Introduction An 1-year-old boy is brought to the emergency department by his parents due to increased irritability and an "enlarging head." The parents deny any trauma but has noticed their infant appears weaker than his sister when she was his age. They did not receive adequate prenatal care due to the distance and cost to arrive to their closest obstetrician. On physical exam, the infant is inconsolable and has an increased head circumference for his age. Magnetic resonance imaging (MRI) of the head shows hypoplasia of the cerebellar vermis with cystic dilatation of the fourth ventricle leading to a non-communicating hydrocephalus. Introduction Clinical definition login to view 4 more bullets Epidemiology login to view 2 more bullets Associated conditions login to view 2 more bullets Presentation Symptoms login to view 6 more bullets Physical exam login to view 3 more bullets Imaging Prenatal ultrasound login to view 9 more bullets MRI login to view 6 more bullets Treatment Conservative login to view 9 more bullets Operative login to view 3 more bullets