Neural tube defects in children
Introduction
Introduction to pediatric neural tube defects If a woman is pregnant within 3 months, the process of neural tube closure during embryo development is affected, that is, fetal brain or spinal cord dysplasia, which will form a deformity of the brain or spine, called the deformity of neural tube (DNT). DNT is an important public health problem worldwide. China is a well-known DNT country in the world. DNT is one of the main causes of maternal abortion and stillbirth. It is also one of the main causes of infant death and lifelong disability. It not only affects the quality of the birth population, but also threatens the physical and mental health of women and children, and imposes a heavy burden on families and society. At present, the prevention and treatment of DNT has been highly valued. basic knowledge The proportion of illness: 0.0015% Susceptible people: children Mode of infection: non-infectious Complications: hydrocephalus, brain swelling, cleft lip
Cause
Causes of neural tube defects in children
Genetic factors (20%):
In the study of the pathogenesis of DNT, it is difficult to distinguish the role of multiple genes from the effects of complex environmental factors, such as some families may be related to the environment in which they live together. Thus, in the pathogenesis, some characteristics are usually attributed to the results of genetic factors, such as the change of DNT incidence in different regions and ethnic groups, the incidence of close relatives with DNT is high, and the risk of recurrence in the DNT family is high.
Family studies have shown that pregnant women with a family history of DNT have a higher birth probability for DNT infants than the general population. According to Cater and Evans, as long as one parent has a history of DNT, the incidence of DNT in his offspring is 3%, significantly higher than the general population. Mothers who have had 2 or more DNT fertility experiences have a 10% increased risk of having DNT infants. In addition, the incidence of DNT in twins is higher than that in the general population, and the incidence of DNT is higher than that of double-oval twins.
These findings support the role of genetic factors in DNT. The results of genetic studies on DNT cannot be explained by single-gene mutations in Mendel's genetic law, but rather on the basis of genetic inheritance, ie, micro-genes. There is no recessive or dominant difference between the micro-effect genes, and the effect is cumulative. The effect accumulation and environmental factors can reach a certain threshold to cause disease. Therefore, the occurrence of DNT is caused by polygenic inheritance. As for the role of genetic factors in the occurrence of DNT, it has not been determined.
Folic acid deficiency (15%):
More research is related to the relationship between the lack of folic acid and other multivitamins (including vitamin A, B1, B2, C, D, E, niacin, etc.) and DNT in the first trimester of pregnancy, especially the relationship between folic acid and DNT. Breakthroughs have been made since the 1980s. It has been determined that early folate deficiency in women is the leading cause of DNT. Insufficient intake, malabsorption, metabolic disorders or increased need can lead to folate deficiency, resulting in DNk synthesis disorders, which affect cell division and proliferation.
Folic acid is a water-soluble vitamin that is essential for early fetal development. Early pregnancy is at the stage of embryo differentiation and placenta formation. Cell growth and division are very strong. If the folic acid deficiency in pregnant women will affect the normal development of the fetal nervous system - the normal development of the neural tube, the skull or spine will be poorly coupled and DNT will appear. Cause spontaneous abortion, stillbirth.
Zinc deficiency (18%):
Zinc deficiency in the mother's early pregnancy is also an environmental factor that causes DNT in the fetus. Insufficient intake of other trace elements such as copper, calcium, selenium, etc. can also induce DNT, but its exact role is still unclear.
Zinc-rich foods include: lean beef, pork, lamb, chicken hearts, fish, oysters, egg yolks, skimmed milk powder, wheat germ, sesame, walnuts, beans, peanuts, millet, radish.
Severe pregnancy reaction (8%):
As for the cause of DNT induced by severe pregnancy reaction, it may be because severe vomiting causes water loss to cause temporary dehydration, resulting in the deficiency of trace elements (such as zinc) or vitamins (such as folic acid).
In the early pregnancy (about six weeks after menopause), the increase of chorionic gonadotropin (HCG) in pregnant women, decreased gastric acid secretion and prolonged gastric emptying, leading to dizziness, loss of appetite, acid or food, or disgusting greasy nausea, morning vomiting, etc. A series of reactions, collectively referred to as pregnancy reactions. These symptoms generally do not require special treatment. After 12 weeks of gestation, as the level of HCG in the body decreases, the symptoms naturally disappear and the appetite returns to normal.
