Anatomy Lecture 10_ Brachial Plexus

Question 1

What 6 arm movements are innervated by C5-T1?

Answer 1

Abduction of the shoulder (C5) Extension of wrist (C6) Extension of fingers (C7) Flexion of wrist (C7) Flexion of fingers (C8) Abduction/Adduction of fingers (T1)

Question 2

Where are dermatomes tested for C5, C6, C8, and T1

Answer 2

C5 - just below the shoulder C6 - Towards the end of the thumb C8 - Pinky metacarple T1 - Medial edge of the forearm

Question 3

What nerves contribute to the Axillary Nerve? What muscles does it innervate?

Answer 3

Arises from C5-C6. Innervates Teres minor Deltoid

Question 4

What nerves contribute to the Musculocutaneous Nerve? What muscles does it innervate?

Answer 4

Arises for C5-C7. Innervates: Coracobrachialis Biceps brachii Brachialis

Question 5

What nerves contribute to the Median Nerve. What Muscles does it innervate?

Answer 5

Arises from C6-T1. Innervates Forearm: Anterior compartment of forearm (except flexor carpi ulnaris and ½ of flexor digitorum profundus) Hand: Thenar muscles of hand (except adductor pollicis) and first two lumbricals

Question 6

What nerves contribute to the Ulnar Nerve? What muscles does it innervate?

Answer 6

Arises from C8-T1. Innervates Forearm: Flexor carpi ulnaris and ½ of flexor digitorum profundus Hand: Intrinsic muscles of the hand except the three thenar muscles and first two lumbricals

Question 7

What nerves contirbute to the Radial Nerve?

Answer 7

Arises from C5-C8 Innervates Arm: Posterior compartment muscles Forearm: Posterior compartment muscles Hand: None!

Question 8

From what nerves does the Dorsal Scapular nerve arise? What does it innervate?

Answer 8

Arises from Root of C5. Innervates Levator Scapulae and Rhomboids

Question 9

From what nerves does the Suprascapular nerve arise? What does it innervate?

Answer 9

Arises from C5 & C6 (upper trunk) Innervates Supraspinatus and Infraspinatus

Question 10

From what nerves does the Subclavian nerve arise? What does it innervate?

Answer 10

Arises from the trunk of C5 & C6 (Upper trunk). Innervates the Subclavius.

Question 11

From what nerves does the Long Thoracic nerve arise? What does it innervate?

Answer 11

Arises from Roots of C5-C7. Innervates the Serratus Anterior

Question 12

What are the 4 supra clavicular nerves?

Answer 12

Dorsal Scapular n. Suprascapular Subclavian Long Thoracic

Question 13

What are the three posterior cord nerves? From what nerves do the arise and what do they innervate?

Answer 13

Upper Subscapular n (C5) - Subscapularis Lower Subscapular n (C6) - Subscapularis and Teres Major Thoracodorsal (C6-C8) - Latissimus Dorsi

Question 14

What are the Medial and Lateral Cord Nerves? Where do they arise nd what do they innervate?

Answer 14

Lateral pectoral (C5-C7) - Pectoralis Major Medial pectoral n. (C8-T1) - Pectoralis minor

Question 15

Where is peripheral nerve testing done for each of the peripheral nerves?

Answer 15

See attached

Question 16

Where is reflex testing done for C5-C7?

Answer 16

See attached

Question 17

Erb-Duchenne “Erb” Palsy, what is injured and how does it manifest?

Answer 17

1. Lesion: C5-C6 roots –upper plexus injury
2. Impact: anterior and posterior branches of upper trunk, especially the axillary,
musculocutaneous, and suprascapular nerves. Other peripheral nerves with upper trunk
contribution will be impacted.
3. Symptoms:
a. Paralysis of abductors and lateral rotators of shoulder (suprascapular and axillary
nerves)
b. Paralysis of elbow flexors and forearm supinators (musculocutaneous nerve)
c. Clinical appearance: “waiter’s tip”
d. Loss and wasting of deltoid muscle, arm hangs at side
e. Internal rotation of arm
f. Pronation at forearm (loss of biceps)
g. Flexed wrist and fingers –possible weakening of extensors (radial nerve) relative to
tonus of flexors, recall C6 is extension at the wrist and C7 is flexion
h. Sensory loss at shoulder and lateral arm/hand (loss of C5-C6 dermatomes)

Question 18

Klumpke Paralysis or Palsy, what causes it how does it appear?

