Topic Overview

Dermatomes of Upper Limb

Introduction

• A dermatome is the area of skin supplied by the sensory fibers of a single spinal nerve root.

• There are 31 pairs of spinal nerves (except C1, which is motor only), and each has a corresponding dermatome.

• Dermatomes provide important clinical information:

  • Help in localizing nerve root lesions.

  • Used in neurological examination.

  • Guide for regional anesthesia.

Key Dermatomes of Upper Limb

• C3 → Root of neck, supraclavicular fossa.

• C4 → Skin over acromion, shoulder region.

• C5 → Lateral aspect of arm (upper arm, regimental badge area).

• C6 → Lateral forearm, thumb.

• C7 → Middle finger.

• C8 → Little finger, medial side of hand & forearm.

• T1 → Medial aspect of arm, near axilla.

• T2 → Axilla and upper part of chest wall (supplied by intercostobrachial nerve).

Clinical Anatomy

• Radiculopathy (nerve root compression):

  • Cervical disc prolapse can compress roots.

  • Example: C6 root compression → numbness and tingling in thumb.

  • C7 compression → symptoms in middle finger.

• Herpes Zoster (Shingles):

  • Reactivation of varicella zoster virus in dorsal root ganglion.

  • Produces painful vesicular rash restricted to one dermatome.

• Root Lesion vs Peripheral Nerve Lesion:

  • Root lesion → segmental sensory loss (dermatome).

  • Peripheral nerve lesion → patchy sensory loss (depending on nerve distribution).

  • Example: Axillary nerve injury → sensory loss only over regimental badge area, not entire C5 dermatome.

• Neurological Testing:

  • C5 → sensation over lateral upper arm.

  • C6 → sensation over thumb.

  • C7 → sensation over middle finger.

  • C8 → sensation over little finger.

  • T1 → sensation over medial forearm.

• Referred Pain:

  • Cardiac pain radiates to inner arm (T1–T2) via intercostobrachial nerve.

• Regional Anesthesia:

  • Knowledge of dermatomes essential in brachial plexus blocks and spinal/epidural anesthesia.