two parts, the proximal one, composed of costoclavicular

space and the distal one, composed of axilla. The proximal

division is more critical for neurovascular compression. It is

bounded superiorly by the clavicle and inferiorly by the first rib,

anteromedially by the costoclavicular ligament and

posterolaterrally by the scalenus medius muscle along with long

thoracic nerve. The scalenus anticus muscle divides the

costoclavicular space into two compartments, the anterior one

containing subclavian vein and the posterior one contains the

subclavian artery and brachial plexus. This compartment is

bounded by scalene anticus anteriorly, scalene medius

posteriorly and the first rib inferiorly, is called scalene triangle. In

this area accessory cervical ribs, taut or anomalous scalene

muscles and aberrant bands may individually or collectively be

involved in compressive process. The structures not only encircle

the artery but also contiguous brachial plexus constituting the

neurovascular bundle which continues as a unit through axilla.

The subclavian vein which lies anteriorly, also joins the nerve-

artery combination for making a unit that proceeds together

peripherally to pass between the clavicle and first rib into axilla.

At this junction, the subclavius, costocoracoid ligament and

possibly aberrant tissue cross over the neurovascular bundle

which proceeds over the pectoralis minor muscle and inferiorly

beneath the pectoralis major muscle. All these structures

become involved in the motion of the shoulder, the only human

universal joint which is ordinarily maintained in motor balance by

the attachment of twenty four muscles and eighteen ligaments1.  

FUNCTIONAL ANATOMY2

The cervicoaxillary canal, particularly its proximal portion, the

costoclavicular space has ample room for passage of

neurovascular bundle. Narrowing of this space occurs during

functional maneuvers. It narrows during abduction of the arm

because clavicle rotates backwards towards the first rib and the

insertion of scalenus anticus muscle. In hyper abduction, the

neuro vascular bundle is pulled around the pectoralis minor

tendon, the coracoid process and the head of humerus. The

coracoid process tilts downwards and exaggerates the tension

on the bundle. The sternoclavicular joint which ordinarily forms

an angle of 15-20 degrees forms a smaller angle when outer end

of the clavicle descends as in drooping of the shoulders in poor

posture and narrowing of the costoclavicular space may occur.

During normal inspiration the scalene anticus muscle raises the

first rib and narrows the costoclavicular space .The subclavian

artery and brachial plexus traverses the scalene triangle on the

first rib. Anatomical variations may narrow the superior angle of

the triangle and cause impingement on the upper components of

the brachial plexus and produce upper type of scalene anticus

syndrome that involves the trunk containing elements of C5-C6.If

the base of the triangle is raised, compression of the subclavian

artery and trunks containing components of C7-C8 and T1

results in the lower type of scalenus anticus syndrome.  

There are three major types of thoracic outlet syndrome : 

1.Nerurogenic type 90-95%.

2.Arterial type.

3.Venous type.  

ETIOLOGY OF THORACIC OUTLET SYNDROME3  

CONGENITAL ACQUIRED 

Osseous. Fractured clavicle.

Cervical rib. Callous and pseudo arthritis,

Long C7 process Fractured first rib,

Abnormal or anomalous first rib Exostosis or tumors.

Soft tissue

Anomalous ant. scalene insertion. Scalene muscle injury

Middle scalene insertion Previous operation scar

Scalene muscle hypertrophy . Reattachment of ant.

Scalene minimus. Scalene muscle.

Abnormal ligaments and fibrous bands Soft tissue tumors

Prefixed or post fixed Brachial plexus tumors.

Brachial plexus Direct brachial plexus injury.

Posture. Sagging shoulders,

Sagging breasts. 

CONTRIBUTING FACTORS:-

Mechanical pressure- All the shoulder girdle compression

syndromes have one common feature, namely compression of

brachial plexus, subclavian artery and vein usually between the

first rib and the clavicle. With elevation of upper limb, there is

scissor like approximation of the clavicle superiorly and the first

rib inferiorly. 

Trauma- The role of trauma to scalene muscles was first

reported by Ocshner and colleagues. There can be direct trauma

to brachial plexus due to Whiplash flexion extension injury to the

neck after a rear end automobile accident. Indirect trauma can be

due to work related repetitive micro stress trauma in patients

whose jobs demand repeated elevation of upper limb or heavy

weight lifting. A neurochemical theory suggests that an initial

injury whether gross or from micro stress produces a local

perineural inflammation in the soft tissues.

HISTOPATHOLOGY-Machleder and coworkers subjected frozen

specimen of anterior scalenus muscle from patients of thoracic

outlet syndrome to fibretyping. Normal human skeletal muscle

has two main types of fibres with respect to histochemical

staining. They are in equal percentage. 

