Pediatric spina bifida

　　One, Etiology

　　To study the causes of spina bifida, it is necessary to understand the normal process of neural embryonic development. On the 16th day of human embryonic development, the ectoderm above the notochord thickens to form a neural plate, which then increases bilaterally to form neural folds and converge towards the midline, fusing to form the neural tube. The fusion of the neural tube first appears on the 22nd day, at the level of the third somite, which is the future brainstem formation area. The fusion starts from the optic vesicle and develops towards both the head and tail. The anterior neural tube closes between the 23rd and 26th day of embryonic development, and if it does not close completely, it can lead to craniorachischisis and anencephaly. The posterior neural tube closes between the 26th and 30th day of embryonic development, and if it does not close completely, it can lead to spina bifida.

　　Two, Pathogenesis

　　Spina bifida is a neural tube defect (NTD), and NTD is a polygenic genetic disease with an extremely complex pathogenesis, involving multiple aspects. Many factors can interfere with the process of onset, and according to animal experiments, clinical observations, and epidemiological studies, it is believed that NTD is the result of the combined effects of genetic factors and environmental factors (uterine environment):

　　1. Genetic Factors In the study of the pathogenesis of NTDs, it is difficult to distinguish between the effects of polygenic or multifactorial action and the complex effects of environmental factors, such as the common living environment in certain families. Therefore, in the pathogenesis, certain characteristics are usually attributed to the effects of genetic factors, such as changes in the incidence rates of NTDs among different regional and ethnic populations, high incidence rates of NTDs in consanguineous marriages, and high recurrence risks of NTDs within NTD families.

　　Family studies have shown that pregnant women with a family history of NTDs have a higher probability of giving birth to NTD infants than the general population. The research by Cater and Evans suggests that if either parent has a history of NTDs, the incidence rate of NTDs in their offspring is 3%, which is significantly higher than that of the general population. The risk of giving birth to an NTD infant is increased by 10% for mothers who have had two or more NTD pregnancies. Additionally, the incidence rate of NTDs in twins is higher than that of the general population, and the incidence rate of NTDs in monozygotic twins is higher than that in dizygotic twins. These research results all support the role of genetic factors in NTDs.

　　The research results on the genetics of NTDs cannot be explained by Mendelian genetic laws of single-gene mutations, but rather by the basis of multiple gene inheritance, that is, minor genes. There are no recessive or dominant differences between the minor genes, and their effects are cumulative. The occurrence of disease can be triggered when the cumulative effects and the effects of environmental factors reach a certain threshold. Therefore, the occurrence of NTDs is caused by polygenic inheritance, and the role of genetic factors in the occurrence of NTDs has not yet been determined.

　　2. Environmental Factors Environmental teratogens usually act on the mother in the early stages of pregnancy, typically within the first 3 months, leading to obstacles in the development of the neural tube and causing malformations. Common environmental factors associated with NTDs include deficiencies of folic acid and various vitamins during the early stages of pregnancy, deficiencies of zinc and other trace elements, severe pregnancy reactions, viral infections, the use of certain drugs, alcoholism, radiation exposure, and contact with certain chemical substances.

　　Research has focused on the relationship between the deficiency of folic acid and various vitamins (including vitamin A, B1, B2, C, D, E, niacin, etc.) during the early stages of pregnancy and the occurrence of neural tube defects (NTDs), especially the relationship between folic acid and NTDs, which has made breakthrough progress since the 1980s. It has now been confirmed that folic acid deficiency during the early stages of pregnancy is the main cause of NTDs. Various reasons such as insufficient intake, poor absorption, metabolic disorders, or the need for increased intake can lead to folic acid deficiency, causing obstacles in DNA synthesis and thus affecting cell division and proliferation. Folic acid is a water-soluble vitamin and an essential nutrient for the early neural development of the fetus. The early stages of pregnancy are the time when the embryo is differentiating and the placenta is forming, with intense cell growth and division. If the pregnant woman lacks folic acid, it will affect the normal development of the fetal nervous system, the雏形 of the neural tube, and later may lead to poor fusion of the skull or vertebral bones, resulting in NTDs and causing spontaneous abortion or stillbirth.

