Nerves - Upper Extremity

Question 1

Spinal Accessory Nerve

Answer 1

CNXI

Runs deep to trapezius with the superficial branch of the transverse cervical artery

IMPORTANT: This nerve innervates trapezius - the only muscle of the upper extremity that does not receive its innervation from the brachial plexus

Question 2

Supraclavicular Nerves

Answer 2

Sensory nerves in the pectoral region

Originate from the Cervical Plexus

Sensory innervation of the area over the clavicle and the superolateral part of pec major

Question 3

Intercostal Nerves (T2 - T12)

Answer 3

Sensory nerves that form the dermatome banding pattern

T4 - level of nipples

T10 - Level of Umbilicus

Question 4

Dorsal Scapular Nerve

Answer 4

Comes off the brachial plexus at the level of the RAMI

Origin: comes off C4 and C5 superiorly

Runs posteriorly along the medial border of the scapula with the dorsal scapular artery

Motor to levator Scapula and Rhomboids (Major and Minor)

Question 5

Long Thoracic Nerve

Answer 5

Comes off the brachial plexus at the level of the RAMI; comes off C5, C6, and C7 inferiorly

Input: C5-C7

Goes behind C8 and T1, and runs inferiorly along the thoracic wall with the lateral thoracic artery towards serratus anterior

Motor to Serratus Anterior

Question 6

Suprascapular Nerve

Answer 6

Origin: Superior Trunk of the Brachial Plexus

Input: C4, C5, C6

Comes off the superior trunk superiorly

Runs posteriorly towards the suprascapular notch where it runs below the transverse scapular ligament and into the supraspinous fossa (accompanied by the subrascapular artery which runs above the ligament).

It winds around the Spinoglenoid notch, and continues into the infraspinous fossa of the scapula

Motor to Supraspinatus and Infraspinatus

Sends a sensory branch to the glenohumeral joint

Question 7

Nerve to Subclavius

Answer 7

Origin: Superior Trunk of the Brachial Plexus

Juts out straight forward toward the clavicle and runs parallel to the floor towards subclavius

Motor to Subclavius

Question 8

Lateral Pectoral Nerve

Answer 8

Origin: Lateral Cord of the Brachial Plexus

Input: C5, C6, C7

Comes off the lateral Cord at the level of the thoracoacromial truck artery at the superior edge of pec minor

Runs around pec minor into the deep surface of pec major

Motor to Pectoralis Major

Question 9

Musculocutaneous Nerve

Answer 9

Origin: Terminal Branch of the Lateral Cord of the Brachial Plexus

Input: C5, C6, C7

Pierces Coracobrachialis

Sits between the biceps brachii and brachialis muscles

Ends at the level of the elbow where it becomes the lateral antebrachial cutaneous nerve

Lateral Antebrachial Cutaneous Nerve emerges superficially lateral to the biceps between the biceps brachii and brachialis muscles; it sits on the brachialis muscle and descends in the subcutaneous tissue to the lateral aspect of the forearm until is is found superficially in the anatomic snuffbox

MC: Motor to the muscles of the anterior compartment of the arm

Lateral cutaneous: Sensory to the lateral aspect of the forearm

Question 10

Upper Subscapular Nerve

Answer 10

Origin: Posterior Cord of the Brachial Plexus

Input: C5, C6

Runs straight to subscapularis muscle

Motor to subscapularis

Question 11

Thoracodorsal Nerve

Answer 11

Origin: Posterior Cord of the Brachial Plexus

Input: C6, C7, C6

Runs inferiorly towards Latissimus Dorsi with the Thoracodorsal Artery

Motor to Latissimus Dorsi

Question 12

Lower Subscapular Nerve

Answer 12

Origin: Posterior Cord of the Brachial Plexus

Input: C5, C6

Runs parallel to the subscapular artery as it branches off the axillary artery

Gives Motor branches to Teres Major and Subscapularis

Motor to: subscapularis and Teres Major

Question 13

Axillary Nerve

Answer 13

Origin: Terminal Branch of the Posterior Cord of the Brachial Plexus

Input: C5, C6

Exits the axilla posteriorly

Found in the quadrangular space with the Posterior Circumflex Humeral Artery

Motor to Deltoid and teres minor

Sensory to GH joint

Gives a superior lateral cutaneous branch that is sensory to the area overlying the deltoid

Question 14

Radial Nerve

Answer 14

Origin: Terminal Branch of the Posterior Cord of the Brachial Plexus

Input: C5, C6, C7, C8, T1

Found in the triangular interval with the profunda brachii artery

Motor to the Muscles in the posterior compartment of the arm.

