CASE 173: THORACIC OUTLET SYNDROME, Dr NGUYỄN PHƯỚC BẢO QUÂN, MEDIC CENTER in HUẾ

Female  33 years old complains pain in right arm when she has her arm in abduction and elevated position.

Ultrasound findings:

Fig 1: Right side of the image indicates normal dimension on transversal section of the R subclavian artery (arrow) before the test by which the patient elevates her arm in external rotation; left side of the image indicates small dimension on transversal section of the R subclavian artery during the test due to compression between the anterior scalene muscle anteriorly (white arrow head) and exostosis of the first rib posteriorly (black arrow).

Figure 2:The spectrum waveform of the radial artery before and during the test. 

Fig 3: Longitudinal section of the R subclavian artery indicates the stenosed segment with high flow velocity displayed by aliasing phenomenon and  post-stenotic dilatation segment as well. Note that focal thickening of the wall of the R subclavian artery at stenotic region (white arrow).

Fig 4: CT Angio images of the R subclavian artery demonstrate the stenosed segment due to exostosis of the first rib (red arrow) and poststenotic dilatation segment.

Diagnosis: Thoracic outlet syndrome in the first space.

Discussion: Thoracic outlet syndrome (TOS) is the name of a variety of conditions attributed to compression of the neurovascular structures as they traverse the thoracic outlet. (TOS) can occur at 3 spaces: 1/ The first space is the interscalene triangle. It is bordered by the anterior scalene muscle, the middle scalene muscle, and the upper border of the first rib. The interscalene triangle is the most common site for neural compression, vascular compression. 2/ The second space is the costoclavicular triangle, which is bordered by the clavicle, first rib, and scapula and contains the  subclavian artery and vein and the brachial nerves; 3/ The third and final space is beneath the coracoid process just deep to the pectoralis minor tendon; it is referred to as the subcoracoid space.

Reference: 

 1.Daryl A Rosenbaum, MD; Chief Editor: Sherwin SW Ho, MD. Thoracic Outlet Syndrome . http://emedicine.medscape.com.

2/ Paul B. Kreienberg, Dhiraj M.Shah et al. Thoracic outlet syndrome. Vascular diagnosis. Elsevier Saunders. 2005. P.512-522