Neural Tube Defects in the Neonatal Period Treatment & Management
- Author: Richard G Ellenbogen, MD; Chief Editor: Ted Rosenkrantz, MD more...
The myelomeningocele is a saccular protrusion containing a neural placode bathed in cerebral spinal fluid (CSF), as shown below.
The surface of the sac is covered by arachnoid but no dura or skin. The sac appears velvety red or yellow with thin fragile vessels embedded in the arachnoid. The nerve roots pass forward into the sac and the spinal cord remains tethered to the bony defect in the spine. In many cases, the spinal cord is attached to the superior aspect of the sac. The myelomeningocele has many other associated CNS anomalies that require attention.
Table 2. Anomalies of the CNS Associated with Myelomeningocele (Open Table in a new window)
|Anomalies Associated with Myelomeningocele||Approximate Percent of Patients|
|Chiari II malformation||>90%|
|Brainstem malformations (cranial nerve)||75%|
|Cerebral ventricle abnormalities||>90%|
|Agenesis of the corpus callosum||12%|
Chiari II malformation
Symptoms of a Chiari II malformation can occur anytime after birth and very few patients require decompression after their first year of life for a symptomatic Chiari II malformation. The symptomatic Chiari II presentation can be as subtle as new hoarseness and pneumonia or as obvious as a progressive quadriparesis. A brain and cervical cord MRI in patients with myelomeningocele invariably demonstrates a Chiari II malformation with a herniated vermis and syringomyelia. The surgeon must first and foremost check to see if the ventricular peritoneal (VP) shunt apparatus is functioning. Most of the time, a partial or complete obstruction of a VP shunt (based on a shunt tap or surgical exploration) is the etiology of the new brainstem findings. A shunt malfunction causes the hindbrain to herniate and compress the cord, thus causing many of the presenting symptoms. Timely repair of the shunt leads to a good outcome with reversal of most deficits.
Pathophysiology of Chiari malformations has fascinated neurosurgeons and provided a constant stream of literature for the past century on the presentation and presumed etiology. Although originally thought to be a rare neuroembryological disorder associated with neural tube defects, Chiari malformations have been recognized with increased frequency over the past 5 decades, temporally associated with the widespread application of MRI. Another increase in patient referrals has occurred relatively recently with improved understanding of the rather wide spectrum of clinical presentation.
In 1883, John Cleland published "Contribution to the study of spina bifida, encephalocele and anencephalus" in the Journal of Anatomy and Physiology. Cleland made several novel observations regarding hindbrain malformations on infant autopsy specimens. He described an elongated brainstem and cerebellar vermis, which protruded into the cervical canal in a full-term infant with spinal bifida and craniolacunae. Eight years later, Hans Chiari, professor of morbid anatomy at Charles University in Prague, published similar observations on congenital anomalies in the cerebellum and brain stem and commented on the a priori contributions of Cleland. Chiari further separated his patients into 3 different classifications of hindbrain abnormality; to ensure no confusion, the descriptions were accompanied by beautiful and detailed illustrations first in 1891, and then later in 1896.
Many textbooks and papers still refer to these hindbrain malformations as Arnold-Chiari malformations. However, the name Arnold-Chiari malformation is not historically accurate. The relatively minor contribution of Arnold to the understanding of this malformation was a report in 1894, which consisted of a description of one infant with a teratoma and cerebellar herniation. In 1907, students of Arnold, namely Schwalbe and Gredieg, erroneously suggested the term Arnold-Chiari Malformation. Unfortunately, this 1907 article failed to correctly attribute the rather significant contributions of Cleland. The subsequent 93 years have not corrected this misnomer. Attempts to name this malformation, Cleland-Arnold-Chiari or Cleland-Chiari malformation have not succeeded. Therefore, for the remainder of this article, the author adheres to a more historically accurate term and refers to these hindbrain anomalies simply as Chiari malformations.
The different Chiari malformations of the hindbrain were later classified as Chiari types I-III, terms that have been employed in a relatively consistent manner over the last century. These lesions are at the extreme ends of the spectrum, and patients with these anomalies are difficult to treat from a surgical perspective.