Runs in the radial groove on the posterior surface of the humerus (with the profunda brachii artery)

Pierces the lateral antebrachial septum at the level of the lateral epicondyle and come to sit anteriorly between brachioradialis and brachialis

Spilts into superficial and deep branches behind brachioradialis

Deep branch winds around the head of the radius posteriorly, pierces the supinator, and becomes the posterior interosseous nerve; this branch is motor to the muscles of the posterior compartment of the forearm

Superficial branch runs deep to brachioradials, then peeks out superficially in the lateral third of the forearm on its way to the anatomic snuffbox. Passes superficially across the anatomic snuffbox and then branches into dorsal digital nerves that are sensory to the radial side of the dorsum of the hand (radial to the line bisecting the 4th digit and proximal to the distal phalanges)

Question 15

Medial Pectoral Nerve

Answer 15

Origin: Medial Cord of the Brachial Plexus

Input: C8, T1

Pierces Pec Minor and runs through to Pec Major

Motor to Pec Major and Pec Minor

Almost always has a communicating branch with the Lateral Pectoral Nerve

Question 16

Medial Brachial Cutaneous Nerve

Answer 16

Origin: Medial Cord of the Brachial Plexus

Input: C8, T1

Often joins the INTERCOSTOBRACHIAL NERVE (T1) on its way to the subcutaneous tissue of the arm.

Sensory to the medial aspect of the arm

Question 17

Medial Antebrachial Cutaneous Nerve

Answer 17

Origin: Medial Cord of the Brachial Plexus

Input: C8, T1

Passes through the arm into the forearm

Initially runs with the ulnar nerve, but in the forearm it runs more superficially in the subcutaneous tissue

Sensory to the medial aspect of the forearm

Question 18

Intercostobrachial Nerve

Answer 18

Origin: T2 (could be T1)

Comes from the T2 intercostal space of the thoracic wall and communicates with the medial brachial cutaneous nerve.

Sensory to the medial aspect of the arm.

Question 19

Median Nerve

Answer 19

Origin: Formed by Branches of the Lateral and Medial Cords of the Brachial Plexus (forms the center of the M)

Runs anterior to the axillary artery then lateral to the brachial artery

Passes through the arm without supplying anything.

Passes in front of the brachial artery proximal to the cubital fossa, then they run together through the cubital fossa into the forearm

Passes BETWEEN THE HEADS OF PRONATOR TERES when it reaches the forearm

In the forearm, it is motor to Pronator Teres, FCR, Palmaris Longus, and FDS

Runs deep to FDS , and gives off a branch called the ANTERIOR INTEROSSEOUS NERVE, which runs along the interosseous membrane with the anterior interosseous artery. This branch is motor to the lateral part of FDP, Flexor Pollicis Longus, and Pronator Quadratus. The anterior interosseous nerve and artery pass between FDS and the tendon of FPL and descend medial to FPL in the forearm

Also gives off a palmar cutaneous branch proximal to the flexor retinaculum that goes into the center of the hand and is sensory to the palm of the hand radial to the line bisecting the 4th digit.

The continuing branch passes into the hand deep to the flexor retinaculum in the carpal tunnel. it gives off the following branches in the hand:

Recurrent branch - runs radially towards the thumb. Motor to all the thenar muscles except adductor pollicis and the deep head of flexor pollicis brevis

Medial and Lateral branches - motor to Lumbricals 1 and 2. Give off common proper digital branches which branch into proper palmar digital branches at the level of the MCP joints. These branches are sensory to the palmar surface of digits 1, 2, 3, and half of 4, and to the dorsal aspect of the distal phalanges of those digits

Question 20

Ulnar Nerve

Answer 20

Origin: Terminal Branch of the Medial Cord of the Brachial Plexus

Input: C7, C8, T1

In the arm, it initially runs medial to the brachial artery and median nerve in the ANTERIOR compartment. It then turns posteriorly, piercing the medial intermuscular septum along with the superior ulnar collateral artery.

It runs behind the medial epicondyle into the posterior compartment of the forearm, where it passes BETWEEN THE HEADS OF FLEXOR CARPI ULNARIS

It runs deep to FCU with the ulnar artery in the forearm, where it is motor to FCU and the medial half of FDP

In the forearm (before Guyon’s canal) it gives off a dorsal branch that passes into the hand posteriorly. In the back of the hand, this branch spilts into dorsal digital branches. these branches and the dorsal branch are sensory to the medial dorsum of the hand and the dorsum of the 5th and medial half of the 4th digits

Continuing Ulnar N. Passes superficial to the flexor retinaculum and deep to the palmar carpal ligament through Guyon’s canal (between the pisiform and hook of the hamate) into the palm of the hand. When it reaches the palm, it gives a PALMAR BRANCH that is sensory to the skin on the medial palm (medial to the line bisecting the 4th digit)

Continuing ulnar nerve then spits into superficial and deep branches.

Superficial branch: spilts into common palmar digital branches and then proper palmar digital branches that are sensory to the palmar surfaces of the medial 1.5 digits. (add “of the ulnar nerve” when naming)

Deep Branch: Motor to all intrinsic muscles of the hand except 2LOAF