Words cannot express the joy and love we feel when we look at a newborn baby, can they? But sometimes, our babies can come into this world with health problems that we don't expect. Today, we are going to talk about a birth defect that is a bit complicated, but one that we should be aware of.
What is Holoprosencephaly (HPE)?
Simply put, Holoprosencephaly, also known as HPE, is a congenital condition that occurs while a baby is still in the womb. This is a birth defect. In this condition, the brain of a fetus does not properly separate into right and left hemispheres as it develops. Did you know that our brain is normally divided into two main parts, the right hemisphere and the left hemisphere. These two hemispheres are connected to each other and exchange information through a bundle of nerve fibers called the corpus callosum. Also, each of these hemispheres is divided into other parts, such as the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe.
This division of the brain into parts is very important. Because this division helps the brain process a lot of information at the same time and perform different activities. So, as in the case of `(HPE)`, if this division does not occur while the brain is developing properly, it can cause a number of physical and nervous system-related problems.
This condition, called ‘HPE’, occurs very early in the fetal development. This means that it may even be before you know you are pregnant. There are different types of holoprosencephaly, and their severity and symptoms vary. The way the condition affects each child can also vary.
What are the main types of holoprosencephaly (HPE)?
There are three main types of holoprosencephaly (HPE). Let's look at them in order of most to least severe:
Alobar holoprosencephaly
This is the most severe type . What happens here is that the fetal brain does not separate into two hemispheres at all. As a result, the structures located between the brain and the face are lost, and the brain cavities merge. Along with this, severe facial deformities are seen. Most often, babies with this type of `(HPE)` are stillborn or die shortly after birth.
Semilobar holoprosencephaly
In this type, the fetus's brain is only partially divided into two hemispheres . This happens because the left side of the brain is connected to the right side in areas called the ``frontal lobes`` and the ``parietal lobes``. Also, the dividing line between the right and left hemispheres of the brain, the ``interhemispheric fissure,`` is only at the back of the brain.
Lobar holoprosencephaly
In this type, the fetal brain is largely divided into two hemispheres , but not completely. Although there are two hemispheres (right and left), the cerebral hemispheres are connected together at the frontal cortex. This is the least severe form of HPE.
Middle Interhemispheric (MIH) variant
In addition to these three main types, there is a fourth subtype called the Middle Interhemispheric (MIH) variant. This is where the fetal brain is connected together in the middle.
What is the difference between hydranencephaly and holoprosencephaly?
You may be confused by these two names. Hydranencephaly and holoprosencephaly are both birth defects related to the baby's brain, but there is a difference between the two.
Hydranencephaly is the loss of part of your baby's brain. This is a very rare condition called hydrocephalus (water head). Babies with this condition usually have an enlarged head.
However, Holoprosencephaly is when the brain does not properly separate into right and left hemispheres during the embryonic stage. Do you understand that difference?
Who does this condition affect? How common is it?
Holoprosencephaly (HPE) is a condition that affects fetuses developing in the womb. It usually occurs during the second and third weeks of fetal development. This means that often before you even know you are pregnant.
Researchers estimate that holoprosencephaly affects about 1 in 250 fetuses during the early embryonic stage (the second and third weeks of pregnancy). However, most of these pregnancies end in miscarriage or stillbirth.
Therefore, holoprosencephaly is a rare condition in live births, occurring in approximately 1 in 16,000 live births.
What are the symptoms of holoprosencephaly (HPE)?
Because there are different types of holoprosencephaly (HPE), the severity and symptoms can range widely. This means that these symptoms can vary from one child to another.
Common symptoms
Common symptoms associated with HPE include:
- Developmental delays .
- Intellectual disability.
- Epilepsy and seizures.
- Having a small head (microcephaly).
- Having a large head (macrocephaly).
- Excessive fluid accumulation in the brain (hydrocephalus).
- Facial abnormalities .
- Dental abnormalities (for example, having a single central incisor).
- Cleft lip and/or palate.
- Difficulty controlling body temperature, heart rate, and breathing.
- Difficulty eating.
Characteristics of Alobar HPE
This is the most severe type, so the symptoms are more severe:
- Having a single eye (cyclopia), having eyes set too close together (ethmocephaly), or having no eyes at all (anophthalmia).
- Having very small eyeballs (microphthalmia) and a tube-like nose (proboscis).
- A flat nose with close-set eyes (orbital hypotelorism) or a cleft lip that occurs in the middle of the lip (median cleft lip) or on both sides (bilateral cleft lip).
Characteristics of Semilobar HPE
- Closely spaced eyes (orbital hypotelorism), very small eyeballs (microphthalmia), or one or more eyes (anophthalmia).
- Flattening of the bridge and tip of the nose.
- A single nostril.
- Median cleft lip or bilateral cleft lip.
- Cleft palate.
Characteristics of Lobar HPE
This is the least severe type, but you may see these symptoms:
- Bilateral cleft lip.