Type I is described as downward herniation of the cerebellar tonsils through the foramen magnum. Type II malformation is herniation of the cerebellar vermis and brainstem below the foramen magnum. Type II malformation also has kinking of the cervicomedullary junction, an upward trajectory of the cervical nerve roots, and associated syringomyelia. The medulla often protrudes below the foramen magnum and into the spinal canal, compressing the cervical cord. The medulla then buckles dorsally and forms a "medullary kink." Also, the fourth ventricle often is below the foramen magnum, and the midbrain tectum forms a sharp corner on midsagittal MRI and looks like a beak. Type II malformations are the subject of this section. Type III malformation is essentially a posterior fossa encephalocele or a cranium bifidum with herniation of the cerebellum through the posterior fossa bone and is a more severe neural tube defect.
The only deviation from the consistent terminology described above is the eponym Chiari type IV malformation. The Chiari type IV malformation consists of cerebellar hypoplasia, not herniation, and is no longer considered a Chiari malformation.
Description and diagnostic studies
- A Chiari II malformation is downward displacement of the cerebellar vermis, fourth ventricle, and brainstem below the foramen magnum into the cervical canal, as shown below.
Sagittal T1 MRI image of a child with a myelomeningocele and associated Chiari II malformation. Note the cerebellar vermis and part of the brainstem has herniated below the foramen magnum and into the cervical canal (arrow). This patient had multiple brainstem symptoms and findings to include stridor and cranial nerve paresis (cranial nerves III, VI, IX, X) despite having a well-functioning ventricular-peritoneal shunt. He required a posterior fossa decompression of his hindbrain in order to relieve the symptoms of hindbrain herniation and brainstem compression. A minority of myelomeningocele patients require a Chiari II decompression. Those that do usually present in their first year of life with similar symptoms, stridor and cranial nerve paresis. A functioning shunt is imperative prior to exploring the posterior fossa in these children. Often times, especially in older children, a shunt revision may alleviate some of the symptoms of hindbrain compression.
- The terms "hindbrain herniation, displacement, descent," and "ectopia" have been used synonymously in a wide range of posterior fossa conditions. From a historical point of view (prior to MRI), the diagnosis of Chiari II malformations were most often made using autopsy, air or contrast myelogram, or CT/myelography. Thus, the diagnosis was made infrequently, although all patients with myelomeningocele were thought to have a Chiari II malformation.
- The radiological diagnosis is made using MRI. The crucial measurement in relation to descent of the hindbrain and vermis below the foramen magnum usually is assessed on sagittal section of MRI. The hindbrain or vermis displacement is measured from a straight line drawn between the basion to the opisthion of the foramen magnum. A perpendicular line dropped from the basion/opisthion line to the vermis tip is considered the extent of the herniated brain.
- Syringomyelia is a cavitation of the spinal cord whose walls are composed of glial tissue, whereas hydromyelia is a cavitation or dilatation of the central canal lined by ependyma. The author uses the term syringomyelia in this article, instead of the more descriptive term syringohydromyelia, to avoid generating scientific and semantic confusion. The association of Chiari II malformation with syringomyelia varies from 80-90%, depending on the patient population studied.
- Syringomyelia, the common finding associated with Chiari malformation, is derived from the Greek words, syrinx (meaning tube or pipe) and muelos (meaning marrow). Estienne, from France, first described the spinal cord cavitation called syringomyelia in human cadavers in 1546. In 1824, Charles Ollivier d'Angers provided the very descriptive name syringomyelia to the cylindrical dilatation of the spinal cord, which, in his illustrative case report, communicated with the fourth ventricle. In 1892, Abbe and Coley from New York performed a myelotomy to drain the syrinx cavity. This was the first recorded surgical procedure to treat syringomyelia.
- Hindbrain malformations are the leading cause of syringomyelia. This cavitation of the spinal cord usually is gradually progressive and can cause neurologic deterioration over time.
- The fluid in the syrinx is identical to the CSF found elsewhere in the subarachnoid space; therefore, theories based on aberrant CSF physiology are invoked to explain the relationship of syringomyelia in patients with Chiari II malformation. Nevertheless, the pathophysiologic mechanisms that cause these 2 disorders are not well understood.
