Pachygyria: the “smooth” brain – The Beautiful Mind

The pachygyria It is a congenital malformation of the cerebral cortex. It is the result of poor neuronal migration, causing abnormally thick gyri.

Children with pachygyria usually They often have varying degrees of intellectual disability, developmental delays, and seizure disorders.as main symptoms.

What is the cause of pachygyria? How is it diagnosed and what symptoms accompany it? Can it be treated? Keep reading to get the answer.

What is the cerebral cortex and what does it look like?

The cerebral cortex covers the surface of the two cerebral hemispheres. The bark has a highly folded structure. This makes it possible to have a large surface area in a small space compared to the surface area of ​​a smooth brain of the same size.

Thus, on the surface of the cortex you can distinguish indentations, which are grooves and fissures of variable size; and gyri, which are protuberances located between the slits.

The bark It is composed mainly of glial cells and neuronal cell bodies.sy is organized into six layers in which neurons are organized precisely.

What is pachygyria?

The pachygyria It is a malformation that belongs to the lissencephaly family. (disorders characterized by a smoothing of the surface of the cortex). It is found between agyria, -the total absence of convolutions-, and polymicrogyria (malformation of the cortex that presents excessive convolutions).

The pachygyria It is a serious congenital malformation (with a fairly high mortality rate) in which the organization of the neurons of the cerebral cortex and its structure are altered. Causes that the cerebral cortex is thinner than normalbecause some of the six layers that make up the cortex are absent or their cells are not well organized.

Furthermore, the main feature is that the bark has slightly pronounced indentations and thicker and wider convolutions than normal. This makes the appearance of the bark smoother, less “folded”.

Symptoms of pachygyria

The most common thing is that children with pachygyria present the following: symptomatic triad: intellectual disability, seizures, and severe developmental impairment. However, they usually present a wide variety of symptoms that we will see below:

Epileptic seizures(present in 90% of children) that usually appear between the fourth and seventh month of lifewhich are life-threatening and resistant to treatment.
Developmental delays and disorders, both in motor development and in language development. They usually present hypotonia in the extremities (which makes it difficult for them to walk and stay upright) and poor speech. In addition, they usually present microcephaly.
Intellectual disability from severe to profound that limits all cognitive functions and the autonomy of the person.
Behavioral alterations and other mental disorders.

How is it diagnosed?

The absence of characteristic facial or physical features can make diagnosis difficult. The diagnosis, therefore, is based on the clinical examination of symptoms and neuroimaging techniques that allow us to appreciate the cerebral cortex in detail.

CT (computed axial tomography) provides images of the brain with high spatial resolution. However, cortical malformations are easier to visualize in vivo, Therefore, MRI is more useful, since it offers greater contrast and better differentiation of the gray matter and white matter regions.

In the images you can see thickened cerebral gyri with few shallow indentationsas well as the incomplete development of the Sylvian fissure.

Causes of pachygyria

Pachygyria is caused by a interruption in the fetal neuronal migration process. This failure may be caused by environmental influences or genetic alterations, which we will briefly address.

Neuronal migration occurs between the seventh and twentieth week of gestation. The objective of this migration is formation of the six layers that form the crust. However, in pachygyria, only four of the six layers are present (which makes the crust thinner than normal).

Simply put, in a brain with pachygyria the first layer (molecular or plexiform) is present and is the same as in a normal brain, but the second, third and fourth layers have a smaller number of cells than a healthy brainas well as a thinner structure.

As we mentioned, this alteration in neuronal migration can be caused by environmental influences, such as exposure to certain substances or elements (radiation, alcohol, mercury…).

Regarding the genetic alterations responsible for pachygyria, they are too complex to be addressed in this article. However, we must point out that The most common genetic alterations that cause pachygyria are usually related to the X chromosome and chromosome 17.. Likewise, the absence of the LIS1 gene seems to cause lissencephaly.

There is no treatment

As with almost all rare diseases, There is still no treatment that is not simply symptomatic. In this case, the administration of antiepileptic drugs to treat seizures is essential.

As we have mentioned, it is a serious malformation that causes the death of the majority of children born with pachygyria. However, when this malformation does not affect the cortex, it is compatible with life and the child’s involvement will depend on the region affected by the malformation.

In case of survival, Collaboration between different professionals will be essentialfrom physiotherapists who help work on motor disorders such as hypotonia, to special education teachers who make a curricular adaptation for teaching the child.

And counting, of course, on the collaboration of doctors, nurses, occupational therapists and psychologists, which improve the quality of life of children and promote their autonomy, to the extent possible.

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