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What Is It?

Congenital hydrocephalus refers to an abnormality of the normal flow of fluid in and around the brain which is present from the time of birth. While some of the causes may overlap, it should be distinguished from adult hydrocephalus which is acquired later in life.

Hydrocephalus is a condition which is characterized by an abnormality in the normal flow of cerebrospinal fluid, the water-like liquid which surrounds the brain and spinal cord and fills the ventricles, the fluid-filled spaces within the brian. Blockage of the normal flow or re-absorption of this fluid leads to a build up of fluid which causes an increase in pressure within the skull. This increased pressure can increase the size of the ventricles and put pressure on the brain, leading to neurological symptoms.

Congenital means a condition which is present at or around the time of birth. Therefore, congenital hydrocephalus refers to hydrocephalus which occurs in very young children, starting at or around the time of birth. This specific type of hydrocephalus can have several different causes:

• Hemorrhage: In some children, bleeding into the fluid-filled spaces in the brain at or around the time of birth can lead to hydrocephalus. This type of hemorrhage is more common in premature infants and can be termed perinatal hemorrhage or germinal matrix hemorrhage.
• Birth Defects or Malformations: Some congenital malformations of the nervous system may be associated with pediatric hydrocephalus. For example, some forms of spina bifida can be associated with hydrocephalus. Malformations of the normal anatomy of the ventricles in the brain can also lead to the blockage of fluid flow and absorption. One example of this is congenital aqueductal stenosis.
• Infection: Some congenital infections, such as toxoplasmosis, rubella or mumps, can lead to congenital hydrocephalus. Additionally, as in adults as well, bacterial meningitis in a young infant, an infection in the fluid space around the brain and spinal cord, can lead to pediatric hydrocephalus.
• Tumor: Rarely, a brain tumor which blocks the normal flow of cerebrospinal fluid can cause hydrocephalus in a newborn. An example is a tumor of childhood called a medulloblastoma. While it is more common for these to present later in childhood, they can occasionally present at birth.

• Idiopathic: Some forms of congenital hydrocephalus may not have an obvious cause. These cases may be related to genetic or other factors which are not easily identified. Medical conditions for which we do not know or understand the cause are termed idiopathic.

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What Types of Symptoms Are Typical?

In very young children, the increased pressure of pediatric hydrocephalus leads to enlargement of the head which can be noticeable at birth or may progressively enlarge so that it is noticeable later. The reason for this is that the bones of the skull are not yet fused together. Therefore, pressure in the head pushes them apart, enlarging the skull. Additionally, the soft spot on the top of the baby's head (the fontanelle) can feel very firm or bulge out.

As the pressure in the head increases it can cause other symptoms such as vomiting, irritability, lethargy, and poor feeding. The pressure can also cause a disorder of the movements of the eyes so that it is difficult for the baby to look up and it appears that they are gazing downward most of the time.

In children while more minor forms of hydrocephalus or who develop the condition later, after birth, it may not present itself until later with head growth that is beyond what should be expected for the child's age and developmental delay.

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How Is The Diagnosis Typically Made?

Congenital hydrocephalus is often diagnosed early after birth by a physical examination demonstrating an increased head size followed by some form of imaging study which reveals larger than normal ventricles. In a young infant this can often be done with an ultrasound test which uses a small probe to obtain images of the baby's brain through the soft spot on the top of their head. Alternatively, a CT scan or MRI scan can also reveal the abnormality.

In the case that congenital hydrocephalus is not detected at birth, regular measurement of the circumference of the head of the growing child at regular doctor visits will usually demonstrate that the head is growing faster than the rest of the body for the child's age. This will prompt one of the imaging studies discussed above.

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What Are Some Common Treatments?

Treatment of congenital hydrocephalus varies depending on the cause and the specifics of each case. In general, most cases will require some means of removing the excess fluid which is building up and causing pressure in the head. This generally means implanting a device called a shunt. This consists of a rubber catheter which is placed within the brain and is tunneled under the skin, shunting the fluid down to the abdomen. These so-called ventriculoperitoneal shunts help to divert the excess fluid to somewhere where it can be absorbed, decreasing the pressure in the head. In some cases the fluid is drained externally for some period of time prior to implanting the shunt.

In the case of other diseases such as infection or a brain tumor the treatment plan may vary considerably. The specific treatment is highly variable and is tailored to the specific needs of each patient. These treatment plan decisions should be discussed with the patient's own physician team and cannot be generalized.