Upper Extremity Nerves

What nerve roots is the long thoracic nerve derived from?

C5, C7, and C7

What muscle does the long thoracic nerve innervate?

serratus anterior

What is the function of the serratus anterior?

protract the scapula

What does damage to the long thoracic nerve and/or the muscle it innervates result in?

winged scapula

What nerve root is the dorsal scapular nerve derived from?

C5

What muscles does the dorsal scapular nerve innervate?

levator scapulae and rhomboids (major and minor)

What is the function of the levator scapulae and rhomboids?

elevate (levator scapulae) and stabilize (rhomboids) the scapula medially

What does damage to the dorsal scapular nerve and/or the muscles it innervates result in?

winged scapula

What nerve root is the nerve to the subclavius derived from?

C5

What muscle does the nerve to the subclavius innervate?

subclavius

What is the function of the subclavius?

depress the clavicle

What is the most commonly broken long bone?

clavicle

What may result from a clavicle fracture?

pain and damage to the subclavius muscle

Where does the suprascapular nerve originate from?

upper trunk

Where does the suprascapular nerve traverse, and where does it pass?

traverses the posterior triangle of the neck & passes posterior to the scapula through the suprascapular notch

What muscles does the suprascapular nerve innervate?

supraspinatus and infraspinatus (2 of the 4 rotator cuff muscles)

Where do the upper and lower subscapular nerves originate from?

posterior cord

What muscles do the upper and lower subscapular nerves innervate?

subscapularis (1 of the 4 rotator cuff muscles) & teres major

Where does the teres major insert?

on the shaft of the humerus, not the head

What nerve innervates the teres minor (1 of the 4 rotator cuff muscles)?

axillary nerve

What are the rotator cuff muscles, and what nerves innervate them?

- supraspinatus (suprascapular nerve)

- infraspinatus (suprascapular nerve)

- teres minor (axillary nerve)

- subscapularis (upper and lower subscapular nerves)

What does a tear to the rotator cuff muscles/related shoulder ligaments or inflammation (tendonitis or bursitis) result in?

shoulder pain, difficulty in abduction and posterior rotation, weakness lifting

What innervates the latissimus dorsi?

thoracodorsal nerve (middle subscapular nerve)

What is the function of the latissimus dorsi?

adductor of the arms

Where does the axillary nerve originate from?

posterior cord (C5-C6)

What muscles does the axillary nerve innervate?

deltoid & teres minor

Where does the axillary nerve travel?

into the posterior shoulder, passing through the quadrangular space

What does damage to the axillary nerve result in?

inability to abduct the upper extremity

What does the musculocutaneous nerve originate from?

lateral cord (C5, C6, C7)

What muscle does the musculocutaneous nerve pierce as it leaves the axilla?

coracobrachialis muscle

What does the musculocutaneous nerve innervate?

the anterior compartment of the arm

- coracobrachialis

- biceps brachii

- brachialis

What might cause musculocutaneous nerve injuries?

penetrating trauma to the anterior compartment, although this is pretty rare

What is a more likely cause of damage to the musculocutaneous nerve?

trauma to the brachial plexus nerve roots C5, C6, C7 (as with axillary nerve)

What would damage to the musculocutaneous nerve result in?

inability to flex at the elbow & weak supination of the forearm

What nerve roots does the axillary nerve originate from?

C5 and C6

What can cause injury to the C5 and C6 spinal roots?

trauma resulting in an increased angle between the head and shoulder (drop, fall, or during the birthing process)

What is injury to the C5 and C6 spinal roots called?

Erb's palsy

What is Erb's palsy?

paralysis of the arm caused by injury to the upper trunk (C5-C6)

What does Erb's palsy result in?

inability to abduct the upper extremity, weak elbow flexion, and weak supination of the forearm

Signs of Erb's Palsy

- loss of sensation in the arm and paralysis and atrophy of the deltoid, biceps, and brachialis muscles

- the arm hangs by the side and is rotated medially; the forearm is extended and pronated (waiter's tip hand)

Avulsion

tearing of the nerve roots at the spinal cord

True or False: An avulsion is generally repairable.

False, an avulsion is generally unrepairable.

Rupture

tear of the peripheral nerve

Can a rupture be surgically repaired?

Yes, with potential regrowth of axons occurring

Neuroma

scar tissue formation on a stretched or damaged nerve

True or False: Neuroma recovery is possible.

True

Neurapraxia

stretching of the nerve might damage the nerve covering or the nerve itself

True or False: Recovery of neurapraxia over time is likely.

True

What spinal roots does the ulnar nerve originate from?

C8 and T1

What is the ulnar nerve a terminal branch of?

the medial cord

Where does the ulnar nerve descend?

the medial arm in the anterior compartment

Where does the ulnar nerve go as it travels into the forearm?

posterior to the medial epicondyle and through a tendinous tunnel (cubital tunnel)

What does the ulnar nerve supply?

not the arm, but branches and supplies the forearm and hand

What can happen to the ulnar nerve as it travels thorugh the cubital tunnel?

it can become irritated or compressed, causing paresthesia or pain over the distribution of the medial aspect of the forearm and hand (hitting your funny bone)

What are casual causes of compression of the ulnar nerve?

leaning on elbows or holding arm flexed (reading phone or sleeping with flexed elbow)

What do the branches of the ulnar nerve in the proximal forearm supply?

flexor carpi ulnaris & medial half of the flexor digitorum profundus (digits 3, 4, and 5)

What does the ulnar nerve control?

