Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) are disorders of the upper extremity, which are caused by compression of the brachial plexus and subclavian artery or vein by bony, soft tissue or muscular anomalies as they emerge from the thoracic outlet.  Vascular TOS usually occurs in young patients and athletes who are involved in repetitive overhead motion, such as swimming or baseball. 

Arterial Thoracic Outlet Syndrome

Arterial thoracic outlet syndrome is a result of compression of the subclavian artery as it branches off of the aortic arch and travels, alongside the brachial plexus, between the anterior and middle scalene muscles, over the first rib and underneath
the clavicle.

Symptoms

Symptoms in the upper extremity are a result of thromboembolization (clot formation & dislodgement of the clot) and include arm fatigue, distal ischemia (lack of blood supply) of part of the hand in more than 50% of cases, Raynaud's phenomenon or stroke.  A bony abnormality causes trauma to the subclavian artery from compression that occurs with arm movement, especially repetitive overhead activities.  The bony abnormalities could be a cervical rib, long C7 transverse process, articulated first rib or a rib or clavicle fracture.

Diagnosis

Arterial thoracic outlet syndrome is diagnosed by physical examination with supplemental imaging studies obtained at times, to confirm the diagnosis.  The imaging studies may be a CT angiogram, MR angiogram or conventional angiography.  All of the imaging studies should be performed with dynamic views, that is, with the affected arm placed above the head to assess for active compression of the subclavian artery in this position.

Treatment

The treatment of arterial thoracic outlet syndrome is surgical removal of the bone or soft tissue causing the compression along with repair of the subclavian artery.  This may involve surgical decompression of the subclavian artery, repair of an aneurysm (bulging of the artery wall) or lesions causing partial or complete occlusion of the artery, upper extremity revascularization for treatment of ischemia or sympathectomy.

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Venous Thoracic Outlet Syndrome

Venous thoracic outlet syndrome (TOS) is also known as Paget-Schroetter syndrome or subclavian vein effort thrombosis.  Paget determined that the symptoms of the upper extremity (ie, arm swelling) were a result of subclavian vein thrombosis.  Von Schroetter further proposed that the upper extremity venous symptoms were a result of thrombosis of the subclavian vein at the thoracic outlet.

At the level of the thoracic outlet, the subclavian vein passes over the first rib, anterior to the insertion of the anterior scalene muscle.  This space is called the costoclavicular space and is located between the clavicle and subclavius muscle, superior to the subclavian vein with the first rib being inferior to the subclavian vein.

Venous TOS is a result of extrinsic compression of the subclavian vein, which results in injury of the vein, and eventual, stenosis (narrowing) and thrombosis (clotting).  Bony abnormalities are unusual.  The most common causes of extrinsic compression of the subclavian vein are a narrow costoclavicular space or muscular hypertrophy of the subclavius or anterior scalene.

Symptoms

Symptoms of venous TOS are caused by subclavian vein thrombosis and/or stenosis.  The symptoms involve the upper extremity (arm), and include:  swelling, heaviness or aching, and cyanosis.  An individual may notice prominent, distended veins in the upper chest and shoulder region, especially after activities which require repetitive use of the involved extremity.  Rarely, a pulmonary embolism may occur.  

Diagnosis

Venous TOS is usually diagnosed after a careful history and physical examination.  Physical findings include, arm swelling and cyanosis, distended veins, and dilated superficial collateral veins.  Imaging studies may be obtained to confirm the diagnosis, as well as, to provide information about the extent of the subclavian vein stenosis or thrombosis.  An ultrasound or MRI may be ordered.  In addition, a conventional venography, with the upper extremity placed in multiple overhead positions, may be obtained.

Treatment

The mainstay of treatment involves opening the subclavian vein thrombosis and/or stenosis, and thereby, reestablishing normal blood flow in the arm.  Treatment may include taking an anticoagulant (ie, warfarin or Lovenox) and elevating the arm as much as possible.  Surgical intervention may include the use of thrombolytic therapy (ie, tPA) in the operating room, followed by balloon angioplasty and/or stenting to keep the subclavian vein open.  Lastly, a thoracic outlet decompression may be warranted to remove the source of extrinsic compression (ie, removal of the first rib).

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