Hydrocephalus is a condition in which cerebrospinal fluid accumulates within the ventricles of the brain, causing them to dilate and potentially compress the surrounding brain tissue. On neonatal cranial ultrasound, hydrocephalus is diagnosed by measuring the ventricular dimensions and calculating the ventricular-to-hemispheric ratio. Causes include intraventricular hemorrhage, congenital malformations, infection, and tumors that obstruct the normal flow of cerebrospinal fluid. On prenatal ultrasound, ventriculomegaly, defined as a lateral ventricle measuring greater than 10 millimeters at the level of the atrium, is an important finding that prompts further evaluation for underlying causes. Serial ultrasound measurements track the progression of hydrocephalus and help guide decisions about the need for surgical intervention.
Sonography Term