Congenital hydrocephalus is a condition present at birth in which excess cerebrospinal fluid (CSF) collects within the brain. The brain's passageways (ventricles) may not drain or absorb fluid properly, leading to increased pressure within the brain.

The most obvious symptom of hydrocephalus is an unusually large head, which will most likely be noticed at birth or within the first 9 months of life. Other symptoms in an infant may include irritability, excessive sleeping, vomiting, and poor feeding.

Congenital hydrocephalus may result from either genetic or other causes, such as prenatal hemorrhage (bleeding before birth in the fetus) or infections such as toxoplasmosis, rubella, syphilis, or mumps. It may be associated with other birth defects, especially neural tube defects.

The main way to treat hydrocephalus is with a shunt, a type of small tube that is placed in the brain to allow the excess fluid to drain so it can be absorbed. Shunts usually are permanent, but they sometimes need to be replaced because of malfunction or infection.

Left untreated, the increasing pressure caused by CSF buildup can lead to brain damage or death. With prompt diagnosis and treatment, some serious problems can be prevented or limited.