Continuing Education Activity

Neural tube defects are a spectrum of congenital anomalies that includes cranial defects and open or closed spinal dysraphism. Open spinal dysraphism or spina bifida aperta are visible lesions and include several malformations such as myelomeningocele. The etiology is often multifactorial, which includes environmental, maternal, and genetic factors. It is described as a fluid-contained sac that protrudes at the affected vertebral level. Therefore, early medical and surgical management are essential in preventing further complications and neurological damage. This activity will review the etiology, pathophysiology, presentation, and management options for myelomeningocele.

Objectives:

• Identify the most common causative factors responsible for the development of myelomeningocele.
• Describe the common physical signs seen in patients with myelomeningocele.
• Outline the treatment and management options for patients with myelomeningocele.
• Summarize how the healthcare system should offer accessible and coordinated care for patients with myelomeningocele. It is usually provided by a specialized team of physicians and therapists to improve the prognosis and quality of life in patients.

Introduction

Neural tube defects are a spectrum of congenital anomalies that include cranial defects and open or closed spinal dysraphism. Open spinal dysraphisms or spina bifida aperta are often seen during the physical examination as visible lesions and include malformations such as myelomeningocele. On the other hand, closed spinal dysraphisms or spina bifida occulta are non-visible lesions, usually with no apparent signs recognized during physical examination. Thus, patients are often asymptomatic with no future complications and usually, do not require treatments. Myelomeningocele generally occurs during embryonic development due to incomplete closure of the spinal neural tube during the first month of pregnancy. It ultimately leads to an exposed neural tissue or meninges with a fluid-filled sac that protrudes at the affected vertebral level.[1][2][3] Myelomeningocele can cause several neurological deficits and complications which are dependent on the involved vertebral site. It can lead to devastating morbidity and multiple disabilities; hence, the prognosis is often worse if diagnosed late or left untreated.[4][5]

Etiology

The etiology behind myelomeningocele is often multifactorial and includes environmental, maternal, and genetic factors. Environmental factors include exposure to radiation, different types of pollution, pesticides, organic solvents, and teratogens. Maternal factors are numerous and include irregular maternal nutrition, low folic acid supplementation, caffeine and alcohol consumption, smoking, the use of anticonvulsants, in addition to certain maternal illnesses such as diabetes, obesity, hyperthermia, and anxiety. However, most of the cases of myelomeningocele are sporadic in origin and occur in a non-genetic pattern. Though, some genetic factors might increase the risk of occurrence, for instance, the presence of chromosomal anomalies of trisomy 18 or 13 and patients with an affected twin or first-degree relative. Also, there are more than 40 genetic strains detected in animal models, specifically in mice, were associated with spina bifida aperta. In humans, in contrast, specific genetic mutations of amino-acid altering in the sequencing of coding regions such as planar cell polarity pathway genes and folate one-carbon metabolism encoding enzymes were reported in some patients with spina bifida.[2][6]

Epidemiology

Nearly 140000 cases of neural tube defects per year reported globally.[2] While the incidence of spina bifida is about 0.5 of 1000 births worldwide and in the United States, it is estimated to be more than 3 per 10000 births.[1] The prevalence of myelomeningocele, on the other hand, is approximately 0.8 to 1 per 1000 live births worldwide, whereas, in the United States, the incidence is estimated to be 0.2 to 0.4 per 1000 live births.[7][8]  Researchers performed a study in northern China that showed that the recurrence risk in neural tube defects in subsequent pregnancies was 1.7%, which was higher than in the United States.[9] Alternatively, the risk of recurrence in myelomeningocele was reported to be 2 to 5% in the United States.[10] Another study showed that the recurrence rate in myelomeningocele was approximately 2% to 3% in consecutive pregnancies. Additionally, higher incidence rates were reported in females, increased maternal age, and lower socioeconomic status. Considering ethnicity, Latins were the most affected population in the united states.[8]

