Dermatome

Dermatomes are areas of the body where sensation is subserved by a single nerve root.

Peripheral nerves generally receive contributions from more than one dermatome.

Peripheral nerve lesions and nerve root lesions may sometimes be distinguished in part by the pattern of sensory loss. A classic example is splitting of the ring finger in median nerve or ulnar nerve lesions, which does not occur in C8 nerve root injuries.

There are 8 cervical nerves (C1 being an exception with no dermatome), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain.

A dermatome also refers to the part of an embryonic somite.

Along the thorax and abdomen the dermatomes are 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. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.