Nerve Injuries

Question 1

What is the sensory distribution of the median nerve in the hand?

Answer 1

• Lateral ⅔ of the palm of the hand
• Lateral (radial) 3½ digits on the palmar side

Question 2

What is the motor distribution of the median nerve in the hand?

Answer 2

Thenars except AdP. Lateral 2 lumbricals.

LOAF

• Lateral 2 lumbricals
• Opponens pollicis
• Abductor pollicis brevis
• Flexor pollicis brevis

Question 2

What is the sensory distribution of the ulnar nerve in the hand?

Answer 2

• Medial 1/3 of the palm & dorsum of the hand
• Medial 1 1/2 fingers on the palmar & dorsal side

Question 3

What are the clinical features of median nerve injury at the elbow?

Answer 3

Damaged at the Elbow
Mechanism of injury: Supracondylar fracture of the humerus.

Motor functions:
The flexors and pronators in the forearm are paralysed, with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus.
The forearm constantly supinated, and wrist flexion is weak (often accompanied by adduction, because of the pull of the flexor carpi ulnaris).
Flexion at the thumb is also prevented, as both the flexor pollicis longus and flexor pollicus brevis muscles are paralysed.
The lateral two lumbricals are affected, and the patient will not be able to flex at the MCP joints or extend at IP joints of the index and middle fingers.

Sensory functions: Lack of sensation over the areas that the median nerve innervates.

Characteristic signs: The thenar eminence is wasted, due to atrophy of the thenar muscles. If patient tries to make a fist, only the little and ring fingers can flex completely. This results in a characteristic shape of the hand, known as hand of benediction.

Question 4

What are the clinical features of median nerve injury at the wrist?

Answer 4

Mechanism of injury: Lacerations just proximal to the flexor retinaculum.

Motor functions: Thenar muscles paralysed, as are the lateral two lumbricals. This affects opposition of the thumb and flexion of the index and middle fingers.

Sensory functions: Same as an injury at the elbow. (sensory loss to palmar aspect of lateral (radial) 3 ½ fingers & Lateral ⅔ of the palm of the hand)

Characteristic signs: The hand is held in the same position as damage at the elbow (hand of benediction), but the forearm is unaffected (not supinated or adducted, wrist flexion likely unaffected, depending on the location of the lesion).

Question 5

What are the clinical features of ulnar nerve injury at wrist?

Answer 5

Partial claw hand

sensory loss to palmar aspect of medial (ulnar) 1 ½ fingers & medial 1/3 of the palm of the hand

Question 5

What is the Ulnar paradox?

Answer 5

• In more proximal ulnar nerve injuries, there will be paralysis of the medial ½ of the FDP which will decrease flexion of the IP joints resulting in a less pronounced deformity.
  • The paradox is that with more injury there is less deformity

Question 6

What are the clinical features of radial nerve injury at wrist?

Answer 6