What is hydrocephalus?
The brain and spinal cord are surrounded by cerebral spinal fluid. Small chambers in the brain are called ventricles. Normally, cerebral spinal fluid is produced primarily in the two lateral ventricles. Then, the cerebral spinal fluid drains through the third and fourth ventricles and is circulated around the brain and spinal cord. This cerebral spinal fluid acts as a cushion for the brain and is reabsorbed by the membrane covering the brain. With hydrocephalus, the cerebral spinal fluid backs up in the ventricles, causing them to expand and push on the surrounding brain. This increased size in the ventricles may be referred to as ventriculomegaly. Ventriculomegaly occurs when the two lateral ventricles are greater than 1 cm in width but less than 1.5 cm. Sometimes ventriculomegaly will regress or return to normal size and there is no long-term problem. Hydrocephalus occurs when the two lateral ventricles are greater that 1.5 cm in width. The ventricles can fill to such an extent that the head size becomes enlarged in the fetus. The major causes of hydrocephalus include:
- The flow of cerebral spinal fluid is blocked.
- Abnormal circulation of cerebral spinal fluid causes inadequate absorption by the membranes covering the brain.
- The brain size is small (cerebral atrophy or there is a localized injury) and the fluid volume appears large as it fills in space.
- Very rarely, it may be inherited.
Cerebral spinal fluid production normally increases late in gestation so the ventricles and head size need close monitoring to determine whether there is really a concern. Ventriculomegaly may be the first sign of another anomaly, either with the central nervous system or outside the central nervous system. It is estimated that 50 to 80 percent of fetuses with hydrocephalus will have another anomaly outside the central nervous system and approximately a third will have an associated anomaly within the central nervous system. Hydrocephalus occurs more frequently in males (64 percent males versus 36 percent females). Hydrocephalus occurs in approximately 1 out of every 2,000 live births. We do not know the cause of hydrocephalus. We know it is not related to anything the mother did or did not do during pregnancy.
Prenatal diagnosis of hydrocephalus:
Hydrocephalus may be diagnosed on a routine ultrasound. The ventricles within the head will measure larger than normal. The head circumference may remain within the normal limits or it may become enlarged as the pregnancy progresses. Your obstetrician will likely refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists. The perinatologist will perform a targeted ultrasound to examine the anatomy of the brain to confirm ventriculomegaly. They will also be looking for any associated anomalies.
Hydrocephalus is occasionally associated with chromosomal abnormalities. The perinatologist typically will offer an amniocentesis to look for chromosomal issues. Another test that may be recommended is a fetal MRI. Ultrasound imaging can be limited by the mother's body habitus, the surrounding amniotic fluid and the position of the fetus. Fetal MRI is a non-invasive diagnostic test that produces better images of soft tissue, and bone or dense tissue does not interfere with the image. The biggest limitation of fetal MRI is that the best images are obtained when the fetus stays still.
How does hydrocephalus affect my baby?
The amount of pressure on the brain from the increased size of the ventricles can impact the affect hydrocephalus has on your baby.Most children with simple hydrocephalus (no associated anomalies) that is diagnosed and treated early will function normally.Approximately 75 percent of children with hydrocephalus will have some form of motor disability.Many will have some type of learning disability.
How does hydrocephalus affect my pregnancy?With the finding of ventriculomegaly on a routine ultrasound, your physician may refer you to a specialist who manages high-risk pregnancies. These physicians are called perinatologists. The perinatologist will perform a targeted ultrasound to examine the anatomy of the brain to confirm ventriculomegaly. the perinatologist will also look for any associated anomalies, which have been reported in 54 to 84 percent of hydrocephalus cases. These associated anomalies may be disorders within the brain (intracranial) or disorder outside of the brain (extracranial). Between 12 and 25 percent of cases also have an associated genetic disorder.
It is important to rule out an intrauterine infection such as cytomegalovirus, toxoplasmosis, syphilis, intracranial hemorrhage and tumor of the central nervous system. These causes of hydrocephalus typically lead to increased size in the lateral ventricles but not an increase in the head size. This is because the cerebral spinal fluid is filling in space from damage caused to the brain from the infection or injury. Often, these babies will have microcephaly or a smaller than average size head.
