Most cases of hydrocephalus are a result of developmental malformations. Although the defect usually is apparent in early infancy, it may become evident at any time from the prenatal period to late childhood or early adulthood. Other causes include neoplasms, CNS infections (e.g., meningitis, encephalitis), and trauma (e.g., shaken baby syndrome). An obstruction to the normal flow can occur at any point in the CSF pathway to produce increased pressure and dilation of the pathways proximal to the site of obstruction. Table 11-3 describes the most frequent sites of obstruction and the consequences.