scalene hiatus

The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term "scalene fissure" is also used).

It can affect one or more of the nerves that innervate the upper limb and/or blood vessels as they pass between the chest and upper extremity; specifically in the brachial plexus, the subclavian artery, and - rarely - the subclavian vein, which does not normally pass through the scalene hiatus.