- Many excellent theories have been suggested; however, none have been conclusively proven or universally accepted. Examination of the spinal cord in many neonates with myelomeningocele reveals atrophic or poorly developed anterior horn cells, incomplete posterior horns, and small nerve roots.
- A Chiari II malformation is downward displacement of the cerebellar vermis, fourth ventricle, and brainstem below the foramen magnum into the cervical canal, as shown below.
- The initial neurologic examination of a neonate born with a neural tube defect should focus on the neurologic sequelae of the neural tube defect. Specifically, evaluate (1) site and level of the lesion, (2) motor and sensory level, (3) presence of associated hydrocephalus, (4) presence of associated symptomatic hindbrain herniation (eg, Chiari II malformation), and (5) presence of associated orthopedic deformity.
- The lesion is first examined after the birth of a neonate. Myelomeningocele is a consequence of failed closure of the dorsal neural tube. Thus, the lesion appears as a red, raw neural plate structure devoid of dura and skin covering. The sac comprising arachnoid laced with thin, fragile vessels can be filled with CSF escaping from the central canal. A meningocele, in contradistinction, does not have neural tissue in the sac and usually has a nearly complete skin covering.
- Open neural tube defects should be immediately covered with a saline-moistened sponge to avoid rupture of the sac and drying of the exposed neural placode. Avoid using wet gauze, as the fibers can stick to the exposed tissue. The neonate is maintained and examined in the prone or lateral recumbent position. An intravenous line is placed, and feedings are held until a full assessment can be completed. The neonate is treated with systemic antibiotics consisting of ampicillin at meningitic doses and gentamicin. Common neonatal organisms, such as group B streptococci, and nosocomial organisms must be prevented from entering the CSF, especially through a leaking myelomeningocele.
- The neonatologist, pediatric geneticist, pediatric neurosurgeon, and pediatric orthopedist should immediately evaluate the child. Possible cardiac abnormalities are evaluated with ultrasonography. Initial ultrasonography of the head may also be performed to evaluate for hydrocephalus. Urologic examination using ultrasonography followed by a complete pediatric urologic evaluation may be performed initially or at a later date. Orthopedic evaluation is performed shortly before discharge because as many as 10% of neonates with a neural tube defect may have hip dislocations. A higher motor level lesion, such as L3-L4, can predispose some children to hip dislocations due to the unopposed hip flexors. In addition, presence of a varus or valgus extremity disorder is documented.
- The pediatric neurosurgeon carefully evaluates the patient to assess the site and type of lesion, including assessment of lower extremity function. Evaluate the symmetry of the motor and sensory levels affected by the neural tube defect. Flaccid paralysis below the L4 level may reveal a strong psoas, but not hip adduction, knee hyperextension, or foot inversion deformities. Flaccid paralysis of the foot with a weak gastrocnemius-soleus complex may result in foot dorsiflexion deformities.
- Attention to the anus helps to assess sacral nerve root function. Flaccid musculature in the S2-4 region often presents with a flat buttocks, absence of a well-developed gluteal cleft, and a patulous anus with no anal wink. The thoracic or lumbar region may have a large hump due to kyphosis or scoliosis of the spine; this can be so severe that it impedes the ability to place skin flaps over the neural tube defect and may compromise the infant's respiratory function.
- Head ultrasonography can be performed during the neonatal period to evaluate the extent of ventricular enlargement. Initially, the ventricles may be normal or only slightly enlarged. However, after the neural tube defect is surgically closed, the ventricles often enlarge. Incidence of hydrocephalus associated with myelomeningocele ranges from 80-95%. In 2 studies performed in the 1980s and 1990s, approximately 85-90% of all patients with neural tube defect required a VP shunt for progressive hydrocephalus. The highest incidence in shunt dependence occurs in thoracic lesions; the lowest incidence occurs in sacral lesions. The risk of shunt revision in this population may be no different from that of other children with shunts. Approximately 40-50% of all children with neural tube defects require shunt revision in the first year and approximately 10% every year after that.
