Dermatomes

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].

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].