Dermatomic area

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.

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

Conversely, herpes zoster infections, colloquially known as shingles, can reveal dermatomic areas. Herpes zoster is a virus that is dormant in the dorsal root ganglion and migrates along the spinal nerve to irritate 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.

Important dermatones:

• T4 - nipples.
• T6 - xiphoid process.
• T10 - umbilicus.
• L1 - pubic bone area.