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Holoprosencephaly: types, symptoms and treatments

Holoprosencephaly: types, symptoms and treatments

September 25, 2022

When we imagine a brain, whether human or not, the image that comes to mind is usually composed of an organ whose outer layer is riddled with folds, between which we can see some indentations that allow us to appreciate the presence of two halves or brain hemispheres.

This separation is something that most human beings have, forming during our fetal development. But not all: there are children whose brains are not divided or whose hemispheres are fused: we are talking about Children suffering from holoprosencephaly .

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Holoprosencephaly: what is it?

It is called holoprosencephaly a a type of malformation throughout fetal development in which there is no division between the different structures of the forebrain: there is a fusion between the cerebral hemispheres, as well as between some subcortical structures and the cerebral ventricles. This fusion, or rather non-separation, can occur at a complete or partial level (the hemispheres being completely fused or only in some parts).


Usually, the division of the brain into different lobes and hemispheres It occurs around the fourth week of gestation. In holoprosencephaly, this division does not occur or it can not be completed, which has severe repercussions both before and after birth. This condition usually comes together with the presence of cranial and facial malformations, existing alterations such as hypertelorism or eyes together, cyclopia or a single eye, alterations of the nose, cleft lip, cleft palate or hydrocephalus. Also, it is common that problems appear in the feeding and in the thermal maintenance, cardiac and respiratory alterations and convulsions. It is also associated with different degrees of intellectual disability, in cases sufficiently mild to allow life.


In general, holoprosencephaly has a very poor prognosis, especially in the alobar type: boys and girls they usually pass away either before they are born or before they reach six months of age . In the other types, survival is possible until the year or two years of life. Depending on whether there are other complications and the severity of the disorder. In the milder cases, survival is possible, although in general they will suffer from cognitive deficits to a greater or lesser extent.

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Some of its main main variants

Holoprosencephaly is a medical condition that can occur in different ways, depending on the possible degree of separation of the cerebral hemispheres. They emphasize mainly three first variants, the most habitual ones, although it is necessary to take into account that others exist. These types of holoprosencephaly are the following .


1. Lobar holoprosencephaly

Lobar holoprosencephaly is the mildest form of this type of alteration. In this case, they can be observed the presence of lobes almost perfectly separated , although this separation has not been carried out in the frontal lobes and they do not usually have septum pellucidum.

2. Semiilobar holoprosencephaly

In this variant of holoprosencephaly, there is a division between the hemispheres in part of the brain, but the frontal and parietal lobes are fused. The interhemispheric fissure is only observed in temporal and occipital .

It is common that hypotelorismo is present, that is to say that the eyes of the baby are much less separated of what would be habitual, that are small or that do not exist directly. Cleft lip or palate can also be observed, as well as absence or malformations at the nasal level.

3. Holoprosencephaly alobar

It is the most serious form of holoprosencephaly, in which the hemispheres do not become separated to any degree, being completely fused. There is often a single ventricle and / or a single thalamus.

Many of these children are also born with only one eye, in which case the existence of cyclopia is considered. In fact, probably the emergence of the mythical figure of the cyclops was based on the observation of some case of this type of holoprosencephaly. The nose usually has malformations, being able to have a formation in the form of a proboscis or even not having a nostril (something that can cause the child to suffocate) or only one of them.

4. Interhemispheric holoprosencephaly

This variant, less common than the previous three, occurs when the division of the brain does not occur in the middle part: the posterior parts of the frontal and parietal lobes. There is no corpus callosum (with the possible exception of genu and splenium), although generally at the level of subcortical structures there is no overlap or fusion . Also called syntelencephaly.

5. Aprosencephaly

Although technically it would not be already holoprosencephaly, sometimes aprosencephaly is also considered a variant of this disorder, in which the forebrain is not directly formed.

Causes of this problem

Holoprosencephaly is an alteration that occurs during fetal development, there being a wide variety of possible factors that can lead to its emergence. It has been observed the existence of a large number of cases in which there are genetic alterations in numerous genes (One in four has alterations in the ZIC2, SIC3, SHH or TGIF genes), as well as different syndromes and chromosomal disorders (Patau syndrome or Edwards syndrome among them).

A link with environmental factors has also been observed, such as uncontrolled diabetes in the mother or the abuse of alcohol and other drugs, as well as the consumption of some medications.

Treatment

This condition, generally of genetic type, does not have a curative treatment. The treatments to be applied will generally be palliative , aimed at maintaining their vital signs, correcting difficulties and improving their well-being and quality.

In mild cases that achieve survival, the use of occupational therapy and cognitive stimulation is recommended. The need to apply a multidisciplinary treatment involving professionals from different disciplines, both medicine and occupational therapy, clinical psychology, physiotherapy and logotherapy should be assessed. And this without neglecting the treatment of parents and environment (which will require psychoeducation and counseling, as well as possibly a psychological intervention).

Bibliographic references:

  • Monteagudo, A. & Timor-Tritsch, I.E, (2012). Prenatal diagnosis of CNS anomalies other than neural tube defects and ventriculomegaly (online). Available at: //cursoenarm.net/UPTODATE/contents/mobipreview.htm?9/28/9665/abstract/4-12
  • Cohen, M.M. & Sulik, K.K. (1992). Perspectives on holoprosencephaly: Part II. Central nervous system, craniofacial anatomy, syndrome commentary, diagnostic approach, and experimental studies. J. Craniofac. Genet Dev. Biol., 12: 196.

What is ETHMOCEPHALY? What does ETHMOCEPHALY mean? ETHMOCEPHALY meaning & explanation (September 2022).


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