Causes of Thoracic Outlet Syndrome
Thoracic outlet syndrome (TOS) refers to a condition of arm (and sometimes neck) pain, numbness, tingling, and weakness of the arms and hands. It is caused by pressure on the nerves and/or blood vessels as they pass through the neck and travel down the arm. TOS can affect one or both sides.

In this article, doctors from Turkey report on the case of a 22-year-old woman who was diagnosed with TOS after an accident. TOS can be caused by unusual anatomy, poor posture, tumors, or accidents. In this case, the young woman had both a congenital (present at birth) cause and a traumatic factor.

Her symptoms of numbness, tingling, and fatigue in the right arm were present before the accident. After the accident, she had similar symptoms in both arms. She also had a condition called hyperhidrosis in both hands. This is an increased amount of sweating. The symptoms were worse when she had her arms overhead or when carrying heavy things.

The condition was diagnosed with an X-ray and a magnetic resonance angiography (MRA). The X-ray showed a decrease in the natural lordosis (curve) in her neck. There was also an extra long transverse process on both sides at C7. The transverse process is a normal bony knob that sticks out from the side of the vertebral bodies.

The MRA is done with a dye injected into the bloodstream. It shows the blood shape and location of the blood vessels. In this case, they found a narrowing of the subclavian arteries on both sides.

The authors concluded TOS in this young woman was the result of both congenital and acquired causes. If she hadn't reported similar symptoms before the accident, the diagnosis might have been delayed or overlooked. The more recent traumatic event made her condition worse.
References
Malas FÜ, et al. Etiological Factors in Thoracic Outlet Syndrome. In Orthopedics. June 2007. Vol. 30. No. 6. Pp. 425.