Functional motor innervation of brachial plexus roots. An intraoperative electrophysiological study.

OBJECTIVE: To study the functional motor innervation of C5-T1 nerve roots of the brachial plexus electrophysiologically. PATIENTS AND METHODS: The electrophysiological properties of normal brachial plexus roots and their functional motor innervation were examined in 15 patients with brachial plexus injuries, while the contralateral healthy side C7 root transfer was operated on. Different nerve roots of the brachial plexus were stimulated and maximum amplitudes were recorded in the following 12 muscles: deltoid, biceps, infraspinatus, brachiaradialis, flexor carpi radialis, triceps, extensor digitorum communis, latissimus dorsi, flexor digitorum profundus, abductor brevis, abductor digiti minimi and flexor carpi ulnaris. RESULTS: Functional motor innervation of brachial plexus roots showed the following results: a. C5 mainly forms the axillary nerve to innervate deltoid muscle; b. C6 mainly constructs the musculocutaneous nerve to innervate biceps muscle; c. C7 mainly forms the radial nerve to innervate triceps muscle; d. C8 mainly forms the median nerve to innervate the flexor digitorum muscle; e. T1 mainly forms the ulnar nerve to innervate the intrinsic muscles of the hand. CONCLUSIONS: The brachial plexus is functionally divided into three groups: C5, 6 innervate shoulder and elbow; C8T1 innervate the hand; and C7 innervates shoulder, elbow, wrist and hand. Theoretically, any division of the nerve root alone may not cause damage to limb function.