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Overview of thoracic outlet syndromes

Kaoru Goshima, MD
Section Editors
Joseph L Mills, Sr, MD
John F Eidt, MD
Jeremy M Shefner, MD, PhD
Deputy Editor
Kathryn A Collins, MD, PhD, FACS


Thoracic outlet syndrome (TOS) refers to a constellation of signs and symptoms that arise from compression of the neurovascular bundle by various structures in the area just above the first rib and behind the clavicle, within the confined space of the thoracic outlet [1]. Historically, several names have been coined to describe pathology involving the thoracic outlet, including cervical rib syndrome [2], scalene anticus syndrome [3], costoclavicular syndrome [4], and hyperabduction syndrome [5]. The term "thoracic outlet syndrome" was coined to collectively encompass the spectrum of syndromes related to the general region of the thoracic outlet [6].

Distinct terms are used to describe the predominantly affected structure, including neurogenic (nTOS) from brachial plexus compression, venous (vTOS) from subclavian vein compression, and arterial (aTOS) from subclavian artery compression [7]. Neurogenic TOS accounts for greater than 95 percent of cases of thoracic outlet syndrome, whereas vTOS accounts for 3 percent and aTOS accounts for 1 percent of cases. Compression of the brachial plexus leads to upper extremity numbness, dysesthesia and weakness; venous compression may cause deep vein thrombosis and extremity swelling; and arterial compression can lead to distal thromboembolism, arm pain with exertion ('claudication') or acute arterial thrombosis [8,9].

An overview of the anatomy, pathogenesis, clinical evaluation and approach to the management of the thoracic outlet syndromes will be reviewed with an emphasis on the features that distinguish these syndromes from one another.


The thoracic outlet is bounded by the bony structures of the spinal column, first ribs, and sternum (figure 1). Compromise of the neurovascular structures that traverse the thoracic outlet occurs in three distinct spaces: the scalene triangle, the costoclavicular space, and the pectoralis minor space.

Scalene triangle – The scalene triangle is the space most commonly involved in TOS and is the most common site of brachial plexus compression. The anterior scalene muscle, which originates from the transverse processes of the third through sixth cervical vertebrae (C3-C6) and inserts on the inner borders and superior surfaces of the first rib, forms the anterior boundary of the scalene triangle. The middle scalene muscle, which arises from the transverse processes of the second through seventh cervical vertebrae (C2-C7) and inserts broadly onto the posterior aspects of the first rib, forms the posterior wall of the scalene triangle. The superior border of the first rib forms the base of the scalene triangle. The trunks of the brachial plexus and the subclavian artery pass between the anterior and middle scalene muscles while the subclavian vein courses anteromedial to the scalene triangle. Cervical ribs and anomalous first ribs may compress the scalene triangle (figure 2).

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Literature review current through: Nov 2017. | This topic last updated: Jun 09, 2017.
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