Dermatome

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A Dermatome is an area of skin associated with a pair of dorsal roots from the spine. The significance of dermatomic regions is important as pain in a dermatomic area may indicate spinal damage or neurological stenosis. A compressed spinal nerve may show as pain elesewhere on the body, according to the dermatomic area covered by the compressed nerve. A similar area innervated by peripheral nerves is called a peripheral nerve field.

The body can be divided into regions that are mainly supplied by a single spinal nerves. There are eight cervical (one for the head, and one for each cervical vertebra), twelve thoracic, five lumbar and five sacral spinal nerves.

This innervates the body in a patterned form. Along the thorax and abdomen it is simply like a stack of discs forming a human, each supplied by a different spinal nerve.

Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs.

Clinical significance

Dermatomes are useful in neurology for finding the site of damage to the spine. viruses that infect spinal nerves such as Herpes zoster infections (shingles), can reveal their origin by showing up as a painful dermatomic area. Herpes zoster, a virus that is dormant in the dorsal root ganglion, migrates along the spinal nerve to affect only the area of skin served by that nerve. Symptoms are usually unilateral but in the immune suppressed, they are more likely to become bilateral and symmetrical, meaning that the virus is present in both ganglia of a dorsal root ganglion pair.