Meningocele is one of the variants of spina bifida, a neural tube defect demarcating incomplete closure of the spinal cord. In this form, herniation of the meninges in a cyst-like formation is seen from birth. The cause includes genetic and environmental factors, such as obesity and poor nutrition. Imaging studies are used to make the diagnosis. Treatment is surgical and the prognosis depends on the involvement of the spinal cord.
Clinical presentation may start as early as in utero, when regular check-ups can reveal the presence of a fluid-filled sac protruding from the spinal cord. In newborns and children, this sac is prominently seen and most commonly appears in the lumbosacral spine . Symptoms somewhat vary depending on the location. Saccral meningocele can be asymptomatic, while radiculopathy, back pain and right lower quadrant abdominal pain may be reported . Numerous neurological deficits may be encountered , including inadequate sphincter control, muscle weakness and clubfoot deformity . Rare cases of thoracic meningocele that have developed anteriorly have been described, and symptoms such as respiratory distress and cyanosis are reported due to compression of lungs and major vessels . It is important to mention that once patients reach late childhood and adulthood, various psychiatric illnesses such as depression, anxiety and stress because of disability caused by this defect can be encountered .
The diagnosis in newborns and infants is straightforward, as the lesion is clearly visible during physical examination. To confirm meningocele and differentiate between other forms of spina bifida, imaging studies are necessary. Ultrasonography, which is especially important in making the diagnosis during the perinatal period, is the initial method of choice, as it is able to detect the contents of the herniated sac with great specificity . MRI is another useful diagnostic method and should be used whenever possible for confirmation. In terms of laboratory tests, levels of AFP should be evaluated because of its very strong correlation with neural tube defects. Fortunately, AFP is measured on a regular basis during proper prenatal care, as it constitutes the "triple test" with βhCG and unconjugated estriol. AFP is measured in the amniotic fluid, however, and amniocentesis does carry a small risk for the fetus.
The goal of therapy is to prevent further spinal cord damage and development of meningitis, which can be achieved by performing surgery as soon as possible. A detailed preoperative assessment through imaging studies is necessary in order to determine the optimal approach . Surgery is usually performed within 48 hours after birth, but fetal surgery has shown its advantages as well . Because the spinal cord is continuously exposed to harmful effects of the amniotic fluid, the rationale for fetal surgery is to prevent early deterioration and good results have been observed with this approach . Surgery comprises repair of the protruded meninges, but exploration of the spinal canal, evaluation of cord injury and repair of the spinal cord that may be tethered are also constitutive parts .
Several factors determine the prognosis of patients with meningocele, such as the level of the lesion, severity of spinal cord involvement and the time of diagnosis. Meningocele and other forms of spina bifida have a much worse prognosis if located in the thoracic and cervical spine, as incontinence and limb movement may be severely affected . Patients with minimal injury of the spine can almost completely recover, but significant impairment in the quality of life is not uncommon, which is why this condition should be thought of during follow-ups of pregnant women, especially during the first few months.
A multifactorial etiology has been proposed in meningocele. Firstly, numerous genetic mutations have been identified. VANGL1 and VANGL2 genes are involved in he planar cell polarity pathways (PCP), which are responsible for proper cell aligning during embryogenesis , while methylene tetrahydrofolate reductase (MTHFR) genes involved in vitamin B12 metabolism have also exhibited mutations  . Genetic mutations appear de novo in most patients, but a familial component should not be completely excluded, as much more frequent rates of spina bifida are encountered among monozygotic twins and patients with positive first-degree relatives. In addition to genetics, deficiency of folate and vitamin B12 through malnutrition are considered as one of the main non-genetic factors in the etiology of meningocele .
When compared to other congenital diseases, neural tube defects (NTDs) can be considered as a somewhat common finding in general practice, with prevalence rates reaching 0.5-0.8/1000 births in the United States and Europe . The number of patients has dramatically decreased in the past few decades , but these estimations suggest that approximately 140 000 new cases appear worldwide . Significant geographic variations exist, as incidence rates of these disorders have shown to be much higher in China and other Asian countries compared to the Western world . Ethnic differences exist as well. Spina bifida was much more commonly encountered in Hispanic individuals , whereas African American ancestry has an inverse relation with the incidence of neural tube defects. Numerous risk factors have been established, with the most important being folate and B12 deficiency . Folate (vitamin B9) and vitamin B12 are considered to be vital for normal embryogenesis and the formation of the neural tube and numerous studies have identified reduced folate supplementation with increased rates of spina bifida . Additional risk factors include obesity, diabetes mellitus, alcohol abuse, smoking, caffeine and valproate use during pregnancy, malnutrition, low socioeconomic status, but also air pollution .
Under physiological conditions, the process of neurulation (transformation of the neural plate into the neural tube) starts at the beginning of the fourth week of gestation. Through the process of closure and canalization, formation of the spinal cord is completed during the next several days, but if failure of this process occurs, the neural tube remains exposed to the in utero environment. As a result, neuronal damage and death occurs due to the effects of the amniotic fluid on exposed neural tissue . Although genetic, nutritional and environmental factors have been described as significant in determining the onset of spina bifida and meningocele, their exact roles remain unknown. The pivotal function of folate in synthesis of cells and amino acids has been well-described, which may explain why its reduced concentrations significantly increase the risk for this condition. Regardless, the neural tube remains open and can differentiate into several forms, one of them being meningocele, which considered to be one of its mildest forms. Namely, a sac-like formation herniates at some point along the spinal cord, but contains only cerebrospinal fluid and the meninges, thus causing little damage to the central nervous system per se. Unfortunately, many patients suffer from lesions of the spinal cord, such as tethered cord syndrome and cord adhesion to the dura . For these reasons, spinal cord injuries and associated defects are not uncommon, which could be one of the reasons why in utero surgery is advocated - to prevent further damage.
