Ulnar nerve anatomy and palsy

Question 1

Nerve roots?

Answer 1

C8-T1

Question 2

Motor function?

Answer 2

-Innervates the intrinsic muscles of the hand (EXCEPT 2 LUBRICALS and the THENAR MUSCLES)
• Hypothenar muscles (a group of muscles associated with the little finger)
• Medial two lumbricals
• Adductor pollicis
• Palmar and dorsal interossei of the hand
• Palmaris brevis

• Innervates the Flexor carpi ulnaris : Flexes and adducts the hand at wrist
• Innervates medial half of the flexor digitorum pronfundus: flexes the ring and little fingers at the distal interpharangeal joint

Question 3

Sensory function

Answer 3

-Anterior and posterior surfaces of the medial one and a half fingers and associated palm areas

Question 4

Anatomy

Answer 4

• Down medial aspect of upper arm
• Posterior to medial epicondyle
• Pierces the flexor carpi ulnaris
• At wrist enters the hand via Guyon’s Canal

Question 5

Trauma at elbow presentation?

Answer 5

• Flexion of the wrist can still occur, but is accompanied by abduction (due to paralysis of flexor carpi ulnaris and medial half of flexor digitorum profundus).
• Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
• Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).
• Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).

Question 6

Trauma at wrist?

Answer 6

• Only the intrinsic muscles of the hand are affected.
• Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
• Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).
• Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).
• Sensory loss over palmar side of medial one and a half fingers only.

Question 7

Frontmens sign?

Answer 7

• The patient is asked to hold a piece of paper between the thumb and index finger, as the paper is pulled away.
• They should be able to hold the paper there with no difficulty (via adduction of the thumb).
• A positive test is when the patient is unable to adduct the thumb. Instead, they flex the thumb at the interphalangeal joint to try to maintain a hold on the paper.

Question 8

Cubital syndrome

Answer 8

• Second most common nerve entrapment
• Cubital tunnel between Medial epicondyle and olecranon, with fascial bands from FCU as roof
• Patient has numbness on ulnar side of hand and difficulty with fine tasks.

Question 9

What is the ulnar paradox?

Answer 9

More clawing in a distal lesion than in a proximal lesion.

In the proximal lesion the flexion of the FDP is maintained