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) Branches (6) – 2 terminal branches from each cord
    
    medial pectoral nerve (C8, T1): pierces pec minor; supplies pec minor and major
    
    medial brachial cutaneous nerve (T1)
    
    medial antebrachial cutaneous nerve (C8, T1)
    
    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

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T