Upper extremity nerves

Question 1

Ulnar nerve: what does it innervate? Where can it be injured? From which cord?

Answer 1

innervates intrinsic hand muscles and 2 muscles in the flexor forearm (flexor carpi ulnaris and ulnar part of flexor digitorum profundum).
may be injured at the medial epicondyle (proximal; may occur years before the symptoms) or by the hamate hook.
from medial cord

Question 2

Ulnar nerve injury: manifestations

Answer 2

proximal: see ok sign when you try to make a fist
distal lesion: ulnar claw at rest ( ring and pinky straight at MCP and bent at PIP/DIP)
radial deviation of wrist with flexion (d/t flexor carpi ulnaris problems); hypothenar atrophy, loss of sensation over medial 2 fingers

Question 3

Median nerve: what does it innervate? where can it be injured? From which cord?

Answer 3

innervates most of flexor forearme except flexi carpi ulnaris and ulnar part of flexor digitorum profundum. May be injured proximally at supracondylar fracture of the humerus or distally at the carpal tunnel
From lateral and medial cords.

Question 4

Median nerve: manifestations of injury

Answer 4

Proximal injury: pope sign when making a fist
distal injury: median claw at rest/extension (thumb and first 2 fingers bent)
ape hand: atrophy of the thenar eminance
also loss of wrist and lateral finger flexion, thumb opposition. loss of sensation over the palmar first two fingers

Question 5

Injury to the recurrent branch of the median nerve: manifestations, mechanism

Answer 5

seen with superficial laceration of the palm. causes motor loss of intrinsic hand muscles in median distribution: thenar atrophy, no opposition, abduction, or flexion. no loss of sensation

Question 6

Axillary nerve: how injured? manifestations/muscles? from which cord?

Answer 6

injured with a fracture to the surgical head of the humerus. causes deltoid flattening, teres minor problems. can’t abduct >15 degrees. loss of sensation over deltoid muscle. from posterior cord

Question 7

Musculocutaneous nerve: from which cord? Manifestations/muscles? how injured?

Answer 7

from lateral cord

injured by upper trunk compression. causes loss of flexion and supination (biceps, anterior arm)

Question 8

Radial nerve: from which cord? How injured? manifestations?

Answer 8

from posterior cord. injured by midshaft fracture of the humerus (remember radial groove), or compression of the axilla (Saturday night palsy, crutches). responsible fro posterior arm and forearm. see wrist drop, decreased grip strength (from wrist drop), loss of posterior arm/forearm sensation, and sensation over thumb part of dorsum of hand

Question 9

Thenar hand muscles. nerve

Answer 9

OAF: opponens pollicis, abductor pollicis brevis, flexor pollicis brevis. median nerve

Question 10

Hypothenar hand muscles. nerve

Answer 10

ulnar nerve. OAF: opponens digiti minim, abductor digiti minimi, flexor digiti minimi brevis.

Question 11

Interosseous muscles

Answer 11

DAB and PAD: dorsal abduct; palmar adduct.