Thoracic outlet syndrome: Year of the Zebra

Thoracic outlet syndrome refers to a group of neurovascular symptoms that arise from compression of the nerves and blood vessels passing through the narrow space between the collarbone and first rib, called the thoracic outlet. This condition can be caused by a variety of factors that can compress the thoracic outlet and its structures. Factors can include neck injuries; certain cancers that invade the thoracic outlet or surrounding area; anatomical variants that predispose to neurovascular compression, such as the presence of an extra cervical rib; and certain activities or sports involving repetitive movements of the arm and shoulder, like swimming or baseball.

Regardless of the cause, thoracic outlet syndrome can present with a variety of symptoms which vary depending on the specific structures that are affected; and symptoms are usually unilateral, occuring on only one side of the body. The most common symptoms result from compression of the nerves that innervate the upper limb, which can cause muscle weakness, numbness, and tingling in the arm and hand on the affected side, especially when performing overhead activities or carrying heavy objects.

On the other hand, compression of the veins that drain the upper limb decreases blood drainage from the affected arm and hand, leading to swelling of the upper limb and dilation of the veins of the neck and chest.

Finally, arterial compression decreases blood supply to the affected arm and hand muscles, resulting in a cold and pale extremity, numbness, and cramping pain that occurs during activity and is relieved with rest. Individuals with arterial compression may also have weak pulses and a lower blood pressure in the affected arm.