Upper Extremity Nerves

Question 1

What dermatomes does the axillary nerve innervate?

Answer 1

C5-C6

Question 2

What types of injuries damage the axillary nerve?

Answer 2

1. Fractured surgical neck of the humerus

2. Anterior dislocation of the humerus

Question 3

What is the presentation of an axillary nerve injury?

Answer 3

1. flattened deltoid
2. loss of arm abduction at shoulder (> 15 degrees)
3. loss of sensation over the deltoid muscle and lateral arm.

Question 4

What dermatomes does the musculocutaneous nerve innervate?

Answer 4

C5-C7

Question 5

What types of injuries damage the musculocutaneous nerve?

Answer 5

1. midshaft fracture of the humerus
2. Compression of the axilla (e.g. due to crutches or sleeping with am over chair) –> commonly referred to as “Saturday night palsy”

Question 6

What is the presentation of a musculocuatenous nerve injury?

Answer 6

1. Wrist drop: loss of elbow, wrist, and finger extension
2. Decrease grip strength (wrist extension is necessary for maximal action of the flexors)
3. Loss of sensation over the posterior arm/forearm and dorsal hand.

Question 7

What dermatomes does the median nerve innervate?

Answer 7

C5-T1

Question 8

What types of injuries damage the median nerve?

Answer 8

1. supracondylar fracture of the humerus (proximal lesion)
2. carpal tunnel syndrome
3. Wrist laceration (distal lesion)

Question 9

What is the presentation of a median nerve injury?

Answer 9

1. “Ape Hand”
2. “Pope’s Blessing”
3. Loss of wrist flexion, flexion of lateral fingers, thumb opposition, lumbricals of 2nd and 3rd digits
4. Loss of sensation over the thenar eminenceand dorsal and palmar aspects of the lateral 3 1/2 fingers with proximal lesions
5. Tinel sign: tingling on percussion of median nerve seen in carpal tunnel syndrome.

Question 10

What dermatomes does the ulnar nerve innervate?

Answer 10

C8-T1

Question 11

What types of injuries damage the ulnar nerve?

Answer 11

1. Fracture of the medial epicondyle of the humerus (“funny bone”), proximal lesion
2. Fractured hook of the hamate, distal lesion

Question 12

What is the presentation of an ulnar nerve injury?

Answer 12

1. “Ulnar Claw” on digit extension
2. Radial deviation of the wrist upon flexion, proximal lesion
3. Loss of wrist flexion, flexion of the medial fingers, abduction and adduction of fingers (interossei), actions of medial 2 lumbrical muscles
4. Loss of sensation over medial 1 1/2 of fingers including the hypothenar eminence.

Question 13

What dermatomes does the recurrent branch of the median nerve innervate?

Answer 13

C5-T1

Question 14

What types of injuries damage the recurrent branch of the median nerve?

Answer 14

1. Superficial laceration of the palm

Question 15

What is the presentation of a recurrent branch of the median nerve injury?

Answer 15

1. “Ape hand”
2. Loss of the thenar muscle group: opposition, abduction, and flexion of the thumb.
3. No loss of sensation is present.