Brachial Plexus

Question 1

Dorsal scapular nerve

Answer 1

• This nerve will emerge very early from the brachial plexus, from the C5 root
• it is the first branch off of the plexus
• you will be able to see it running posteriorly to the rhomboids and levator scapulae.

Question 2

Suprascapular nerve

Answer 2

• This nerve will run posteriorly from the brachial plexus towards the scapula.
• this branches off the superior trunk of the brachial plexus
• It runs through the suprascapular notch inferior to a ligament forming a bridge across the notch (called the transverse scapular ligament) to reach the supraspinatus and then through the spine of the scapula to reach the infraspinatus.

Question 3

Lateral pectoral nerve

Answer 3

This nerve runs from the lateral cord of the brachial plexus to the pectoralis major.

Question 4

Medial pectoral nerve

Answer 4

This nerve is usually the first branch from the medial cord, and it runs through the pectoralis minor, innervating it on its path to the pectoralis major.

Question 5

Medial brachial and medial antebrachial cutaneous nerves

Answer 5

These nerves will branch distal to the medial pectoral nerve off of the medial cord. They run to the skin of the medial arm and forearm.

Question 6

Long thoracic nerve

Answer 6

• this branches off the C5 root of the brachial plexis
• This nerve runs tight to the thoracic wall, innervating the serratus anterior muscle.
• This is also visible running with the serratus anterior on the superficial dissection

Question 7

Thoracodorsal nerve

Answer 7

This nerve can be seen branching off the posterior cord and running to the latissimus dorsi muscle.

Question 8

Upper subscapular and lower subscapular nerves:

Answer 8

These nerves branch from the posterior cord, with the upper branching proximal to the thoracodorsal nerve and the lower branching distal to the thoracodorsal nerve, in most cases.

They run posteriorly to the subscapularis and teres major (lower only) muscles

Question 9

Axillary nerve

Answer 9

• this is a terminal branch of the brachial plexus
• This nerve branches from the posterior cord and runs posterolaterally.
• It travels with the posterior circumflex humeral artery through a space between the surgical neck of the humerus
• innervates teres minor and the deltoid

Question 10

Radial nerve

Answer 10

• This nerve branches from the posterior cord and runs to the posterior side of the arm. It is larger than the axillary nerve.
• runs through the radial groove of the humerus
• this is a terminal branch
• this innervates the deep and superficial muscles of the posterior forearm and arm as well as the triceps brachii and the brachioradialis

Question 11

Ulnar nerve

Answer 11

• The ulnar is the most medial terminal branch of the brachial plexus, branching from the medial cord.
• It continues along the medial side of the arm and passes around between the medial epicondyle and the olecranon of the humerus

This nerve is responsible for our “funny bone.”

• innervates the flexi carpi ulnaris and 1/2 of the flexor digitorum profundus
• It also innervates all muscles in the hand (adductor policis brevis, lumbricals, hypothenar, PAD, DAB) except 1/2 LOAF
• You can also see it enter the hand and send branches to the skin of the 5th digit and lateral aspect of the 4th digit.

Question 12

Median nerve

Answer 12

• this is a terminal branch
• this is the the middle nerve formed from the “M” of the brachial plexus, as it receives contributions from both the medial and lateral cords.
• It travels through the anterior arm and forearm and innervates most of the muscles of the anterior arm
• travels through the carpal tunnel to the hand
• innervates all the muscles of the anterior compartment of the forarm (except what is innervated by the ulnar nerve)
• innervates 1/2 LOAF of hand
  lumbricals (lateral two), opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis

Question 13

Musculocutaneous nerve

Answer 13

• this is the terminal branch off of the lateral cord
• The musculocutaneous nerve pierces (and supplies) the coracobrachialis muscle in the arm
• runs between the biceps brachii and brachialis muscles (and innervates them)
• It emerges on the lateral aspect of the arm as the lateral antebrachial cutaneous nerve.
• remember that the sensory information doesn’t quite match up because it is not going to the anterior arm it is the anterolateral forearm

Question 14

what is a good way to remember what roots innervate what parts of the arm

Answer 14

the nerves that emerge from the most proximal roots will innervate the most proximal muscles

Question 15

dermatome

Answer 15

the sensory distribution of a spinal nerve

Question 16

myotome

Answer 16

this is the motor function of a spinal nerve root

Question 17

what is the dermatome of C5

Answer 17

this is over the lateral shoulder and makes its way down to the lateral arm and upper forearm

Question 18

what is the dermatome of C6

Answer 18

this is the anterior aspect of the lateral forearm down to the thumb and the posterior lateral forearm to the thumb of the index finger

Question 19

what is the dermatome of C7

Answer 19

this does the middle finger and the anterior aspect of the pointer finger

Question 20

what is the dermatome of C8

Answer 20

medial aspect of hand (ring finger and pinky)

Question 21

what is the dermatome of T1

Answer 21

this is the medial aspect of the elbow

Question 22

what is the myotome of C5

Answer 22

this is shoulder abduction

Question 23

what is the myotome of C6

Answer 23

this is elbow flexion

Question 24

what is the myotome of C7

Answer 24

this is elbow extension

Question 25

what is the myotome of C8

Answer 25

this is for grip, pinch, and opposition

Question 26

what is the myotome of T1

Answer 26

this is finger abduction

Question 27

what is important to remember about the sensory innervation of the terminal branches

Answer 27

the sensory distribution of the terminal branches will be slightly different than the nerve roots because they are a combination of multiple nerve roots

Question 28

sensory distribution of radial nerve come from what and goes where?

Answer 28

- C5,C6,C7,C8,T1 | - this goes to the lateral anterior arm and then most of the posterior arm and forearm

Question 29

sensory distribution of axillary nerve come from what and goes where?

Answer 29

- C5,C6 | - lateral shoulder

Question 30

sensory distribution of musculocutaneous nerve come from what and goes where?

Answer 30

- C5,C6,C7 | - this innervates the lateral, anterior forearm

Question 31

sensory distribution of median nerve come from what and goes where?

Answer 31

- C5,C6,C7,C8,T1 | - this is on the palmer side of the thumb, the palmer side of the lalteral hand and the posterior side of the digits 1-3

Question 32

sensory distribution of ulnar nerve come from what and goes where?

Answer 32

- C8,T1 | - hypothenar group and posterior aspect of the medial hand