Topic Overview

⚡ Nerves of the Hand

---

Overview

The hand is richly supplied by three major nerves:

1. Ulnar nerve – chief nerve of the hand (supplies most intrinsic muscles).

2. Median nerve – supplies the thumb, index, and middle fingers (precision grip).

3. Radial nerve – purely sensory in the hand (to dorsum of thumb region).

---

1. Ulnar Nerve

---

Root Value

• C8 – T1 (branch of medial cord of brachial plexus).

---

Course in Hand

1. Enters palm superficial to the flexor retinaculum through the ulnar (Guyon’s) canal, lateral to the pisiform bone and medial to the ulnar artery.

2. At the level of pisiform → divides into:

   • Superficial terminal branch (mainly sensory).

   • Deep terminal branch (mainly motor).

---

Branches

A. Superficial Branch

• Muscular branch → Palmaris brevis.

• Digital branches →

  • Common palmar digital nerve → divides into proper digital nerves for:

    • Medial 1½ fingers (little + half of ring finger).

  • Supply skin of palmar and dorsal aspects of these fingers.

B. Deep Branch

• Passes between abductor and flexor digiti minimi → accompanies deep branch of ulnar artery.

• Supplies:

  • All hypothenar muscles (3).

  • 3rd & 4th lumbricals.

  • All interossei (palmar and dorsal).

  • Adductor pollicis.

  • Deep head of flexor pollicis brevis.

---

Area of Sensory Supply

• Palmar surface: medial 1½ fingers and adjoining palm.

• Dorsal surface: medial 1½ fingers up to distal interphalangeal joints.

---

Clinical Anatomy of Ulnar Nerve

---

1. Sites of Injury

• At elbow (cubital tunnel).

• At wrist (Guyon’s canal).

---

2. Ulnar Nerve Injury at Elbow

Causes: Fracture or dislocation near medial epicondyle.
Effects:

• Paralysis of flexor carpi ulnaris & medial half of FDP.

• Loss of finger adduction & abduction (interossei).

• Claw hand deformity: hyperextension at MCP & flexion at IP joints of ring and little fingers.

• Sensory loss in medial 1½ fingers.

---

3. Ulnar Nerve Injury at Wrist (Guyon’s Canal Syndrome)

Causes: Compression in ulnar canal by ganglion or occupational trauma.
Effects:

• Intrinsic hand muscle weakness (except lateral two lumbricals & thenar muscles).

• Sensory loss limited to palmar side (dorsum spared).

• Flattening of hypothenar eminence.

---

4. Clinical Tests

• Froment’s Sign: Patient grips paper between thumb and index; flexion of thumb IP joint = adductor pollicis paralysis.

• Card Test: Paper between fingers slips easily → interossei weakness.

---

---

2. Median Nerve

---

Root Value

• C5 – T1 (from lateral and medial cords of brachial plexus).

---

Course in Hand

1. Enters hand deep to the flexor retinaculum through the carpal tunnel.

2. Lies beneath palmar aponeurosis and divides into:

   • Recurrent (thenar) branch → motor.

   • Digital branches → sensory and lumbrical branches.

---

Branches

A. Muscular Branch (Recurrent Thenar Branch)

• Curves upward to supply:

  • Abductor pollicis brevis.

  • Opponens pollicis.

  • Superficial head of flexor pollicis brevis.

---

B. Digital Branches

• Emerge beneath palmar aponeurosis.

• Supply:

  • Lateral two lumbricals.

  • Palmar skin of lateral 3½ fingers.

  • Dorsal nail beds of same fingers (via distal branches).

---

Area of Sensory Supply

• Palmar: Lateral 3½ digits (thumb → radial half of ring finger).

• Dorsal: Terminal phalanges of same digits.

• Palm: Lateral two-thirds via palmar cutaneous branch.

---

Clinical Anatomy of Median Nerve

---

1. Carpal Tunnel Syndrome

Cause: Compression beneath flexor retinaculum (commonest site).
Features:

• Tingling & numbness in thumb, index, middle, and half of ring finger.

• Weakness or wasting of thenar muscles.

• Loss of thumb opposition (flat thenar = ape-hand deformity).

• Sensory sparing of thenar skin (palmar cutaneous branch lies superficial).

---

2. Median Nerve Injury at Elbow (Supracondylar Fracture)

Effects:

• Loss of pronation (pronator teres & quadratus).

• Wrist flexion weak and deviated to ulnar side.

• Loss of flexion of thumb & index (FPL + lateral FDP).

• Hand of Benediction: seen when patient tries to make a fist → index & middle fingers remain extended.

---

3. Anterior Interosseous Nerve Lesion

Effect: Loss of flexion at thumb IP & index DIP → “Pinch sign” (unable to make OK gesture).

---

4. Clinical Tests

• Opposition Test: Ask patient to touch thumb to little finger → fails in median nerve palsy.

• Thumb abduction test: Raise thumb perpendicular to palm → weak in carpal tunnel syndrome.

• Benediction test: Attempt to make fist → failure of index & middle finger flexion.