What is hydranencephaly?

Hydranencephaly is a rare birth defect that drastically affects brain development. Babies born with this neurological condition are missing the right and left hemispheres of the cerebrum. The cerebrum normally forms the front of the brain. In place of the missing hemispheres, cerebrospinal fluid, or the fluid that cushions the brain and spinal cord, fills the cranial cavity.

Hydranencephaly is incurable. It’s not uncommon for babies with this condition to die in utero or within a few months after birth.

Babies born with hydranencephaly may have obvious symptoms at birth. In some cases, it may take weeks or months for obvious signs to appear. One of the most noticeable symptoms of hydranencephaly is an enlarged head size. Infants with the disease may have increased muscle tone, but limited movement.

Other common hydranencephaly symptoms include:

  • seizures and uncontrolled movements
  • lack of growth
  • breathing and digestion problems
  • difficulty regulating body temperature
  • vision problems
  • intellectual disability

Hydranencephaly is the result of injury to a baby’s nervous system or an abnormal formation of it. It occurs during the earliest stages of development in the uterus. But it’s not entirely clear what causes these problems. Hydranencephaly may be an inherited condition.

One theory about the abnormal brain development is that there’s blockage in the carotid artery. That’s the blood vessel that carries blood to the brain. However, researchers don’t have an explanation for why the carotid artery would become blocked.

Other possible causes include:

  • an infection of the uterus early in the pregnancy
  • a mother’s exposure to environmental toxins
  • other circulation problems with the baby

Diagnosing hydranencephaly isn’t always done at birth. Sometimes it may take a few months before symptoms become noticeable.

One common diagnostic test is transillumination. This is a painless procedure. During the procedure, your baby’s doctor will shine a bright light at the base of their head to see if there’s fluid under the skin. This test can often reveal whether there’s abnormal brain formation.

Your baby’s doctor may also use a special X-ray to take images of your baby’s blood vessels using a dye. This is called an angiogram. It helps reveal abnormalities with circulation.

Another imaging test your baby’s doctor may use is called a CT scan. This test can provide the doctor a detailed and layered look at the brain.

Hydranencephaly affects the mental and physical health of a child. There are several conditions that tend to go hand in hand with hydranencephaly. Among them are:

  • Asthma or reactive airway disease (RAD): Asthma can’t usually be diagnosed until a child is older, so the more general diagnosis of RAD is made when there’s an obvious respiratory problem. The specific cause is unknown.
  • Cerebral palsy: A group of disorders affecting muscle movement and coordination. Vision, hearing, and sensation are also often affected.
  • Constipation: This is sometimes made worse by a limited diet and medications to control seizures.
  • Diabetes insipidus: A condition in which the kidneys can’t conserve water. Your child will have excessive urine output and higher sodium levels in their bloodstream.
  • Failure to thrive: Feeding a child with hydranencephaly is challenging. This then affects overall health, growth, and survival.
  • Irritability: This may be related to muscle spasms and gastrointestinal distress.

Because hydranencephaly currently has no cure, treatment focuses on managing symptoms.

To help remove excess cerebrospinal fluid from the brain, a surgeon can place a shunt, or one-way valve, inside the skull. The shunt is attached to a catheter, a flexible tube. The catheter will run into the abdominal cavity, where the fluid is transferred from the brain. This procedure can help relieve painful pressure inside your child’s head. It may also prolong life.

Seizures can be treated with medications, including anticonvulsants, as well as other therapies. Diet and calming techniques can sometimes reduce seizures, too.

Calming and relaxation strategies may also help reduce irritability. Medications, such as stool softeners, may also be helpful in treating constipation.

It’s important that treatment for all symptoms and complications are coordinated by your child’s doctor. This will help to avoid overmedication or unwanted side effects from multiple medications and procedures.

Each case of hydranencephaly is unique. The condition may be so severe the baby doesn’t survive pregnancy.

But there are more cases of children living for a few years with hydranencephaly. Still, the odds of reaching adulthood are slim. The emotional impact of having a child with hydranencephaly is profound. Don’t hesitate to seek counseling and support to help you get through this challenging chapter in your life.

Research into the causes and prevention of fetal neurological diseases continues. Information about research, clinical trials, and resources for patients and families affected by hydranencephaly is available at the National Organization for Rare Disorders.