Pathophysiology

The normal spinal cord development during embryogenesis occurs in three stages between the second till the sixth week of gestation. These stages include gastrulation, primary, and secondary neurulation. Usually, defects in primary neurulation result in open and closed spinal dysraphisms. The neural plate forms in the first stage of gastrulation, which occurs at the end of the third week of gestation. It happens when the endoderm and ectoderm form the bilaminar embryonic disc. With rapid cell division of the embryonic disc, the cells are then migrated to form the mesoderm which eventually will convert to a trilaminar disc. Finally, the notochord interacts with the ectoderm to form the neuroectoderm, and neural plate which begins at the midline then proceeds cranially and caudally. During primary neurulation, the neural folds arise with a small central depression called the neural groove. The neural folds are then going to be gradually fused to convert the neural plate to the neural tube. The primary neurulation ends with the closure of the cranial and caudal ends of the neural tube. Any defects in caudal neural tube closure would result in exposed neural tissue called placode. The presence of neural placode and the meningeal lining is mostly associated with myelomeningocele. It is one of the main essential features to distinguish between myelomeningocele and myelocele.

Furthermore, the caudal end is composed of pluripotent cells, which eventually will form a caudal cell mass that contains neurons and vacuoles. In a process called cavitation, the neurons and vacuoles are will developed further and connect to create the central canal. Eventually, these cells will undergo apoptosis to form filum terminale, ventriculus terminalis, and conus medullaris.[11]

History and Physical

The presentation of a newborn in the postnatal period often involves the presence of a sac extending from the vertebral column, covered with meninges, filled with cerebrospinal fluid and neural tissue.[3][8] The clinical presentation is dependent on the site of the spinal lesion at the vertebral column. The higher the level affected, the more deficits occur, and the worse the prognosis of the patient.[3][12] Myelomeningocele is one of the most prevalent causes of neurogenic bladder in children. Patients can have a life-long functional disability and other problems such as paraplegia, sphincter dysfunction, motor and sensory impairments in which they all can deteriorate with age.[8][12] Besides, some might experience abnormal sexual development in adulthood.[12] On the other hand, renal, respiratory, and cardiac complications are common causes of mortality in patients with spina bifida.[12] The presence of other disorders such as Arnold-Chiari II malformation can complicate the condition of the patient and lower the rate of survival.[12] A cerebellar tonsillar herniation characterizes the condition; downward displacement of the brainstem and the fourth ventricle more than 5 mm below the foramen magnum as well as the presence of myelomeningocele, hydrocephalus, with or without syringomyelia.[13] Other clinical features experienced in childhood include pain, hypertonia, vertebral anomalies, tethered cord, psychological, and cognitive complications.[14] The degree of neurological impairment predominantly depends on the affected spinal cord level. Myelomeningocele can lead to abnormal motor and sensory functions. It is usually a result of compressive lesions causing myelopathy or neuropathy. For instance, quadriplegia often arises from cervical lesions. Whereas paraplegia is mostly associated with thoracic and lumbosacral lesions.[15] 

Children can exhibit delays in developmental milestones, especially in motor function. The absence of leg movements is usually a result of lower motor neuron dysfunction caudal to the lesion. However, children may show spontaneous leg movements, which is due to functional neuronal conduction. These movements can be preserved with therapeutic strategies and physiotherapy.[16] On the other hand, sensory impairment is dependent on the dermatomal level of the spinal lesion that is affecting the afferent fibers. There are two aspects of sensation that should be examined to localize sensory loss. It includes light touch and two-point discrimination tests, which can help exclude any problems in spinothalamic and dorsal column pathways.[15]

