There are three types of TOS
Doctors classify TOS into one of three types, based on the primary structure that is affected. In general, compression of one of the vital structures that passes through each thoracic outlet determines the type of TOS.
To clarify, three vital structures pass through the thoracic outlet on each side:
In each thoracic outlet, compression or injury of each of these vital structures may occur. However, different signs and symptoms result from compression of the different vital structures. Thus, patients can suffer one or more of the three types of TOS.
Five nerve roots arise from the spinal cord on each side of the neck. Next, these nerve roots travel out of the bony spine to the thoracic outlet on each side. In each thoracic outlet, the nerve roots form a complex branching network, called the brachial plexus. Compression of the brachial plexus or tension on the brachial plexus results in neurogenic TOS. Given the complexity of the structure of the brachial plexus, patients can suffer a broad range of symptoms.
Thus, doctors see a complex clinical presentation, since compression may involve different parts of the brachial plexus. Symptoms include pain, numbness, tingling, coldness and weakness of the affected upper extremity.
A single, large subclavian vein drains almost all of the blood from each arm. Compression of this vein can cause impaired venous drainage of the arm. When compression is severe or prolonged, it can cause damage to the inner vein wall. As a result, blood clot can form within the vein. Symptoms include swelling, heaviness and cyanosis (abnormal blue color) of the affected arm. In addition, blood clots can break off and travel to the lungs or, rarely, to the brain, causing a stroke.
A single, large subclavian artery provides most of the blood flow to each arm. Compression of this artery causes damage to the arterial wall. Damage to the inner wall can cause scar tissue and stenosis (narrowing of the artery). In contrast, damage to the full thickness of the wall can result in an aneurysm (focal ballooning of the artery). As a result of this aneurysm, a doctor may feel a pulsatile mass in the thoracic outlet. When arterial damage occurs, blood clots may form. These clots can break off and travel to distal arteries. As a result, blood flow stops, and gangrene of the affected area may develop.