thoracic outlet syndrome
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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.
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