Snapshot A 52-year-old female presents to her primary care physician with a chief complaint of pain and tingling in the right distal forearm and right hand. She has had these symptoms for several years but they have slowly been getting worse. At the beginning she would only have mild intermittent pain after waking or after long drives, but recently she feels that the symptoms have been almost constant and have interfered with her ability to live a normal life. Physical exam reveals weakness and loss of fine touch sensation in the lateral 3 and 1/2 fingers of her right hand and tapping on the wrist reproduces the symptoms. She is diagnosed with carpal tunnel syndrome and referred to a surgeon for consultation about a release. Overview Pathologies of Roots and Trunks of Brachial Plexus Brachial Plexus roots C7 root can be compressed by cervical disk lesion trunks upper trunk can be damaged by birth trauma traction on head during delivery of infant lesions can cause Erb's palsy lower trunk can be compressed by extra cervical rib pancoast lung tumor compression causes catching self on arm while falling (grabbing tree branch to break fall) Klumpke's palsy Pathologies of Terminal Branches of Brachial Plexus General compression syndromes can result in pain, paresthesias, or weakness of the innervated muscle groups Musculocutaneous nerve in arm compressed by brachialis muscle sheath coracobrachialis muscle in cubital fossa compressed by bicepital aponeurosis Median nerve in cubital fossa compressed by supracondylar fracture of humerus pronator teres syndrome in wrist compressed by carpal tunnel syndrome dislocated lunate in forearm anterior interosseous nerve, a branch of median nerve, compressed in deep forearm in hand recurrent branch of median nerve lesioned by superficial laceration Ulnar nerve in cubital fossa lesioned by repeated minor trauma fracture of medial epicondyle of humerus in hand lesioned by trauma to heel of hand fracture of hook of hamate axillary nerve lesioned by fracture of surgical neck of humerus dislocation of humerus intramuscular injections radial nerve in axilla compressed by incorrect use of crutches in spiral groove of humerus lesioned by midshaft fracture of humerus in forearm deep branch of radial nerve stretched by subluxation of radius Dermatomes of Upper Limb Innervation of Hand Hand median nerve passes through carpal tunnel with 9 tendons palmar cutaneous branch of median nerve supplies skin of central palm recurrent branch of median nerve supplies thenar muscles cutaneous branches of median nerve supply skin of radial 3.5 digits ulnar nerve cutaneous branch of ulnar nerve supplies skin of base of medial palm branches via ulnar before ulnar nerve enters hand ulnar nerve passes through Guyon's canal to hand deep branch of ulnar nerve supplies interossei muscles and adductor pollicis