What is Holoprosencephaly?
Holoprosencephaly is a fetal abnormality of the brain in which the brain of the fetus remains underdeveloped and does not divide into two hemispheres which is the actual norm. Holoprosencephaly can result in the way the face and head of the baby develops at the time of birth. Holoprosencephaly has been divided into four types depending on the severity of the condition.
These types are alobar, semi-lobar, lobar, and middle interhemispheric type Holoprosencephaly. The more severe the condition is the more severe the deformity of the face and head will be of the child due to Holoprosencephaly. Children with the most severe type of Holoprosencephaly tend to have only one eye and the nasal structure of the nose is tubular located above the eye.
In the less severe forms of Holoprosencephaly both eyes are present but are extremely close to each other. Such children will have intellectual disability and learning problems and will always require special education. The reason for Holoprosencephaly as of yet is not known but there are certain genetic factors which studies suggest may play a role in development of Holoprosencephaly.
The prognosis for children with Holoprosencephaly is extremely poor and in severe forms of this condition the child is usually a stillbirth or may at maximum survive till six months of life as a result of Holoprosencephaly.
What are the Causes of Holoprosencephaly?
As stated above, the exact cause of Holoprosencephaly is still not known but some studies suggest that the abnormality occurs within the first few weeks of pregnancy. Onset of diabetes when the female is pregnant puts the fetus at risk for having Holoprosencephaly, although in majority of the cases of Holoprosencephaly there is no known intrauterine cause for it.
Some studies suggest a genetic role in the development of Holoprosencephaly. It has been seen that about 40% of children born with this condition have a chromosome abnormality of which the most common chromosome abnormality is a condition called trisomy 13 in which there are three copies of chromosome 13 instead of the usual 2, one from each parent. In some cases, there is a change in a specific gene which causes the gene to act abnormally resulting in development of Holoprosencephaly.
What are the Symptoms of Holoprosencephaly?
The symptoms of Holoprosencephaly vary depending on the severity of the condition and to the category to which the condition belongs to. Holoprosencephaly can present within a broad variety of clinical severity. As stated above, Holoprosencephaly is divided into four subtypes depending on the extent the separation of the hemispheres takes place and as such the symptoms are different for each subtype.
Symptoms of Alobar Holoprosencephaly: In this form of Holoprosencephaly, there is absolutely no division of the brain and as such the child tends to have just one eye, tubular shaped nasal structure, cleft lip which may be unilateral or bilateral, and flattened nose
Symptoms of Semi-Lobar Holoprosencephaly: In this form of Holoprosencephaly, the division of the hemispheres occurs but the left hemisphere is fused into the right hemisphere in the frontal and parietal lobes. Children who fall into the category of Holoprosencephaly will have very eyes that are very close to each other and the eyeballs may be abnormally small or in some cases even absent. Additionally, the bridge and the tip of the nose will be flattened and there will be presence of cleft lip, one nostril, and a cleft palate.
Symptoms of Lobar Holoprosencephaly: In this form of Holoprosencephaly, the brain gets divided into two hemispheres but the cerebral hemisphere is fused. Symptoms may include bilateral cleft lip, eyes which are very close to each other, and flattened nose.
Symptoms of Middle Interhemispheric Holoprosencephaly: In this form of Holoprosencephaly, the brain is fused from the middle and symptoms include eyes that are very close to each other and flattened and narrow nose.
Additionally children with Holoprosencephaly will tend to have a variety of other symptoms as well which include:
- Neural tube defects
- Pituitary dysfunction
- Extremely short stature
- Feeding problems
- Developmental delays
- Intellectual disability.
How is Holoprosencephaly Diagnosed?
Since Holoprosencephaly is a defect which can be easily seen at the birth of the child, there are no definitive tests to confirm the diagnosis; however, by imaging studies like an MRI or CT scan of the brain the extent of the disease and its subtype can be diagnosed. Additionally, Holoprosencephaly can also be diagnosed prenatally by abdominal ultrasound of the mother which will clearly show the abnormality in the facial features confirming the diagnosis of Holoprosencephaly.
What is the Treatment for Holoprosencephaly?
The treatment for Holoprosencephaly is usually supportive and specific to the deformity that the child has and thus depends on a case to case basis. To identify any pituitary abnormalities an evaluation by an endocrinologist may be done. For treatment of seizures, medications can be given to control them and thus a neurologist needs to be consulted also.
Plastic surgery needs to be consulted for correction of cleft lip and palate and reconstruct other facial deformities that are a part of Holoprosencephaly. For developmental delays, a specialist in this field of medical science can be of great help in helping the parents and the child.
All in all, treatment of Holoprosencephaly requires a multidisciplinary approach to include neurologist, plastic surgeons, special education teachers, and psychologist who can formulate a plan on how to best treat the child and keep him or her comfortable during treatment of Holoprosencephaly. It is a very tough for the parents of the affected child to cope up with the disease process and hence counseling sessions are also quite helpful for parents who have a child with Holoprosencephaly.
What is the Prognosis or Life Expectancy in Holoprosencephaly?
The prognosis of Holoprosencephaly is variable and depends on the subtype of the disease condition. The alobar form of Holoprosencephaly which is the most severe form has the most poor prognosis and majority of children do not survive past the six months mark. The much milder affected children may survive up until a year or more. Children with semi-lobar or lobar subtype may survive for about two years post the diagnosis of Holoprosencephaly.
- “Holoprosencephaly.” National Institute of Neurological Disorders and Stroke (NINDS). https://www.ninds.nih.gov/Disorders/All-Disorders/Holoprosencephaly-Information-Page
- “Holoprosencephaly.” Genetic and Rare Diseases Information Center (GARD). https://rarediseases.info.nih.gov/diseases/6837/holoprosencephaly
- “Holoprosencephaly: Overview and More.” Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/21429-holoprosencephaly
- “Holoprosencephaly: A Multidisciplinary Approach to Management.” Journal of Pediatric Neurosciences. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3678009/