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Thoracic Outlet Syndrome (TOS) | Radiology Reference Article

The Neurological Associates of West Los Angeles brings you the latest information from the fields of neurology, neurosurgery, and neurosciences. For diagnosis and treatment options of thoracic outlet syndrome (TOS) and other or neurological disorders call our offices at (310) 829-5968 for an appointment with a neurologist.

 

The thoracic outlet syndrome (TOS) refers to a group of clinical syndromes caused by congenital or acquired compression of brachial plexus or subclavian vessels as they pass through the thoracic inlet. Signs and symptoms are a result of compression or irritation of the neurovascular bundle and are related to the degree of involvement.

Clinical presentation

Compression of brachial plexus is much more common (90 – 95%) than compression of the subclavian vessels (5 – 10%).

Brachial plexus compression results in pain, paraesthesia and/or numbness of the upper limb. Subclavian artery compression causes ischaemia with coolness, pallor, claudication, paraesthesia and decreased upper limb pulses. Subclavian veincompression causes upper limb swelling and pain and may result in venous thrombosis (Paget-Schroetter syndrome). Combined neurovascular symptoms and signs may be present. The findings are exacerbated by certain arm positions and manouvers, particularly with the arms raised above the head.

Pathology

There are 3 commonest sites of compression:

The scalene triangle is defined by the first rib and the anterior and middle scalene muscles and is the most medial compartment. The subclavian artery and branches of the brachial plexus pass through the borders of this triangle while the subclavian vein passes anterior to it.

Possible causes of compression of the brachial plexus or subclavian vessels include a congenital cervical rib, bone abnormality of the first rib or malunion of a clavicular fracture, aberrant insertion of the scalene muscle, abnormal fibrous bands, and hypertrophy or fibrosis of the surrounding musculature.

Causes

Radiographic features

Plain radiography is indicated to exclude an underlying bone abnormality.

Imaging with ultrasound, contrast-enhanced CT, MRI or conventional angiography is useful for detecting vascular compression. Imaging is performed with the patient’s arms both in the raised and neutral position (for comparison). Imaging may show the vascular stenosis and complications such as thrombosis, false aneurysm and distal emboli. Imaging of the bones and soft tissues may reveal the cause.

MR angiography with dynamic positioning is particularly useful in the diagnosis of vascular subtypes of thoracic outlet syndrome.

Treatment and prognosis

Treatment of arterial thoracic outlet syndrome is surgical intervention. Treatment is required to treat or prevent acute thromboembolic events.

Treatment of venous thoracic outlet syndrome depends primarily on the presence and extent of associated venous thrombosis and may include anticoagulation, thrombolysis, or surgical decompression.