Parencephaly is a congenital abnormality, in the presence of which the surface of the brain connects with one of the lateral ventricles (the cavity in which the cerebrospinal fluid is located) and is covered with cone-shaped grooves (deep into the brain).
Most often formed in the area of the middle cerebral artery.
Parencephaly is divided into two types: false and true.
False view of anomaly
False – has cystic formations in the brain tissues that do not connect with its ventricles, and do not reach its surface, and can communicate with each other.
Basically, these cystic formations are in the white matter and can be placed in one or both of its hemispheres. The pattern of the cerebral cortex in this case is preserved, and the walls of the false cystic formations include scar tissue.
In this case, cystic formations are diverticula of the ventricles of the brain, directed to its surface. It is extremely rare for cysts to be in a separate position in relation to the brain and not communicate with its ventricles.
The sizes of cystic cavities are very diverse and occupy most of the hemisphere. Inside, the cavity has a smooth structure and consists mainly of an ependymoid shell.
In the case when the cyst is isolated and does not have a common passage with the ventricles of the brain, its filling consists of a yellow protein liquid, if it is reported, its content consists of cerebrospinal fluid.
Most often in the walls of the cystic cavity can be traced tissue with defects in the structure of the cerebral cortex. In some cases, they reveal hemoglobinogenic pigmentation, as a result of hemorrhages, as well as minor anoxic necrosis.
In the region where the cyst connects with the ventricles of the brain, the lateral ventricles are often dilated and have an irregular shape.
The picture of the cerebral cortex in the place of cystic formation is practically absent (this region of the cerebral hemisphere is covered by a thin layer consisting of the soft sheath of the brain and the medulla) or immersed radially in the direction of the cavity.
In the convolutions of the cerebral cortex that are closest to the cyst, histological changes are detected, which are characterized by a violation of the orientation of the cell layers, as well as by the rarefaction of the ganglion cells. May be present and focal microses in the soft shell of the brain. This kind of disturbance is the result of true parencephaly.
There are various degrees of abnormal development, but the most pronounced is the cystic brain (two large bladders filled with cystic fluid), characterized by a pathological process involving the hemispheres, the basal nuclei, as well as the brain stem. It should be noted that with this type of pathology, cystic changes of the cerebellum are extremely rare.
Etiology of the disorder
This disease can be as a result of brain injury, early cerebral microsome, and fetal disturbance of the nervous system.
Such defects in the development of the brain as cystic cavities are most often intrauterine pathologies, and not only due to impaired uterine circulation, but also a defect in the process of morphogenesis.
Sometimes cystic formations can appear at any age and be a consequence of brain injury, hemorrhage, infectious and inflammatory processes, various types of tumors of a destructive effect on the white and gray matter of the brain.
In the process of filling cavities with cystic fluid, the medulla is displaced, which often causes secondary brain tissue damage. There is also a violation of the orientation of the cell layer.
With this disease, the total brain mass decreases by 20–25%, insufficient development of the frontal lobes and cerebral hemispheres is detected, nerve cells are not differentiated and are practically absent on the surface of its cortex.
There is a lack of development of the vascular system, as well as disrupted the process of maturation of the sheath of nerve fibers.
Young children have epilepsy episodes, asymmetry of the cranium is observed, in which the affected side erupts somewhat in the temporal region, significant mental retardation, nerve cell disorders in the cranial region, and paralysis of the extremities is also observed.
Often revealed a violation of the development of the corpus callosum, microcephaly, as well as other defects in the development of organs.
Causes of pathological development
Like most intrauterine malformations, the risk of developing parencephaly occurs due to the influence of harmful factors during pregnancy (smoking, alcohol, various types of infection, structural features of the internal organs of the mother), which lead to disruption of the development of the vascular system of the brain.
The same risk factor may be previous abortions, premature pregnancies, the age of the mother (the most successful is the age from 17 to 30 years).
Transmitted infectious diseases during gestation can lead to impaired uteroplacental circulation, which can lead to intrauterine asphyxia of the fetus.
In the case of immunological incompatibility, the mother’s body produces antibodies that, having crossed the placenta, penetrate into the nervous system of the fetus, exerting a toxic effect on it.
Diagnosis and treatment options
More recently, it was almost impossible to detect the presence of parencephalia, as well as to distinguish it from other malformations, and it was detected only during the autopsy.
However, today there are various research methods that can confirm or deny the presence of this anomaly.
The diagnosis is based on various neurological examinations: ultrasound, CT, brain MRI. In some cases, this disease causes hydrocephalus.
Treatment depends on the degree of damage to the brain tissue, as well as the location of the cysts, their volume and quantity.
Often, patients show only minor symptoms of the nervous system, which is accompanied by normal mental development. In this case, supportive therapy is prescribed, with the help of medicines, physiotherapy.
In case of deterioration of the patient’s condition, accompanied by the development of secondary hydrocephalus and an increase in epilepsy attacks, surgical intervention is carried out.
In the course of surgical treatment, parencephalic cysts are dissected and the brain tissue excised by the vascular plexuses located in the depth of the cavity is excised.
In case of ineffective surgical treatment, the cystic contents of the ventricles of the brain are pumped out with the aid of a ventriculoperitoneal shunt. However, with a large volume of affected areas of the brain, the outcome is unfavorable.
With congenital brain parencephaly, the prognosis is unfavorable, if the cavities (cysts) are large enough, children die during the first months of life.
In the case of single cysts of a small size, the patients are diagnosed with mental retardation, and the probability of epileptic seizures and paresis of the extremities is also quite high.
In the case of false parencephaly (when cyst formation occurs as a result of infections or head injury), the child develops absolutely normally before the development of the underlying disease.