Fetal hydrocephalus.

Fetal hydrocephalus is a dynamic process. Its natural progression is not completely understood, but it is almost always associated with other intracranial and extracranial anomalies. Fetal hydrocephalus might begin as mild ventriculomegaly and progress to a more serious state. Mild ventricular enlargement without an increase in head size might be a normal variant. Careful prenatal evaluation is always indicated when the diagnosis of ventricular enlargement has been made, and it should include a detailed anatomic survey and genetic amniocentesis. Therapeutic options need to be discussed in detail with the patient. If multiple associated anomalies--especially other CNS anomalies--are present, the prognosis for a viable outcome is dismal. If isolated hydrocephalus is seen, gender determination is appropriate in the consideration of X-linked hydrocephalus secondary to aqueductal stenosis. Communicating hydrocephalus can also be mistaken for obstructive ventriculomegaly, but it can usually be excluded by demonstration of dilation of the subarachnoid cistern. There is a small subset of fetuses that have isolated hydrocephalus that might benefit from prenatal surgical intervention. Feasibility studies are in progress to assess the therapeutic benefit of this type of therapy. Gestational age requirements and strict criteria are being evaluated. As with the multiple therapies discussed in this issue, many interventions are becoming more and more feasible, and antenatal surgery is likely to be limited only by the ability to think imaginatively and to act creatively.