- Close-up of the eyes.
- Flat or sunken nose.
This condition, called holoprosencephaly, can also occur as part of several different genetic syndromes. Each of these syndromes has its own unique signs and symptoms.
What causes holoprosencephaly (HPE)?
Normally, the fetal brain divides into two hemispheres early in development. Holoprosencephaly (HPE) occurs when the front part of the brain, the prosencephalon, does not properly separate into right and left hemispheres. That is, instead of the left and right sides of the front part of the brain being completely separate, there is an abnormal connection between the two.
Specifically, holoprosencephaly can be caused by:
- Mutations occur in at least 14 different genes .
- Chromosome abnormalities .
- Certain genetic syndromes .
However, in many cases, doctors cannot find the exact cause.
Genetic mutations
A genetic mutation is a change in the sequence of your DNA. This sequence of DNA gives your cells the information they need to do their jobs. So, if part of a sequence of DNA is incomplete or damaged, you may experience symptoms of a genetic condition.
A baby can inherit a genetic mutation from one or both parents, depending on how the mutation is passed on. However, some mutations also occur randomly, meaning that no one in the family has a history of the mutation.
Scientists have linked mutations in the following genes to the condition (HPE):
- `SHH`
- `SIX3`
- `TGIF1`
- `ZIC2`
- `PTCH1`
- `FOXH1`
- `NODAL`
- `CDON`
- `FGF8`
- `GLI2`
These mutations cause the genes and the proteins they produce to not function properly. This is what affects the development of the fetal brain and causes holoprosencephaly.
Chromosome abnormalities
We all have 46 chromosomes in our cells, arranged in 23 pairs. These chromosomes carry our DNA. Simply put, they contain the instructions for our bodies to grow and function. We get one set of chromosomes from our mother and one set from our father.
About one-third of babies born with holoprosencephaly have a chromosomal abnormality. The chromosomal abnormality most commonly associated with HPE is the presence of three copies of chromosome 13, known as trisomy 13. Trisomy 18 (three copies of chromosome 18) and triploidy (the presence of 69 chromosomes in a cell instead of the normal 46) can also cause HPE.
Genetic syndromes
Sometimes holoprosencephaly can occur as part of certain genetic syndromes that cause other medical problems in addition to HPE.
Some of the genetic syndromes associated with HPE are:
- `(Hartsfield syndrome)`
- `(Kallman syndrome two)`
- `(Steinfeld syndrome)`
- `(Smith-Lemli-Opitz syndrome)`
- `(Stromme syndrome)`
How is holoprosencephaly (HPE) diagnosed?
Doctors can often diagnose holoprosencephaly (HPE), especially severe cases, before a baby is born, using a prenatal ultrasound scan. The condition can also be diagnosed prenatally with a fetal MRI (Magnetic Resonance Imaging) scan.
Although these prenatal imaging tests can detect HPE, HPE is often diagnosed after the baby is born , when facial abnormalities or neurological problems begin to appear. Imaging tests of the head are then performed to confirm the diagnosis.
Babies with very mild forms of holoprosencephaly may not be diagnosed until they are about a year old. In such cases, developmental delays may be a clue that there may be a problem with the nervous system. Doctors will then order brain imaging tests.
Diagnostic tests
Doctors use the following imaging tests to diagnose holoprosencephaly after the baby is born:
- Head ultrasound: Ultrasound (also called sonography) is a painless, noninvasive imaging test that uses high-frequency sound waves to produce live images or videos of tissues such as internal organs or blood vessels.
- Magnetic resonance imaging (MRI) brain scan: An MRI scan is a painless test that produces very clear pictures of the structures and tissues in your child's brain. An MRI uses a large magnet, radio waves, and a computer. It does not use X-rays.
- Head computed tomography (CT) scan: A CT scan is a test that uses X-rays and a computer to create many three-dimensional (3D) images of the body part being examined (in this case, your child's head and brain).
If possible, doctors will perform DNA studies, including chromosomal analysis, cytogenetic and molecular tests, to determine the exact cause of HPE.
If genetic testing reveals a chromosomal or genetic problem associated with holoprosencephaly, your doctor may recommend that you seek genetic counseling if you are planning to have another child.
What are the treatments for holoprosencephaly (HPE)?
Sadly, there is currently no cure or major treatment for the condition holoprosencephaly (HPE). Instead, doctors treat each child with HPE based on their specific symptoms. This means that treatment options vary from child to child.
This treatment may require the combined efforts of a team of different specialists, including:
- Pediatricians
- Neurologists
- Endocrinologists
- Plastic surgeons
- Occupational and physical therapists
- Palliative care team
- Complex care team
People like that can be included.
Common treatments
Here are some of the most commonly used treatments for HPE:
- Anti- seizure medications to prevent, reduce, or control seizures.