- An MRI may reveal defects in cellular migration in the cerebral cortices. These include gray matter heterotopia, schizencephaly, gyral abnormalities, agenesis and thinning of the corpus callosum, abnormal thalami, and abnormal white matter findings.
- Meaningful surgical treatment of myelomeningocele was not undertaken until the invention of the shunt valve by Holter in the 1950s. Prior to that, closure of a myelomeningocele was possible, but the ensuing uncontrolled hydrocephalus decreased the chance of survival. In the 1980s, the US Department of Health and Human Services issued the Baby Doe directive, stating that medical and surgical treatment could not be withheld simply because a neonate is handicapped. Although the directive was struck down, the decision to operate on neural tube defects in neonates was already an accepted practice in the United States. Furthermore, outcome studies by McClone,[10, 21, 22] Shurtleff, and others presented a more positive outcome than had previously been thought for these children.
Timing of myelomeningocele repair
- In the 1960s, the birth of a patient with myelomeningocele was a neurosurgical emergency, and immediate closure of the defect was required. Studies have subsequently shown that closure within 48 hours is both safe and effective. A study by Charney et al comparing delayed closure (3-7 d) to immediate closure (< 48 h) showed little difference in survival, ventriculitis, or worsening paralysis. The implications of this study were immense: Surgeons could plan a deliberate but thorough evaluation of a neonate with a neural tube defect. Parents would have time to ask questions and be acclimated to the intensive surgical therapy that was about to commence. In the author's Children's Hospital setting, a great deal of time is spent performing a detailed workup and counseling parents. Closure is performed on the next available elective operative time, usually within 72 hours after birth.
- The American College of Obstetricians and Gynecologists (ACOG) recommends maternal-fetal surgery for myelomeningocele at centers that have the expertise with the surgical intervention and the multidisciplinary teams, services, and facilities to provide the required intensive care.
- Any major procedure on a neonate with myelomeningocele must be performed in such a fashion as to avoid hypovolemia, hypothermia, and airway compromise. Operative techniques vary by institution but, in general, the goal is similar: to circumnavigate the neural placode without injuring any of the neural elements. Once that is completed, the neural placode is placed into the spinal canal.
- The next step entails the identification and dissection of the dura. The neural placode is covered by the dura by a watertight closure. If the dura is absent, as sometimes occurs, the muscle fascia is reflected off the muscle and used to create a watertight tube to enclose the neural placode. Skin closure is achieved by mobilizing the skin from the underlying paraspinal fascia in an avascular plane. The skin is then closed in layers, and an attempt is made to ensure little tension is placed on the wound. The skin may look somewhat pale immediately after closure, especially if the slightest bit of tension is present on the wound.
- Care is taken to avoid necrosis or ischemia of the skin flap. The skin closure is protected with a sterile dressing.
Shunt placement during myelomeningocele closure
- Approximately 20% of all patients with myelomeningoceles have significant hydrocephalus at birth; another 60-70% of patients develop it after the myelomeningocele is closed. In select patients, placement of a shunt during the same operation for closure of a myelomeningocele is entirely reasonable. At the author's institution, patients who manifest ventriculomegaly after birth undergo shunt placement after myelomeningocele closure but while under the same anesthetic. Contemporaneous shunt placement not only decreases future anesthetic risk, but also decreases the chance of CSF leaking through the myelomeningocele closure.
Treatment of Chiari II malformations
In Chiari II malformations, decompression of the posterior fossa and/or cervical cord, with its variable anatomy, is surgically challenging and requires an experienced surgeon. The torcular can come in low near the foramen magnum, the cerebellum is often adherent to the medulla, and many venous sinuses are present. Catastrophic blood loss is the major risk when a sinus is inadvertently opened. Prior to decompressing a Chiari II malformation, ensure the shunt is functioning. CT scan findings can be misleading because ventricles can remain small despite an obstruction in the shunt. Shunt tap or exploration is the most reliable test prior to embarking on a Chiari decompression.
