Brachial Plexus - Anatomy


Introduction
Standard: C5, C6, C7, C8, T1 – 77% of patients Prefixed: Prefixed (contributions from C3, C4) – 22% Postfixed (roots caudal to T1) – 1%
Anatomy
Remember: Robert Turner Drinks Cold Beer Roots (5): ventral rami of C5-T1, superior and posterior to subclavian dorsal scapular nerve (C5): through levator scapula to supply levator scapula, rhomboid major & minor long thoracic nerve (C5, 6, 7): posterior to plexus onto thoracic wall to supply serratus anterior Trunks (3): emerge from triangle formed by anterior scalene, middle scalene, first rib superior (C5,6 roots) suprascapular nerve (C5, 6): through suprascapular notch to supraspinatus, infraspinatus, AC and glenohumeral joints nerve to subclavius (C5, 6) middle (C7) inferior (C8, T1) Divisions (6): 3 anterior, 3 posterior (each trunk gives 1 anterior and 1 posterior division) Cords (3): Posterior Cord: formed from 3 posterior division upper subscapular nerve (C5, 6): subscapularis lower subscapular nerve (C5,6): subscapularis, teres major thoracodorsal nerve (C6, 7, 8): latissmus dorsi Lateral Cord: ant divisions of superior & middle trunks (C5, 6, 7) lateral pectoral nerve (C5, 6, 7): pectoralis major, communication with medial pectoral nerve Medial Cord: anterior division of inferior trunk (C8, T1) medial pectoral nerve (C8, T1): pierces pec minor; supplies pec minor and major medial brachial cutaneous nerve (T1) medial antebrachial cutaneous nerve (C8, T1) Branches (6) – 2 terminal branches from each cord Posterior cord: axillary nerve (C5, 6): through quadrilateral space to teres minor, deltoid, major nerve supply to glenohumeral joint, superior lateral brachial cutaneous nerve radial nerve (C5 – T1): runs with long head of triceps (triangular interval) into radial groove on posterior humerus; supplies elbow & forearm extensors, supinator; posterior brachial cutaneous, inferior lateral brachial cutaneous, posterior antebrachial cutaneous, superficial radial (post. radial hand) Lateral cord: lateral cord of median nerve (C5 – C7): joins medial cord anterior to axillary artery then travels with artery: wrist flexors (except FCU, ulnar ½ FDP), pronators, radial two lumbricals, OP, APB, superficial head FPB); sensory distribution in hand musculocutaneous (C5, 6, 7): most superficial branch, pierces coracobrachialis (1.5-9 cm from origin) to supply biceps, coracobrachialis, brachialis, ends as lateral antebrachial cutaneous nerve Medial cord: medial cord of median nerve (C8, T1): see above ulnar nerve (C8, T1): FCU, ½ FDP, adductor pollicus, deep head FPB, hypothenar, intrinics (except radial 2 lumbricals), sensory to hand