Pachygyria is a congenital malformation of the cerebral cortex. It results from poor neuronal migration, causing abnormally thick folds of the brain.
In general, children with pachygyria have varying degrees of intellectual disability. Other important symptoms include developmental delays and seizure disorders.
But what causes pachygyria? How is it diagnosed and what are the symptoms? Is there a treatment for it? Keep reading to find out.
What is the cerebral cortex and what does it look like?
The cerebral cortex covers the surface of the two cerebral hemispheres. The cortex has a very pleated structure, which makes it possible to have a large surface area in a small space compared to the surface of smooth brains of the same size.
Furthermore, you can distinguish two things on the surface of the cortex. First, gorges. These are grooves of variable size. Second, pleats, which are bulges that are located between the slots.
The cortex mainly consists of glial cells and neuronal bodies. It is organized in six layers in which neurons are precisely arranged.
Pachygyria: What Is It Exactly?
Pachygyria is a malformation belonging to the lissencephaly group. To clarify, the latter refers to conditions characterized by a smoothness of the surface of the cortex. It ranges from agyria (the total absence of brain folds) to polymicrogyria (a malformation of the cortex that shows excessive folds.
Furthermore, pachygyria is a serious birth defect with a fairly high mortality rate. There is a change in the organization of the neurons of the cerebral cortex and its structure. It causes the cerebral cortex to be thinner than normal because some of the six layers that make up the cortex are absent or their cells are not well-ordered.
In addition, the main characteristic is that the cortex has few pronounced fissures and thicker and wider folds than normal. This makes the cortex look smoother (less ‘folded’).
The Symptoms of Pachygyria
The most common symptoms in children with pachygyria include intellectual disability, seizures, and severe developmental disabilities. However, there are other symptoms worth mentioning:
- Seizures (present in 90% of children). They usually appear between the fourth and seventh month. These are quite resistant to treatment, thus endangering the life of the child.
- Developmental delay and disturbances, both in motor development and in language development. These children usually exhibit hypotonia in their limbs, which makes it difficult for them to walk and remain upright. They also have impaired speech. Furthermore, they usually have microcephaly.
- Severe to profound intellectual disabilities that limit the child’s cognitive functions and autonomy.
- Behavioral disorders and other mental disorders.
The absence of characteristic facial features or physical features can hinder the diagnostic process. Therefore, the diagnosis is based on the clinical examination of the symptoms and on neuroimaging techniques that allow medical professionals to evaluate the cerebral cortex in a more detailed way.
CAT (Computerized Axial Tomography) scans provide high spatial resolution images of the brain. However, the malformations of the cortex are easier to visualize in vivo. For that reason, magnetic resonance imaging is more useful because it provides greater contrast and better differentiation of gray and white matter.
In the images, it is possible to see thickened cerebral convolutions with few shallow fissures, as well as the incomplete development of the Sylvian fissure.
The Causes of Pachygyria
The cause of this condition is a disruption of the fetal neuronal migration process. Environmental influences or genetic changes can cause this failure. Let’s discuss this further.
Neuronal migration occurs between the seventh and twentieth week of pregnancy. The purpose of this migration is to form the six layers that make up the cortex. However, in pachygyria, only four of the six layers are present, making the cortex thinner than normal.
Furthermore, in brain with pachygyria, the first layer (molecular or plexiform) is present and is the same as in normal brain. However, the second, third and fourth layers have fewer cells than healthy brains and they have a thinner structure.
As we mentioned above, environmental influences can cause this change in neuronal migration. For example, consider exposure to certain substances or elements (including radiation, alcohol and mercury).
The genetic changes responsible for pachygyria are too complex to discuss in this article. However, we should point out that the most common genetic changes that cause pachygyria are related to the X chromosome and the 17th chromosome. Also, the absence of the LIS1 gene appears to be the cause of lissencephaly.
Lack of treatment
As with almost all rare diseases, only symptomatic treatment exists. In this case, the administration of antiepileptic drugs to treat seizures is essential.
As you can read, this is a serious deformity that causes death in most children born with it. However, if this malformation does not affect the cortex, you can live with it and the child’s involvement depends on the area affected.
In the event that the child survives, it is necessary to work with a variety of professionals, from physiotherapists who help work on motor disorders such as hypotonia, to special education teachers who can adapt a curriculum for the child’s education .
Of course, these are not the only professionals to work with, as doctors, nurses, occupational therapists and psychologists are essential. They can help improve the child’s quality of life and help them become as autonomous as possible.