A band of skin innervated by the sensory root of a single spinal nerve is called what?

• A. Peripheral nerve field
• B. Dermatome
• C. Synapse
• D. Asterixis

Answer: (B)

Dermatomes are defined as the band of skin innervated by the sensory fibers from a single spinal nerve root. Each spinal nerve carries afferent fibers in its dorsal (sensory) root, and the skin area those fibers supply forms one dermatome. This concept helps localize neurologic or infectious processes to a specific spinal level—hence shingles (varicella-zoster) often follows a single dermatome. Dermatomes can overlap between adjacent levels, which is why symptoms may cross borders but still point to a particular spinal nerve root.

By contrast, a peripheral nerve field encompasses skin areas supplied by a peripheral nerve that draws fibers from multiple spinal levels, not just one dorsal root. A synapse is a neural connection between neurons, not a skin innervation map. Asterixis is a clinical sign of metabolic encephalopathy, not related to dermatomal distribution.