Block 3: TBL 6, Brachial Plexus

Question 1

f(x) of the brachial plexus

Answer 1

to supply motor and sensory innervation to the muscles of the arm, forearm, and hand

Question 2

Roots of the brachial plexus

Answer 2

anterior rami of C5-T1

Question 3

What are the divisions of the brachial plexus?

Answer 3

anterior (supply flexors) and posterior (supply extensors) divisions

Question 4

Describe an upper brachial plexus trunk injury

cause
damaged roots
result

Answer 4

cause: extreme flexion of the head and depression of the shoulder (ex: babies: too much traction pulling the shoulders down during delivery; adults: motorcycle injury)

damaged roots: C5-C6

result: arm hangs limply at the side and is internally rotated; the forearm is pronated and the wrist is flexed, causing the “waiters tip” sign

Question 5

Describe a lower brachial plexus injury

cause
damaged roots
result

Answer 5

cause: extreme abduction of the arm (ex: babies: pulled by the arm from the birth canal; adults: grabbing on to a tree branch when falling)

damaged rots: C8-T1

result: compromises muscles in the lower forearm and hand (Klumpke’s Palsy)

Klumpkes Palsy: “claw hand”, in which the fingers are flexed

Question 6

Long thoracic nerve innervates

Answer 6

the serratus anterior muscle

Question 7

F(x) of the serratus anterior muscle

Answer 7

protracts and upwardly rotates the scapula; keeps the scapula tight against the thoracic cage during arm movement

Question 8

What happens if there is injury to the long thoracic nerve ?

Answer 8

medial winging of the scapula;

Question 9

How to test thoracic nerve injury

Answer 9

ask the patient to support their weight with their hands while pushing against a wall

damage to the long thoracic nerve will present as a medial winging of the scapula

Question 10

When will long thoracic nerve injuries most likely occur?

Answer 10

during a mastectomy

Question 11

Where does the axillary nerve first course?

Answer 11

through the quadrangular space

Question 12

What is the function of the axillary nerve?

Answer 12

motor: to innervate the deltoid and teres minor
sensory: skin over the posteriolateral shoulder (sargeant’s patch)

Question 13

Where is the axillary nerve suspect to injury

Answer 13

fracture of the surgical neck of the humerus or shoulder dislocation

Question 14

Describe the consequences of axillary nerve injury

Answer 14

1. loss of shoulder abduction above 15 degrees b/c of paralysis of the deltoid muscle
2. paralysis of the teres minor leads to weakened external rotation of the shoulder & decreased shoulder joint stability
3. loss of cutaneous sensation over the posterolateral aspect of the shoulder

Question 15

What does the radial nerve supply?

Answer 15

the posterior compartment muscles (extensors) and the sensory innervation to the skin on the dorsal side of the arm, forearm and hand

Question 16

Describe the course of the radial nerve

Answer 16

it travels around the body of the humerus to lie within the radial groove, then travels across the elbow joint anterior to the lateral epicondyle of the humerus

Question 17

What is at risk with a humeral shaft fracture injury

Answer 17

the radial nerve

Question 18

What are the branches of the radial nerve?

Answer 18

superficial: cutaneous only; sensory innervation of the dorsum of the thumb and radial 1/2 of the hand

deep (also known as posterior interosseous nerve): motor supply to the posterior forearm by piercing the supinator muscle

Question 19

What is the main characteristic of radial nerve damage?

Answer 19

wrist drop

Question 20

Radial nerve injury proximal to the triceps innervation causes

Answer 20

inability to extend the triceps brachii

Question 21

When is the radial nerve most likely to be injured?

Answer 21

1. fracture of the shaft of the humerus
2. nerve compression (crutches, a textbook)
3. someones head sleeping under your arm “honeymooners palsy”

Question 22

Musculocutaneous nerve f(x)

Answer 22

motor innervation to the 3 muscles in the flexor compartment of the arm, terminates as the lateral antebrachial cutaneous nerve

Question 23

Damage to the musculocutaneous nerve causes

Answer 23

loss of sensory component
loss of elbow flexion
severely weakened forearm supination

Question 24

Ulnar nerve f(x)

Answer 24

innervates:
flexor carpi ulnaris
1/2 FDP
motor to the hypothenar muscles and all other intrinsic hand muscles except for the thenar muscles and 1st 2 lumbricals

Question 25

What types of injuries are common with musculocutaneous nerve?

Answer 25

entrapment as it passes by the medial epicondyle of the humerus
fracture of the medial epicondyle of the humerus
trauma to the wrist