The main signs and symptoms of a Chiari II malformation that requires decompression are those of brainstem compression. For example, neonates can have stridor, central apnea, dysphagia, quadriparesis, or failure to thrive. Patients may have subtle signs, such as worsening strabismus, nystagmus, myelopathy, or aspiration of unclear etiology. In the author's experience, symptomatic Chiari II malformation is the leading cause of death in patients with myelomeningocele. (Approximately 30% of children die that develop brainstem symptoms when < 5 y.) Symptomatic deterioration from a Chiari II malformation can constitute a neurosurgical emergency and, despite urgent decompression, children can die from hindbrain compression. Patients who fare the worst are those who have ventilatory difficulties shortly after birth. Autopsies on these clinically challenging patients often show brainstem anomalies, such as disorganized brainstem nuclei, as well as cortical and subcortical abnormalities.
Signs and symptoms of problematic Chiari II malformation in neonates include the following:
Stridor with vocal cord paralysis
Progressive brainstem function
Nystagmus, strabismus, progressive
Swallowing difficulties, poor suck
Although this skin-covered neural tube defect is beyond the scope of this article, a few salient points should be included here. The neonate often presents with a skin-covered mass above the buttocks, as shown below.
The natural history of these lesions consists of eventual neurologic deterioration. Appropriate prophylactic surgical treatment of these lesions can halt the progression of the neurologic deficits and improve neurologic function, and the risk of surgery in skilled hands is quite low.
The surgical goal in treating these lesions is to detach the lipoma of the buttocks from the lipoma that emerges through the dura, fascia, and bony defect. The technique requires the surgeon to identify normal anatomy and travel down to the location where the lipoma pierces the dura and enters the spinal cord. Often with use of microsurgical technique and/or a carbon dioxide laser, the lipoma is disconnected from the spinal cord, as shown in the image below.
All of the lipoma need not be removed. Take care to leave some lipoma on the cord in order to avoid injuring the underlying neural substrate. The filum terminale also is divided to further untether the cord. A patulous graft is then placed over the dural opening to establish a pool of CSF around the cord to help prevent retethering.
Over the past decade, fetal surgery for neural tube defects (NTDs), specifically myelomeningocele, has been developed. Interest in this approach to the treatment of neural tube defects stems from a growing body of literature that supports the 2-hit hypothesis. Initially, most investigators believed that all the neurologic deficits seen in neural tube defects resulted from the neurulation defect that occurs during days 26-28 of gestation. However, some have suggested that, in addition to the neurulation embryologic defect, secondary damage occurs when exposed neural tissue is in contact with amniotic fluid. Thus, covering the neural placode with skin in utero could theoretically decrease the damage inflicted to the exposed neural structures by amniotic fluid. In addition, the loss of cerebral spinal fluid (CSF) through the central canal may be halted by in utero closure of the neural placode, thereby reversing some of the potentially devastating neurologic sequelae of neural tube defects.
The 2 neurologic sequelae of major concern are shunt-dependent hydrocephalus and hindbrain injury from progressive hindbrain herniation through the foramen magnum (Chiari II malformation). In 1999, Vanderbilt University researchers, led by pediatric neurosurgeon Noel Tulipan, MD, and obstetrician Joseph P. Bruner, MD, reported in JAMA their experience with in utero surgery for neural tube defects over the previous decade. This was a single-institution nonrandomized, observational study conducted from 1990-1999. A cohort of 29 patients with isolated myelomeningocele underwent intrauterine repair of the neural tube defect between 24-30 weeks' gestation. These patients were compared to 23 lesion-matched controls who underwent postnatal surgery. The main outcome measure was requirement for placement of a ventriculoperitoneal shunt for the treatment of hydrocephalus.
Results of the study have been promising. Patients with neural tube defects who underwent in utero surgery experienced a lower incidence of hydrocephalus than the control group (59% versus 91%). Also, a reduced incidence of hindbrain herniation was evident in the in utero group (38% versus 95%). One death occurred in the in utero group, as did an increased risk of oligohydramnios (48% versus 4%), and an earlier age of delivery by about 4 weeks.
