Who is affected by TOS?

Thoracic outlet syndrome affects both males and females of all ages.  TOS is more common in women.  It usually occurs on one side of the body but can occur on both sides of the body.  The shape of the rib cage and large breasts may influence the development of TOS by creating poor posture. 

TOS symptoms typically begin between the ages of 20 and 80 years old, peaking in a person's 40s.  Among children and teenagers, the presence of structural abnormalities is more likely the cause of TOS symptoms.  Structural abnormalities may include an extra first rib in the lower part of the neck or a fibrous band (ligament) connecting the spine to the rib cage.