Answer 18

1. Lesion: C8-T1 –lower plexus injury
2. Impact: lower trunk, loss of ulnar nerve and weakness in median nerve
3. Symptoms: loss to intrinsic muscles of hand (flexors) with weakness/loss to the extrinsic
hand flexors, especially those innervated by the ulnar nerve:
a. Clinical appearance: “claw hand”
b. Muscle wasting, especially flexor carpi ulnaris, ulnar half of flexor digitorum
profundus, and all intrinsic hand muscles
c. Arm supination and wrist extension (from tonus of extensors and supinators)
d. Hand in full claw position (due to function of long flexors innervated by the median
nerve, tonus of extensors, and loss of lumbricals which result in flexion at the IP
joints, but extension at the MCP joint).
e. Sensory loss to medial forearm and hand (C8-T1 dermatomes)
f. May be accompanied by Horner Syndrome from T1 loss of sympathetics to the chain
i. Ptosis: drooping eyelid
ii. Miosis: pupil constriction
iii. Anhidrosis: lack of sweat on affected side

Question 19

Radial Nerve Palsy “Saturday night palsy” What causes it and how doe it manifest?

Answer 19

1. Lesion: radial nerve
2. Impact: generally from compression of the radial nerve in the radial groove of the
humerus, also caused by a break in the humeral shaft.
3. Symptoms: some weakness in triceps, loss of all muscles in the posterior compartment
of forearm (wrist and finger extensors). Possible sensory loss to posterior cutaneous
nerve of the forearm (test at dorsum of hand between thumb and index finger).
4. Clinical appearance:
a. “wrist drop” –inability to extend the wrist and the fingers at the MCP. The relaxed
wrist assumes a flexed position because of tonus of antagonists (flexors).
b. Also compression in the supinator canal (where the deep branch of the radial nerve
passes into the supinator muscle).

Question 20

Median Nerve Palsy what causes it and what is its clinical sign?

Answer 20

1. Lesion: median nerve
2. Impact: impact varies depending on where along median nerve the lesion occurs, at
elbow, carpal tunnel, or in between.
3. Symptoms: muscle weakness loss for those innervated by the median nerve below
lesion. May cause sensory loss to anterior lateral hand (test at tip of index finger.
Remember, ulnar innervation is not impacted.
4. Clinical appearance:
a. “sign of the benediction” –inability to flex distal interphalangeal joint of digit two and
flex digits two and three into a fist. This classic sign is an ACTIVE TEST!
demonstrated only when patient is asked to make a tight fist. Generally suggests
loss of median nerve at cubital tunnel at elbow.
b. “simian hand” –inability to bring thumb into opposition and thinning of thenar
eminence suggests loss of the median nerve at carpal tunnel.
c. Pronator syndrome: impingement on median nerve as it passes between the two
head of the pronator teres and the fibrous arch of the flexor digitorum superficialis
from overactive pronation.
d. Anterior interossious syndrome the deep branch arises underneath the pronator
teres muscle and goes deep to supply the deep muscles of the forearm. Superficial
muscles and intrinsic muscles of the hand still function.

Question 21

Ulnar Nerve Palsy what causes it and what does it look like?

Answer 21

1. Lesion: ulnar nerve
2. Impact: most frequently where the ulnar nerve passes the medial epicondyle of the
humerus“funny bone” effect. Impact varies depending on where along the nerve the
lesion occurs.
3. Symptoms: Symptoms: muscle weakness loss for those innervated by the ulnar nerve
below lesion. Remember, median innervation is not impacted.
4. Clinical appearance:
a. “ulnar claw” distinct from the “claw hand” of Klumpke Palsy as well as the “sign of the
benediction” of the median lesion. The MCP 4 and 5 joints become hyperextended
with the IP joints flexed. This clawing is a passive clinical sign.
b. Abduction/adduction will also be compromised.
c. Can include atrophy of first interosseous muscles
d. Possible sensation loss to medial hand.