Overview
The thoracic outlet is the area between the rib cage and collarbone. As blood vessels and nerves pass through this space on their way to the arms, they may not have enough space. Thoracic outlet syndrome is the result of pressure of these nerves and blood vessels.
Causes
Overstress from some types of manual work or exercise
Injury or trauma
Malformation
Tumor
Having an extra cervical rib
Symptoms
Pain, numbness, and tingling in the pink and ring fingers and the inner forearm
Pain and tingling in the neck and shoulders which may be worsened by carrying a heavy load
Poor circulation in the and or forearm (bluish color, cold hands, swollen arm)
Weakness of the muscles in the hand
Diagnosis
Physical examination and medical history consultation
EMG
CT scan
MRI
X-ray
Treatment
Physical therapy
Blood thinning medication
Surgery
Source: https://www.ncbi.nlm.nih.gov/