TYPES OF THORACIC OUTLET SYNDROME
Thoracic outlet syndrome (TOS) is the term for a collection of at least four distinct problems at the thoracic outlet. The thoracic outlet is the area at the base of the neck (on either side) where the nerves, artery, and vein pass back and forth from the center of the body to the arms.
Neurogenic TOS (NTOS): The most common form of TOS (approximately 80%), this is caused by compression of the nerves by the triangle formed by the first rib, anterior scalene muscle, and posterior scalene muscle. Symptoms are classically numbness, tingling, pain, and/or weakness the hand and forearm, COMBINED with pain at the base of the neck, often radiating to the shoulder, chest, underarm, or head. Symptoms tend to be worse with arms overhead, exertion, and driving, and headaches are very common. Diagnosis is relatively subjective, and thus the syndrome is often confused with neck problems, rotator cuff injury, or other nerve problems, and the diagnosis is often obscure.
Venous TOS (VTOS): Also called “Paget-Schroetter Syndrome,” this occurs in about 20% of cases, and results from either intermittent positional (arm up) obstruction of the vein (causing intermittent swelling, often with exercise), or complete occlusion by clotting (causing fixed swelling). The arm is blue, swollen, and often tender. This very commonly occurs in athletes, often those whose arms are overhead (baseball and softball pitchers, tennis players, swimmers), and after exertion, leading to the term “Effort Thrombosis.” .
Arterial TOS (ATOS): This is the rarest form of TOS, occurring sporadically and almost always in patients with visible, objective abnormalities such as an extra (cervical) rib. It is defined by the Society for Vascular Surgery as an actual abnormality of the artery itself, and is NOT diagnosed by loss of the wrist pulse with arms overhead (which is fairly common in the general population). Symptoms can include fixed loss of blood flow to the hand (painful blue fingers) or a pulsatile mass above the collarbone.
Dialysis-access-associated VTOS: A form of venous TOS, this has only recently been recognized as a distinct problem, probably because few clinicians are familiar with both syndromes. The anatomy of the front part of the thoracic outlet is the same for everyone – the vein is potentially pinched between the front of the rib and front of the collarbone. Effort Thrombosis and other forms of VTOS are caused by muscle buildup and/or arms overhead, but in patients with an arteriovenous fistula for dialysis access, the very high volume blood flow can create turbulence, which in turn creates scar tissue formation on the inside of the blood vessel and narrowing. This is a fairly common problem causing severe arm swelling in this patient population.
Recurrent TOS: Unfortunately, TOS can recur, even after proper treatment, in 10 to 20% of patients. Reoperation at times can lead to excellent results, but it is critically important to find a surgeon with extensive experience in recurrent disease.
CLINICAL CHALLENGES WITH THORACIC OUTLET SYNDROME
- Diagnosis and treatment of TOS is often subjective, complex, and associated with significant complications. It is recommended that patients should seek out providers with extensive experience in this condition.
- Very few objective diagnostic tests are helpful or necessary in the diagnosis of NTOS. In particular, nerve conduction studies and arteriography have not shown to be helpful and are not recommended by the Society for Vascular Surgery.
- “Less-invasive” first rib resection, either robotic or thoracoscopic, have not yet been shown to be as effective as conventional resection, as less of the rib is removed and opportunities for muscle and scar tissue resection or venous or arterial reconstruction are limited. Research is ongoing, but at this point the general TOS community does not recommend these treatments.
- Treatment for venous TOS should NOT be blood thinners alone. This strategy has been associated with up to 50% persistent (lifelong) symptomatology.
- The nerves to the upper arm are sensitive to pressure in more than one location (“Double Crush Syndrome”). Patients with persistent symptoms after carpal or cubital tunnel release may also have NTOS.