Behavioral and Physical Concomitants of Congenital Hydrocephalus in a Rhesus Macaque (Macaca mulatta) Neonate.

A colony-born male rhesus monkey neonate was assigned to an ongoing protocol assessing behavioral and physiologic development in nursery-reared infants. It was sacrificed at day 20 because of poor weight gain, inability to self-feed, and generalized weakness. An asymmetric internal hydrocephalus was the only notable gross finding at necropsy. A retrospective analysis was performed comparing physical and behavioral measures for it with values for age-matched nursery-reared peers. Weight gain and formula intake lagged behind others in its cohort. The affected macaque spent more time in sleep and awake/quiet states and less time in an awake active state than did its peers. Behaviors during a neonatal temperament/reflex examination were indicative of high levels of irritability, poor muscular tone, nonexistent voluntary motor activity, and slower overall responding. In addition, asymmetric responses for some motor items were observed. However, vestibular/ocular reflexes appeared normal. The occasional observation of hydrocephalus in infants, as well as its prevalence throughout the primate order, indicates that hydrocephalus should be considered in the differential diagnosis for infants with feeding difficulties and motor dysfunction.