Spina bifida is one of the most common defects of the neural tube and occurs in approximately 0.5 per 1000 live births, stillbirths and pregnancy terminations . It can appear in several forms, meningocele being one of them, which is described as herniation of the meninges through the spinal canal in a sac-like formation covered by the skin . The sac most commonly protrudes posteriorly in the lumbosacral spine, but thoracic and cervical locations have been documented as well  . The cause of neural tube defects, in general, has been attributed to genetic and environmental factors. Various mutations have been identified, such as those involving Vangl proteins (VANGL1) that are known for their function during embryogenesis, but their most prominent role is establishing planar cell polarity  . In fact, the planar cell polarity pathway (PCP) has been strongly related to the pathogenesis of neural tube defects , whereas a myriad of risk factors have been found. The most important ones are inadequate folate and vitamin B12 intake during pregnancy  . Obesity, alcohol and caffeine use, smoking, low socioeconomic status and use of valproic acid have all shown to be important determinants . Although meningocele does not directly damage spinal cord and has the best prognosis of all spina bifida variants, numerous additional lesions involving the spinal cord have been identified in these patients. Tethered cord syndrome, fibrous band tethering and spinal cord adhesion to the dura are most common . The presence of these findings significantly determines the outcome, but also the clinical presentation, having in mind the fact that meningocele is a benign lesion that often presents with a normal neurological examination  . Depending on the level of meningocele appearance, various neurological deficits may be observed, but the most prominent sign is the presence of a herniating sac from the spine. In rare cases, anterior herniation may occur and cause compression of various organs, including the lungs and the heart, producing symptoms such as recurrent lung infections and respiratory distress . The initial diagnosis can be made in utero or during physical examination at birth, but in order to inspect the content of the herniated sac, ultrasonography and magnetic resonance imaging (MRI) are recommended imaging studies . Additional tests may include evaluation of alpha fetoprotein levels (AFP), a constitutive part of the "triple test", together with beta-human chorionic gonadotropin (βhCG) and unconjugated estriol. These methods provide important information when determining the optimal therapeutic method. In all cases, surgical treatment of meningocele is indicated, which can be done either in utero or within 48 hours after birth, with a goal of preventing central nervous system infections . Widespread folate and B12 supplementation during pregnancy have led to substantially reduced rates of all forms of spina bifida in the general population . For this reason, this form of prevention should be advocated in all pregnant women.
Meningocele is one of the forms of spina bifida, a condition in which improper development of the spinal cord occurs during the first few weeks of fetal maturation. Normally, the spinal cord is formed from the neural tube through the process of neurulation that occurs during the 4th week of gestation. For still unclear reasons, defects of this process lead to incomplete closure of the spinal cord and its exposure to the amniotic fluid that is considered toxic for neurons. In this particular subtype, a sac-like formation eventually develops at some point along the spine and contains cerebrospinal fluid together with the meninges. It is hypothesized that the cause stems from both genetic mutations and other events such as folate and B12 deficiency, whereas numerous risk factors have been identified. Obesity, diabetes mellitus, alcohol abuse, smoking, as well as caffeine and valproate use during pregnancy have all shown to increase the risk for this condition. The most common site of occurrence is the lumbosacral region, although any point along the spine may be the site of occurrence and the clinical presentation depends on the location of meningocele. Cases involving the sacrum may be asymptomatic, whereas most common complaints include abdominal and back pain, as well as nerve root compression. Individuals that develop meningocele in the thoracic or cervical spine have a much worse prognosis, as various neurological impairments including urinary incontinence and inability to control sphincters can be noted. Although meningocele is considered to be the most benign form of spina bifida, it is frequently accompanied with lesions of the spinal cord, such as tethered cord syndrome, which can cause significant disability. In fact, depression and anxiety are often encountered in adults suffering from this condition. The diagnosis can be made during fetal life by using ultrasonography and magnetic resonance imaging (MRI), but due to inadequate perinatal care and lack of experience, the diagnosis is frequently made soon after birth, when a large sac protruding from the spine is observed. Detection of elevated levels of alpha fetoprotein (AFP) in amniotic fluid is a highly indicative sign of spina bifida, which is perhaps the reason why it is a constitutive part of the "triple test", one of the most important perinatal screening tests. Treatment invariably includes surgery, which can be performed even before pregnancy if the diagnosis is made early on. Fetal surgery is advocated in order to prevent further exposure of the spinal cord to the amniotic fluid and this approach has shown much better outcomes than surgery after birth. Because neural tube defects are somewhat common (roughly occurring 1 in 1500 births) and because significant disability may be caused, prevention strategies through supplementation of pregnant women with folate and vitamin B12 are essential in reducing the burden of these diseases in the population. Additionally, ensuring cessation of smoking and reduction in alcohol consumption, as well as maintaining a well-balanced diet and restriction of substances such as caffeine and valproate are important steps in prevention as well.