dermatomes

Dermatomes are specific areas of skin innervated by sensory fibers from a single spinal nerve root. The body is organized in a segmental pattern, with cervical, thoracic, lumbar, and sacral nerves contributing to cutaneous sensation. In healthy individuals the borders between dermatomes are not sharply defined; adjacent dermatomes overlap, providing redundancy so that sensation can be preserved even if one nerve root is only partially affected.

Dermatome maps are used clinically to localize the level of nervous system injury or disease. They help distinguish radiculopathy (nerve root involvement) from peripheral nerve lesions and guide diagnostic testing. Variation exists among individuals, and age or prior surgery can alter mapping. Although named by spinal level (for example, cervical C2–C8, thoracic T1–T12, lumbar L1–L5, sacral S1–S5), exact boundaries are approximate.

Clinical significance includes the characteristic dermatomal distribution of herpes zoster (shingles), caused by reactivation of varicella-zoster virus in a dorsal root ganglion. The rash and pain typically follow a single dermatome and do not cross the midline. Dermatomal testing—using light touch, pinprick, or temperature—can aid in assessing sensory loss and determining the injured level in cases of trauma or disease affecting the spinal cord or nerve roots.

Dermatomes are distinct from myotomes (muscle groups innervated by a single nerve root) and from purely peripheral nerve territories, though all systems interrelate in sensory and motor function.