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Thoracic Outlet Compression Syndrome

Thoracic Outlet Compression Syndrome

1. Definition

Compression of the subclavian vessels and brachial plexus at the superior aperture of the chest, most commonly against the first rib. Other terms for this syndrome include scalenus anticus syndrome, costoclavicular syndrome, hyperabduction syndrome, cervical rib syndrome, and first thoracic rib syndrome.

2. Anatomy

A. Surgical Anatomy
1) The first rib divides the cervicoaxillary canal into a proximal space and a distal space (the axilla)
2) Most neurovascular compression occurs in the proximal section, which consists of the costoclavicular space and the scale triangle
3) Costoclavicular space boundaries: clavicle (superior), first rib (inferior), costoclavicular ligament (anteromedial), and scalenus medius/long thoracic nerve (posterolateral)
4) Scalene triangle boundaries: scalenus anticus (anterior), scalenus medius (posterior), and first rib (inferior)
5) The subclavian vein lies anteromedial to the scalenus anticus; the subclavian artery and brachial plexus run posterolateral to this muscle
B. Functional Anatomy
1) Certain movements and position of the arm and shoulder girdle, as well as anatomic variations, can narrow the costoclavicular space or scalene triangle
2) Arm abduction rotates the clavicle toward the first rib
3) Arm hyperabduction pulls the neurovascular bundle around the coracoid process and head of the humerus
4) Poor shoulder posture lessens the angle of the sternoclavicular joint as the distal end of the clavicle "droops"
5) Severe emphysema or excessive muscular development causes abnormal lifting of the first rib
6) Anatomic variations narrow either the superior angle or the base of the scalene triangle, producing upper and lower types of compression syndromes, respectively

3. Etiology

There are many factors which can cause neurovascular compression at the thoracic outlet. Bony abnormalities are present in about 30% of patients, and some of these may be visualized on plain chest x-ray.
1. Anatomic Factors
Interscalene compression
Costoclavicular compression
Subcoracoid compression
2. Congenital Factors
Cervical rib
Rudimentary first rib
Scalene muscle abnormalities
Fibrous bands
Bifid clavicle
First rib exostosis
Enlarged C7 transverse process
Omohyoid muscle abnormalities
Anomalous transverse cervical artery
Postfixed brachial plexus
Flat clavice
3. Traumatic Factors
Fractured clavice
Humeral head dislocation
Upper thorax crush injury
Sudden effort of shoulder girdle muscles
C-spine injuries/cervical spondylosis

4. Clinical Presentation

The character and pattern of symptoms will vary depending on the degree to which nerves, blood vessels, or both are compressed
A. Neurogenic
1) More frequent than vascular compression
2) Pain and paresthesias present in 95% of patients
3) True motor weakness with atrophy of hypothenar/interosseus muscles found in 10%
4) Sensory fibers lie on the outside of the nerve bundles and are the first to be affected by compression
5) Symptoms usually have ulnar nerve distribution (medial arm and hand, 4th and 5th fingers)
6) Pain is insidious and involves neck, shoulder, arm and hand
7) Strenuous physical exercise preciptates the symptoms, with arm in abduction and neck hyperextended
B. Vascular
1) Pain is usually diffuse and associated with coldness, weakness, and easy fatiguability of the hand and arm
2) Unilateral Raynaud's phenomonen in about 7.5% of patients, which can be precipitated by hyperabduction or carrying heavy objects
3) There may be signs of distal embolization, poststenotic dilation or aneurysm of the subclavian artery, or true arterial occlusion
4) Venous obstruction is much less common and is known as "effort thrombosis" or "Paget-Schroetter syndrome"
5) The affected arm is edematous, discolored, and aches

5. Diagnosis

A. Clinical maneuvers
1) Positive findings for all tests include a decrease or loss of the radial pulse, or reproduction of symptoms
2) Adson/scalene test: patient holds a deep inspiration, fully extends neck, and turns head to the side
3) Costoclavicular test: shoulders drawn inferiorly and posteriorly
4) Hyperabduction test: arm is hyperabducted to 180 degrees
B. Radiologic tests
1) CXR and C-spine films can detect cervical ribs and degenerative changes
2) Cervical CT should be performed if osteophytic changes and intervertebral space narrowing are present
3) Angiography is indicated for a pulsating paraclavicular mass, absent radial pulse, or paraclavicular bruit
C. Ulnar nerve conduction velocity
1) Points of stimulation include the supraclavicular fossa, middle upper arm, below elbow, and wrist
2) Normal value across the thoracic outlet is 72 m/sec; any value less than 70 m/sec indicates compression
Grading of Compression
66-69 m/secSlight
60-65 m/secMild
55-59 m/secModerate
less than 54 m/secSevere

6. Differential Diagnosis

A. The differential diagnosis for thoracic outlet syndrome is quite broad and includes neurologic, vascular, pulmonary, cardiac, and esophageal disorders.
B. Some of the more common conditions include herniated cervical disk, cervical spondylosis, and peripheral neuropathies

7. Treatment

A. Physical therapy should be initiated in all patients
B. Most patients with an UNCV above 60 m/sec will improve with conservative therapy
C. Surgical intervention should be considered if symptoms persist after physical therapy and the UNCV shows minimal or no improvement

8. Operative Technique

A. Always document preoperative neurologic findings
B. Transaxillary first rib resection avoids division of major muscle groups, ensures complete removal of the first rib, and has the best cosmetic result
C. Position the patient in the lateral position with the affected arm abducted 90 degrees and loosely suspended (straight up to the ceiling)
D. Transverse incision in the axilla between pectoralis major and latissimus dorsi
E. Dissect along the external thoracic fascia to the first rib
F. Divide the scalenus anticus at its insertion on the rib
G. Remove middle and anterior portion of first rib after periosteal elevation
H. Divide costoclavicular ligament and remove posterior portion of first rib
I. Always protect the brachial plexus and vessels
J. Remove the entire first rib, as any residual portion may cause recurrence

9. Results

A. Almost all patients will have relief with conservative therapy, with about 5% requiring surgery
B. Symptoms recur in about 10% of patients
C. Less than 2% will require reoperation
D. A recent study from the Annals of Thoracic Surgery of over 2200 patients showed excellent or good results after operation in over 90% of cases

10. Recurrent Thoracic Outlet Syndrome

A. About 1-2% of patients will have persistent or progressively more severe symptoms after their operation
B. Most have recurrence within 3 months of operation
C. Symptoms, physical examination, and UNCV findings should be diagnostic before reoperation
D. Pseudorecurrence occurs in patients in whom a cervical rib or the second rib was resected instead of the first rib, or the first rib was resected instead of the causative cervical rib
E. True recurrence occurs in patients in whom the first rib was incompletely resected or there was excessive scar development around the brachial plexus
F. The posterior thoracoplasty approach provides the best exposure
G. Persistent or recurrent bony remnants should be excised
H. Careful neurolysis of the nerve root and brachial plexus is performed along with dorsal sympathectomy
I. One series of over 400 patients had improvement in symptoms in about 80% of patients; 7% required a second reoperation