Evaluation

The diagnosis of myelomeningocele is possible in the first trimester of pregnancy. Amniocentesis is helpful and usually favored for high-risk patients. For instance, there are reports of elevated levels of alpha-fetoprotein in amniotic fluid samples in patients with anencephaly and myelomeningocele.[2] However, ultrasonography is non-invasive, safe, effective, and often used for second-trimester anomaly scanning. It usually involves a careful examination of the fetal spine preferably from the sagittal plane, looking for any visible sacs, cystic extensions, spinal lesions, or vertebral distortions.[2] Additionally, a biparietal diameter of less than the 5th percentile was shown to be associated with 50% of patients with spina bifida.[17]

Various signs can be detected through ultrasound and can be seen in spina bifida, especially in Arnold-Chiari II malformation such as banana and lemon signs. Banana sign is usually seen at the posterior fossa when the cerebellar hemispheres are elongated, compressed, and displaced downward resembling the shape of a banana. This sign can also be associated with obliterated cisterna magna. However, the lemon sign refers to an abnormal convexity and indentation of the frontal bones correlated with ventriculomegaly.[18]

Other cranial features of spina bifida that are visible through ultrasound include hydrocephalus, microcephaly, small-shaped cerebellum, and abnormal cranial bones. The presence of chromosomal anomalies, as well as dilated renal tract or talipes, are other associated conditions that might be detectable through an ultrasound. Fetal karyotyping and magnetic resonance imaging (MRI) could also be an option if the tests were not sufficient for the diagnosis.[2] Moreover, MRI would show a better visualization of the spine and neural elements as well as other organ systems associated with spina bifida. It can aid the physician to plan for delivery and prepare for fetal surgery. It also evaluates for spinal alignment, detects different types of spinal dysraphisms, and can show any abnormalities within the spinal cord.[17]

Treatment / Management

Once the diagnosis has made, early surgical repair of the spinal lesion is essential in preventing further deficits and neurological damage. Prenatal surgery was proven to be more effective than postnatal surgery in lowering the occurrence of future complications.[1][2][5][8][19][20]

A trial study about the management of myelomeningocele (MOMS) occurred in the United States on 60 pregnant ladies who had fetal myelomeningocele closure for their fetuses from 2011 till 2017. The results of the study showed that fetal surgical repair was more effective than postnatal surgery in improving and preserving the neurological function as well as reducing the need for the reversal of hindbrain herniation and shunting.[21][22]

However, reports exist of high rates of pregnancy complications in the literature, such as uterine rupture at the time of delivery. Consequently, the delivery of the child should take place via cesarean section at early term or late preterm.[8][19][20] However, in postnatal surgery, the fetus should be delivered full term to avoid the risk of prematurity complications.[8] A detailed examination of the newborn should be done after delivery avoiding the use of latex gloves. Most of the children with spina bifida experience latex allergy, which makes them prone to severe problems such as anaphylaxis.[12] Postnatal surgery is usually done within 24 to 48 hours after birth to prevent the risk of infections.[23][24] Postnatal surgical repair of myelomeningocele is done first by placing the patient in a prone position and under general anesthesia. After sterilizing the area, a surgical incision of the spinal lesion follows, until the dura becomes visualized. Then the dural sac is everted, and the neural placode placed within the dural canal. The closure of the fascia then achieves the repair. Small-sized lesions are coverable by primary repair. However, the closure of large-sized myelomeningoceles could require either a flap or graft repair.[7][25][26] Antiseptic techniques should be ensured, and antibiotics should be given to avoid the risk of infections. Radiological imaging should be followed to exclude other associated anomalies. If Arnold-Chiari II malformation were present, a posterior decompression surgery with occipital-cervical fusion would be effective in reducing the patient's symptoms as well as a ventriculoperitoneal shunt in patients with hydrocephalus.[27][28] Ultimately, multidisciplinary medical management must be ensured and should focus on preventing further complications and neurological deficits.[4]

