Malformations of the CNS

CNS malformations include a wide spectrum of anomalies that arise during the ontogenesis of the brain and spinal cord. They have a variable clinical picture depending on the type and extent of the defect. They are a common cause of intrauterine fetal death and also a common cause of death in children during the first year of life. Brain malformations can be the cause of epilepsy and psychomotor retardation. Dysgenesis of the cerebral cortex is one of the most common causes of epilepsy in children.

Most malformations of the CNS arise as a result of disruption of the early embryonic development of the central nervous system (CNS), through the action of external or internal noxia or genetically conditioned factors. The basis for the development of the CNS is the neural plate (a plate of thickened ectoderm), which is established around the 18th day of gestation and closes during the 3rd and 4th week to form the brain sacs and the spinal cord. The ventricular system forms in the 8th week and the corpus callosum in the 10th week. Other important events are: cell proliferation (division of nerve cells), cell migration, cell differentiation and cell death.

Malformations of the CNS by period of onset

 * Defects arising during the period of dorsal induction (3rd-4th week of gestation)


 * Anencephaly; encephalocele; myeloschisis; spina bifida ; malformations of the spinal cord; malformation of the cerebellum.


 * Defects arising during the period of ventral induction (5th-6th week of gestation)


 * Holoprosencephaly ; less severe facial dysmorphia.


 * Disorders of neuronal and glial proliferation (2nd-5th month of gestation)


 * Microcephaly; microlissencephaly, megalencephaly, hemimegalencephaly,…


 * Neurocutaneous syndromes


 * Tuberous sclerosis ; Hippel-Lindau disease ; Sturge-Weber syndrome


 * Disorders of cell migration and cortical organization


 * Lissencephaly; gray matter heterotopia; schizencephaly; polymicrogyria; pachygyria


 * Hydrocephalus group


 * Arnold-Chiari malformation ; Dandy-Walker malformation


 * Brain damage in the process of cellular differentiation (from the 5th month of gestation) and myelination (from the 7th month of gestation).



Dorsal induction disorders – dysraphia
The incidence of these defects in the Czech Republic in the years 1994–2010 was as follows (total incidence, i.e. births and non-births - prenatally diagnosed): anencephaly 2.75 per 10,000, encephalocele 1.14 per 10,000, spina bifida 4.09 per 10,000 live born.

Anencephaly [ edit | edit source ]
Anencephaly ( cranioschisis totalis ) is a congenital absence of the brain due to non-closure of the cerebral compartment of the neural tube. This defect is not compatible with life. It is often accompanied by polyhydramnios. Thanks to advances in prenatal diagnosis, this defect is almost non-existent at birth.

Encephalocele [ edit | edit source ]
Encephalocele is a prolapse of brain tissue into the cranial cleft, most often in the frontal or occipital regions. The tissue in the keel is often damaged. Using sonography, CT and MRI, we can determine the contents of the hernia. This malformation is often isolated, without other associated anomalies.

Spina bifida [ edit | edit source ]
Video in English, definition, pathogenesis, symptoms, complications, treatment. Spina bifida is a congenital spina bifida. It most often affects the lumbar and lumbar region.

Spina bifida occulta [ edit | edit source ]
Spina bifida occulta is a split of one or more vertebrae that does not involve the spinal cord or the spinal cord. The skin above the defect tends to be more hairy and pigmented. It is usually an asymptomatic, incidental finding,  occurring in about 10% of otherwise healthy individuals. If the defect is associated with a spinal anomaly, lipoma, tethered cord syndrome, etc., it may have significant neurological symptoms, usually paraparesis of the lower limbs, sometimes with micturition and defecation disorders.

Spina bifida cystica [ edit | edit source ]
Spina bifida cystica is a split of the spine, in which a sac formed by the spinal cord covers (meningocele) penetrates through the defect into the subcutaneous tissue, or and spinal cord with spinal nerves (meningomyelocele).


 * Meningocele

Herniation of the meningeal sheaths of the spinal cord into a cyst, usually located in the lumbosacral region. If the hernia is perforated, the child is at risk of meningitis. Neurological findings on the lower limbs may be minor.


 * Meningomyelocele

Herniation of the meningeal sheaths, nerve roots and spinal cord into the dorsal cleft. 80% of meningomyeloceles are found in the thoracolumbar, lumbar and lumbosacral regions. Meningomyelocele is often associated with Chiari malformation II. type (Arnold-Chiari). There is often a significant neurological deficit - paraparesis, micturition and defecation disorders.

Myeloschisis [ edit | edit source ]
Myeloschisis ( rhachischisis ) is a split of the spine with exposure of nerve tissue that is not covered by skin or spinal cord sheaths. This malformation is always associated with severe spinal cord dysfunction.

Separate malformations of the spinal cord [ edit | edit source ]

 * Syringomyelia
 * Hydromyelia



Disorders of ventral induction

 * Holoprosencephaly
 * Less severe facial dysmorphia

Disorders of neuronal and glial proliferation
This group of malformations is characterized by a reduction or, conversely, an increase in the number of cellular elements, which also have an abnormal appearance (giant neurons, balloon cells).


 * Microcephaly with simplified gyrification


 * It arises as a result of suppression of cell proliferation.
 * Findings on the brain: severe microncephaly, poor gyrification, shallow grooves, cortical layer normally thick or reduced (probably due to premature depletion of the germinal matrix).
 * Clinical picture: microcephaly, abnormal neurological picture, usually refractory epilepsy from an early age.
 * Autosomal recessive inheritance.


 * Microlissencephaly


 * Findings on the brain: noticeably small brain, poor gyrification, agyria or pachygyria, distinctly thickened cortex.
 * Clinical picture: microcephaly, abnormal neurological picture, epilepsy.
 * Mostly autosomal recessive inheritance.


 * Hemimegalencephaly


 * It arises as a result of excessive cell proliferation. The entire hemisphere or only part of it grows disproportionately.
 * Findings on the brain: Enlargement of part or the entire hemisphere, cortical dysplasia (pachygyria, polymicrogyria), white matter abnormalities, heterotopia. Neurons have an atypical shape.
 * Clinical picture: epilepsy, mental retardation, sometimes hemiparesis and hemianopsia.
 * Occurrence in isolation or within genetic (neurocutaneous) syndromes (hypomelanosis Ito, neurocutaneous melanosis, naevus sebaceus syndrome, Klippel-Trenaunay,...).


 * Bearing cortical dysplasia type 2


 * Probably the most common anomaly demonstrated in patients with refractory focal epilepsy.
 * Findings on the brain: abnormal balloon cells, disturbed organization of cortical layers, increased astrocytes. Most often in pericentral areas and frontally.
 * Occurrence in isolation or in patients with tuberous sclerosis.


 * Focal cortical dysplasia type 2 with neoplastic changes



Disorders of cell migration and cortical organization
During brain development, neurons migrate from the germinal matrix to the cortex, and then their spatial arrangement and interconnection ("organization") occurs. These processes can be disturbed by endogenous (hereditary) and exogenous influences (intrauterine infections, toxins, bleeding).

Diagnostics

 * MRI – the most accurate imaging method.
 * CT, sonography - differentiates only gross morphological changes, has only indicative value.
 * EEG – to determine the severity of the morphological findings.
 * SPECT (single photon emission computed tomography), magnetic proton spectroscopy (1H-MRS), positron emission tomography (PET) – reflect metabolic changes in the dysplastic cortex.
 * Genetic testing.
 * Histology and histochemistry.

Related Articles

 * Hydrocefalus (neonatologie)
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