Brachial plexus

Question 1

What is the course of the brachial plexus?

Answer 1

• originates in neck
• passes laterally and inferiorly over rib 1
• enters axilla

Question 2

What makes up the roots of the brachial plexus?

Answer 2

ventral rami of spinal nerves C5-T1

Question 3

How many trunks are there?

Answer 3

3: superior, middle, inferior

Question 4

What makes up the superior trunk?

Answer 4

roots C5 and C6 joining

Question 5

what makes up the middle trunk?

Answer 5

root of C7 alone

Question 6

what makes up the inferior trunk?

Answer 6

roots of C8 and T1 joining

Question 7

what are divisions made of?

Answer 7

each of the trunks have an anterior and posterior division

Question 8

what do the 3 anterior divisions form?

Answer 8

forms part of the brachial plexus that ultimately give rise to peripheral nerves associated with anterior compartment of arm/forearm

Question 9

what do the 3 post divisions combine to form?

Answer 9

form parts that give rise to nerves associated with posterior compartments

Question 10

what are the cord positions described with respect to?

Answer 10

to the axillary artery

Question 11

what makes up the posterior cord?

Answer 11

posterior divisions of all 3 trunks
contributions from C5-T1
posterior to second part of axillary artery

Question 12

what makes up the lateral cord?

Answer 12

anterior divisions of superior and middle trunk
contributions from C5-C7
lateral to 2nd part of axillary artery

Question 13

what makes up the medial cord?

Answer 13

anterior divisions of inferior trunk alone
contributions from C8-T11
medial to second part of axillary artery

Question 14

where do the nerves associated with the anterior compartment come from?

Answer 14

medial and lateral cord

Question 15

where do the nerves associated with the posterior compartment come from?

Answer 15

posterior cords

Question 16

what are the major terminal branches of the brachial plexus?

Answer 16

• musculocutaneous nerve
• median nerve
• axillary nerve
• radial nerve
• ulnar nerve

Question 17

what does the musculocutaneous nerve innervate?

Answer 17

• innervates all of anterior compartment of arm
• brachialis, biceps brachii, coracobrachialis
• branches off lateral cord

Question 18

what does the median nerve innervate?

Answer 18

• most of the flexors of wrist
• thenar muscles
• formed by joining of medial and lateral cords

Question 19

what does the axillary nerve innervate?

Answer 19

• deltoid and teres minor

- branches off posterior cord

Question 20

what does the radial nerve innervate?

Answer 20

• all posterior arm and forearm
• some sensory innervation to hand
• terminal branch of posterior cord

Question 21

what does the ulnar nerve innervate?

Answer 21

• some flexors (FCU, half of FDP)
• most of intrinsic muscles of hand
• terminal branch of medial cord

Question 22

what are the branches off the roots?

Answer 22

• long thoracic nerve

- dorsal scapular nerve

Question 23

what is the long thoracic nerve? what does it innervate?

Answer 23

• innervates serratus anterior

- contributed by C5, 6, 7 ventral rami directly

Question 24

what is the dorsal scapular nerve? what does it innervate?

Answer 24

• branch of ventral rami of C5

- innervates rhomboids

Question 25

what happens when there is damage to the dorsal scapular nerve?

Answer 25

patient unable to bring their inferior angle of the scapula together

Question 26

what are the branches off the trunks?

Answer 26

- originate from superior trunk - suprascapular nerve - nerve to subclavius muscle

Question 27

what is the suprascapular nerve? what does it innervate?

Answer 27

- direct branch of superior trunk | - innervates supraspinatus, infraspinatus, glenohumeral joint

Question 28

what is the nerve to the subclavius? what does it innervate?

Answer 28

innervates subclavius | C5/6

Question 29

what are the branches off the lateral cord? (not terminal branches)

Answer 29

lateral pectoral nerve

Question 30

What is the lateral pectoral nerve?

Answer 30

- branch of lateral cord | - innervating pec major

Question 31

what are the branches off the medial cord? (not terminal branches)

Answer 31

- medial pectoral nerve - medial cutaneous nerve of arm - medial cutaneous nerve of forearm

Question 32

what is the medial pectoral nerve?

Answer 32

- branch of medial cord | - innervates pec minor

Question 33

what is the medial cutaneous nerve of the arm?

Answer 33

- innervates upper part of medial surface of arm/ floor of axilla

Question 34

what is the medial cutaneous nerve of forearm?

