The Scalene Muscles
s anterior), a medial scalene (scalenus medius), and a posterior scalene (scalenus posterior). They derive their name from the Greek word skalenos and the later Latin scalenus meaning “uneven”, similar to the scalene triangle in mathematics, which has all sides of unequal length. These muscles not only have different lengths but also considerable variety in their attachments and fiber arrangements. As you will see from the descriptions below, these muscles are in a very crowded place and are related to many important structures such as nerves and arteries that run through the neck. The scalene muscles are three paired muscles of the neck, located in the front on either side of the throat, just lateral to the sternocleidomastoid.
What is Thoracic Outlet Syndrome?
Thoracic outlet syndrome (TOS) is a term used to describe a group of disorders that occur when there is compression, injury, or irritation of the nerves and/or blood vessels (arteries and veins) in the lower neck and upper chest area. Thoracic outlet syndrome is named for the space (the thoracic outlet) between your lower neck and upper chest where this grouping of nerves and blood vessels is found.
What Causes Thoracic Outlet Syndrome?
The disorders caused by TOS are not well understood. Yet, it is known that when the blood vessels and/or nerves in the tight passageway of the thoracic outlet are abnormally compressed, they become irritated and can cause TOS. Thoracic outlet syndrome can be a result of an extra first rib (cervical rib) or an old fracture of the clavicle (collarbone) that reduces the space for the vessels and nerves. Bony and soft tissue abnormalities are among the many other causes of TOS.
The following may increase the risk of developing thoracic outlet syndrome:
- Sleep disorders
- Tumors or large lymph nodes in the upper chest or underarm area
- Stress or depression
- Participating in sports that involve repetitive arm or shoulder movement, such as baseball, swimming, golfing, volleyball and others
- Repetitive injuries from carrying heavy shoulder loads
- Injury to the neck or back (whiplash injury)
- Poor posture
The signs and symptoms of TOS include neck, shoulder, and arm pain, numbness or impaired circulation to the affected areas.
The pain of TOS is sometimes confused with the pain of angina (chest pain due to an inadequate supply of oxygen to the heart muscle), but the two conditions can be distinguished because the pain of thoracic outlet syndrome does not occur or increase when walking, while the pain of angina usually does. Additionally, the pain of TOS typically increases when raising the affected arm, which does not occur with angina.
Signs and symptoms of TOS help determine the type of disorder a patient has. Thoracic outlet syndrome disorders differ, depending on the part(s) of the body they affect. Thoracic outlet syndrome most commonly affects the nerves, but the condition can also affect the veins and arteries (least common type). In all types of TOS, the thoracic outlet space is narrowed, and there is scar formation around the structures.