Hydrocephalus is anticipated in approximately what percentage of infants after back closure?

• A. 70%
• B. 90%
• C. 50%
• D. 100%

Answer: (B)

The main idea here is that hydrocephalus is a very common companion to myelomeningocele due to disruption of CSF flow from Chiari II malformation. Even after the back closure repair, the factors that hinder CSF circulation often persist, leading to hydrocephalus in a large majority of infants as they grow and CSF dynamics evolve. Because of this strong association, hydrocephalus is anticipated in about nine out of ten infants with this condition. This high frequency explains why clinicians monitor head growth and plan for CSF diversion, typically with a ventriculoperitoneal shunt, soon after or within the first year of life. While it’s not universal—some infants do not develop hydrocephalus—the estimate sits in the high range, commonly cited around 70–90%, making 90% a reasonable and commonly taught figure.