Brachial Plexus

Overview

Introduction

• Standard: C5, C6, C7, C8, T1 – 77% of patients
• Prefixed: Prefixed (contributions from C3, C4) – 22% 
• Postfixed (roots caudal to T1) – 1%

COMPOSITION: “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)
    • Erb’s palsy 
      • tear of upper trunk (C5-C6 roots) that is usually caused by traction during delivery or trauma later in life
      • leads to difficulty with abduction, lateral rotation, and flexion/supination
  • 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):  supplies medial aspect of 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 lateral aspect of pec 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 space) 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