Differential Diagnosis

1. Terminal myelocystocele: A rare skin-covered lesion defined as one of the types of neural tube defects. It is caused by a dilation of the central spinal canal at the caudal end of the vertebra.[29]
2. Sacrococcygeal teratoma: A germ cell tumor mostly derived from multipotent stem cells of the primitive streak and usually grows at the base of the coccygeal bone.[30]
3. Caudal neural tube defect: It encompasses other forms of spina bifida such as meningocele and myelocele.[30]
4. Tail remnants: Benign fibrofatty lesions that usually occur at the perianal area and do not adhere to the coccygeal bone.[30]
5. Rhabdomyosarcoma: One of the malignant soft tissue tumors derived from the primitive muscle cells.[30]
6. Curarinos syndrome: Characterized by a triad of anorectal malformation, presacral mass, and sacral bone defect and usually inherited in an autosomal dominant pattern.[30]
7. Neuroenteric cyst: One of the rare duplicated congenital lesions derived from the endoderm during embryonic development when there is an impaired remodeling of the neurenteric canal.[30][31]
8. Caudal regression syndrome including sacral agenesis or hypoplasia: occurs when there is an incomplete development of the coccygeal bone during embryogenesis.[32]

Prognosis

Delayed diagnosis of myelomeningocele is associated with poor prognosis and lower rates of survival. It accounts for approximately 50% of infant death in underdeveloped countries. Moreover, delayed and neglected management has links to various complications such as dependence, immobility, functional disability, muscle weakness, bladder, and bowel dysfunction.[12] The presence of other disorders, such as hydrocephalus, increases the mortality rate in patients with myelomeningocele.[24][33][34]

According to a study was done in Washington, United States, the survival rates have increased from 60 % to 90% in the 1960s to 1985, respectively. The increased rate is attributable to the improvements and advances in medicine and surgery throughout the past years.

Nevertheless, the presence of hydrocephalus can influence the long-term outcomes in patients with myelomeningocele. The same study showed that patients with a shunt had a survival rate of 75% at the age of 34. However, unshunted individuals had a survival rate of 94% at the age of 34.[35][36] Therefore, patients with asymptomatic hydrocephalus can be treated conservatively without a shunt. Nevertheless, shunt insertion is usually indicated in symptomatic unstable ventriculomegaly. Indications include signs of elevated intracranial blood pressure, rapidly increased ventricular size on imaging, and worsening symptoms of Arnold-Chiari II malformation.[37] Aggressive treatments and early surgical repair are effective in improving neurological recovery, increasing survival rates, and enhancing the long-term prognosis in patients with myelomeningocele.[4][38]

Bowel dysfunction was associated with a lower score of health-related quality of life than bladder dysfunction in patients with spina bifida.[39] Various factors were associated with bowel dysfunction, including urinary tract disorders, male sex, and obesity.[40] Chances of improvements in bowel function are possible with the use of conservative bowel management of retrograde and antegrade bowel enema, as well as surgical bowel management. However, most studies suggest that surgery remains the last option for treatment due to the high rates of complications.[41]

Renal failure remains one of the most common causes of mortality in patients with spina bifida. Hence, to prevent the occurrence of neurogenic bladder and renal damage, a full urological examination should be obtained after birth. The examination is done by assessing the pelvic floor muscle activity and sustaining low bladder pressure. After surgical repair, all patients should have a clean intermittent catheterization, followed by antimuscarinic therapy and low dose chemoprophylaxis. These will help to maintain low bladder pressure, avoiding overactive detrusor muscle activity, and preventing the risk of urinary tract infections.[42][43]

Complications

Complications of myelomeningocele classify as either surgical or non-surgical complications.