- If your child has hydrocephalus, it can be treated with a ventriculoperitoneal (VP) shunt.
- Medications and occupational and physical therapy can help with movement disorders such as muscle stiffness (spasticity) and involuntary movements (dystonia).
- Plastic reconstructive surgery for cleft lip and palate or other facial features.
- Medications to treat hormonal imbalances in the pituitary gland.
- Taking steps to improve the nutritional intake of children with feeding difficulties. For example, feeding through a tube into the stomach (gastrostomy tube - G-tube).
All of this is done to provide the child with the best possible quality of life.
Can holoprosencephaly (HPE) be prevented?
Unfortunately, most cases of holoprosencephaly (HPE) cannot be prevented. This is because it is often caused by "hidden" inherited genetic problems. If you are planning to have a child, it is a good idea to talk to your doctor about genetic testing to understand your child's risk of having a genetic condition or inherited gene mutation like HPE.
However, scientists have identified some risk factors that may increase the chance that a fetus will develop holoprosencephaly. These include:
- Having diabetes: If you had type 1 or type 2 diabetes before you became pregnant, you may be at increased risk of having a baby with HPE. This is not to be confused with gestational diabetes, which occurs during pregnancy.
- Folate (folic acid) deficiency: Folate, the natural form of vitamin B9, is essential for healthy fetal development, especially the brain and spinal cord. Folate deficiency before and during pregnancy may increase the risk of having a baby with HPE.
- Exposure to teratogens: Teratogens are substances or factors that cause problems with fetal development and lead to birth defects. Exposure to teratogens, such as ethanol (alcohol), retinoic acid, and mycotoxins (mold toxins) from food, may increase the risk of having a baby with holoprosencephaly.
Therefore, it is very important to follow a healthy lifestyle, eat a balanced diet, and follow medical advice during and before pregnancy.
What is the prognosis for holoprosencephaly (HPE)?
The outlook, or prognosis, for holoprosencephaly (HPE) varies depending on the severity of the condition and the specific cause.
The outlook for moderate to severe HPE is generally poor. Very few children with moderate to severe HPE survive to adulthood. Children with mild to moderate HPE usually survive to adulthood, but they often have to live with medical complications related to HPE.
Many children with holoprosencephaly require daily medications and treatments to prevent seizures and treat other complications.
Life expectancy
The life expectancy of someone with holoprosencephaly (HPE) depends on the type of HPE they have and the underlying cause of the condition.
Babies with Alobar HPE (the most severe form) usually die as stillbirths, either shortly after birth or within the first six months of life.
More than 50% of children with semilobar or lobar HPE, and without other organ abnormalities, survive for at least 12 months.
Children with mild cases of HPE usually survive into adulthood.
If my baby has holoprosencephaly (HPE), what should I expect?
This is very important. Remember that no two children with holoprosencephaly (HPE) are affected in the same way. There is no way to know for sure how your child will be affected. The best thing you can do to prepare for the future is to talk to specialists who research and treat holoprosencephaly. They can give you more information about this.
How do I care for my baby with holoprosencephaly (HPE)?
To help care for your child with holoprosencephaly (HPE), follow these tips from their doctors:
- Administer any prescribed medications as directed.
- Refer for developmental assessments and therapies.
- Be sure to attend all follow-up medical visits.
Holoprosencephaly can cause cognitive, neurologic, and/or motor problems. Many children with HPE have developmental problems and may need help with daily activities throughout their lives.
Your child's medical team can answer your questions and provide you with support. They can also direct you to support groups in your area or online. Remember that you are not alone.
When should I see my child's doctor?
If your child has been diagnosed with holoprosencephaly (HPE), they will need to see their medical team regularly to make sure their treatment is working and to assess their developmental progress.
Finding out that your baby has holoprosencephaly can be difficult to cope with. But know that you are not alone. There are many resources available to help you and your family. It is important to talk to a doctor who is knowledgeable about this condition. This will help you learn more about how your baby will be affected and how to prepare for it.
Finally, things to remember (Take-Home Message)
Holoprosencephaly (HPE) is a complex birth defect that occurs when a baby's brain does not properly separate into two hemispheres in the womb.
- There are different types and levels of severity , so symptoms vary from child to child.
- Often genetic causes and chromosomal abnormalities are involved, but sometimes the cause cannot be found.
- Although it can be detected before birth with ultrasound or MRI, it is often only detected after birth.
- There is no specific cure , but there are various treatments to control symptoms and support the child.
- The outlook varies depending on the severity of the condition. In mild cases, children may survive into adulthood.
- If you are pregnant or planning to become pregnant, be careful about things like controlling your diabetes and taking folic acid.
- You are not alone in this situation. You can get help from doctors, counselors, and support groups. Accurate information and support are very important.
` Holoprosencephaly, HPE, brain disorders, birth defects, fetal development, genetic diseases, chromosomal abnormalities, pregnancy health, child health
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