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Dermatomes

Authors: Claire Jordan Wiggins, Riyad N.H. Seervai, Medical Students, Baylor College of Medicine, Houston, TX, USA. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. June 2020.


What is a dermatome?

A dermatome is an area of skin that is primarily supplied by a single nerve root: communicating sensation from this skin region to the brain. The umbrella of somatosensation includes feedback from mechanoreceptors, thermoreceptors, proprioceptors, pain receptors, and chemoreceptors [1].

Dermatomes

Credit: https://www.grepmed.com/images/2963/dermatomal-dermatomes-diagnosis-cutaneous-anatomy-nerves-roots

Where are dermatomes located?

Dermatomes form a stack of horizontal layers on the trunk and run lengthwise in the extremities.

  • There are eight cervical nerves (although C1 does not have its own dermatome), 12 thoracic nerves, 5 lumbar nerves, and 5 sacral nerves.
  • The 5th cranial nerve is divided into three divisions; V1, V2, and V3, which are responsible for sensation in the face.
  • Contiguous dermatomes overlap, and each individual’s exact dermatomal pattern is unique [1].

What is the clinical relevance of dermatomes?

Knowledge of dermatomes aids in the diagnosis of several diseases.

  • Herpes zoster (shingles), a viral infection caused by varicella-zoster virus. The virus can lie dormant in the spinal nerve ganglia, producing a rash and pain along the corresponding dermatome [2].
  • Lumbar radiculopathy, a radiating back pain extending down a dermatome is due to compression of a spinal nerve root (sciatica) [3].
  • Referred pain from a visceral organ can be perceived at a location other than the site of the stimulus or origin in a nearby dermatome [4].

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References

  1. Whitman PA, Adigun OO. Anatomy, Skin, Dermatomes. 2019. Available at: www.ncbi.nlm.nih.gov/pubmed/30571022 [accessed February 4, 2020].
  2. Cohen KR, Salbu RL, Frank J, Israel I. Presentation and management of herpes zoster (shingles) in the geriatric population. PT 2013; 38: 217–27. PubMed Central
  3. Gore S, Nadkarni S. Sciatica: detection and confirmation by new method. Int J Spine Surg 2014; 8: 15. DOI: 10.14444/1015. PubMed
  4. Fernández-de-las-Peñas C, Dommerholt J. Basic concepts of myofascial trigger points (TrPs). In: Trigger Point Dry Needling: An Evidence and Clinical-Based Approach. Elsevier; 2013: 3–19. DOI: 10.1016/B978-0-7020-4601-8.00001-3. Available at: www.researchgate.net/publication/287266879_Basic_concepts_of_myofascial_trigger_points_TrPs [accessed June 4, 2020].

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