A 5-day-old infant is diagnosed with a non-communicating hydrocephalus. Which of the following is most likely to lead to such a condition?

(a) Source: GAS 101, 834; GA 445 Non-communicating hydrocephalus, also known as obstructive hydrocephalus, is due to an obstruction to flow of CSF within the ventricular system. Excess production of CSF or disturbed resorption of CSF gives rise to communicating or non-obstructive hydrocephalus. An increased size of the head can occur as a result of hydrocephalus but would not be a causative factor for hydrocephalus. Failure of the neural tube to close may lead to anencephaly or spina bifida, depending on the portion of the tube affected, but would not result in hydrocephalus.