The Cutaneous Innervation of the Upper Limb

Shoulder Region

The cutaneous sensation to the shoulder region is supplied mainly by the supraclavicular nerve, axillary nerve, and intercostobrachial nerve.

• Supraclavicular nerves (C3–C4) – arise from the cervical plexus and supply the skin over the clavicle, upper pectoral region, and superior shoulder.
• Axillary nerve (C5–C6) – arises from the posterior cord of the brachial plexus and gives rise to the upper lateral cutaneous nerve of the arm. This branch supplies skin over the lower part of the deltoid muscle (the regimental badge area).
• Intercostobrachial nerve (T2) – the lateral cutaneous branch of T2 and supplies the axilla and proximal medial arm.

By TeachMeSeries Ltd (2025)

Fig 1
Peripheral nerve cutaneous innervation to the upper limb

Upper Arm

In the upper arm, sensory supply is delivered through branches of the radial nerve, the medial brachial cutaneous nerve, and communicating branches from the intercostobrachial nerve.

The radial nerve gives rise to two main branches that supply sensation to the upper arm:

• Lower lateral cutaneous nerve of the arm – supplies the lower lateral aspect of the upper arm.
• Posterior cutaneous nerve of the arm – supplies the posterior aspect of the upper arm.

The medial cutaneous nerve of arm is a direct branch of the medial cord of the brachial plexus, containing fibres from C8 and T1. It supplies the medial arm and overlaps with the intercostobrachial nerve.

The medial cutaneous nerve of the forearm primarily supplies the forearm but may also contribute sensory fibres to the distal medial upper arm, creating additional overlap in this region.

Forearm

The forearm is supplied by the lateral, medial, and posterior antebrachial cutaneous nerves.

• Lateral cutaneous nerve of forearm – the terminal sensory branch of the musculocutaneous nerve and supplies the lateral forearm.
• Medial cutaneous nerve of forearm – direct branch of the medial cord of the brachial plexus, containing fibres from C8 and T1. It supplies the anterior and posterior medial forearm.
• Posterior cutaneous nerve of forearm – arises from the radial nerve and supplies the posterior forearm to the wrist.

Hand

The cutaneous innervation of the hand is provided primarily by the median, ulnar, and superficial branch of the radial nerve.

Sensation is ultimately delivered to the digits via common palmar digital nerves (which run in the palm) and proper palmar digital nerves (which supply the sides of each finger).

Median Nerve

The median nerve arises from both the lateral and medial cords of the brachial plexus, containing fibres from C5–T1. Proximal to the carpal tunnel, it gives rise to the palmar cutaneous branch – which runs superficial to the flexor retinaculum to innervate the palm.

After passing through the carpal tunnel, the nerve gives off sensory branches that supply the digits:

• Lateral branch – gives proper digital nerves to the palmar aspect of the thumb and the radial side of the index finger.
• Medial branch – gives two common palmar digital nerves. Each divides into proper palmar digital nerves that supply:
  • Ulnar side of the index finger and radial side of the middle finger.
  • Ulnar side of the middle finger and radial side of the ring finger.

The median nerve also gives dorsal digital branches to the nail beds of the thumb, index finger, middle finger, and radial side of the ring finger.

Ulnar Nerve

The ulnar nerve arises from the medial cord of the brachial plexus (C8–T1). It gives off a palmar cutaneous branch in the distal forearm that supplies the hypothenar region of the palm, and a dorsal cutaneous branch that supplies the dorsoulnar hand and proximal phalanges of the ring and little fingers.

After passing through Guyon’s canal at the wrist, it divides into a superficial branch (sensory) and a deep branch (motor). The superficial branch gives rise to:

• Common palmar digital nerve – bifurcates into proper digital nerves that supply the ulnar side of the ring finger and radial side of the little finger.
• Proper palmar digital nerve – for the ulnar side of the little finger.

It also contributes dorsal digital branches to the dorsal aspects of these digits.

Superficial Radial Nerve

The superficial branch of the radial nerve arises from the radial nerve in the proximal forearm. It travels deep to brachioradialis before emerging near the wrist.

It supplies the dorsolateral hand, including the dorsal thumb and the proximal dorsal aspects of the index, middle, and radial side of the ring finger. The fingertips of these digits are instead innervated by the median and ulnar nerves.

Dermatomes

Dermatomes refer to a region of skin supplied by nerve fibres from a spinal root. They are most commonly used when assessing for spinal cord pathology

The dermatomes of the upper limb are as follows:

• C4 – superior shoulder
• C5 – lateral upper arm
• C6 – lateral forearm and thumb
• C7 – index and middle fingers
• C8 – little finger and medial hand
• T1 – medial forearm
• T2 – distal medial upper arm
• T3 – proximal medial upper arm and axilla