Brachial Plexus

Question 1

Organization

Answer 1

1. Roots: ventral rami C5-T1
  A. Dermatome: pre-axial to post-axial
  B. Myotome: proximal to distal
2. Trunks: upper, middle, and lower
3. Divisions: anterior and posterior
4. Cords: lateral, medial, posterior
5. Nerves: musculocutaneous, axillary, radial, median, ulnar

Question 2

C5 contributions

Answer 2

1. Dorsal scapular
2. Long thoracic
3. Supraclavicular
4. Subclavian
5. Upper subscapular
6. Axillary
7. Radial
8. Lateral pectoral
9. Musculocutaneous

Question 3

C6 contributions

Answer 3

1. Supraclavicular
2. Long thoracic
3. Subclavian
4. Lateral pectoral
5. Musculocutaneous
6. Axillary
7. Radial
8. Thoracodorsal
9. Lower subscapular
10. Median

Question 4

C7 contributions

Answer 4

1. Long thoracic
2. Lateral pectoral
3. Musculocutaneous
4. Median
5. Thoracodorsal
6. Radial

Question 5

C8 contributions

Answer 5

1. Thoracodorsal
2. Radial
3. Medial pectoral
4. Medial cutaneous of arm/forearm
5. Median
6. Ulnar

Question 6

T1 contributions

Answer 6

1. Medial pectoral
2. Medial cutaneous of arms/forearms
3. Median
4. Ulnar

Question 7

Myotomes

Answer 7

Set of muscles innervated by specific nerve root
1. Proximal to distal
2. Tests:
  A. Abduction of arm = C5
  B. Wrist extension = C6
  C. Finger extension = C7
  D. Wrist flexion = C7 
  E. Finger flexion = C8
  F. Adduction/abduction fingers = T1
3. Reflex testing:
  A. Biceps reflex = C5
  B. Brachioradialis reflex = C6
  C. Triceps reflex =C7

Question 8

Dermatomes

Answer 8

Area of skin innervated by specific nerve root
1. Pre-axial to post-axial
2. Lots of overlapping
3. Testing:
  A. C5 = deltoid area

Question 9

Axillary nerve

Answer 9

C5-C6
1. Muscular branches
  A. Deltoid
  B. Teres minor
2. Sensory branch
  A. Superior lateral cutaneous nerve

Question 10

Musculocutaneous nerve

Answer 10

C5-C7
1. Primary innervation to anterior compartment of arm
2. Muscular branches
  A. Coracobrachialis
  B. Biceps brachii 
  C. Brachialis
3. Sensory branch
  A. Lateral cutaneous n. Of forearm

Question 11

Median nerve

Answer 11

C6-T1
1. Median and ulnar split compartment
2. Muscular branches:
A. Forearm: anterior compartment
*except flexor carpi ulnaris and 1/2 flexor digitorum profundus
B. Hand: thenar muscles and first 2 lumbricals
*except adductor pollicis
3. Sensory branches:
A. First 7 proper palmar digital n.
B. First 3.5 digits on palm
C. Distal tips of fingers 1 and 2 of palm and dorsum

Question 12

Ulnar nerve

Answer 12

C8-T1
1. Muscular branches:
A. Forearm: flexor carpi ulnaris and 1/2 flexor digitorum profundus
B. Hand: intrinsic muscles of hand
*except 3 thenar and 2 lumbricals
2. Sensory branches:
A. Common and proper palmar and dorsal digitalis (for last 1.5 digits on palmar, 2.5 on dorsal)

Question 13

Radial nerve

Answer 13

C5-C8
1. Muscular branches:
A. Arm: posterior compartment muscles
B. Forearm: posterior compartment muscles
2. Sensory branches:
A. Inferior later brachial cutaneous n. Of forearm
B. Dorsal digitalis for first 2.5 digits

Question 14

Supraclavicular nerves

Answer 14

1. Dorsal scapular: lavator scapulae and rhomboids
2. Suprascapular: supraspinatus and infraspinatus
3. Subclavian: subclavius
4. Long thoracic: serratus anterior

Question 15

Posterior cord nerves

Answer 15

1. Upper subscapular: subscapularis
2. Lower subscapular: subscapularis and teres major
3. Thoracodorsal: latissmus dorsi

Question 16

Medial and lateral cord nerves

Answer 16

1. Muscular branches:
  A. Lateral pectoral n. (Both pecs)
  B. Medial pectoral n. (Major only)
2. Sensory branches
  A. Medial cutaneous (arm and forearm)