Dermatomic area

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Dermatomic area (also known as a dermatome) is an area of skin that is supplied by a single pair of dorsal roots. An area innervated by peripheral nerves is a peripheral nerve field.

The body can be divided into regions that are mainly supplied by a single spinal nerve. 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.

[edit] Clinical significance

Dermatomes are useful in neurology for finding the site of damage to the spine.

Herpes zoster infections (shingles) can reveal dermatomic areas. 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 can be bilateral and symmetric, meaning that the virus is present in both ganglia of a dorsal root ganglion pair.

[edit] Additional images

Sensory areas of the head, showing the general distribution of the three divisions of the fifth nerve.	Distribution of cutaneous nerves. Ventral aspect.	Distribution of cutaneous nerves. Dorsal aspect.	Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Anterior view.
Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Posterior view.	Diagram of segmental distribution of the cutaneous nerves of the right lower extremity. Front view.	Diagram of the segmental distribution of the cutaneous nerves of the right lower extremity. Posterior view.	Diagram of the segmental distribution of the cutaneous nerves of the sole of the foot.