Each spinal nerve (except C1) receives sensory input from a specific area of skin called a dermatome. This dermatome map shows the cutaneous regions innervated by each spinal nerve. Yet, this map is oversimplified because there is a 50% overlap at the edges of the dermatomes. This is why it is necessary to anesthetize three successive spinal nerves to produce a total loss of sensation from only one dermatome. Spinal Nerve, Spinal Cord, Medicine