Extracranial abnormalities have been seen in as many as two-thirds of babies with hydrocephalus. The major extracranial defect associated with hydrocephalus is mylomeningocele.
Your baby's head growth and ventricle size will be monitored closely throughout the remainder of the pregnancy. The method of delivery is determined by the baby's head size and his or her well-being at the time of labor and delivery, as with any pregnancy. Hydrocephalus does not, by itself, necessitate a Caesarian section delivery.
How is hydrocephalus treated?
Treatment will be necessary if the ventricles continue to expand and the head circumference grows too fast. Your baby will be evaluated after birth for the need of a shunt. If a shunt is deemed necessary, your baby will need surgery. A shunt is a thin tube. One end of this tube is placed in the ventricle and the other end is passed underneath the skin and drains into the abdominal cavity where the body can reabsorb the cerebral spinal fluid. As the baby grows, the shunt will need to be replaced approximately every two to four years.
If the ventricles are thought to be large because of severe brain damage, we can openly discuss other treatment options such as palliative care.
What about after surgery?
If it is determined a shunt is necessary, your baby will need surgery. After surgery the baby may need some help breathing. A special tube is placed in surgery and may stay in place until your baby is able to breath effectively on his or her own.
Some special IV lines may also by placed. The umbilical cord normally has two arteries and one vein. A line may be placed in the vein as a means to provide nourishment until the baby is able to eat. Another line may be placed in one of the arteries. This is called an arterial line. Fluids and medication can be given through this line as well as blood pressure monitored and blood removed for lab work.
Until the baby is able to eat it will receive total parenteral nutrition. This is an IV solution that contains protein, fats, sugar, vitamins, and mineral. It will supply all your baby's nutritional requirements until he or she is able to take food by mouth.
Your baby will be observed for infection, proper shunt drainage and the head circumference will be monitored. You will be able to start learning how to care for, feed and monitor your baby in preparation for when he or she goes home. Sometimes the shunt can become clogged or may stop draining effectively, which causes an increase in the pressure inside your baby's head. You will be trained to recognize signs and symptoms of this and other potential complications.
Will I be able to care for my baby?
Yes. Please ask your baby's nurse about ways to interact with and care for your baby. If you had planned to breastfeed your baby, you can begin to pump and freeze breast milk while you are still in the hospital. A lactation consultant can assist in answering your questions. Your milk will be frozen and stored in the Neonatal Intensive Care Unit until your baby is ready for it. The NICU has breast pumps and private rooms available to you when you are visiting. You can bring in pictures, small toys, booties and blankets for your baby while he or she is in the NICU.
When can my baby go home?
Your baby will go home when he or she is eating and tolerating enough food to maintain and allow them to grow and gain weight. A baby with simple hydrocephalus that requires shunt placement may be home within two weeks. If there are any other complicating defects, the stay would be prolonged according to the severity of those anomalies.
If you have decided to pursue palliative care for your baby, you also have the option of taking your infant home with the support of hospice services. This option will be discussed with you.
What is my baby's long term prognosis?
Prognosis is dependent on any associated defects that may be related to the cause of hydrocephalus as well as the amount of pressure exerted on the brain tissue prior to shunting. The affects of hydrocephalus vary and is partly dependent on the cause and treatment required, as well as your baby's response to treatment. The key to a good prognosis is early detection and treatment and the prevention of infections. Most of the newborns born with hydrocephalus will have a normal lifespan and approximately 40 to 50 percent will have normal intelligence. Seizure disorders have been diagnosed in about 10 percent of these children. The mortality rate for infants with hydrocephalus is approximately 5 percent.
Studies have shown that the risk of shunt failure in the infant's first year is 30 percent. Shunts, on average, are revised about two times in the first 10 years. The risk of intellectual disability is approximately 35 percent. Your baby's pediatrician and pediatric neurologist will provide follow-up care once your baby is home.
Learn more about the Craniofacial Clinic at Children's Hospital of Wisconsin.