Thoracic Outlet Syndrome
What is the Thoracic Outlet Syndrome?
Thoracic outlet syndrome (TOS) is a group of medical conditions which are caused by compression of nerves or blood vessels in the thoracic outlet, the area between the base of the neck and the armpit, including the front of the shoulders and chest.
There are three types of TOS:
1. Vascular
A compression of the artery and vein may be the pressure at the TOS.
2. Neurogenic
The nerves at the TOS may be compressed from an extra cervical rib, present at birth.
3. Disputed or painful form
No neurological damage is observed but patients show neurological symptoms and pain.
Typically Electromyography (EMG) studies of these patients are found to be normal but they still complain of pain.
What are the causes of thoracic outlet syndrome (TOS)?
The reasons of thoracic outlet syndrome are:
1. An enlargement of the tissues in or near the thoracic outlet may be due to:
a. Trauma or injury
b. Weight lifting
c. Cervical rib (an extra rib extending from the neck present at birth)
d. Weight gain
e. Growth of a tumor
2. A change of the tissues in or near the thoracic outlet.
Thoracic outlet syndrome can happen from injury, disease or a congenital problem such as an abnormal cervical rib.
It is more frequent in women than in men with an excess of between 3- and 9-fold.
Obesity and poor posture may make the condition worse.
Psychological changes are present in patients with thoracic outlet syndrome.
These psychological changes may be the cause or the effect of the syndrome.
There is no obvious cause present in patients who suffer from TOS.
Over 90% of all TOS cases are due to neurogenic causes whereas 3-5% are venous.
Less than 1% is arterial.
The true neurological form does not affect more than 1 person in 1 million
The incidence is reported as between 3 and 80 per 1,000.
The beginning of the TOS is from the 2nd to the 8th decade with the highest in the 4th decade.
What are the symptoms of thoracic outlet syndrome (TOS)?
Symptoms are dependent on which compression of nerves or blood vessels are done.
Nerve compression symptoms are much more frequent than symptoms from blood vessel compression.
A. Pressure on the nerves (brachial plexus)
1. Neck, shoulder, and arm pain
Nerve pressure may cause a vague, aching pain in the neck, shoulder, arm, or hand.
2. Numbness in the arm, hand or fingers
Pain, numbness or tingling may be present on the inside of the forearm and the fourth and fifth fingers of the hand.
3. Weakness in the shoulders, arm and hands
Weakness may make the hand clumsy.
B. Pressure on the blood vessels
1. Impaired circulation to the extremities (causing discoloration)
Blood vessel pressure can decrease the flow of blood out of the arm which results in redness and swelling of the arm.
2. Less frequently, pressure can reduce the blood flow into the arm and hand, causing the arm and hand feeling cool and easily tired.
Head activities are especially difficult because they make worse both types of compression.
A depression in the shoulder or swelling or discoloration in the arm is present.
The range of motion may be limited.
How is TOS diagnosed?
The proper diagnosis of thoracic outlet syndrome will need the expert examination of experienced neurologists and nerve specialists.
Elevated arm stress test
The elevated arm stress test is often done by doctors to help them diagnose thoracic outlet syndrome.
The doctor will have you raise the arms over the head, then open and close the fists for approximately 3 minutes.
If this reproduces the symptoms, it is likely that you have thoracic outlet syndrome.
This elevation of arm stress test is clear in the diagnosis.



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