Surgical complications include infections at the site of the lesion, bleeding, delayed wound healing, re-tethering of the spinal cord, and cerebrospinal fluid leakage.[44]

Non-surgical complications include:

1. Neurological complications: Hydromyelia, Arnold-Chiari II malformation, hydrocephalus, seizures, paraplegia, motor, and sensory impairments, neurogenic bladder, and bowel dysfunction.[8][12][45]
2. Musculoskeletal complications: Vertebral anomalies such as scoliosis as well as muscle weakness.[8][12]
3. Physical complications: Immobility and delayed age of ambulation.[8][12]
4. Psychological and cognitive complications: Depression, suicide, and intellectual disability.[12][46]
5. Social complications: Educational problems, dependence, and unemployment.[12]
6. Sexual complications: Erectile dysfunction, impotence, and fertility problems.[12]
7. Others include obesity, renal failure, in addition to cardiac and respiratory diseases.[12] 
8. Latex allergy: most patients with spina bifida have a sensitivity to rubber, which is a latex allergenic protein. Exposure to latex can lead to an allergic reaction due to the activation of IgE immunoglobulins. The immunological reaction can lead to a life-threatening condition known as anaphylaxis.[12][47]

Postoperative and Rehabilitation Care

Postoperative care primarily depends on the type of surgical procedure. If prenatal surgical closure of myelomeningocele takes place, and fetal delivery is preterm, the baby should stay at a specialized neonatal intensive care unit in a latex-free environment.[8] Subsequently, coordinated medical care should be followed to prevent other complications related to prematurity or fetal surgery. Thus, assuring accessible medical services to meet the best outcomes for patients. Although fetal surgery exhibits optimal results than postnatal surgery, patients could be at higher risks of intraoperative and postoperative complications.[48] There are specific indications for fetal surgery, for instance, the presence of associated anomalies such as hydrocephalus, Arnold-Chiari malformation, significant thoracolumbar defects in addition to the absence of abnormal fetal leg movements or feet clubbing.[49] Various postoperative complications have been reported in prenatal and postnatal surgeries, including wound infection and dehiscence, shunt infection and failure, postoperative ileus, necrotizing enterocolitis, pneumonia, symptomatic Arnold-Chiari malformation, and others related to kyphectomy.[44] 

To preserve the functional neurological level and improve the quality of life, long-term rehabilitation care should be followed postoperatively to expand the recovery of the patient. Preventive measures must be included, focusing on improving the musculoskeletal system with the aid of physical therapy and exercises. Therefore, avoiding the risk of developing pressure ulcers, wound infections, deep vein thrombosis, obesity, and metabolic syndrome. Moreover, patients with hydrocephalus should have regular ophthalmology visits to screen for visual impairments and papilledema. Also, urodynamic testing is recommended for patients complaining of any urological problem to rule out the presence of neurogenic bladder. Bowel management is achievable by teaching the patient, and caregivers about a reflex-triggered bowel evacuation program as well as dietary modifications and laxative use. All the measures mentioned earlier should be continued until the patient reaches a successful transition to adult care. Adult healthcare offers specialized medical care and activities tailored to promote autonomy and provide prolonged and continued care for the patients.[45]

Deterrence and Patient Education

Myelomeningocele is one of the forms of spina bifida and described as a fluid contained sac containing neural tissue protruding from the back. It occurs when there is an incomplete closure of the spinal cord during the first month of pregnancy. Many factors can lead to myelomeningocele, and a vast majority of cases are preventable with adequate maternal nutrition and folic acid supplementation during pregnancy.

Children can be at higher risk of developing complications such as urinary problems, difficulties in passing stool, troubles in walking, and some might experience learning disabilities in the future.

Some children might have other associated problems, such as scoliosis and muscle weakness. Others might have a condition called hydrocephalus, which happens when the fluid in their brain ventricles exceeds the average ratio causing head enlargement. If a child has a diagnosis of hydrocephalus, he or she might require shunt surgery. Surgeons perform shunt surgery by inserting a hollow tube into the brain to drain excess fluid from the ventricles. Also, it is advised to stay away from latex products as some children might be allergic to latex.

