Other congenital causes

Some people are born with an extra band of tissue underneath their skin around the thoracic outlet area called a fibrous band. This can act a bit like an extra rib and cause compression of the thoracic outlet in some people. Anomalous (or extra) muscles around the thoracic outlet that you may be born with can also cause narrowing and compression. Also, some people are born with an enlarged or elongated part of a vertebra in their neck which can cause compression in their thoracic outlet.