Congenital Hydrocephalus: Diagnosis

Most cases of congenital hydrocephalus are diagnosed during a physical exam soon after birth based on the larger-than-normal size of the baby's head. In rare cases, a diagnosis is made later in childhood. There may be reasons other than congenital hydrocephalus for why a baby has a larger-than-normal head.
With sophisticated imaging technologies, congenital hydrocephalus can be detected in a fetus as early as the third or fourth month of pregnancy. By the fifth or sixth month, abnormal dilation of brain cavities is more clearly detectable. Tests to identify the condition include:

• Ultrasound -- Performed by a radiologist or perinatologist, this test will establish if there is an abnormal collection of fluid but may not show the obstruction. Imaging tests are usually done to see whether congenital hydrocephalus is a possibility.

• Amniocentesis -- This, or a needle aspiration of intrauterine fluid, may be performed to detect the presence of other birth defects associated with hydrocephalus.

Congenital hydrocephalus, however, is frequently diagnosed at birth or shortly after. Sometimes it's not diagnosed until after birth.

A computed tomography (CT) scan, magnetic resonance imaging (MRI), or ultrasound may be done to help confirm the diagnosis or to provide a more detailed picture of the brain and its structures.