　　Maternal early pregnancy zinc deficiency is also an environmental factor that can cause NTD in the fetus. Other trace elements such as copper, calcium, selenium, etc., may also induce NTD, but their exact role is not yet clear. As for the cause of NTD induced by severe pregnancy reaction, it may be due to temporary dehydration caused by severe vomiting, resulting in a lack of trace elements (such as zinc) or vitamins (such as folic acid).

　　Virological studies have shown that maternal early pregnancy infection with cytomegalovirus or type A influenza virus can cause developmental disorders of the fetal central nervous system, and NTD may occur. Early pregnancy toxoplasmosis infection may also lead to NTD. Maternal early pregnancy abdominal or pelvic radiation exposure often affects the development of the fetal central nervous system, and some develop NTD.

　　Pregnant women with epilepsy taking antiepileptic drugs such as valproate, phenobarbital, and phenytoin sodium, and their offspring are prone to develop NTD. Taking oral contraceptives during the early pregnancy, taking certain antitumor drugs such as methotrexate, adenine (aminopurine), and mercaptopurine, as well as the large or continuous application of cortisone or prednisolone (prednisolone), can induce NTD. The mechanism of action may be related to the interference of folic acid metabolism.

　　1. Complications of spina bifida can occur cyanosis and edema of the lower limbs, which are prone to occur nutritional ulcers, even gangrene, there are often muscle contractures, and sometimes hip dislocation, clubfoot deformity, etc.

　　2. Spina bifida with associated malformations Spina bifida may be associated with some other rare malformations such as:

　　(1) Hydrocephalus of the spinal cord: It often occurs in the thoracic, thoracolumbar, or lumbar sacral regions, with much fluid accumulating in the central canal of the spinal cord, and only atrophic spinal cord tissue in the cyst.

　　(2) No spinal cord: The undeveloped spinal cord is often accompanied by anencephaly, and the child often dies soon after birth.

　　(3) Dermoid cysts, lipomas, or teratoma tissue: may invade the dura mater or spinal cord.

　　3. Malformations coexisting with spina bifida: The malformations that commonly coexist with spina bifida include hydrocephalus, deformed feet, cranial cavity, meningocele, encephalocele, cleft lip, congenital heart disease, etc.

　　I. Clinical manifestations

　　The symptoms of the nervous system are related to the extent of involvement of the spinal cord and spinal nerves. The more common symptoms of the nervous system include paralysis of the lower limbs, incontinence of urine and feces, etc. If the lesion is located in the lumbar sacral region, there may be flaccid paralysis and muscle atrophy of the lower limbs, disappearance of sensation and tendon reflexes, lower limbs often showing lower temperature, cyanosis and edema, which are prone to occur nutritional ulcers, even gangrene. There are often muscle contractures, and sometimes hip dislocation. The lower limbs often show clubfoot deformity, and there are often incontinence of urine and feces. In some mild cases, the symptoms of the nervous system may be very mild, and the symptoms of the nervous system often worsen with the increase of the child's age, which is related to the growth rate of the vertebral canal being faster than that of the spinal cord, and the traction on the spinal cord and spinal nerves gradually increases.

　　Second, classification

　　Posterior spina bifida can be divided into the following categories:

　　1. Occult spina bifida (spinabifidaocculta):This kind of malformation is very common. There is only a defect in the vertebral canal, and the spinal cord itself is normal, so there are no neurological symptoms, and it has no effect on health. It was previously thought that this disease was related to enuresis or other urinary tract diseases, but in fact, the incidence of隐性脊柱裂is similar in normal children and children with urinary tract diseases. There are often some abnormal phenomena on the skin above the defect site, such as a tuft of hair, a small depression, a mole, hyperpigmentation, and thickening of subcutaneous fat. There may be congenital cysts or lipomas above the defect. X-ray examination can be used to confirm the diagnosis.