Severe pregnancy reaction: a small number of pregnant women reacted particularly severely with persistent vomiting, and even could not eat or enter the water, which is called "pregnancy spit." In addition to vomiting food, there are also mucous foams, and there may be bile or bloody substances. Pregnant women are in a state of dehydration due to frequent vomiting. If the condition continues to worsen, serious symptoms such as convulsions, coma, and jaundice may occur, and even death may result. Once the disease occurs, you need to go to the hospital for a timely visit.
Viral infection (20%):
Virological studies have shown that infection of cytomegalovirus or influenza A virus in the first trimester of pregnancy can cause fetal central nervous system developmental disorders, and DNT can occur.
Cytomegaoviyns (CMV) is a herpesvirus DNA virus. Widely distributed, other animals can be infected, causing infections in various systems, mainly genitourinary, central nervous system and liver disorders, ranging from mild asymptomatic infections to severe defects or death.
Influenza A virus is a common influenza virus. The symptoms after infection are mainly high fever, cough, runny nose, myalgia, etc. Most of them are accompanied by severe pneumonia. In severe cases, heart, kidney and other organ failures lead to death, mortality. Very high. The disease can be transmitted through various routes such as the digestive tract, respiratory tract, skin damage and conjunctiva.
Toxoplasma infection (10%):
Toxoplasmosis infection in early pregnancy may also cause DNT.
Any animal that ingests cysts, oocysts or living organisms of Toxoplasma gondii can be infected with toxoplasmosis. In the feces of felines, oocysts are often found. It can pollute grasslands, pastures, vegetables, fruits, etc. Toxoplasma cysts and living bodies are often found in the body and in the mouth of cats. Direct contact with cats is susceptible to infection. The dog is the intermediate host of Toxoplasma gondii, but it can also infect Toxoplasma gondii, but its feces and excretions are not contagious, so it is not infective with dogs to infect with toxoplasmosis. Other livestock, poultry, such as chickens, ducks, geese, pigs, cattle, horses, sheep and other animals sometimes have toxoplasma cysts and living bodies. Therefore, meat and egg milk may also be infected, and sometimes there are toxoplasma cysts or living bodies in the fish. Fish is also a source of infection, and some blood-sucking insects can also be infected when biting people.
People can also be infected with each other. Pregnant women can transmit Toxoplasma gondii to the fetus through the placenta. In women with toxoplasmosis, the fetus must be infected if there is a blood-staining period (ie, toxoplasma, swallow body, and pointed body activity) during pregnancy. 80% of all fetuses are insidious chronic toxoplasmosis patients, carrying a lifetime. Some of them become ill-type physiques, which are actually patients with multiple disease-type toxoplasmosis. Few parts become deformed and mentally retarded. In the lactation period, because the baby becomes "immunized with disease", even if the breast has Toxoplasma gondii, the baby is not a serious problem, and every time the milk is fed, a live vaccine is given. Babies can grow and develop as usual. But the symptoms are different.
Taking anti-epileptic drugs (5%):
Pregnant women with epilepsy take anti-epileptic drugs such as valproic acid, phenobarbital and phenytoin, and their offspring are prone to DNT.
Taking birth control pills (5%):
Oral contraceptives in the first trimester, taking certain anti-tumor drugs such as methotrexate, adenine and guanidinium, as well as large or continuous application of cortisone or prednisolone (prednisolone), can induce DNT. Its mechanism of action may be related to interfering folate metabolism.
Radiation exposure (10%):
During the first trimester of pregnancy, the mother or the pelvis receives radiation, and the development of the fetal central nervous system is often affected, and some DNT occurs.
Prevention
Pediatric neural tube defect prevention
Neural tube defects (including spina bifida) are generally considered to be a polygenic genetic disease. Although the etiology is not fully understood, women taking 400 g of folic acid daily before pregnancy to 3 months of pregnancy can reduce the occurrence of neural tube defects.
1. Add folic acid.
2. Genetic counseling: DNT's genetic counseling mainly includes pre-marital, pre-pregnancy and pregnancy counseling, understanding the family history of both couples, the pregnancy history of pregnant women, the diet of this pregnancy, medication and exposure to radiation, harmful chemicals, pathogenic microorganisms In other cases, health care for pregnant women to reduce the incidence of children with DNT.
