Nerve Supply of the Upper Limb

• The lecture focuses on the nerve supply of the upper limb and related injuries.
• By the end of this lecture, students should be able to describe the anatomy of the nerves that supply the upper limb

Nerves of the Upper Limb

• Axillary Nerve.
• Musculocutaneous Nerve.
• Median Nerve.
• Ulnar Nerve.
• Radial Nerve.
• Focus will be on their origin, course, branches, and potential injuries.
• The upper limb receives its innervation from the brachial plexus.

Axillary Nerve

• Originates from the posterior cord of the brachial plexus at the levels of C5 and C6.
• Leaves the axilla through the quadrangular space along with the posterior circumflex humeral vessels.
• Directly related to the posterior surface of the surgical neck of the humerus.

Axillary Nerve Branches

• Muscular Branches: Supplies the deltoid and teres minor muscles.
• Articular Branches: Supplies the shoulder joint.
• Cutaneous Branches: Gives rise to the superior lateral cutaneous nerve of the arm.
• The superior lateral cutaneous nerve of the arm provides sensory innervation to the skin over the inferior part of the deltoid muscle.

Axillary Nerve Injury

• Causes: Fracture of the surgical neck of the humerus, inferior dislocation of the shoulder joint, compression from quadrangular space syndrome, or use of crutches.
• Effect: Paralysis of the deltoid and teres minor, leading to loss of the round contour of the shoulder, loss of abduction from 15-90 degrees, and sensory loss over the inferior part of the deltoid.

Musculocutaneous Nerve

• Origin: It originates from the lateral cord of the brachial plexus (C5, C6 and C7).
• Course: It penetrates the coracobrachialis muscle and passes between the biceps and brachialis muscles.
• Runs deep within the fascia and continues as the lateral cutaneous nerve of the forearm.

Musculocutaneous Nerve Branches

• Muscular: Supplies all muscles of the anterior compartment of the arm.
• Cutaneous: Becomes the lateral cutaneous nerve of the forearm.
• The lateral cutaneous nerve of the forearm provides sensory innervation for the skin on the lateral surface of the forearm.

Musculocutaneous Nerve Injury

• Causes: Can occur from direct injury or surgery, or entrapment by the coracobrachialis muscle.
• Effect: Leads to atrophy of the biceps brachii, weakness in elbow flexion and supination, and sensory loss or paresthesia in the skin at the lateral forearm.

Ulnar Nerve

• Origin: It originates from the medial cord of the brachial plexus, with nerve roots C7, C8 and T1.
• Course within the arm:
  • The ulnar nerve lies on the medial cord of brachial plexus.
  • The ulnar nerve is medial to the axillary and brachial arteries.
  • In the middle of the arm the ulnar artery penetrates the medial intermuscular septum, to inter the posterior compartment of the arm.
  • It then passes posterior to the medial epicondyle of the humerus.
• Course within the forearm:
  • The ulnar enters the anterior compartment of the forearm.
  • It then passes between the 2 heads of the flexor carpi ulnaris (FCU) muscle.
  • The ulnar artery then passed the flexor carpi ulnaris FCU and then the flexor digitorum profundus muscle

Branches in the Forearm

• Muscular branches: Supplies the flexor carpi ulnaris and the medial half of the flexor digitorum profundus.
• Dorsal branch (cutaneous): Supplies skin of the medial 1/3 of dorsum of hand and the posterior surfaces of the medial 1.5 fingers.
• Palmar branch (cutaneous): Supplies the skin of the medial 1/3 of palm.

Branches in the Hand

• Muscular branch: Supplies the palmaris brevis muscle and all intrinsic muscles in the hands, other than the thenar muscles and the lateral two lumbricals
• Cutaneous Palmar digital: Supplies the skin on the palmar surfaces of the medial one and a half fingers.

Ulnar Nerve Injury

• Causes: Elbow dislocation and fractures or long-term pressure on the elbow.
• At the Wrist Effect: Leads to paralysis of small hand muscles resulting in "Claw Hand".
  • Sensory loss in the area of the ulnar nerve.
• At the elbow Effect: Paralysis of all muscles with limited ulnar nerve supply
  • Abduction of the wrist.

Radial Nerve

• Originates from the posterior cord of the brachial plexus (C5,6,7,8,T1).
• Course in the arm: originates in the anterior compartment of the arm.
• Lies posterior to the brachial artery.
• Passes through the triangular interval with the profunda brachii artery to enter the posterior compartment of the arm.
• Lies in the radial groove directly on the bone.
• Passes through the lateral intermuscular septum to enter the anterior compartment of the arm.
• Course in the forearm: Lies between the brachialis and brachioradialis muscles.
• It divides into deep and superficial branches.

Radial Nerve Branches

• Muscles of the arm; Triceps, Brachialis, Brachioradialis, Extensor Carpi Radialis Longus (ERCL), Anconeus
• Deep Branch: Supplies the remaining muscles in the posterior compartment of the forearm.
• Gives articular Branches to the wrist.
• Enters the posterior compartment of the forearm.
• Superficial Branch: Passes into the hand
• Cutaneous Branch: The inferior lateral cutaneous nerve of the arm originates in the arm.
• The posterior cutaneous nerve of the forearm originates in the arm.
• The superficial branch innervates skin on the posterolateral surface of the hand and dorsum of the lateral 3.5 fingers, except their terminal part.

Radial Nerve Injury

• Causes are fracture mid shaft of the humerus and Compression.
• Effect: Paralysis of all the muscles on the back of the forearm causing weakness, wrist drop and finger drop and the elbow can't be extended.
• Injury to posterior interosseous nerve will cause paralysis of supinator causes failure of supination of the extended arm.