Thoracic outlet syndromeis a condition resulting from the compression of nerves, blood vessels or bothdue to inadequate thoracic outlet or way out between the base of the neck andthorax to pass to the axilla (armpit). The muscles named as scalene muscles, first rib and clavicle surround the thoracic outlet. It is observed that any movement or enlargement of tissues of or near the thoracic outlet can cause the syndrome. This can include activities like muscle enlargement due to weightlifting, congenital extra rib, increase in the weight, tumors or aftersustaining injuries. Many a times no specific cause for this condition is found.
Some believe that evolutionary changes that led to the upright stature of human beings are responsible for this thoracic outlet syndrome. It led to flattening of chestand shoulder joint was shifted backwards as compared to the four-legged position of the primates. This caused reduction in the thoracic outlet.