Type 1 fibres are slow twitch, has high oxidative enzyme capacity

and lower glycolytic activity. Type 11. fibres are fast twitch, quick

reacting has low oxidative capacity . There is marked increase in

type 1 fibres in cases of thoracic outlet syndrome (85%).  

Double crush hypothesis- was reported by Upton and Mc Comas

in 1973.It states that a proximal source of nerve compression will

render the distal nerve segment more susceptible to second site

of compression. The authors hypothesized that one site alone

would not cause a clinical disturbance but summation of two sites

would cause clinical disturbance. This hypothesis is directly

applicable to brachial plexus compression in that several

anatomical structures may compress the brachial plexus. The

association between carpal and cubital tunnel syndromes and

thoracic outlet syndrome is supported by double crush syndrome.

With increase in jobs requiring repetitive activity like assembly

lines and keyboarding, a cumulative trauma disorder or repetitive

stress disorder is now recognized. This disorder relates to

multiple level nerve compression4. 

ANOMALIES- In a study carried out by authors5 34% of 200

cases, no structural anomaly was discernible from the axillary

approach.8.5% had a cervical rib articulating with first rib directly

or by a fibrocartilaginous extension.10%had scalene minimus

muscle inserted on first rib or sibsons fascia.19% had an

anomaly of the subclavius tendon or its insertion.43% had an

anomaly of scalene muscle development or insertion. In 30%

cases there were other cartilaginous anomalies which could not

be related to the specific development characteristics. More than

one abnormality was recognized in 22.5% of cases. In 33 cases

presenting with spontaneous axillo-subclavius thrombosis (Paget

Schrotter syndrome) 55% had hypertrophy of subclavius tendon

associated with enlargement of insertion tubercle in males

(70%). 

First rib and cervical rib anomalies- During development

C7 rib forms and then regresses to C7 transverse process.

Various stages in evolution range from a complete C7 rib to a

rudimentary form associated with fibrocartilaginous band. A

cervical rib is associated with prefixed type of brachial plexus in

which there is major contribution from C4 and minor contribution

from T1.Fibrocartilaginous bands extending from the end of

incompletely formed cervical ribs are best thought of as an

anomaly of the cervical rib formation. The anomalies have been

classified as type 1and type 2 bands by Roos and coworkers. 

Scalene muscle ABNORMALITIES. The separation of muscle

bundles interdigitating between neurovascular structures

accounts for the muscular bridges seen between the middle and

anterior scalene muscles that often penetrate the brachial plexus.

They are not pathological but result in neurogenic symptoms as a

consequence of abnormal growth.. Unique configuration of

scalene muscle insertion that leads to compression of

neurovascular structures in the inter scalene triangle which

accounted for 43% of the congenital variations. 

CLINICAL FEATURES 

Despite the congenital nature of the anomalies the onset of

symptoms is in early to middle adult life has been recorded

virtually by all the surgeons. The delay in onset is most often

related to post natal development. The widening of the chest and

the growth of the clavicle continues up to the age of 22-25 years

after which the pectoral girdle begins to descend .Still later, with

loss of strength and tone of the supporting musculature of the

shoulder girdle, there is further traction on the neurovascular

bundle at the thoracic outlet. The symptoms of thoracic out let

syndrome depend upon whether brachial plexus, blood vessels

or both are compressed. Neurogenic manifestations are more

frequent than vascular symptoms. Neurogenic symptoms consist

of pain and paraesthesias which are present in approximately

90% of the cases. Motor weakness and occasionally atrophy of

the hypothenar and interosseous muscles occur which is ulnar

type of atrophy. The symptoms occur most commonly in areas

supplied by the ulnar nerve including the medial aspect of the

arm and hand, fifth finger and lateral aspect of the 4th.finger.The

onset of pain is usually insidious and commonly involves the

neck, shoulder, arm and hand. The pain and paraesthesias may

be precipitated by strenuous exercise or sustained physical

efforts with arm in abduction and the neck in hyperextension. 

Symptoms may be initiated by sleeping with arms abducted and

hand clasped behind the neck. The symptoms related to upper

plexus from C4-C7 is correlated with symptoms involving head,

neck and upper back. The lower plexusC8-T1 is usually related

anatomically to the medial aspect of the arm and hand. 

The patients with neurogenic thoracic outlet syndrome are

usually women in their 3rd to 5th decade. Female to male ratio is

4:1.The onset is usually abrupt. Certain activities such as typing,

painting and lifting weights may precipitate the problem. 

