Meningocele

Meningocele (meningomyelocele) is a type of pathological condition that refers to anterior cerebral hernias caused by congenital deficiency of bone tissue in the area of the bottom of the anterior cranial fossa during embryonic development under the influence of certain external (infection) and internal (genetic) causes, resulting in a delay in the closure of the proto-vertebral brain plates (Kolliker plates), which leads to the formation of holes in the lower wall of the anterior cranial fossa, through which the brain matter prolapses. These hernias are called anterior cerebral hernias.

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Causes meningocele

There is a hypothesis of meningocele development that links the occurrence of primary ectopia of the meninges and brain through primary skull defects due to the cessation of skull development in the embryonic period. Springs explains the origin of brain hernias and meningocele by pathological changes in the cranial vault that arose as a result of meningoencephalitis suffered by the fetus during pregnancy. Klein believes that the cause of meningocele is intrauterine hydrocephalus, which leads to divergence of the skull bones and its perforation in the area of natural openings.

As already noted, they are formed by prolapse of the meninges, which form a sac filled with cerebrospinal fluid, and then, if the opening is large enough, by the exit of the brain tissue into this sac. Usually this prolapse occurs through the opening in the area of the root of the nose and glabella. Brain hernias and meningocele are divided into two types:

1. lying along the midline (nasofrontal);
2. lying on the sides of the root of the nose (nasothelial) and in the inner corner of the eye socket (nasoorbital).

There are various "theories" about the occurrence of meningocele.

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Risk factors

In addition to genetically determined meningocele, bone tissue defects in the anterior cranial fossa (as well as in other parts of the skull) can occur as a result of intrauterine, transplacental infection transmitted from the mother, intrauterine or birth trauma, as well as other unfavorable factors that negatively affect the body of a pregnant woman.

A significant role is played by the disruption of vitamin A and folic acid metabolism, calcium metabolism, as well as the effects of ionizing radiation and some teratogenic toxic substances. Each of the above pathogenic factors can lead to disruption of embryonic development during the period of laying the primary brain plate and its closure into the brain tube, which subsequently leads to the occurrence of malformations of the skull.

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Pathogenesis

The bone defect is in most cases located in the midsagittal plane, less often in the area of the occipital foramen and most often in the area of the frontonasal suture, nasopharynx and orbit. The diameter of the bone defect in meningocele varies from 1 to 8 cm, and the length of the bone canal, which has an internal and external opening, in which the hernia stalk is located, can be up to 1 cm.

Nasofrontal meningoencephalocele is always located in the area of the blind opening of the frontal bone, and its canal can be directed forward, downward or laterally, which determines the types of localization of the hernial sac: downward and laterally directed form nasoethmoid hernias, and downward and outward - nasoorbital. The structure of the hernial sac consists from the outside to the inside of the skin, hard, soft and arachnoid membranes of the brain and the substance of the brain.

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Symptoms meningocele

Signs of meningocele are divided into subjective and objective. The former mainly concern only complaints of the child's parents or an adult patient about the presence of a tumor in the area of the hernia prolapse. As a rule, there are no other complaints. The size of this "tumor" can vary from a lentil to a large apple, sometimes imitating a "second nose". To the touch, this formation is of a soft elastic consistency, sometimes its stalk goes deep into the root of the nose. The swelling can pulsate synchronously with heart contractions, increase with straining (a child's scream or cry), and decrease with pressure on it. These signs indicate a connection between the tumor and the cranial cavity.

An additional sign of anterior meningocele and brain hernias is deformation of the facial skeleton.

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Complications and consequences

Complications of meningocele are a serious phenomenon, usually ending in death. These include meningoepcephalitis, which occurs when the meningocele wall becomes ulcerated. However, these complications most often occur as a result of surgical removal of the hernial sac. These complications are:

1. intraoperative (shock, blood loss);
2. immediate postoperative (meningitis, meningoencephalitis, cerebral edema);
3. delayed postoperative (hydrocephalus, intracranial hypotension, cerebral edema, seizures);
4. late (epilepsy, mental disorders, intellectual disabilities).

Postoperative complications may include subarachnoid space fistulas, cerebrospinal fluid leaks, recurrent meningoceles and cerebral hernias.

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Diagnostics meningocele

The diagnosis is based on the following signs:

1. typical position of the hernial sac;
2. innate character;
3. the presence of dehiscences determined by palpation and radiography.

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Differential diagnosis

Differential diagnosis is difficult with small meningoceles. Such formations should be differentiated from dermoid cysts, meningioma, old organized hematoma, aneurysm, retrobulbar angioma, deforming nasal polyposis and paranasal sinus cysts, syphilitic gumma, brain echinococcus, various brain and skull tumors.

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Treatment meningocele

Congenital meningocele hernias are a rare disease, and not all children born with such a defect undergo surgical treatment, since some of them die shortly after birth. Treatment of meningocele and cerebral hernias in operable cases is only surgical. Treatment periods vary depending on many indicators, and the question of surgical treatment is decided in each case individually, taking into account the child's age, type of hernia, size of the defect and swelling, as well as the risk of complications.

Some surgeons are of the opinion that the operation should be started in the first months of life. P.A. Herzen (1967) believed that a child should be operated on in the first year of life. In case of brain hernias with rapid swelling growth and the risk of complications (inflammation or rupture of thinned tissues), it is necessary to operate in the first days after birth. If conditions allow for the use of a wait-and-see tactic, then the surgical intervention should be performed at the age of 2.1/2-3 years. At this age, complex plastic surgeries are used with the use of bone grafts. Such surgical interventions are within the competence of neurosurgeons.

Forecast

With surgical treatment, the prognosis for life is favorable. However, according to foreign statistics, even with a flawless surgical intervention, the mortality rate from secondary complications can reach 10%.

The evolution of the process depends on the stage of hernia development and the treatment applied. In incurable forms, when a significant part of the brain with vital centers is located in the hernial sac, death can occur at the age of 5-8 years, the cause of which is usually meningoencephalitis.

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