Hydrocephalus literally means “water on the brain.” In this case, though, the “water” is really a fluid that protects the brain. Hydrocephalus occurs when fluid builds up in the ventricles (cavities) deep in the brain, putting extra pressure on the brain.
The brain floats in the cerebrospinal fluid (CSF) so that its weight doesn’t cut off blood supply to the lower parts. CSF also serves as a cushion to stop contact of the brain with the hard, boney skull. The fluid’s constant circulation around the brain and spinal cord provides nutrients and removes waste products.
Too much of this fluid leads to an abnormal enlargement of the head. Think of blowing up a balloon in a container. Eventually the balloon gets too big and has nowhere to go. The pressure keeps building up until something breaks.
Hydrocephalus can permanently damage the brain, leading to severe problems with mental and physical development.
There are two main types in infants and children.
- Congenital hydrocephalus is present at birth. It can be the result of some diseases the mother had during pregnancy, such as rubella. There can be a hereditary reason passed down in families. In other cases, a failure of the spine to close entirely occurs.
- Acquired hydrocephalus develops at birth or sometime after. Instead of being present at birth, it comes from injuries or illnesses such as infections of the brain and spinal column (meningitis), bleeding from burst blood vessels in the brain, severe head injuries, brain tumors or cysts. Acquired hydrocephalus can also occur spontaneously.
You may also hear your child’s doctor talk about communicating or non-communicating hydrocephalus.
- Communicating is when the blockage of CSF happens outside of the brain. It is called “communicating” because CSF can still circulate between the two halves of the brain or ventricles.
- Non-communicating hydrocephalus happens when the flow of CSF is blocked along the narrow passageways that connect the ventricles. This may also be called obstructive hydrocephalus.
What causes hydrocephalus is not well known. It has been linked to genetic abnormalities and things that go wrong during development in the womb. It can be seen as a complication of premature birth such as bleeding inside the brain and diseases including meningitis and traumatic head injury.
One of the main risk factors for hydrocephalus is when the mother has an infection during pregnancy. Specific types that have been linked include:
A family history of multiple children born with hydrocephalus is another risk factor. Genetic testing is possible in some families.
Trauma is another contributor to hydrocephalus development. Injuries to the head during birth or in accidents throughout childhood should be a reason to closely watch your child for symptoms.
Symptoms in infants (birth to 1 year*)
Signs and symptoms of hydrocephalus in infants include:
- Bulging or tense soft spot (fontanel) on the top of the head
- Poor feeding
- Poor growth
- Rapid increase in the size of the head
- Unusually large head
Symptoms in toddlers and older children**
Signs and symptoms of hydrocephalus in toddlers (age 1 to 3) and older children (age 4 to 18) include:
- Abnormal enlargement of the head
- Blurry or double vision
- Changes in personality
- Decline in academic performance
- Delay in meeting milestones, or losing skills the child previously had
- Difficulty remaining awake or waking up
- Nausea or vomiting
- Poor appetite
- Problems with coordination
- Trouble balancing
Tests and Diagnosis
During pregnancy, hydrocephalus can be caused by the abnormal development of the baby's nervous system or by certain infections of the uterus. Ultrasound screening, which bounces safe sound waves off your baby and other nearby structures, can show birth defects or early increases in the size of the baby’s head.
Blood tests may also be used to look for specific proteins that signal an increased risk for fetal problems.
After birth and through childhood, the first step in the diagnosis is a history and physical examination. You will be asked questions about any signs and symptoms you may see. In younger children where the soft spot remains, doctors will look at the area for hardening or bulging.
Next will be a neurological exam to assess brain function. Doctors will assess your child’s reflexes, muscle strength and tone, sense of touch, vision and eye movements. If your child is old enough, the exam will include hearing tests, and an assessment of his or her mental status and mood.
Brain imaging tests use X-rays or ultrasound to look for large ventricles caused by extra cerebrospinal fluid. They may also help identify tumors, cysts or other blockages in the brain.
Ultrasound uses safe sound waves that bounce off tissues and structures in the brain. It is mainly used for a first assessment in infants because it is a simple and low-risk procedure. It can also be used to find hydrocephalus before birth.
Magnetic resonance imaging can be used. It produces a three-dimensional picture that is much more detailed than ultrasound. While painless, it can require the infant or child stay still for an extended time. This may mean that the child needs to be sedated before the procedure.
Computed tomography is a special kind of X-ray that produces cross-section views of the brain. This, too, requires a child lie still for a long period. It is used mainly for emergencies.
Surgery is an effective treatment for hydrocephalus, and prompt treatment helps minimize brain damage. This is done to help improve the flow of cerebrospinal fluid (CSF).
For some children, other concerns such as an infection or additional medical problems may require that surgery be put off for a while. Medications are available to lessen the pressure. However, this is not a long-term solution like surgery.
The neurosurgery team will try to remove the blockage if possible. If the blockage can’t be removed, a shunt may be used. In this operation, a flexible tube is placed in the brain that sends the CSF to another part of the body where it can be absorbed. Think of this as being similar to pumping water out of a pool and into a pipe that takes it to a river.
If there are signs of infection, antibiotics will be given. This is important because an infection can be a reason the shunt has to be removed.
After treatment, your child will need regular check-ups to make sure there are no further problems. Tests are regularly done to check the child's developmental and for intellectual, neurological or physical problems.
Visiting nurses, social services, support groups and local agencies can provide emotional support and assist with the care of a child with hydrocephalus who has significant brain damage.
What is hydrocephalus?
Hydrocephalus is a condition in which excess fluid builds up in and around the brain, creating potentially harmful pressure inside the head.
How common is hydrocephalus in infants?
Hydrocephalus affects about 1 in every 500 newborns and it is one of the most common birth defects.
What are the causes of hydrocephalus in infants?
It usually occurs because of problems with the blockage, absorption or flow of cerebrospinal fluid (CSF).
What are the symptoms of hydrocephalus in infants?
Common symptoms include an abnormal increase in the size of the head and a bulging of the soft spot (fontanel) on top of the head.
How is hydrocephalus diagnosed?
It can usually be diagnosed during prenatal screenings after the third month of pregnancy.
What are the treatments for hydrocephalus?
After birth, surgery is the main treatment. Doctors implant a device to drain the excess fluid out of the brain.
What are some risk factors for hydrocephalus in infants?
Risk factors include abnormal development of the baby's nervous system during pregnancy and certain infections of the uterus.
What is the outlook for hydrocephalus in infants?
Hydrocephalus can affect the mental and physical development of the baby, though early intervention helps limit problems.