In vascular thoracic outlet syndrome, arterial symptoms vary from

digital vasospasm to gangrene depending upon degree of

compression and irritation. Irritation of the vessel wall by bony

prominence may lead to damage of intima, thrombosis and

embolisation or to the media resulting in aneurysm formation.

Arterial insufficiency, embolisation, atherosclerosis, vasospasm

associated with Raynaud's disease and reflex vasomotor

dystrophy must be considered in differential diagnosis. 

In the presence of complete cervical rib , the supraclavicular

course of the subclavian artery is displaced. There is an upward

extension of the thorax so that the subclavian artery passes high

in the neck as it emerges from the lateral border of scalenus

anticus muscle , it is elevated and readily palpable well above the

clavicle. There is suparaclavicular mass represented by the

cervical rib at its articulating site with the first rib6. Short

described two variants of cervical rib. In type [a] subclavian

artery crosses the first rib medial to its exostosis. In this type, he

found all major vascular symptoms. In type [b],the subclavian

artery crosses the first rib lateral to its exostosis. The symptoms

are generally neurogenic than vascular. 

The prolonged compression of subclavian artery may lead to- 

1 Structural changes of the arterial wall leading to the thickened

vessel wall adherent to the surrounding structures.

2 Stenosis at the site of compression.

3 Post stenotic dilatation due to turbulence of blood.

4  Subclavian aneurysm may lead to thromboembolic changes7.

Small emboli may lodge into digital and palmer arteries

producing picture like Raynaud’s phenomenon. Large emboli

blocking the bifurcation of brachial artery may result in major

ischemia or gangrene of the hand and fingers. 

Venous symptoms consists of tingling, aching ,tired and painful

limb associated at times with cyanosis, swelling and distended

distal veins are the result of obstruction of axillo-subclavian

venous system. Other venous disorders including effort

thrombosis, thrombophlebitis, heart failure, tumors and aneurysm

of the mediastinum and thoracic outlet canal and A-V fistulas

must be differentiated. 

While taking the patients history, it is important to elicit and

closely evaluate the exact postural attitudes adopted during work

or play that provoke the symptoms for example athletic practices

such as swimming, volley ball, hiking with back pack. Work

habits involved in painting, carpentry, paper hanging, hair drying

and routine household work like hanging clothes and washing

windows. It is important to question sleeping habits especially

when related to hyper abduction of the arms. 

It is necessary to carry out a thorough general physical

examination with emphasis on posture, anatomical abnormality in

the neck , localized swelling and tenderness, deficiency in

brachial blood pressure or pulses of the arm, venous cyanosis or

distension of the veins, bruit in the neck, skin temperature

changes in hands and neurological evaluation of the brachial

plexus. 

Finally three classical maneuvers must be carried out precisely

since these maneuvers are often misinterpreted after being

inaccurately performed.

Adson Test-( Scalene test) In 1927 Adson and Coffey

demonstrated the influence of the scalene anticus muscle by

asking the patient to elevate the chin , extend the neck and

rotate the head to the affected side while taking the deep breath.

This will produce paraesthesias over the distribution of the

brachial plexus and frequently obliterate the pulse at the wrist of

the affected side6. 

Costoclavicular manouver- (Military position) Falconer and

Weddel demonstrated this test in 1943.Back ward and downward

bracing of the shoulders as in military position will cause

costoclavicular compression of the subclavian artery. This

position may be simulated by carrying heavy weights or in

services by marching with full back pack.. This manouvre is

opposite of hyper abduction. 

Hyper abduction manouvre1 -It is also called Elevated Arm stress

test It was introduced by Roos. Both arms are abducted at

90degree and externally rotated with shoulders braced

posteriorly for three minutes. Most patients of neurogenic

thoracic outlet syndrome will not be able to complete the test as

there will be severe pain and numbness along the distribution of

the brachial plexus if there is compression.  

Differential diagnosis of thoracic outlet nerve compression

 

Carpal tunnel syndrome Shoulder disorders

Ulnar compression at the elbow. Rotor cuff tendinitis

Cervical spine pathology Biceps tendinitis

Cervical spine injury Myositis of the shoulder

Cervical disc herniation muscles.

Spinal stenosis Sympathetic disorders.

Neurological disease of the spine Raynaud’s disease

Spinal canal tumors. Reflex sympathetic

Miscellaneous conditions dystrophy

Angina

Investigatios4 

1. Cervical spine x-ray films for assessment of arthritic or

degenerative changes and presence of cervical ribs.