- flexing of 3rd, 4th, and 5th digits at the distal phalanges

- intrinsic hand muscles (lumbricals)

Where do the ulnar nerve (and artery) pass into the hand?

superficial to the carpal tunnel and lateral to the pisiform bone in a tunnel called Guyon's tunnel

What does the ulnar nerve supply in the hand?

the 14 intrinsic muscles of the hand

What is the ulnar nerve sensory to?

the 5th digit (pinky) and half of the 4th digit (ring)

What is damage to roots C8 and T1 or lower trunk dysfunction related to?

ulnar nerve; Klumpke's Palsy

What is a symptom of Klumpke's Palsy/ulnar nerve damage?

flexion of fingers (since ulnar is responsible for many intrinsic hand muscles)

What else does T1 supply?

sympathetics to the superior cervical ganglion

What is another complication of lower trunk damage (considering sympathetics)?

Horner's Syndrome

What does ulnar nerve damage at the wrist (thus deinnervation of hand muscles) cause?

permanent flexion of fingers (despite the role the ulnar nerve serves in supplying flexor digitorum profundus)

What "hand" might result from ulnar nerve injury?

claw hand (inability to extend fingers at interphalangeal joints, results in permanent flexion)

What "hand" might result from median nerve injury?

ape hand (inability to oppose thumb) / hand of benediction

What "hand" might result from radial nerve injury?

wrist drop (inability to extend the hand, inability to fully extend the forearm)

What spinal roots does the median nerve originate from?

C5-T1 (both lateral and medial cords)

Where does the median nerve travel?

on the medial side of the arm, passing between the biceps and brachialis muscles

What does the median nerve supply?

only the forearm and hand (not the arm)

Where does the median nerve enter the forearm?

passes through the cubital fossa

Where is the median nerve found in the cubital fossa?

lateral to the pronator teres & medial to the biceps tendon and brachial artery

What covers the median nerve?

the biceps aponeurosis

What does the median nerve supply in the proximal forearm?

- pronator teres

- palmaris longus

- flexor carpi radialis

- flexor digitorum superficialis

Where do potential compression points of the median nerve occur?

- before it enters the cubital fossa

- as it is leaving the cubital fossa through the two heads of the pronator teres

What might pinch the median nerve?

an extension of the pronator teres to a supercondylar spur (in a small percentage of people, 1%)

What does compression of the median nerve result in?

forearm weakness (particularly pronation) and sensory deficits

Where does the median nerve travel down the forearm?

between the flexor digitorum superficialis and flexor digitorum profundis

What branches off the median nerve midway down the forearm?

anterior interosseous nerve

What does the anterior interosseous nerve supply?

- flexor policis longus

- pronator quadratus

- lateral 1/2 of flexor digitorum profundus (digits 2 and 3)

What does anterior interosseous syndrome result in?

motor deficits only

What would palsy of the anterior interosseous nerve result in?

patient would be unable to make an OK sign (no thumb opposition)

Where does the remainder of the median nerve pass through?

the carpal tunnel and into the palmar surface of the hand to supply thenar muscles and lateral lumbricals

What might compression of the median nerve cause?

carpal tunnel syndrome

What spinal roots does the radial nerve originate from?

posterior cord, and has components of all 5 spinal roots

How does the radial nerve travel through the arm?

through the axilla (along with the axillary artery) on top of the subscapularis, teres major, and latissimus dorsi muscles; it then enters the posterior arm

Where does the radial nerve extend?

down the arm in the posterior compartment

What does the radial nerve supply?

posterior compartment muscles (triceps) and extensor compartment muscles (forearm) along the way

What muscles do motor branches of the radial nerve in the axilla supply?

long and medial head of triceps

What muscles do motor branches of the radial nerve in the arm supply?

- lateral head of triceps

- anconeus

- brachioradialis

- brachialis (dual innervation with musculocutaneous)

What does the radial nerve become in the forearm?

posterior interosseous nerve

What muscles does the posterior interosseous nerve supply in the forearm?

most extensors

What muscles does the posterior interosseous nerve supply in the hand?

none after the wrist, but note the muscle bellies for the digit extensors are all in the forearm

What is Saturday night palsy?

radial nerve compression in the axilla (common)

What will radial nerve compression in the axilla result in?

- inability to extend the forearm & wrist (wrist drop or fingers)

- paresthesia on the radial portion of the hand (lateral, dorsal hand; doesn't extend onto the fingers)

What type of nerve is the posterior interosseous nerve (PIN)?

a motor nerve

What does PIN compression result in?

weakness in finger extension, but generally spares some wrist extension because extensor carpi radialis longus receives innervation higher up on the radial nerve

What is the area in which the PIN passes through called?

"Arcade of Frohse" (often a site of entrapment of the nerve)

Musculocutaneous nerve (motor, sensory, injury)

Motor = anterior compartment of arm

Sensory = arm and lateral forearm

Injury = can't flex elbow