Hydranencephaly Fast Facts

Hydranencephaly is a condition where part of the brain is absent and is replaced by sacs filled with fluid.

The condition is often present at birth, but a newborn with hydranencephaly may show no symptoms of the disorder at first.

Symptoms of hydranencephaly may include seizures, muscle stiffness, and intellectual impairments.

Many children with hydranencephaly don’t survive past the first year, but survival into later childhood is possible in some cases.

United Brain Association

Symptoms of hydranencephaly may include seizures, muscle stiffness, and intellectual impairments.

What is Hydranencephaly?

Hydranencephaly is a brain condition in which the cerebral hemispheres, the largest parts of the brain, fail to develop normally and are instead replaced by sacs filled with cerebrospinal fluid (CSF). The condition can result from several different causes, and it may occur before or after birth.

Some babies born with hydranencephaly may develop normally at first, but symptoms typically begin to emerge within a few weeks after birth.

Symptoms of Hydranencephaly

Common symptoms of hydranencephaly include:

  • Irritability
  • Stiff muscle tone in the arms and legs
  • Slow growth
  • Enlarged head or smaller than normal head size
  • Feeding difficulties
  • Seizures
  • Exaggerated reflexes
  • Vision impairment
  • Intellectual and cognitive impairment

What Causes Hydranencephaly?

Hydranencephaly is considered to be an extreme form of porencephaly, a condition in which fluid-filled cavities or cysts develop in the brain. Both conditions may be caused by an event or condition that damages the cerebral hemispheres. Infections and conditions that cause bleeding or lack of blood flow in the brain are thought to be the primary causes of this kind of brain tissue damage. Research suggests that a blockage of the baby’s carotid artery before birth may cause at least some cases of hydranencephaly.

Other potential causes include:

  • Infection of the baby just before or just after birth
  • Loss of blood flow to the baby close to the time of birth
  • Trauma or injury during birth
  • Infection of the mother during pregnancy
  • Abdominal trauma or injury to the mother during pregnancy

Is Hydranencephaly Hereditary?

Some cases of hydranencephaly have occurred in more than one member of the same family, suggesting that there is a genetic component to the disorder. In these cases, the condition may be associated with an abnormal change (mutation) in genes called the COL4A1 and COL4A2 genes. The mutation causes weakness in the brain’s blood vessels which may, in turn, lead to bleeding in the brain.

Familial cases of hydranencephaly seem to be inherited in an autosomal recessive pattern. This means that a child must inherit two copies of the disorder-causing gene mutation, one from each parent, to develop the condition. A parent who carries only one copy of the mutation will usually show no symptoms but may pass the mutation to their children. Two parents who each carry the mutation have a 25 percent chance of having an affected child with each pregnancy. Fifty percent of their pregnancies will produce a carrier child. Twenty-five percent of the time, their child will not inherit a mutated gene, meaning they will not have the disorder or be able to pass on the mutation to their children.

How Is Hydranencephaly Detected?

Babies with hydranencephaly are often born with an enlarged head, and these cases may be easily diagnosed at birth. However, in some cases, babies with the disorder appear to develop normally until symptoms emerge weeks or months after birth. In these cases, diagnosis may be delayed.

Early signs of hydranencephaly may include:

  • Irritability
  • Feeding difficulties
  • Slow growth
  • Rigid muscles
  • Seizures
  • Enlarged head that develops after birth

Hydranencephaly sometimes may be detected before birth via ultrasound imaging exams.

How Is Hydranencephaly Diagnosed?

Hydranencephaly is diagnosed by identifying the presence of the condition’s unique physical features. The diagnostic process may include:

  • Assessment of the child’s medical and family history
  • Physical and neurological exams
  • Imaging scans such as computerized tomography (CT) or ultrasound to look for the absence of the cerebral hemispheres and the presence of fluid-filled sacs
  • X-rays using dyes (angiogram) to create images of the brain structure


How Is Hydranencephaly Treated?

Hydranencephaly has no cure, and no treatment will reverse the structural malformations of the disorder. Instead, treatments aim to reduce the severity of symptoms and improve the child’s quality of life. Common treatments and therapies include:

  • Surgery to place a thin tube (called a shunt) in the brain to drain fluid
  • Anti-seizure medications
  • Physical therapy
  • Speech therapy

How Does Hydranencephaly Progress?

Most children with hydranencephaly do not survive past infancy. However, survival into later childhood is possible in some cases. Long-term effects of the disorder vary from case to case, but severe disabilities typically develop.

Potential long-term complications of hydranencephaly include:

  • Vision impairment or blindness
  • Deafness
  • Impaired growth
  • Paralysis
  • Intellectual and cognitive disabilities
  • Seizures
  • Respiratory problems

How Is Hydranencephaly Prevented?