3. Prenatal examination: The prenatal examination of DNT mainly includes amniotic fluid, maternal serum alpha-fetoprotein (AFP) test and B-ultrasound examination. The fetal DNT can significantly increase amniotic fluid AFP level, and the mother serum AFP level also rises. High, B-ultrasound can scan the shape and size of the skull of the fetus or the structure of the spine. For example, the fetus without a brain malformation shows the disappearance of the round aura of the fetal head. The fetus with a meningeal bulge can have a cystic swelling in the defect of the skull wall of the fetal head. Connected to the object, the spine can be found in the spina bifida, the fetus with bulging bulge can find boundary rules and clear cystic bulge in the spine. Once the prenatal examination is found, the pregnancy should be terminated immediately to reduce DNT. The child was born.
Complication
Pediatric neural tube defects complications Complications, hydrocephalus, brain swelling, cleft lip
Can occur without brain malformation, may be associated with other parts of the body deformity, such as cleft palate, cervical spina bifida, narrow chest, imbalance of upper and lower limbs, lack of humerus and thumb, etc., almost all with maternal amniotic fluid, and spina bifida The most common malformations are hydrocephalus, deformed foot, skull cavity, meningocele, brain swelling, cleft lip, congenital heart disease, etc., prone to nutritional ulcers, gangrene, muscle contracture, hip dislocation, horseshoe Foot deformity, often incontinence.
Symptom
Symptoms of pediatric neural tube defects Common symptoms Muscle contracture muscle atrophy Open neural tube defects Hydrocephalus Reflex bone fracture Hip dislocation edema convulsion
Children with neural tube defects DNT is a group of congenital malformations with many different clinical phenotypes, including no brain malformations, spina bifida and brain swelling. The following are some common DNTs:
1, no brain malformation
Anencephalia is a severe DNT, mainly characterized by the loss of all or most of the brain. The skull's defect begins at the top and extends to any part of the occipital foramen. The child suffers from facial deformity due to lack of skull collapse, such as shortening of the anterior cranial fossa and shallowing of the eyelids, causing the eyeball to protrude forward, the lower jaw close to the sternum, the mouth is half open, the auricle is thick, and the front protrudes on both sides of the head. It is a very strange "frog face". May be associated with other parts of the body deformity, such as cleft palate, cervical spina bifida, narrow chest, imbalance of upper and lower limbs, lack of humerus and thumb. Almost all of the mother's amniotic fluid is involved during pregnancy.
2, spina bifida
Most of the spina bifida defects are on the posterior side, and the posterior spina bifida can be divided into the following categories:
(1) Spina bifida with spinal meningocele (meningomyelocele): occurs mostly in the lumbosacral region and can also be seen in the back. The mass is round and may be as large as an orange. In addition to the meninges and cerebrospinal fluid, there are nerve tissues. The outside is covered with very thin skin and may only be covered with a translucent meninges in the center. In newborns, sometimes only granulation tissue, it is easy to have ulcers. The spinal cord tissue enters the upper part of the mass, and the nerve fibers are widely distributed in the mass, and then the lower part is returned to the spinal cord portion of the spinal canal. The dysplastic spinal cord, nerves, spinal membrane, and vertebral muscles are often associated with the skin. In some cases, the spinal cord is not covered with an envelope, and there is no skin covering, which is a valgus deformity. These patients have almost all of the lower limb paralysis and incontinence, and some patients have hydrocephalus. The cerebral palpebral bulging of the ankle occurs under the outlet of the lumbosacral plexus. There is no sputum in the lower limbs, but the urination is still incontinent. When the newborn is crying, it can be seen in the urine. In the male baby, the urine cannot be urinated normally.
(2) Spina bifida occulta: This type of malformation is common. Only the spinal canal defect, the spinal cord itself is normal, so there is no neurological symptoms and no effect on health. In the past, this disease was thought to be related to enuresis or other urinary tract diseases, but the incidence of recessive spina bifida was similar in normal children and children with urinary tract disorders. There are some abnormalities on the skin of the defect site, such as a mane, a small nest, sputum, pigmentation, and subcutaneous fat thickening. There may be congenital cysts or lipomas on the defect. X-ray examination can confirm the diagnosis.
(3) Spinal fissure with meningocele: There are cysts in the spinal defect, which occur more in the lumbosacral region. The mass is round and may grow very large. There is only the meninges and cerebrospinal fluid, and there are no spinal cords or other nerve tissue. Children with simple meningocele have no paralysis or other neurological symptoms. If the outside of the wall is normal skin, the tumor is rarely infected. If the wall of the capsule is thin or has been ruptured, it often forms a cerebrospinal fluid leak or a combined infection.
