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Dermatomes

The dermatomes is a word of greek origin which means ‘areas of skin’. Dermatomes are indeed specific theoretical areas upon the human body that are derived from the cells of a certain somite. The areas are spread out according to the dominant spinal nerve that happens to innervate it.

Pathological processes, mostly viral infections, that occur in certain spinal nerve or its ganglion, most often manifest as the skin lesions within the belonging dermatome, so by being familliar with location of specific dermatomes, you will diagnose a condition easily.

Key Facts
Thorax, neck and upper extremity dermatomes C2 - occipital protuberance
C3 - supraclavicular fossa
C4 - acromioclavicular joint
C5 - lateral antecubital fossa
C6 - thumb
C7 - middle finger
C8 - little finger
T1 - medial antecubital fossa
T2 - apex of the axilla
Pelvis and lower extermity dermatomes L1 - upper anterior thigh
L2 - middle anterior thigh
L4 - medial malleolus
L5 - dorsum of 3rd metacarpal joint
S1 - lateral heel
S2 - popliteal fossa
S3 - ischial tuberosity
S4 - perineal area
Facial dermatomes Ophthalmic nerve V1 - upper face
Maxillary nerve V2 - mid face
Mandibular nerve V3 - lower face
Clinical relation Herpes Zoster infection

This article will discuss the distribution and importance of dermatomes.

Overview

Recommended video: Structure of spinal cord
Full structure of the spinal cord seen from a dorsal view.

The spinal cord has thirty one segments, each with its own bilateral anterior and posterior pair of nerve roots that innervate the anatomical structures with motoric and sensory fibers. The clinical significance of a dermatome is that when a dermatological case presents itself, a rash for example, that is limited to a single dermatome, that outer clinical symptom may indicate the pathological involvement of its related spinal root.

Overview of dermatomes

Dermatome Test Points

A system of points on the body within the region of a dermatome has been devised so that those without direct access to a dermatome map have the ability to localise the pain and correctly diagnose the nerve that may be affected. Here is a list of the dermatome test points, organized by the spinal root that governs each dermatome, along with an approximation of the area that it covers. The list runs through the spinal nerves in a cranial to caudal direction.

Upper Body

  • C2 - Occipital Protuberance
  • C3 - Supraclavicular Fossa
  • C4 - Acromioclavicular Joint
  • C5 - Lateral Antecubital Fossa
  • C6 - Thumb
  • C7 - Middle Finger
  • C8 - Little Finger
  • T1 - Medial Antecubital Fossa
  • T2 - Apex of the Axilla

Lower Body

  • L1 - Upper Anterior Thigh
  • L2 - Mid Anterior Thigh
  • L3 - Medial Femoral Condyle
  • L4 - Medial Malleolus
  • L5 - Dorsum of the third Metacarpal Joint
  • S1 - Lateral Heel
  • S2 - Popliteal Fossa
  • S3 - Ischial Tuberosity
  • S5 - Perianal Area

Face

There are three other dermatome test points that are governed not by the spinal roots but the trigeminal nerve (CN V). The three trigeminal divisions are responsible for the innervation of the face.

Herpes Zoster

Herpes Zoster, or shingles is a viral infection that is limited to one side of the body, usually within the dermatome of the nerve it has affected. A red, painful blistering rash forms due to the presence of the varicella zoster virus (VZV), which is the adult form of the virus that causes chickenpox. It sits latent upon the nerve ganglia and can arise in times of stress or when the immune system is low. The condition usually clears up within a month, although some patients can suffer for years due to nerve damage known as postherpetic neuralgia.

Dermatomes - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 931,206 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

Author:

  • Dr. Alexandra Sieroslawska

Illustrators:

  • Overview of dermatomes - Irina Münstermann
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related diagrams and images

Structure of the spinal cord

Spinal cord in situ

Dermatomes

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