Anatomy of the brachial plexus

Question 1

brachial plexus diagram

Answer 1

Question 2

axillary nerve

Answer 2

c5,6

supplies

• shoulder joint (glenohumeral joint) (axilla)
• DELTOID (scapular region)
• skin over lower half of deltoid (scapular region)
• upper lateral cutaneous nerve of arm to skin over lower half of deltoid (scapular region)
• teres minor (scapular region)

pass posteriorly through quadrangular space with posterior circumflex humeral artery

Question 3

musculocutaneous nerve

Answer 3

c5,6,7

supplies

• CORACOBRACHIALIS (axilla)
• BICEPS (upper arm)
• BRACHIALIS (upper arm)
• elbow joint (upper arm)
• lateral cutaneous nerve of forearm

Question 4

radial nerve

Answer 4

c5,6,7,8, t1

supplies: POSTERIOR (EXTENSOR COMPARTMENT)

• posterior cutaneous part of arm + forearm
• TRICEPS (arm)
• small part of BRACHIALIS (arm)
• BRACHIORADIALIS (arm)
• EXTENSOR CARPI(arm)
• elbow joint (arm)
• EXTENSOR CARPI RADIALIS BREVIS
• SUPINATOR
• EXTENSOR DIGITORUM
• EXTENSOR DIGITI MINIMI
• EXTENSOR CARPI ULNARIS
• ABDUCTOR POLLICIS LONGUS
• EXTENSOR POLLICIS LONGUS
• EXTENSOR POLLICIS BREVIS
• EXTENSOR INDICAS
• skin of lateral side of dorsum of hand and lateral 3.5 fingers

Question 5

median nerve

Answer 5

c5,6,7,8,T1

supplies:

• muscles of the anterior compartment ECXEPT flexor carpi ulnaris + ulnar half of flexor digitorum profundus)
• palmar digital branches to lateral 3.5 fingers

Question 6

ulnar nerve

Answer 6

c8, t1

supplies:

• most intrinsic muscles of hand
• flexor carpi ulnaris + ulnar half of flexor digitorum profundus
• skin of medial side of dorsum of hand and medial 1.5 fingers
• palmar figital branches to medial 1.5 fingers

Question 7

dorsal scapular mainly supplied by

Answer 7

c5

Question 8

Suprascapular mainly supplied by

Answer 8

c5

supplied by c5,6 but mainly c5

Question 9

Lateral pectoral mainly supplied by

Answer 9

c6

supplied by c6,7 but mainly c6

Question 10

nerve to subclavius mainly supplied by

Answer 10

c6

nerve to subclavius supplied by c5,6 but mainly c6

Question 11

long thoracic is mainly supplied by

Answer 11

c5,6

long thoracic is supplied by c5,6,7 but mainly c5,6

Question 12

upper and lower subscapular is mainly supplied by

Answer 12

c5,6

Question 13

medial pectoral is mainly supplied by

Answer 13

c8,t1

Question 14

thoracodorsal is mainly supplied by

Answer 14

c7

long thoracic is supplied by c6,7,8 but mainly c7

Question 15

superior trunk injuries results in

Answer 15

Results in paralysis of the muscle of the shoulder and arm supplied by the C5 and C6 spinal nerve (deltoid, Biceps, brachialis, and brachioradialis).

In order for you to damage the superior trunk, really need to pull the head away from the shoulder so that you stretch the superior trunk and damage it. See it in two situations.

1) during delivery when the shoulder is stuck and they’re trying to pull the baby, they can damage the superior trunk.
2) when someone falls down, and the head stops but the body is still moving because of the weight of the body, so it will still stretch the head away from the shoulder - will stretch the superior trunk and damage it.

Question 16

erb’s paralysis clinical features

Answer 16

• Arm hangs by the side of the body and medially rotated (suprascapular nerve - supplies supraspinatus and infraspinatus - lateral rotation - is injured, no lateral rotation, only left with medial rotation)
• The arm cannot be abducted and laterally rotated (Arm can’t be abducted because of the supraspinatus (is paralyzed so can’t initiate abduction), and the axillary is lost, which supplies the deltoid)
• The elbow is extended and flection is not possible (The elbow is extended because can’t flex —> lost the anterior compartment muscles, which are called flexors muscles if they are a combination, which indicate that the musculocutaneous is lost, which mainly comes from C5 and C6)
• The forearm is pronated and supination is not possible (Main supinatior is biceps, supplied by musculocutaneous, which is lost —> supination is not possible)
• The wrist and fingers are flexed (Wrist and fingers are flexed because the radial, which has contributions from C5, C6, C7, C8, T1, will be weaker if affect the superior trunk. So whatever muscles supplied by the radius will be weaker. However, ulnar will be mainly C8 and T1 - the ulnar supplies flexors of the forearms and the digits - so if the radial extensor is weak, but the ulnar flexor is normal = will get flexion of the wrist and slightly the fingers —> why have the waiter’s tip)
• Referred to as Water’s tip.

Question 17

inferior trunk injury results in

Answer 17

paralysis of the muscle of the forearm and hand supplied by the C8and T1 spinal nerve

a patient who will describe falling from a tree or a window etc, where he had to hang, and by hanging, the arm is pushed away from the body and that would stretch the inferior trunk and damage it

That patient will present with damage/paralysis to all the muscles supplied by

the ulnar - because it has mainly contributions from C8 and T1. Median still has

other contributions, so it will be weaker, but ulnar will be completely damaged.

So that patient when you ask him to do a fist he can’t because ulnar in general allow you to flex your fingers at the metacarpophalangeal joint and kind of extend the interphalangeal joint. So the opposite to this is to extend the metacarpophalangeal joint and to flex the interphalangeal. —> what we call a claw

Question 18

claw hand clinical features

Answer 18

• Paralysis of intrinsic muscles of the hand and long flexors of the hand.
• Medial four fingers are hyperextended at the metacarpo-phalangeal joint and hyper flexed at inter phalangeal joint

Question 19

hyperabduction syndrome, symptoms and may results from:

Answer 19

• The cords are impinged (affect) or compressed between the coracoid process of the scapula and the pectoralis minor tendon.
• May result from prolonged hyperabduction of the arm during performance of manual task.
• Symptoms: pain radiating down the arm, numbness, paresthesia, erythema, weakness of the hands.
• Compression of the axillary artery and vein causes ischemia of the upper limb and distension of the superficial veins.

Question 20

C5 neurological deficit

Answer 20

Clinically: If its at the level of the nerve, simply examine all the muscle supplied by that nerve and will use the sensation associated with the nerve.

Meaning, if I have an axillary nerve injury, I will examine the deltoid and the skin area above the deltoid.

However, if I want to see if the injury is higher up at the level of the root, will try to find out muscles which are maximally supplied by that root value.

For example, C5 maximally supplies the deltoid and biceps, so examine the function of these muscles - will be weaker.

Question 21

C6 neurological deficit

Answer 21

Same thing if go to C6 for example:

Will examine biceps, will examine extensors of the forearm, will do the tendon reflex in the forearm and will examine skin area which is the lateral aspect.

Remember, although we have the skin maps, it is not exactly lined. Meaning, can’t say where the line that separate C5 from C6 - there’s a little bit of overlap, but the map is in general.

That’s why we go in the middle of the area because when you have a myotome and a dermatomes on top of it, there is a mixture - can’t say exactly that this is the line that separates C5 form C6

Question 22

label the following:

Answer 22

Question 23

label the following:

Answer 23

Question 24

label the following:

Answer 24