(4) Other malformations: Spina bifida may be accompanied by some rare deformities such as:
1 Water in the spinal cord: occurs mostly in the thoracic vertebrae, thoracolumbar or lumbosacral region. Many fluid volumes remain in the central canal of the spinal cord, and there is only atrophic spinal cord tissue in the sac.
2 no spinal cord: the spinal cord is not developed often with or without brain malformation, and soon after birth.
3 Dermoid cysts, lipomas or teratoma tissue: may invade the dura mater or spinal cord.
3, cranial fissure, meningocele and brain meningocele
Cranioschisis is a congenital skull dysplasia, which is characterized by tissue, cerebrovascular and dural tissue signals, and other structural changes and deformities in the skull. Craniotomy and spina bifida have the same nature, but are rare, and their incidence is only 1/10 or less of spina bifida, mostly in the occipital bone. Secondly, the frontal bone can also occur on the face, near the nasal bones, even from the nostrils, and is mistakenly considered to be a polyp for biopsy to form an intracranial infection. It usually occurs in the midline, but a few can be developed along any of the sutures. The larger mass of the base often contains brain tissue. The skull X-ray can show the relationship between the cranial fissure and the cranial suture and the main intracranial sinus. CT and MRI can show the contents of the capsule. Cranial fissures may be recessive but rare. Cranial fissures may also be complicated by meningocele or meningoencephalocele. Most of the bulging is accompanied by other brain malformations, often with complications such as mental retardation, convulsions, hydrocephalus, blindness and dyskinesia. Simple meningocele can be cured after resection, but patients with severe neurological symptoms have a poor prognosis.
4, nervous system symptoms
It is related to the degree of involvement of the spinal cord and spinal nerves. The more common neurological symptoms are lower extremity paralysis, incontinence and so on.
If the lesion is in the lumbosacral region, the lower limbs are delayed and the muscles are atrophied, and the sensory and tendon reflexes disappear. Lower extremities often have lower temperature, cyanosis and edema, and are prone to nutritional ulcers and even gangrene. Often muscle contractures, sometimes hip dislocation, lower extremities often show clubfoot deformity. Often incontinence. In some light cases, neurological symptoms may be mild.
As the age of sick children increases, neurological symptoms often worsen. This is related to the fact that the spinal canal grows faster than the spinal cord, and the involvement of the spinal cord and spinal nerves is gradually increased.
Examine
Pediatric neural tube defects examination
First, laboratory inspection
1, blood test: peripheral blood leukocytes significantly increased, suggesting concurrent infection.
2, cerebrospinal fluid examination: cerebrospinal fluid white blood cells significantly increased, suggesting intracranial infection.
Second, auxiliary inspection
1. The skull X-ray film can show the relationship between the cranial fissure and the cranial suture and the main intracranial sinus.
2. CT and MRI can display the contents of the capsule. CT and MRI scans can reveal the bulging of the spinal cord, spinal nerves and meninges, as well as local adhesions.
3, the spine X-ray film shows the absence of laminar spine, the pedicle spacing is widened, the bone defect site is connected with the soft tissue mass.
Diagnosis
Diagnosis and diagnosis of neural tube defects in children
If the cranial fissure occurs on the face, if it is removed from the nostrils, it is easy to mistakenly believe that it is a nasal polyp.
Nasal polyps are the result of tissue edema caused by long-term inflammatory reactions in the nasal mucosa. Most of the nasal polyps are derived from the sinus ostium of the middle nasal passage, the nasal passage complex and the ethmoid sinus. The highly edematous nasal mucosa swells from the middle nasal passage and the sinus ostium to the nasal cavity to form polyps. The anterior nasal examination revealed one or more new creatures in the nasal cavity that were smooth, grayish-white or reddish-translucent, such as freshly lychee-like or peeled grapes or in the form of a storage rubber bag. It is soft, movable, not easy to bleed, and does not feel pain when palpation. According to the above typical findings, the diagnosis is easier.
It is generally not difficult to diagnose according to clinical manifestations and auxiliary examinations. Craniospasm occurs mostly in the midline, but a small number can develop along the suture, and the skull X-ray film can help identify.
