Summary

Using ultrasonography, we confirmed that the areas of the brachial plexus and the subclavian artery becomes narrow in patients with Thoracic outlet syndrome (TOS), and that the nerve plexus and artery areas are significantly difference in the abducted position between the two groups. Thus, our data suggest the possibility that ultrasonography becomes a useful imaging tool for Neurogenic TOS.

Abstract

Introduction

Generally, Thoracic outlet syndrome (TOS) is divided into two categories: Vascular TOS and neurogenic (non-vascular) TOS. Vascular TOS can be diagnosed by imaging devices, while neurogenic TOS exclusively by physical findings in clinical settings. Thus, sufficient objective imaging diagnosis has not been established in neurogenic TOS whose incidence is over 90% in the whole TOS. To establish imaging diagnosis for neurogenic TOS, the present study measured the areas of the brachial plexus and the subclavian artery in various arm position, using ultrasonography.

Methods

Inclusion criteria consisted of: (1) Individuals who had pain/numbness on the upper extremity that was changeable due to arm position, (2) Individuals who had positive sign of Moley test with those of either Roos, Wright, Adson, or Eden test. Exclusion criteria consisted of: (1) Individuals who had cervical or peripheral nerve disorders (e.g. cubital / carpal tunnel syndrome), (2) Individuals who had psychiatric disorder or fractures on the upper limb, (3) Individuals who had apparent stenosis of subclavian artery / vein confirmed by magnetic resonance angiography. Finally, 13 patients with a mean age of 31.8 years were subjects for this study. Seven healthy individuals with a mean age of 22.6 years took part in the present study as controls.
A probe was put on the supraclavicular fossa in sitting position. First, the brachial plexus and subclavian artery were identified at the level of first rib. Then, the nerve and vascular areas were measured at the following position: At-the-side and the abducted position with the arm 90°-abducted and 90°-externally rotated. In addition, reduction rate was calculated as relative ratio of the area measured at the side to the area with the arm 90°-abducted and 90°-externally rotated.

Results

No significant difference on demographic data was noted between both groups. The brachial plexus area was not significantly changed between at-the-side and the abducted position: 0.94±0.26 cm2 to 0.79±0.30 cm2 in TOS group (reduction rate: 84.1%) and 1.21±0.43 cm2 to 1.22±0.28 cm2 in control group (reduction rate: 93.1%). Similarly, the subclavian artery area was not significantly changed: 0.24±0.04 cm2 to 0.24±0.02 cm2 in TOS group (reduction rate: 103.7%) and 0.29±0.03 cm2 to 0.32±0.01 cm2 in AG group (reduction rate: 109.2%). However, there was significant difference of brachial plexus nerve area in the abducted position between both group, as seen in the comparison of the subclavian artery (p>0.05, respectively).

Discussion

& Conclusion
The diagnosis and validation of TOS remains challenging for orthopedic surgeons. Using ultrasonography, the present study successfully evaluated areas of the brachial plexus and subclavian artery at the level of first rib. Despite of the small samples enrolled, we also confirmed that the areas of the brachial plexus and the subclavian artery becomes relatively narrow in patients with TOS, compared with healthy controls. Furthermore, we found that the nerve plexus and artery areas are significantly difference in the abducted position between the two groups. Thus, our data suggest the possibility that ultrasonography becomes a useful imaging tool for diagnosis for Neurogenic TOS.