 

2. Chest x-ray film to identify apical lung pathology and superior

sulcus tumor. 

3.  Nerve conduction studies and electromyography to delineate

the possible significance of neuroforaminal or cervical disc

disease, as well as median nerve compression at the carpal

tunnel or ulnar nerve compression at the cubital tunnel. These

studies are very helpful in patients who have double crush

syndrome. 

4. F-wave studies and somatosensory evoked responses to

evaluate the brachial plexus. 

5. Non Invasive vascular studies. Digital plethysmography and

pulse volume recordings are of limited value in neurogenic

thoracic outlet syndrome. They appear helpful in patients with

ischcaemic symptoms .Duplex scanning of subclavian artery and

vein may reveal an aneurysm or Venous thrombosis and may

provide some anatomic information before angiography.

Intermittent arterial stenosis can usually be localized by B-mode

ultrasound and Doppler1. 

6.  Arteriography:- It is performed only when the patient is

suspected of having arterial complication of thoracic outlet

syndrome such as supraclavicular bruit, a pulsatile mass or

vascular symptoms and signs of upper limb thromboembolism.

Arteriography can be antegrade or retrograde arteriogram of the

subclavian artery and brachial artery.  

7. Venography:- It can diagnose subclavian vein thrombosis or

stenosis at the level of first rib and status of the collateral

circulation. 

8. Impedance plethysmography , venous Doppler survey and

venous duplex scanning can help in diagnosing venous

obstruction early. 

9. C.T. Scan, myelography, M.R.I. are done to rule out cervical

spinal cord tumors, spinal stenosis or a herniated disc. Saggital

M.R.I. in the plane of brachial plexus is under investigation and in

future may provide an accurate means of assessing the point of

actual compression nerves. 

10. Electrophysiological studies:- The tests are beset with

technical problem because of the site of brachial plexus as

compression is often deeply situated in the confines of the bony

inlet and located proximally at the level of nerve roots near the

intervertebral foramina. 

11.Ulnar nerve conduction velocities in neurogenic thoracic outlet

syndrome was popularized by Urschel and Razzuk2.They

reported decrease in ulnar nerve conduction velocities in these

patients and the nerve conduction returns to normal after surgical

decompression. 

TREATMENT:- 

1.       Conservative.

2. Surgical management. 

Conservative treatment1

Once diagnosis of neurogenic thoracic outlet compression

is established, an initial period of supervised conservative

treatment is instituted before operation is recommended for six

weeks. It includes analgesics, muscle relaxants, occupational

adjustment to improve posture or avoid elevating the arm during

work and sleep. Physiotherapy in the form of simple heat and

cold application, massages and ultrasonic wave application to

supraclavicular area is carried out. Shoulder girdle strengthening

exercises are taught to women with poor musculature.

Brassieres with broad and padded shoulder strap is advised for

women with heavy sagging breast. 

SURGICAL MANAGEMENT

It is indicated if there is 

(a) failure of conservative management

(b) worsening of neurogenic symptoms leading to intractable pain

(c) loss of job or interference in daily activity.

(d) acute vascular symptoms.  

The decision to operate should be discussed with the patient

explaining the possibility of neural or vascular complications, the

possibility of achieving partial relief or recurrence of symptoms

should be emphasized when symptoms are more than two and

half years duration. 

OPERATIVE TREATMENT : The controversy surrounding

Neurogenic thoracic outlet syndrome is best explained by

diversity of surgical operations available .Various combination of

operations like scalenotomy , scalenectomy, cervical rib

resection, first rib resection and neurolysis of brachial plexus

may be carried out by four approaches1. 

A:- Supraclavicular

B:- Transaxillary

C:-Infraclavicular

D:-Posterior approach 

Aim of operation

1- Relieving of brachial plexus symptoms

2- Any abnormal osseous structures such as cervical rib,

exostosis, abnormal first rib or fracture callous should be

removed in majority of patients . 

Supraclavicular approach3 : It provides the best route to reach all

the structures . It allows direct visualization of the anatomic

relationship between bony and myofascial structures and the

brachial plexus through scalene space in the thoracic outlet and

related congenital anomalies along with access to the first rib and

clavicle. If the anterior scalene muscle requires decompression, it

must be excised rather than simply divided because of possible

adhesions formation or perforation of the muscle with lower

nerve roots of the brachial plexus. In such cases the original

symptoms would be aggravated by the retraction of the divided

muscle fibres against the imbedded nerves. 

