Principles & Practice of Pain Medicine > Part V. Pain Syndromes > E. Pediatric and Geriatric Pain > Chapter 53. Acute Pain Management in Infants and Children Christine D. Greco, Moris M. Aner, and Alyssa LeBel

Developmental Anatomy and Neurochemistry

"The late fetus and infant are neurologically sophisticated in their ability to transmit pain signals and respond to stress.¹ Cutaneous sensory nerve terminals are present in the perioral region at 7 weeks' gestation and spread to all body areas by 20 weeks' gestation. Nerve growth factors regulate the extension of peripheral nociceptive fibers into the dorsal spinal cord, with the larger A fibers entering prior to the C fibers at 8 to 12 weeks. At birth, A and C fiber territories overlap in the developing substantia gelatinosa.² Therefore, the neonatal response to a nonspecific sensory stimulus is low threshold, nonspecific, and poorly organized. Noxious and non-noxious stimuli produce similar physiologic and behavioral infant responses, complicating an accurate assessment of pain...."