The thoracic inlet allows unobstructed passage of the neurovascular bundle (nerves, arteries and veins) from the root of the neck to the axilla (from the neck to the arm pit).
Signs and symptoms of thoracic inlet syndrome occur if there is some restriction of the passage of the neurovascular bundle between the shoulder and the neck. There are many factors that may be involved, including tight neck muscles or abnormal muscular attachment onto the ribs, cervical ribs (either calcific or fibrous), or postural causes.
The patient will normally present with numbness and pins and needles through one or both arms. Neurological symptoms (pins and needles and pain) predominate in 90% of people and vascular in 10%. They may also complain of incoordination, muscle weakness and pain particularly in the hands and fingers. The symptoms are generally worse with sustained overhead activity and positions. It is quite common in weight lifters and carpenters, or in people who are overweight or with very poor posture.