Transaxillary approach1 : When the clinical picture suggests

costoclavicular or hyper abduction symptoms, surgical

exploration through a trans axillary incision described by Roos

and Owens is usually preferred. Some of the advantages of the

axillary approach include excellent cosmesis ,readily palpable

and easily visible ligaments and bony structures which may be

involved in the compression of neurovascular bundle. At the

same time, it allows access for dorsal sympathectomy when

indicated. 

Author believes that sufficient compression of the brachial plexus

to produce symptoms simultaneously causes measurable

compression of the subclavian vessels even in the absence of

vascular symptoms. At operation, if the patient has been

prepared so that axilla, shoulder and lower neck are exposed

with the arm draped in a sterile field, it is possible to perform

hyper abduction and costoclavicular manoeuvers under

anaesthesia with the thoracic outlet structures directly exposed.

Under these circumstances, the physiology of the compressive

process and the offending structures whether bony or soft tissue,

can be identified and divided or excised. In a series of 194

patients,14 required bone excision and 180 required soft tissue

excision to relieve symptoms with 96% success rate. 

Infraclavicular approach : It is used for bilateral neurovascular

symptoms but cosmetic results are less favourable than other

approaches. It can be used for subclavian venous thrombosis

and first rib excision. 

Posterior approach : It is adopted only when there is history of

previous Operation by other approach. This approach requires

cutting of heavy muscles before reaching the thoracic outlet.

Rationale for sparing the first rib : The first rib is seldom in actual

contact with the brachial plexus except for T1. After neurolysis

and scalenectomy, the brachial plexus runs an unobstructed

course. Resection of first rib is unnecessary and adds to post

operative pain and shoulder immobility with higher risk of pleural

damage at the time of surgery.

Vascular Thoracic outlet syndrome : Three anatomic components

of the disease process namely- arterial compression, subclavian

axillary arterial lesion and distal emboli if present has to be dealt

with simultaneously. 

Arterial reconstruction is necessary in the presence of arterial

aneurysm or mural thrombus. Artery is mobilized after resecting

the cervical and first rib. End to end anatomists is performed.

Aneurysmorraphy can be performed along with internal stenting

of the subclavian artery. Distal embolic occlusion causes major

difficulties in surgical treatment of the patient as they are multiple

in number.  

Thromboendarterectomy can be tried in these patients for distal

emboli.

Venous thrombosis of subclavian vein.: Thrombolytic agents like

urokinase or streptokinase are delivered locally to dissolve the

thrombosis. If there is external compression demonstrated on

venography, it should be relieved by supraclavicular route. 

Complications of operation for thoracic outlet syndrome7

 

Nerve Injury. Vascular Injury

Brachial plexus Subclavian artery

Long thoracic nerve Subclavian vein

Phrenic nerve Thoracic duct injury.

Intercostobrachial nerve Lymphatic fistula

Recurrent laryngeal nerve Lymphoedema

Pleural complications Chylothorax

Pneumothorax Wound

infection

Pleural effusion Lymph collection

Haemothorax  

 

REFRENCES

1.        Stallworth JM. Thoracic outlet compression syndromes in: Text book of vascular surgery. Principles and Techniques. Ed. Haimovici H. W. B. Saunders Philladelphia-Tokyo 3rd edition 1993; pp 829-839.

2.        Urschel HC. Thoracic outlet syndrome in: Glenns Text book of Thoracic and Cardiovascular surgery. Ed. Baue AE. Appleton and Lange. London-New Jersey, 1996; pp 567-580 .

3.        Richard D, Rutolo C. Neurogenic thoracic outlet syndrome in : Text book of Vascular surgery . Ed. Rutherford RB. W. B. Saunders Philladelphia-Tokyo.2000; pp 1184-1199.

4.        Machleder HI. Vascular diseases of the upper extremity And Thoracic outlet syndrome in : Text book of vascular surgery . A comprehensive review . Ed. Moore WS. W.B.Saunders Philladelphia-Tokyo.1993: pp 592-605.

5.        Machleder HI. Thoracic outlet compression syndrome In:Text book on Vascular surgery.Theory and Practice. Eds. Callow AZD, Earnst CB. Appleton &Lange London-New Jersey.1995; pp235-265.

6.        Haimovici H. Arterial thromboembolism due to thoracic outlet complications.in:Text book of Vascular surgery. Principle and Technique. Ed. Haimovici H. W.B. Saunders Philladelphia-Tokyo, 1993; pp 840-852.

7         Kieffer E. Arterial complications of thoracic outlet compression. In: Text book of Vascular surgery Ed . Rutherford RB. W. B. Saunders Philladelphia-Tokyo, 2000; pp 1200-1207.