Pathophysiology
Clinical meaning
Neonatal reflexes, also called primitive or infantile reflexes, are involuntary motor responses to specific stimuli that are mediated by the brainstem and spinal cord. These reflexes are present at birth (or shortly after) in neurologically intact neonates and follow a predictable developmental timeline of emergence and disappearance. Their presence at the expected age indicates normal brainstem and spinal cord function, while their absence, asymmetry, or persistence beyond the expected age signals potential neurological pathology requiring further evaluation. Primitive reflexes are generated by neural circuits in the brainstem and spinal cord that operate independently of cortical (higher brain) control. As the cerebral cortex matures during the first year of life, cortical pathways develop the ability to inhibit these lower-level reflexes. This cortical inhibition causes the gradual disappearance of primitive reflexes, which is replaced by voluntary, purposeful motor behaviors. The persistence of primitive reflexes beyond their expected disappearance age suggests that cortical maturation is delayed or disrupted, as seen in conditions such as cerebral palsy, hypoxic-ischemic encephalopathy, or chromosomal abnormalities. The Moro reflex (startle reflex) is elicited by allowing the neonate's head...