Regardless, the results have encouraged a group of investigators from both Vanderbilt and Children's Hospital of Pennsylvania (CHOP) to propose that a few select centers investigate whether this approach can yield durable results. The CHOP group published their results in The Lancet in 1998. Since that proposal, the National Institutes of Health (NIH) has funded grants to study the efficacy of in utero surgery in this patient population. Currently, 3 centers are conducting this research: CHOP/University of Pennsylvania; Vanderbilt; and University of California, San Francisco.
Specific questions to be answered are as follows:
Will the decreased rate of shunt dependency hold up through time?
Will the decreased incidence of hindbrain herniation translate into a decreased incidence of hindbrain-related neurologic complications?
Will the decreased incidence in hydrocephalus and hindbrain herniation translate into improved neurologic status for both the hindbrain structures and the lower extremities?
Will the significant risks to the fetus and mother be outweighed by the long-term potential benefits to children with neural tube defects?
These questions have yet to be answered, and only further long-term study that compares the experimental results to those of a historical cohort or contemporaneous controls can accurately answer these questions. Until then, this approach is still considered experimental. So far, the Vanderbilt center has performed over 100 in utero surgeries for neural tube defects.
In 2008, a reevaluation by leaders in the fetal surgery field was still cautiously optimistic. Almost 330 cases of intrauterine repair have been performed around the world. The 3 centers in the United States who have randomized their patients to conventional postnatal versus the experimental intrauterine intervention have sought to analyze 2 endpoints. The 2 parameters evaluated are the need for a shunt at age 1 year and fetal and infant mortality. The data will be analyzed after the studies are closed.
Outcome and Prognosis
Major issues in evaluating the outcome of children with myelomeningocele are hydrocephalus, intellect, ambulation, continence, orthopedic problems, and employment and independent living status.
Treatment of neural tube defects (NTDs) in neonates has evolved over the past half century. Historically, there was a period when neonates with neural tube defects were either left untreated or selectively treated. The natural history of neonates with neural tube defects left untreated is poor. Most died of meningitis, hydrocephalus, and sepsis. Laurence described a cohort of 290 children with spina bifida (mostly myelomeningoceles) left untreated in Wales during the 1950s and 1960s. Only 11% of those children lived past the first decade of life. Lorber and Salfield reported their results with selected treatment of neonates with myelomeningocele. More than 80% of the selected neonates lived, whereas 97% of the neonates denied treatment died in the first year of life. The tremendous ethical implications of selected neonatal treatment led to its abandonment.
In the United States during the 1960s, most children with myelomeningocele were treated, which resulted in a higher survival rate (>80% for the first decade) than that in Great Britain. Recognized causes of death include shunt malfunction, seizure, infection, and uncontrolled brainstem symptoms from Chiari II malformations and/or hydrocephalus. During the past 3 decades, aggressive treatment of neonates with myelomeningocele has been pursued in almost all pediatric centers in the United States.
Cognitive ability is, in part, influenced by hydrocephalus, CNS infections, and degree of impairment. In most series, 60-70% of the children with myelomeningocele had intelligence quotients (IQs) greater than 80; the others had IQs in the delayed or severely delayed range. In the McLone series, children who had CNS infections, such as ventriculitis, or shunt infections fared worse than those who did not. Children with myelomeningocele without hydrocephalus had an average IQ of 102; those with hydrocephalus had an average IQ of 95. However, the average IQ dropped to 73 when a CNS infection complicated the picture. Children with moderate physical impairments, in most series, have a better intellectual outcome than those with significant sensory levels and paraplegia. The reasons most likely are multifactorial.
Only 10-15% of all children with myelomeningoceles are continent of urine. This issue often causes the children to be separated from their peers, which, in turn, leads to other neuropsychologic deficits. Despite the development of catheters and Crede manipulation (pushing on the pelvis over the bladder to engender urination), children with NTDs still experience a high rate of infection, vesicoureteral reflux, kidney failure, hydronephrosis, and obstruction. Clean intermittent catheterization (CIC) has led to a marked improvement of the lifestyles and lifespan of these children. CIC can make more than 75% of these children socially continent and significantly decreases the rate of urosepsis. As a result of CIC, urinary diversions are less commonly performed. Use of anticholinergic drugs combined with CIC has resulted in a better self-image and greater educational and vocational opportunities for children with neural tube defects.
