الفهرس 
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Abstract
Thoracic outlet syndrome (TOS) is a common condition that is recognized uncommonly because the manifestations are varied and there is no single definitive test for it (Brantigan, et al., 2004). Thoracic outlet is the area between the neck and shoulder, over the top of the thorax, and under the clavicle. It is formed of four compartments; the sternocostovertebral space, the scalene triangle, the costoclavicular space and the retropectoralis minor space. The subclavian artery, subclavian vein and brachial plexus pass through these compartments (Villamere, 2009). TOS commonly develops during the 3rd or 4th decade, three times as frequent in women as in men, under the combination of a peculiar cervical anatomy and of external factors. Some morphotypes predispose to the syndrome: poor muscular development, droop of scapula, obesity and breast hypertrophy. The patient psychological status may sometimes play an important role in the development of the syndrome: stress and depression can lead to chronic muscle spasm in the neck region and there to decompensation of a previously asymptomatic predisposing anatomy. Other precipitating factors are work-related (static work posture). An antecedent of neck or shoulder trauma is noted in approximately half of the cases (Dubuisson, 1999). Finally, we can conclude that the diagnosis of TOS is clinically based. Imaging is helpful in informing the clinician as to the anatomic structures undergoing compression, the location of that compression, and the anatomic structures responsible for it (whether normal or abnormal). Indeed, all these features may influence the treatment. In the case of neurogenic or neurovascular symptoms, MR imaging in association with postural maneuvers has proved useful, especially in demonstrating brachial plexus compression and the existence of fibrous bands and other soft tissue components. CT with contrast medium injection and postural maneuvers appears effective in demonstrating vascular compression by means of volume-rendered images, which allow analysis of the relations with bony structures (Demondion , et al., 2006). But both CT and MRI share in same practical limitations which are the restriction of arm elevation due to the size of the tunnel (upper limb elevation of >130° is impossible) and the supine position of the patient which undoubtedly has an effect on dynamically induced compression (Antani et al., 2008). Several studies that used CT and MR imaging in assessment of TOS have demonstrated that upper limb elevation does not induce an obvious change in the interscalene triangle but does produce narrowing of both the costoclavicular space and retropectoralis minor space. The costoclavicular space is by far the most frequent site of arterial compression, while the interscalene triangle is the second most frequent site. Neurologic compression appears to be as frequent in the costoclavicular space as in the interscalene triangle. The retropectoralis minor space has rarely been reported as a potential site of compression (Demondion et al., 2006 and Smedby et al., 2000).