17. Brachial Plexus Neuropathy Nir Hus Head position stretching plexus against anchors in shoulder ( A ). Closure of retroclavicular space by chest support with arms at side; neurovascular bundle trapped against first rib ( B ). Head of humerus thrust into neurovascular bundle if arm and axilla are not relaxed ( C ). Compression of ulnar nerve in cubital tunnel ( D ). Area of vulnerability of radial nerve to compression above elbow ( E ).