dermatoom

Dermatoom, often written dermatome in English, refers to a defined area of skin innervated by sensory fibers from a single dorsal root of a spinal nerve. The concept is used in anatomy and clinical neurology to localize lesions of the nervous system and to understand sensory patterns on the body.

In the trunk and limbs, dermatomes form longitudinal bands that typically extend from the midline outward. There is substantial overlap between adjacent dermatomes, which provides some redundancy in sensation. The spinal nerve roots involved are conventionally grouped as eight cervical, twelve thoracic, five lumbar, and five sacral. Common landmarks include C4 around the shoulder region, T4 at the nipple line, T10 at the umbilicus, L4 over the medial malleolus, L5 on the dorsum of the foot, and S1 at the lateral aspect of the foot or the posterior calf. Dermatomal maps are approximate and individual variation is common.

Clinical use of dermatomes includes localizing radiculopathy and guiding assessment of sensory loss following nerve injury or spinal cord disease. Herpes zoster (shingles) characteristically produces a painful vesicular eruption that follows a single or a few dermatomes on one side of the body. Dermatomal testing commonly involves pinprick or light touch to map sensory changes.

Variations in dermatome boundaries occur between individuals, and borders can overlap with peripheral nerve territories. The term dermatoom may reflect alternate transliteration or non-English usage; the underlying concept is dermatome.