　　2. Spina bifida with meningocele:There is a cystic mass at the site of spinal defect, which often occurs in the lumbosacral region. The mass is round and may grow very large. Inside, there are only meninges and cerebrospinal fluid, without spinal cord and other nerve tissues. Children with simple meningocele have no paralysis or other neurological symptoms. If the outer wall of the cyst is normal skin, the mass rarely gets secondary infection. If the wall is very thin or has been溃破, it often forms cerebrospinal fluid leakage or is complicated by infection.

　　3. Spina bifida with meningocele and myelocele:They often occur in the lumbosacral region and can also be seen on the back. The mass is round and may be as large as an orange. In addition to the meninges and cerebrospinal fluid, there are also nerve tissues inside. The outside is covered with very thin skin, and in the central area, there may only be a translucent meninges. In newborns, there may only be granulation tissue, which is very prone to ulcer formation. The spinal cord tissue enters the upper part of the mass, nerve fibers are widely distributed in the mass, and then return to the spinal cord part inside the vertebral canal from the lower part. Malformed spinal cord, nerves, spinal meninges, vertebral muscle and skin are often connected together. Some children with spinal cord herniation have no meninges or skin covering, presenting an extruded spinal cord malformation. These patients almost all have paralysis of the lower limbs and incontinence of urine and feces. Some patients have hydrocephalus. The meningocele of the sacral spinal cord and meninges occurs below the lumbar sacral plexus, and there is no paralysis of the lower limbs, but incontinence of urine and feces. Newborns may see droplets of urine when crying, and in male infants, they cannot urinate normally.

　　Neural tube defects (including spina bifida) are generally considered a polygenic genetic disease. Although the cause is not yet fully understood, taking 400g of folic acid daily from before pregnancy to the third month of pregnancy can reduce the incidence of neural tube defects. According to the "B" ultrasound during pregnancy and the determination of alpha-fetoprotein in the maternal serum and amniotic fluid, neural tube defects can be screened out in the early and middle stages of pregnancy, which greatly reduces the incidence of neural tube defects. Calcium should be supplemented, and more calcium-rich foods should be eaten, such as sheep spine bones (pork bones, cow bones can also be used) for soup to drink for children.

　　Examination items for children with spina bifida:

　　1. Routine blood test, cerebrospinal fluid routine examination (CSF), spinal MRI examination, spinal vertebral plain scan, urinalysis, spinal mobility, spinal examination, and spinal tenderness and percussion pain.

　　2. Hematology refers to the general examination of blood (previously known as routine blood test) results, which is the examination of the number and quality of blood cells in peripheral blood.

　　3. When complications such as infection occur, peripheral blood leukocyte count significantly increases, and when intracranial infection occurs, the cerebrospinal fluid leukocyte count significantly increases.

　　4. X-ray film of the spine shows absence of laminae and spinous processes, widened interpeduncular distances, and the defect site of bone tissue is connected to soft tissue masses. CT and MRI can also show the contents of the cyst.

　　What kind of food should children with spina bifida eat to be good for their health: they should supplement calcium and eat more calcium-rich foods, such as drinking soup made from sheep's spinal bone (pork bone, beef bone can also be used) for children. Avoid seafood. Because sea cucumbers, kelp, seaweed, seafood, etc., contain a certain amount of uric acid, which, when absorbed by the body, can form uric acid crystals in the joints, exacerbating the condition of arthritis. Therefore, patients with spina bifida in children should not eat seafood.

　　1. Pay attention to protect the cyst and prevent it from rupturing. For incomplete surface skin, attention should be paid to cleaning and disinfection. Cysts can be removed for children without neurological symptoms or only with mild symptoms. Generally, it should be waited until 6 months after birth to remove; if the cyst wall is extremely thin and easy to rupture, surgery can be performed soon after birth.

　　2. For paraplegia and muscle atrophy caused by spina bifida, acupuncture and massage can be tried for rehabilitation and symptomatic treatment, but the final effect is not satisfactory.