Answer 34

- innervates skin over medial surface of forearm down to wrist

Question 35

what are the branches off the posterior cord? (not terminal branches)

Answer 35

- thoracodorsal nerve - upper subscapular - lower subscapular

Question 36

what is the thoracodorsal nerve?

Answer 36

- branch of posterior cord | - innervating lattissimus dorsi

Question 37

what is the upper subscapular nerve?

Answer 37

- branch of posterior cord | - innervating upper part of subscapularis

Question 38

what is the lower subscapular nerve?

Answer 38

- branch of posterior cord | - innervating inferior portion of subscapularis and teres major

Question 39

what are the shoulder girdle muscles innervated by? (motor innervation)

Answer 39

C5-7

Question 40

what are the shoulder joint muscles and elbow flexors innervated by? (motor innervation)

Answer 40

C5, C6

Question 41

what are the elbow extensors innervated by? (motor innervation)

Answer 41

C7-8

Question 42

what provides the motor innervation to the wrist and coarse hand muscles?

Answer 42

C6-8

Question 43

what provides the motor innervation to the small muscles of the hand?

Answer 43

C8-T1

Question 44

how do you test the spinal nerve C5?

Answer 44

test sensation just anterior to elbow

Question 45

how do you test the spinal nerve C6?

Answer 45

test sensation in tip of thumb

Question 46

how do you test the spinal nerve C7?

Answer 46

test sensation in middle finger

Question 47

how do you test the spinal nerve C8?

Answer 47

test sensation in little finger

Question 48

how do you test the spinal nerve T1?

Answer 48

test sensation on medial aspect of upper arm

Question 49

what are the branches of the radial nerve?

Answer 49

- posterior cutaneous nerve of arm + forearm - inferior lateral cutaneous nerve of arm - superficial branch

Question 50

what does the radial nerve innervate?

Answer 50

- medial part of posterior upper arm - posterior lateral part of forearm - lateral part of lower arm + forearm - lateral part of dorsal hand - some sensation in thenar eminence

Question 51

what does the ulnar nerve give innervation to?

Answer 51

- medial part of anterior arm below elbow

Question 52

what does the dorsal cutaneous branch of the ulnar nerve give sensation to?

Answer 52

- small digit and half of ring finger on dorsal and palmar sides

Question 53

what does the axillary nerve give innervation to?

Answer 53

- regimental patch | = lateral aspect of upper part of arm near shoulder joint

Question 54

what forms the lateral cutaneous nerve?

Answer 54

given off by musculocutaneous nerve

Question 55

what does the lateral cutaneous nerve supply?

Answer 55

- medial part of anterior aspect of lower 2/3rds of arm | - crosses over at elbow to supply lateral part of anterior distal 2/3rds of forearm

Question 56

what happens when there is injury to the axillary nerve?

Answer 56

- unable to raise arms | - wasting of deltoid

Question 57

what happens when there is injury to the radial nerve?

Answer 57

- can't extend elbow joint or wrist joint - loss of sensation of lateral part of arm/forearm - wrist drop - loss of power grip

Question 58

what happens when there is injury to ulnar nerve?

Answer 58

- ulnar claw | - unable to adduct or abduct fingers

Question 59

what happens when there is injury to median nerve?

Answer 59

- paraesthesia of lateral half of palmar side of hand - muscle wasting of thenar muscles and thenar eminence - hand of benediction (when try to flex fingers, only last 2 will flex)

Question 60

what happens when there is injury to the long thoracic nerve?

Answer 60

- winging of scapula

Question 61

what causes damage to the upper roots?

Answer 61

- hyperextension of spine/neck | - stretching of plexus by excessive pulling shoulder

Question 62

what is damage to the upper roots known as?

Answer 62

Erb's palsy

Question 63

when there is damage to the upper roots, which nerves are affected?

Answer 63

- radial - musculocutaneous - median - axillary

Question 64

what happens when there is damage to the upper roots?

Answer 64

- arm drop, due to loss of deltoid - pronation of hand, due to loss pf biceps - flexion of hand, due to loss of extensor muscles of wrist

Question 65

what causes damage to the lower roots?

Answer 65

- hyperabduction of shoulder due to gripping overhead to break fall - pulling on arm of a child during childbirth

Question 66

what is damage to the lower roots known as?

Answer 66

Kumpke's palsy

Question 67

when there is damage to the lower roots, which nerves are affected?

Answer 67

main issues on ulnar and median nerve

Question 68

what happens when there is damage to the lower roots?

Answer 68

- loss of flexion of wrist - loss of extension of last 2 digits - limited hand movements - loss of thumb movements