Early surgical intervention before or within 24 to 48 hours after birth is essential to prevent more damage. It can improve the quality of living, especially if followed by integrated medical care. It should involve several doctors from different specialties to provide accessible therapeutic services aimed to meet the children’s needs. Hence, early surgical management of myelomeningocele has proven to be effective in increasing the rate of survival and lowering the risk of complications.

Nevertheless, children might require frequent medical evaluation and hospital visits to address their needs and complaints. Early medical management for children complaining of learning and cognitive disabilities in schools can help them prepare for their future education. Parents should be aware that the child might show a particular area of disability. Hence, individualized school programs and community services should be implemented to help patients accommodate their lives according to their physical abilities and limitations. Cognitive impairments in patients with spina bifida, especially problems in executive functioning can improve by achieving specific educational strategies at school. Executive functioning refers to brain skills that are required to perform. They include memory, planning, attention, time management, and flexibility. For example, teaching the child to write important information to remember, providing them clocks to recognize the time, breaking huge tasks into smaller ones, minimizing anxiety, and encouraging them to complete their work.

Having a child with spina bifida would increase the risk of having another affected child in subsequent pregnancies. To avoid the risk of another affected pregnancy, genetic counseling should be required before conception. Genetic counselors help parents understand their family history and the risk of genetic and congenital anomalies that might occur in the future. 

Recent advances in medicine can help children with myelomeningocele improve their quality of life. It is crucial to recognize associated health problems earlier to avoid more complications, particularly in mobility, bowel, and bladder functions. Therefore, early multidisciplinary medical and surgical management are essential to prevent further deficits and increase the chances of improvement in the future.

Enhancing Healthcare Team Outcomes

Myelomeningocele management is best with an interprofessional team. The prevention of neural tube defects should start by increasing people’s awareness through health promotion and educational activities. These activities should take place in schools, communities, and workplaces and include various topics on spina bifida. Healthcare educators, including nurses and pharmacists, should address common genetic, maternal, and environmental factors responsible for the development of neural tube defects such as low folic acid supplementation.

Premarital and antenatal counseling should be a consideration for high-risk individuals. Regular antenatal examination and visits are essential to follow fetal development and address possible fetal and maternal complications. Detailed medical history is important to search for several causative factors such as maternal diabetes, smoking, certain medications, malnutrition, previous affected pregnancy or family history of spina bifida, as well as the exposure to hazardous materials. Females should be advised to take folic acid supplements three months before conception and continue until the end of the first trimester of pregnancy.

The management of myelomeningocele is often interprofessional and involves coordinated care from different specialties. The child and family should receive education about the potential complications and ways to prevent them. Also, safety measures should be implemented in hospitals and the community to avoid further complications.

Increasing awareness about spina bifida is significant to improve the outcomes of patients in their society. Nevertheless, 94% of spina bifida adults have finished a high school degree, and about 62% have completed a college degree. Hence, there are no boundaries for patients to learn or be part of their community. However, ignorance about the disease and its possible complications in addition to delaying therapeutic interventions and not providing adequate medical services would lead to more difficulties in the future and impact the quality of life.[50]

Furthermore, providing training programs and encouraging autonomy as well as community and work participation have shown to be effective in improving the satisfaction and standards of living in patients.[12][50]

Bowel and urinary incontinence are commonly reported complications of myelomeningocele. Since patients with urinary problems might require repeated catheterization, clinicians should address any further complaints to prevent renal failure. It was shown to be one of the causes of death in patients with myelomeningocele.[8][12][51]

Patients with functional disability and mobility problems could require physical therapy, occupational therapy, and strength exercises to improve their muscle power and avoid the development of weakness and contractures.[45]

Considering that patients are in special needs, and may require dependence, some may complain of mental health issues and psychosocial problems. Therefore, health care practitioners of social therapists, psychologists, and psychiatrists can help patients and their caregivers to access appropriate care tailored to their needs.[46] Only through such an interprofessional team approach and open communication can the outcomes be improved. [Level 5]