Thoracic Outlet Syndrome

Thoracic Outlet Syndrome, or TOS, refers to compression of the subclavian artery, subclavian vein, or nerves as they travel through an area called the thoracic outlet on their way to the arms. The thoracic outlet is located in the upper chest just below the clavicle (‘collar bone’). Compression occurs because this space is often too small in some patients or they contain an extra rib called a cervical rib in that location. The artery, vein, or nerves can be pinched against the clavicle by the first rib, scalene muscles, or cervical rib causing symptoms.

The symptoms that occur depend on which of the 3 structures (artery, vein, or nerves) is being compressed. ‘Arterial’ TOS can cause painful ischemia and coldness of the affected arm or hand from lack of blood flow due to the pinched artery itself or from embolization of thrombus (blood clot) from within an aneurysm that can typically form just after the compressed area.

 Embolization is when the thrombus breaks-off, travels down the artery, and lodges itself into a smaller part of the artery further downstream. This can stop blood from flowing down the remainder of the artery. ‘Venous’ TOS, also known as effort thrombosis or Paget-Schroetter syndrome, can cause arm swelling and associated pain from thrombosis (blood clot formation) of the pinched subclavian vein which occludes it and prevents blood return from the arm. ‘Neurogenic’ TOS can cause various forms of pain, numbness, and/or weakness in the affected arm due to compression of the nerves.

Diagnosis of TOS and its complications requires a thorough history and physical exam by a vascular surgeon. An ultrasound and/or computed tomography (CT) scan is usually required. Occasionally, an arteriogram or venogram is required, which involves injection of contrast dye into the artery or vein for imaging.

Treatment of arterial TOS requires removal of the first rib to stop the compression and then repair of the compressed and likely damaged artery and any associated aneurysm that may exist using open surgical grafting. Treatment of venous TOS requires a combination of medical, endovascular and open surgery. Medical therapy involves blood-thinning medication to prevent additional clotting. A procedure to remove the blood clot is then required using minimally invasive (endovascular) treatment with thrombolysis (removal of thrombus with medicine through a catheter), thrombectomy (mechanical disruption and removal of thrombus through a catheter), and possibly also balloon angioplasty to repair the narrowed vein. Finally, open surgery is required to remove the first rib to stop the compression. If the vein is still narrowed due to scarring from years of compression then a stent may be needed to hold it open. Neurogenic TOS is mostly treated with physical therapy. Surgery is rarely needed as it can often worsen the problem.