What is holoprosencephaly (HPE)?
Holoprosencephaly (HPE) is a brain condition in which the two halves of a baby’s brain do not fully separate, as they normally would, while they develop in the womb. The brain is made of two halves, or hemispheres, that are mirror images of each other. If they do not fully separate during development, your baby will receive an HPE diagnosis.
HPE can cause several issues, including:
- Developmental delays
- Facial structure differences, such as eyes that are spaced close together, nasal issues and cleft lip and cleft palate
- Fluid cysts and hydrocephalus (buildup of fluid pressure) in the brain
- Growth problems
- Vision problems
Different forms of holoprosencephaly
We diagnose HPE depending on how separated the two brain halves are:
Lobar HPE is the least severe form of holoprosencephaly. The brain’s halves are mostly separated, only connected in the frontal lobe (the front-most part of the brain). In lobar HPE, the corpus callosum, which allows the two halves of the brain to communicate, is mostly (but not completely) formed.
Semi-lobar HPE is in between the least and most severe form of holoprosencephaly. The halves are mostly connected but separated slightly at the back of the brain.
Alobar HPE is the most severe form of holoprosencephaly. The brain’s halves are completely connected or fused together.
What causes holoprosencephaly?
HPE usually occurs due to a genetic difference in the child, which impacts how the brain develops. Sometimes parents pass genetic differences to their kids and sometimes they are new in the child. There are certain genetic syndromes, such as Trisomy 13, that we often link to HPE.
HPE can also occur because a baby has missing or copied sections of chromosomes (the structure inside cells that contain all our genes). In this case, the child has what is called a micro-deletion syndrome or duplication syndrome. Missing or copied chromosomes can impact a child’s development and the function of other parts of the body, as well.
There are also a handful of single-gene changes that can cause HPE, meaning that a gene within a chromosome has been altered in some way. Some of single-gene changes can cause HPE but don’t cause symptoms in everyone who has them, so a parent can have the same change and not have symptoms of HPE.
Who gets holoprosencephaly?
HPE begins very early in pregnancy. We have not seen signs of the condition to be more common in specific genders or races.
What are holoprosencephaly symptoms?
The symptoms of HPE depend on which type your child has. However, nearly all children with this condition have motor issues and cognitive delays, which affect their mental development.
Low motor skills and slow language development
Children with alobar HPE don’t usually gain motor skills beyond rolling and they usually have limited arm use and language skills as well. They can usually only coo and make other vowel sounds.
Kids with semi-lobar and lobar HPE have more motor and language skills but still fall behind standard developmental milestones. Children with HPE may have difficulty eating and may need a gastrostomy tube (g-tube) for feeding.
Low hormone levels
Low hormone levels can cause slow growth, fatigue (being tired often), low blood sugar levels and low blood pressure levels.
Children with HPE may have visual problems due to small optic nerves or issues with visual pathways in their brain.
Up to 80% of children with alobar HPE and 50% of children with other types of HPE have seizures.
What tests do we use to diagnose holoprosencephaly?
We diagnose HPE using fetal imaging. A fetal MRI is the best way to diagnose HPE while the baby is still in the womb because we can see their brain. Once your baby is diagnosed with HPE, we can do genetic testing such as amniocentesis (testing amniotic fluid) before birth, or genetic testing after birth to help see if your baby has a genetic syndrome. If we diagnose HPE before birth, we usually recommend an MRI after birth to better see their brain structure.
What can I expect from holoprosencephaly tests?
A fetal MRI takes 1 to 2 hours and is painless. For the test, we ask the mother to lie as still as possible so we can get an accurate image. After the MRI, our experienced fetal and neuro radiologists will review the images to make an accurate diagnosis and our team of specialists will discuss the results with you.
How do we treat holoprosencephaly?
HPE treatment focuses on addressing its symptoms. If your baby develops hydrocephalus (extra fluid around the brain), a neurosurgeon would place a shunt to drain the fluid and relieve the pressure. If your baby has a cleft lip or cleft palate, we can offer treatment through our Cleft Lip and Palate Clinic.
To help with any issues with vision, we perform a dilated eye exam to measure the optic nerves after birth. Our ophthalmologists (eye doctors) can offer the best vision care options.
For children with HPE, we recommend regular follow-up appointments with our endocrinologists to check for low hormone levels and start hormone replacement therapy if needed. Children with HPE also need regular therapies, such as physical therapy, occupational therapy and speech-language therapy to help them develop skills for day-to-day living. Because seizures are common in HPE, we may also recommend care from a neurologist. We may prescribe regular medication to help treat seizures.
Why choose us for holoprosencephaly treatment?
HPE is a complex condition that requires several children’s specialists. Children’s Hospital Colorado has all the specialists in one place to care for children with HPE, before and after birth. We have state-of-the-art fetal and postnatal (after birth) MRI imaging as well as renowned neuroradiologists to help give you an accurate diagnosis.
Our Colorado Fetal Care Center has one of the most experienced fetal care teams in the country with experience in caring for this rare condition. After birth, your baby will receive care in our nationally recognized Level IV (four) Neonatal Intensive Care Unit (NICU), which is recognized as providing the highest level of NICU care. With top specialists in endocrinology, genetics, neurology, neonatology, neurosurgery and ophthalmology, Children’s Colorado has the expertise and experience to help provide the best care for your baby, no matter their needs.