[Anatomical route of pain in premature newborn infants]

Recent research about nociceptive pathways in newborn infants have shown that, even very immature, preterm infants have all the anatomical and functional components required for the perception of painful stimuli. However, the perception of pain in preterm infants is thought to be slightly different from that of term infants: because of a lack of myelination of their sensitive fibers and a still immature cortical organization of the somatosensory system, painful stimuli are perceived more widespread and durable. In addition, the threshold of pain seems to be lower in premature infants, probably due to a lack of protection of their spinal and supraspinal inhibitory pathways. Finally, abnormal behavioural imprinting secondary to early painful stimuli is now suggested. Thus in contrast with the former misconception of "insensitivity towards pain", premature infants must be now considered as "hypersensitive" and vulnerable.