Hydranencephaly is a rare disability present at birth that causes a central nervous system disorder. When it occurs, the front hemispheres or cerebrum of a baby’s brain are missing. In their place, the cerebrospinal fluid that typically cushions the brain fills the space.

The condition affects both male and female babies at equal rates. Some babies may be at higher risk of developing it if either of the parents carries genes that are suspected of causing the disorder.

While some scientists suspect genetics may play a role in hydranencephaly, the exact cause is unknown, and there is no cure for the condition. Often, a baby with hydranencephaly will die in the womb or within a few months of birth.

Fast facts on hydranencephaly:

  • According to the Brayden Alexander Global Foundation for Hydranencephaly, only 1 in every 250,000 newborns in the United States has hydranencephaly.
  • Worldwide, the rate of occurrence of the condition is 1 in every 10,000.
  • Newborns that survive may have vision problems, growth impairment, or intellectual disabilities.
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Hydranencephaly in baby's head highlighted by sunlight, held in woman's arms.Share on Pinterest
Hydranecephaly is a condition where parts of the front of the brain are missing at birth.

When a baby is born with hydranencephaly, there may or may not be obvious symptoms that the baby has the disorder. In clear cases, the baby’s head appears enlarged.

When the head is not enlarged, it may take weeks or even months for symptoms to be observed and suspected. Often, a baby may have limited or jerky movement.

Other symptoms of hydranencephaly can include:

  • failure to grow at a normal rate
  • seizures
  • vision difficulties
  • exaggerated muscle reflexes
  • increased muscle tone
  • intellectual disability
  • poor body temperature regulation
  • breathing and digestive problems

Some scientists suspect that hydranencephaly is a disorder inherited from a child’s parents.

Others suspect hydranencephaly occurs due to a blockage of the carotid artery where it enters the head. It is unclear, however, how or why a blockage may occur.

Another theory is that the baby’s central nervous system sustains an injury at a very early stage of development, or does not develop properly.

A few additional causes may include:

  • a mother’s exposure to poisonous substances
  • circulatory problems within the fetus
  • infection of the uterus at an early stage of development
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Hydranencephaly may be diagnosed during a routine ultrasound scan.

Doctors may diagnose hydranencephaly at different points in time for different babies.

In some cases, detection can occur while the baby is still in the womb. An ultrasound scan may reveal that there are physical abnormalities of the fetus that suggest hydranencephaly.

In other cases, a doctor may see characteristic signs of the disorder at birth. However, it may not be until other signs and symptoms appear that a doctor will know more clearly to check for the disorder.

To make a diagnosis, a doctor may:

  • conduct a clinical evaluation
  • review the newborn’s medical history
  • identify physical characteristics
  • order a computerized tomography (CT) scan
  • request an X-ray that uses dye to highlight blood vessels
  • order a transillumination

A transillumination is a relatively simple, painless procedure. Doctors place a bright light at the base of the baby’s head, which allows them to see if the brain has grown irregularly.

Hydranencephaly causes physical and mental health issues for the child. As a result, several potential complications can result from hydranencephaly.

Some complications may include:

  • irritability related to physical discomfort
  • failure to thrive due to malnutrition from feeding issues
  • constipation
  • diabetes insipidus, where the kidneys pass an abnormally large amount of urine
  • cerebral palsy
  • asthma
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Surgery may be recommended to drain fluid from the head.

There is no cure for hydranencephaly. Treatment focuses on managing symptoms associated with the disorder.

Parents and caregivers should follow a doctor’s recommended treatment plan. Medications and therapies should be discussed with a doctor to avoid issues of overmedicating the child.

Treatments will vary from child to child and will be set up to manage the individual’s specific symptoms. For example, if a child is experiencing seizures, a doctor may prescribe anti-seizure medications.

Relaxation therapies may help reduce symptoms of irritability. Stool softeners may be used to help relieve associated constipation.

Doctors will often recommend surgery to drain fluid from the baby’s head. In these cases, a doctor places a one-way valve in the head. A catheter is attached to the valve, and the fluid is drained into the upper body. This procedure relieves pressure and pain in the head and may help extend the life of the child.

In some cases, a fetus may not survive beyond the mother’s pregnancy. In other cases, a baby may only survive a few days after birth before dying.

It is not uncommon for a child with hydranencephaly to survive several years. However, due to the amount of missing brain, many children with hydranencephaly will not survive to adulthood.

Parents and caregivers of a child with hydranencephaly may benefit from seeking additional emotional support. Counseling and other mental health services, such as support groups, can provide help when needed.

Studies into hydranencephaly and its causes are still ongoing. Continued research may lead to ways to prevent hydranencephaly and similar disorders.