Bowel continence is achieved with a combination of medication, diet control, manual disimpaction, and enemas. Most patients with neural tube defects can be continent of stool with these measures.
The ability to ambulate is influenced by the level of the neural lesion, hydrocephalus, pelvic anatomy, limb deformities, tethered cord, scoliosis, kyphosis, and syringomyelia; varying degrees of ambulation are noted. Strong hip flexors, adductors, and quadriceps are required to be ambulatory. Some children can ambulate in the community, some only in the home, others can only stand but not walk, and the rest are wheelchair bound. However, many children with neural tube defects, such as lumbar myelomeningocele, lose their ability to ambulate as they get older. In general, patients with sacral lesions can ambulate, those with thoracic lesions cannot.
Independent living, vocation, education
Steinbok noted that about 60% of children with neural tube defects attended normal classes, and 40% were in special classes or operated below their grade levels.[9, 30] Approximately 10-40% of children with myelomeningocele are probably employable at some level, depending on the individual's intellectual abilities, ambulation status, and environmental influences.
Over the past 2 decades, allergy to latex has been recognized in an increasing number of children with myelomeningocele. As many as 50% of children with myelomeningocele may be latex sensitive. This appears to be a result of a massive immunoglobulin E (IgE) response to the antigen in latex that is derived from the Heva brasiliensis plant. Patients with myelomeningocele should be treated from birth with latex precautions. Surgeons and health care providers should work with latex-free gloves and plastics so that they can avoid latex-induced anaphylaxis, which can be life threatening. Medications such as corticosteroids, diphenhydramine, bronchodilators, and epinephrine should be available as a precaution during surgery on these children.
Neurosurgeons need to be wary of later-life neurologic deterioration in children and adults. The most common deterioration occurs from a tethered spinal cord. A routine MRI reveals a spinal cord that ends in the lumbar or sacral regions in almost all patients with myelomeningocele, shown below.
This can be normal in many patients without any new neurologic complaints. Despite careful surgical closure of the original neural placode, approximately 20% or more of all patients with myelomeningocele require an untethering of their spinal cords later in life. They may present with gait difficulty, back pain, leg weakness, sensory loss, a new foot deformity, or simply a change in their urodynamic data or urinary continence. These patients require surgical exploration to free the neural placode and nerve roots from the dorsal surface of their dura. Patients with tethered cords on MRI but no new complaints do not require reexploration.
Diastematomyelia can be diagnosed using MRI or CT/myelogram. An enlarging syringomyelia can be the result of a symptomatic Chiari II malformation or retethering of the spinal cord. Many functional deteriorations result from progressive orthopedic deformities such as scoliosis, pelvic obliquity, and limb deformities. An orthopedic surgeon well versed in the care of patients with neural tube defects is required to execute a reasonable plan to repair or stabilize treatable disorders.
In general, a multidisciplinary team consisting of neonatologist, pediatrician, pediatric neurosurgeon, pediatric urologist, pediatric orthopedic surgeon, physical therapist, nurse, nutritionist, psychologist, and teacher are required to direct the care of children with neural tube defects.
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|Days of Gestation||Event||Resultant Malformation|
|0-18||Formation of 3 germ layer and neural plate||Death or unclear effect|
|18||Formation of neural plate and groove form||Anterior midline defects|
|22-23||Appearance of optic vessels||Hydrocephalus (18-60 d)|
|24-26||Close anterior neuropore||Anencephaly|
|26-28||Close posterior neuropore||Cranium bifidum, spina bifida cystica, spina bifida occulta|
|32||Vascular circulation||Microcephaly (30-130 d), migration anomalies|
|33-35||Splitting of prosencephalon to make paired telencephalon||Holoprosencephaly|
|70-100||Formation of corpus callosum||Agenesis of the corpus callosum|
|Anomalies Associated with Myelomeningocele||Approximate Percent of Patients|
|Chiari II malformation||>90%|
|Brainstem malformations (cranial nerve)||75%|
|Cerebral ventricle abnormalities||>90%|
|Agenesis of the corpus callosum||12%|