Thoracic outlet syndrome
|Thoracic Outlet Syndrome|
This syndrome results from the compression of neurovascular bundle comprising of subclavian artery and vein, axillary artery and vein and brachial plexus at the thoracic outlet.
Thoracic outlet is a space between the first rib, clavicle and the scalene muscles. The above structures are liable to be compressed. when this space gets narrowed either due to hypertrophy of the existing muscles or due to any other cause like congenital, trauma, etc.
Sites of Compression
The sites of compression might be either supraclavicular, subclavicular or infraclavicular.
Supraclavicular: Interscalene triangle between the anterior scalene muscles.
Subclavicular: Interval between second thoracic rib, clavicle & subclavius.
Infraclavicular: Beneath an enclosure formed by the coracoid process, musculus pectoralis minor , and costocoracoid membrane.
Rare Cause Scissor-like encirclement of arteria axillaris by the median nerve
Arm when in full abduction pulls up the artery by 180° causing compression in the short retroclavicular space.
Vigorous occupation:↑ses the muscle bulk & decreases the space.
Inactive occupation: ↓ses the muscle bulk and thereby increases the space.
Congenital: Cervical rib decreases the interscalene space and decreases the retroclavicular space.
Traumatic: Malunion or nonunion of fracture clavicle.
Anomalies of the first thoracic rib.
• Tumor arising from the upper lobe of the lung.
• Cervicothoracic scoliosis.
• Abnormal variations of the scalene muscles.
Obviously, this syndrome poses two major problems. The first one relates to the compression of the major vessels and secondly to the compression of the nerves. The first problem has a definite clinical entity, while the second one presents a vague picture and makes an accurate diagnosis difficult.
Here the compression could be arterial or venous. During the arterial compression, which is mild within the early stages the patient complains of numbness of the entire arm with rapid fatigue during overhead exercises. If the compression is critical , the patient will complain of cold, cyanosis, pallor and Raynaud’s phenomenon.
Venous compression leaves the limb swollen & discolored after exercises, which disappears slowly with rest.
This involves C8 T1 segment (Klumpke’s paralysis). Patients complain of paraesthesia along the medial aspect of the arm, hand, little and ring fingers.
Intermittent Claudication Test
The arm is abducted and elevated and fingers are exercised. The inference:
• If pain develops after 1 minute; it is negative (normal).
• If pain develops before 1 minute; the test is positive.
Compression of subclavian artery in the neck: Radial pulse decreases.
To determine the adequacy of radial and ulnar arteries, by compressing each one at a time and checking for adequacy.
The patient’s shoulder is braced down and back. The reproduction of the symptoms, change in the radial pulse, bruit heard in infraclavicular area are the positive findings.
Adson’s test: The radial pulse is felt and the patient is asked to take a deep breath and turn the head to the same side. Decrease in the radial pulse indicates positive test.
Wright’s test: The same maneuver as above but the head is tilted towards the opposite side. It should be noted that thoracic outlet syndrome is a diagnosis of exclusion. First, the cervical pathology should be excluded and later the above tests should be performed as the initial screening procedures.
Subclavian artery compression → results in poststenotic dilatation → stasis favors thrombosis → the thrombi break and migrate distally causing embolization → these results in the distal artery blockade causing ischemia and gangrene of the upper limbs.
X-ray of neck: To rule out the intrinsic causes like cervical spondylosis, cervical rib, etc.
Nerve conduction studies: Difficult to work out the nerve conduction velocity through the thoracic outlet, but its biggest value is to rule-out problems like entrapment, e.g. ulnar nerve at elbow, wrist, etc.
• Conservative treatment: Treatment Consists of exercises like shoulder shrugging, physiotherapy,rest etc.
• Surgical treatment
Indications: Gangrene and poststenotic dilatation.
• Removal of the first thoracic rib: This is the most effective treatment as it deals with both supraclavicular and infraclavicular etiological factors in this syndrome.
• Removal of cervical rib: If this is the cause of compression.
• Scalenotomy is indicated in scalenus anticus syndrome.