Because the precise causes of hydranencephaly are not well understood, it is difficult to identify an effective way to prevent the condition. Avoidance of risk factors during pregnancy is the best way to decrease the risk:

  • Get vaccinations as recommended by your doctor and take steps to avoid infections.
  • Don’t use drugs or alcohol during pregnancy.
  • Get good prenatal care to lessen the chance of birth complications.
  • Take safety precautions to avoid injury or trauma during pregnancy.

Parents with a family history of the disorder or who have had another child with hydranencephaly are advised to consult a genetic counselor to assess their risk if they plan to have another child.

Hydranencephaly Caregiver Tips

  • Be an advocate for your child. Learn all you can about hydranencephaly so you can understand the challenges your child faces, and be prepared to educate others about what they can do to help and support you and your child.
  • Caring for a child with a debilitating condition like hydranencephaly will change your life. Trying to do it all yourself will put your health at risk. Don’t hesitate to ask for help from family members and friends, and let them give you time away from caregiving whenever possible.
  • Be grateful for the time you have with your child. You will have beautiful moments with your child amid difficult times. Be sure to stop and appreciate them.
  • Remember that you’re not alone. The Global Hydranencephaly Foundation offers support for families living with the disorder.

Hydranencephaly Brain Science

Mutations in the COL4A1 gene cause familial porencephaly and may also be a factor in familial cases of hydranencephaly. This gene carries instructions for making one part of type IV collagen, a protein vital in creating membranes that help strengthen and hold together tissues throughout the body.

The COL4A1 mutations interfere with the normal production of type IV collagen, and, as a result, tissues are weaker than usual. The brain’s weakened blood-vessel tissue can break down when subjected to trauma such as inflammation or injury during birth. This can cause bleeding in the brain and damage to brain tissue, and the fluid-filled sacs of hydranencephaly develop as a result.

Hydranencephaly Research

Title: Long-term Outcome of Children With Neonatal Intra-Ventricular or Intra-Cranial Hemorrhage (NEONATAL ICH)

Stage: Recruiting

Sub-investigator: Nechama Sharon, MD

Laniado Hospital

Netanya, Israel

Intraventricular hemorrhage (IVH) is the most commonly recognized cerebral lesion on ultrasound in extremely preterm infants. Papile classification is frequently used to grade the severity of IVH. Grade III-IV IVH and other lesions noted on ultrasound, including periventricular leukomalacia (pvl), porencephaly, and ventriculomegaly are well documented to be associated with adverse neurodevelopmental outcomes.

However, the true impact of lower-grade IVH on the neurodevelopment of these extremely preterm infants has not been well described.

Also, the neurodevelopmental outcome for neonatal non-traumatic Intra-cranial Hemorrhage (ICH) is not well established.

This study aims to look retrospectively at babies with neonatal IVH or ICH and follow their radiological, cognitive, motor, and functional outcomes.

The study will focus on postnatal files and images performed as part of the child’s follow-up during hospitalization and after discharge.

The study will be performed as a retrospective chart review with keywords: IVH, ICH of babies discharged from Laniado Hospital Neonatal care service or ICU, or being followed in the pediatric neurosurgical clinic and prematurity/neonatology clinic of the hospital.

All charts of such children will be included to review clinical and radiological available data.

Registration of Clinical, Radiological data as presented or submitted by the parents on Neurosurgical neonatology and Neurological Followups will be performed by PI or CI and coded in the data anonymously.

Follow-up will be performed as clinically indicated without the addition of any specific studies due to the research.


Title: Study of Abnormal Blood Clotting in Children With Stroke

Stage: Completed

National Institutes of Health Clinical Center

Bethesda, MD

Effective treatment and prevention strategies for childhood stroke and porencephaly can only be developed once the causes are understood. There is increasing evidence that inherited and acquired coagulation abnormalities alone or combined with environmental factors predispose to arterial and venous thrombosis. Inherited abnormalities of factor V Leiden, prothrombin, protein C, protein S, and antithrombin III may account for many of these thromboses. At present, there is little information on the existing distribution of these coagulation anomalies in children with thrombosis. Recent reports also suggest that these clotting abnormalities may be responsible for some instances of intracranial hemorrhage, porencephaly, cerebral palsy, and fetal death.

This study will measure the frequency of several coagulation factor abnormalities (factor V Leiden, prothrombin 20210A, protein C, protein S, antithrombin III, and antiphospholipid antibodies) in children with a history of porencephaly and stroke and will compare these to the prevalence of these mutations in population controls and family members. Researchers will also describe the exogenous conditions that, in concert with these coagulation factors, may have led to thrombosis in these children.


Title: COL4A1 Gene-Related Cerebra-retinal Angiopathy (COL4A1)

Stage: Completed

Principal investigator: Hugues Chabriat, MD,PhD

Hôpital Lariboisiere Neurology Department

Paris, France

This prospective multicenter cohort study aims to define the clinical, radiological, and mutational spectrum of the disease related to the COL4A1 gene.

Clinical brain MRI-MRA and genetic testing (COL4A1 mutation screening) will be conducted for each included patient or asymptomatic relatives. Thirteen French investigating centers will participate in the study.

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