The central nervous system (CNS) is made up of the brain and spinal cord, the organs responsible for controlling all of your thoughts and actions. These critical structures have multiple levels of protection, including the hard skull and backbone and a liquid layer called cerebrospinal fluid (CSF). Some of the most important functions of CSF are to circulate nutrients to the nervous system tissue, clear waste from the area, and provide cushion to prevent physical damage.
Although the CSF is incredibly essential in keeping the CNS properly functioning and sufficiently protected, as with most things in life, too much of a good thing can cause problems. Too much CSF is often referred to as “water on the brain”, and the medical term is hydrocephalus (hydro- = water, -cephalus = head). When a baby is born with too much CSF, the condition is called congenital hydrocephalus.
The most common cause of congenital hydrocephalus is a physical disruption in the flow of CSF through the brain. The blockade can be due to a genetic mutation, an infection that leads to inflammation in the brain, or an abnormal growth in the brain, such as a tumor or cyst.
Congenital hydrocephalus may be diagnosed before or after birth. CSF not only surrounds the brain, but it also resides in the spaces within the brain called ventricles. An abundance of CSF will cause the ventricles to enlarge, which can be detected in prenatal ultrasounds beginning around 4 months of gestation. If the condition is not identified during prenatal testing, then diagnosis will likely occur shortly after birth. Because the skull has not yet fused into one complete bone at birth, babies heads can actually swell to accommodate extra CSF. Therefore, a baby with congenital hydrocephalus will have a larger head circumference at birth and/or a head that grows abnormally fast after birth to make room for the additional CSF as it accumulates. Although the baby’s head can adjust in size, the excess CSF will eventually cause enough pressure on the brain to lead to noticeable symptoms that could include downward turning of the eyes, excess sleepiness, irritability, vomiting, and seizures. The Centers for Disease Control and Prevention has published growth charts that include normative values for head circumference based on gender and age, and a size ≥ the 98th percentile will generally be flagged for follow-up testing.
Early treatment of congenital hydrocephalus is critical, as long-term buildup of CSF can lead to irreversible brain damage. Treatment of the majority of cases of congenital hydrocephalus involves surgical intervention. Most often a shunt is inserted that runs from the brain to the abdomen. This tube allows the excess CSF in the headspace to drain into the abdominal cavity, where it can be safely reabsorbed back into the body and prevent the buildup of excess pressure in the CNS. Less frequently, surgery is conducted to make a small hole in the brain that allows CSF to drain around an obstruction. Premature birth is a risk factor for congenital hydrocephalus. If a baby is born extremely early and doctors want to delay surgery until the baby is stronger or until an infection or bleeding in the brain has resolved, medication might be used in the short-term. Certain medications such as acetazolamide can decrease CSF production in the brain, while others such as isosorbide might increase CSF reabsorption. Long-term use of medication, however, is generally not included in a treatment plan for congenital hydrocephalus.
The prognosis of congenital hydrocephalus is quite good if the condition is recognized and treated quickly after birth. If your child is diagnosed with congenital hydrocephalus, your doctor will determine if the condition arose on its own or if it is due to an underlying additional condition, such as spina bifida. These factors will determine the long-term management of your child’s treatment plan and the extensiveness of a required care team.