5. The Brachial Plexus

Question 1

What nervous element forms the roots of the brachial plexus?

Answer 1

Anterior rami C5-T1

Question 2

Name each of the trunks of the brachial plexus and the nerves that run into them

Answer 2

Superior - C5, C6
Middle - C7
Inferior - C8, T10

Question 3

Recall the general branching pattern of the brachial plexus

Answer 3

5 roots (C5-T1)
3 trunks (sup, mid, inf)
Each trunk divides into post and ant divisions
Posterior divisions converge to posterior cord
Anterior divisions of sup and mid trunk converge to form lateral cord
Anterior division of inferior trunk –> medial cord
Cords split to form peripheral nerves

Question 4

What are the main nerves branching from the lateral cord?

Answer 4

Musculocutaneous

Median (via lateral root)

Question 5

What are the main nerves branching from the posterior cord?

Answer 5

Radial

Axillary

Question 6

What are the main nerves branching from the medial cord?

Answer 6

Ulnar

Median (via medial root)

Question 7

Recall the roots that supply the musculocutaneous nerve

Answer 7

C5, C6, C7

Question 8

Recall the roots that supply the axillary nerve

Answer 8

C5, C6

Question 9

Recall the roots that supply the ulnar nerve

Answer 9

C8, T1

Question 10

Recall the roots that supply the median nerve

Answer 10

C6, C7, C8, T1

Question 11

Recall the roots that supply the radial nerve

Answer 11

All in BP (C5–> T1)

Question 12

How are the cords named?

Answer 12

With respect to relationship to axillary artery

Question 13

Recall the branches of the BP that only contain C5 fibres

Answer 13

Dorsal subscapular
Subclavius
Phrenic

Question 14

Recall the branches of the BP that contain C5 and C6 fibres only

Answer 14

Upper and lower subscapular
Suprascapular
Axillary

Question 15

Which nerve root fibres contribute to the thoracodorsal nerve?

Answer 15

C7 and C8

Question 16

Recall the branches of the BP that contain C8 and T1 fibres only

Answer 16

Medial pectoral
Medial brachial cutaneous
Medial antebrachial cutaneous
Ulnar

Question 17

In general, which nerve root fibres supply the shoulder girdle muscles?

Answer 17

C4-C7

Question 18

In general, which nerve root fibres supply the shoulder joint and elbow flexor muscles?

Answer 18

C5 + C6

Question 19

In general, which nerve root fibres supply the elbow joint extensors?

Answer 19

C7 + C8

Question 20

In general, which nerve root fibres are involved in controlling wrist movement and coarse hand movements?

Answer 20

C6, C7 and C8

Question 21

Recall the branches of the BP that contain C5,6 and 7 fibres only

Answer 21

Long thoracic

Lat. pectoral

Question 22

In general, which nerve root fibres are involved in controlling fine hand movements?

Answer 22

C8 - T1

Question 23

Recall the mnemonic used to remember the organisation of the BP

Answer 23

Reach To Drink Cold Beer

Roots Trunks Divisions Cords Branches

Question 24

Recall the mnemonic used to remember the main branches of the BP

Answer 24

Most Alcoholics Must Really Urinate:
Musculocutaneous
Axillary
Median
Radial 
Ulnar

Question 25

Recall the mnemonic used to remember the branches of the posterior cord

Answer 25

``` ULTRA Upper subscapular Lower subscapular Thoracodorsal Radial Axillary ```

Question 26

Recall the mnemonic used to remember the branches of the lateral cord

Answer 26

Must Love Lateral: Musculotaneous Lat. pectoral Lat. median

Question 27

Recall the mnemonic used to remember the branches of the medial cord

Answer 27

``` M4U Medial pectoral Medial cutaneous (arm) Medial cutaneous (forearm) Medial branch of median nerve Ulnar ```

Question 28

Where does the musculocutaneous nerve run and what is its main function?

Answer 28

Deep in biceps | Flexion and extension

Question 29

What is the most likely cause of musculocutaneous nerve damage?

Answer 29

Breast cancer surgery

Question 30

What is the main result of a musculocutaneous nerve injury?

Answer 30

Loss of flexion and supination in forearm

Question 31

Where does the radial nerve run and what is its main function?

Answer 31

Runs posterior to humerus in radial groove | Motor to posterior arm and forearm

Question 32

What are the mian consequences of radial nerve injury?

Answer 32

Loss of sensation at anatomical snuff box Loss of power grip WRIST DROP

Question 33

Where does the median nerve run and what is its main function?

Answer 33

Runs through median cubital fossa and carpal tunnel | Supplies wrist, finger flexors, small muscles of thumb and index finger

Question 34

What are the main consequences of median nerve injury?

Answer 34

Wasting of thenar eminence | Loss of sensation and fine movement in lateral digits

Question 35

Where does the ulnar nerve run and what is its main function?

Answer 35

Runs posterior to medial epicondyle | Motor to small muscles of hand

Question 36

What is the main consequence of ulnar nerve injury?

Answer 36

``` Ulnar claw (due to lumbrical deinnervation) Loss of efficient adduct and abduction in fingers ```

Question 37

What is the most common cause of ulnar nerve injury?

Answer 37

Attempted suicide by cutting

Question 38

Describe the ulnar paradox

Answer 38

Clawing is worse when you injure nerve at wrist than elbow because FDP is also damaged and so flexion of fingers reduced, making appearance seem less clawed

Question 39

How do you test for ulnar nerve damage?

Answer 39

See LA notes

Question 40

What is the course of the axillary nerve and what is its main function?

Answer 40

Winds round surgical neck of humerus | Supplies deltoid and teres minor

Question 41

What is the main consequence of injury to axillary nerve?

Answer 41

``` Deltoid wasting (loss of shoulder-roundness) Loss of lateral cutaneous nerve sensation ```

Question 42

Why is the long thoracic nerve relatively susceptible to damage?

Answer 42

Relatively superficial

Question 43

What does the long thoracic nerve supply?

Answer 43

Serratus anterior - involved in scapula stabilisation

Question 44

What is the main consequence of injury to the long thoracic nerve

Answer 44

Winging of scapula

Question 45

What name is given to the palsy produced if the C5 C6 root is damaged

Answer 45

Erb's palsy

Question 46

What is the most common cause of Erb's palsy?

Answer 46

dystopia or traumatic fall to shoulder

Question 47

What nerves are most likely to be damaged in Erb's palsy?

Answer 47

Musculocutaneous | Axillary

Question 48

Describe the presentation of Erb's palsy

Answer 48

Loss of sensation in regimental patch Atrophy of biceps, brachialis and deltoid "Waiter's tip"

Question 49

What name is given to the palsy produced if the C8 T1 root is damaged

Answer 49

Klumpke's palsy

Question 50

What nerves are most likely to be damaged in Klumpke's palsy?

Answer 50

Median | Ulnar

Question 51

Describe the presentation of Klumpke's palsy?

Answer 51

Clawed hand

Question 52

What is the most common cause of Klumpke's palsy?

Answer 52

Abnormal birth

Question 53

Which muscles are affected by a Klumpke's palsy?

Answer 53

Intrinsic muscles of hand, wrist and finger flexors and forearm pronators