A contraction of the Scalene muscles compresses the brachial plexus and/or subclavian vessels against the first rib in the thoracic outlet
A contraction of the Pectoralis Minor muscles compresses the brachial plexus and/or subclavian vessels against the head and neck of the humerus
Entrapment of the Median Nerve between the wrist bones and transverse carpal ligament.
Tingling often occurs at night and sufferers often complain of being awakened at night by the hand "falling asleep"