Vulnerability of the Brainstem-Cerebellar Respiratory Network in Extreme Prematurity

Survival of extremely preterm infants has significantly improved over the past decades, shifting critical stages of respiratory and brain development into the extrauterine environment. This transition exposes the vulnerable preterm infant to abrupt changes in oxygen tension, intermittent hypoxemia, inflammation, and oxidative stress, which contribute to maldevelopment of the structure and function of immature organs, including the brain and brainstem, with short- and long-term adverse consequences. This review examines how adverse intrauterine and extrauterine exposures during critical developmental periods in extremely low gestational age neonates (ELGANs) born <28 weeks of gestation disrupt the structure and function of key components of the central respiratory network, supporting epidemiological evidence that premature infants have a substantially increased risk of sudden unexpected infant death (SUID) during the first year of life and sleep disordered breathing across the lifespan. ELGANs are born during a period of rapid brainstem and cerebellar development, increasing the vulnerability of these regions to oxidative and inflammatory injury that can cause direct tissue damage and dysmaturation. The medullary serotonergic network and cerebellar fastigial nucleus regulate cardiorespiratory responses at rest and during progressive hypoxia and hypercapnia. We propose that adverse intrauterine and extrauterine exposures during critical developmental windows damage the macro- and microstructures, neurochemistry of these regions, impair protective respiratory responses, and mechanistically contribute to the two- to threefold higher risk of SUID in ELGANs than in term infants. We review fetal neuroprotective responses to hypoxia; the mechanisms and vulnerability of brain injury in ELGANs; the development and intrinsic hypoxic chemosensitivity of central respiratory control; and brainstem and cerebellar dysmaturation. Together, this framework provides a biological basis linking extreme prematurity to impaired ventilatory control, disordered breathing, and increased vulnerability to sudden death during infancy and beyond.