Abstract
Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive disorder characterized by the absence of heat and pain sensation, sweating dysfunction, intellectual developmental disorder, and neurodevelopmental disorder. Sensory nerves involved in heat and pain perception (unmyelinated C fibers and small-diameter myelinated Aδ fibers) and unmyelinated autonomic C fibers (postganglionic sympathetic fibers) responsible for regulating sweating, are embryologically absent. In almost all cases, bilateral Horner syndrome is observed, so we analyzed autonomic nervous system dynamics using pupillometry and examined their association with the pathology. Compared with controls, the initial pupil diameter was smaller, and both the constriction and dilation velocities were lower, indicating functional alterations in the parasympathetic nervous system in addition to the sympathetic system. Given that the sympathetic nervous system contributes to establishing dyadic relationships from early infancy and that unique empathy resulting from a lack of pain perception is assumed in this condition, it is hypothesized that the autonomic nervous system, as an underlying ‘operating system’ for development, may be involved in the pathology of intellectual and neurodevelopmental disorders. Additionally, it was noted that the initial pupil diameter is important for differentiating this condition from congenital insensitivity to pain (being smaller in CIPA).
