Spinal Open Neural Tube Defects Research Articles

Fetal Surgery for Myelomeningocele: Neurosurgical Perspectives.

More than 30years have elapsed since it was recognised that folic acid supplementation could substantially reduce the risk of open neural tube defects (ONTDs). During that time, many countries have adopted policies of food fortification with demonstrable reduction in the incidence of both cranial and spinal ONTDs. Improved prenatal detection and termination has also resulted in a reduction in the number of affected live births. Nonetheless, in the USA about 1500 children, and in the UK around 500 children are born each year with myelomeningocele (MMC) and so the management of MMC and its complications continues to constitute a significant clinical workload for many paediatric neurosurgical units around the world.Until recently, the options available following antenatal diagnosis of MMC were termination of pregnancy or postnatal repair. As a result of the MOMS trial, prenatal repair has become an additional option in selected cases (Adzick et al., N Engl J Med 364(11):993-1004, 2011). Fetal surgery for myelomeningocele is now offered in more than 30 centres worldwide. The aim of this chapter is to review the experimental basis of prenatal repair of MMC, to critically evaluate the neurosurgical implications of this intervention and to describe the technique of 'open' repair, comparing this with emerging minimally invasive alternatives.

Chiari Malformation with Surgically Induced Open Neural Tube Defect in Late Chick Embryos : Characterization by Magnetic Resonance Imaging and Histopathological Analysis.

Chiari II malformation (CM II) is still the main cause of severe morbidity and mortality in children with open neural tube defects (ONTDs). The goal of this study was to validate a CM II model in late-stage chick embryos with surgically induced ONTDs. To make the chick embryo model of ONTD, their neural tubes were opened for a length of 5-6 somites at the thoracic level in Hamburger and Hamilton stage 18 chick embryos (n=150). They were reincubated in ovo. up to a total age of 17-21 days. A total of 19 embryos survived and were assigned to either the postoperative day (POD) 14-15 group (n=6) or the POD 17-18 group (n=13). Magnetic resonance imaging (MRI) and histopathologic findings of embryo heads with spinal ONTDs were compared with age-matched normal chick embryos. The chick embryos with ONTDs demonstrated definite and constant structural changes, such as downward displacement of the cerebellum to just above the foramen magnum and narrow and small cerebrospinal fluid spaces in the crowded small posterior fossa. These morphologic features were more prominent in the POD 17-18 group than in the POD 14-15 group. This is the first description of CM II with spinal ONTD in a late-stage chick embryo model with MRI and histopathological analysis. The morphological changes of the posterior fossa in this study mimic those of CM II associated with spinal ONTD in humans. This model will facilitate investigation of the pathogenesis of CM II.

Experimental models of spinal open neural tube defect and Chiari type II malformation

Experimental animal models are essential for investigation of the pathoembryogenesis, pathophysiology, and management strategy of spinal open neural tube defect (ONTD) and its associated anomalies including Chiari type II malformation. Genetic, chemical/nutrient, and surgical models have been widely used for a variety of purposes. The aim of this article is to review the representative animal models of spinal ONTD and associated Chiari type II malformation with respect to their advantages and disadvantages. Among them, the surgical model was described in detail because it is familiar to neurosurgeons and it is used for evaluations of prenatal repair of spinal ONTDs. The surgical model also has advantages because it allows quantitative analysis of the lesions. A description of our previous studies on spinal ONTDs using a chick surgical model is presented as an example.

Natural history of hydrocephalus in children with spinal open neural tube defect.

Background:The long-term prognosis of patients with Spinal Open Neural Tube Defect (SONTD)-associated hydrocephalus is not well known. This study was conducted to ascertain the incidence and natural history of hydrocephalus in patients with SONTD.Methods:All 82 patients with SONTD referred to Neurosurgery/Spina Bifida Clinics at King Khalid University Hospital, Riyadh, Saudi Arabia (January 1995 - July 2010) were studied and followed for a period of 1-16 years. Patients were divided into three groups: Group “A” with active hydrocephalus treated with ventriculoperitoneal shunt (VPS), or endoscopic third ventriculostomy (ETV); Group “B” with compensated hydrocephalus; and Group “C” with no hydrocephalus. Timing of shunt insertion, complications of treatment and status of hydrocephalus were analyzed.Results:The mean age of the 82 patients was 7.4 years (range 1-16 years). Group “A” included 59 (72%) patients, Group “B” 7 (8.5%) patients, and Group “C” 16 (19.5%) patients. Chiari malformation type II was found in 71 (86.6%) patients, 57 of whom (80%) were in Group “A” with active hydrocephalus. They were treated by VPS (51 patients) and ETV (8 patients). The shunts were revised or replaced in 10 (19.6%) patients due to obstruction or infection. Primary ETV failed in 3/8 patients, and treated by VPS. None of those in Groups “B” or “C” required treatment for hydrocephalus during the follow up.Conclusion:Hydrocephalus affects the majority of patients with SONTD who have Myelomeningocele (MMC) and CM II and requires close surveillance and prompt management. Children with SONTD should routinely undergo MRI examination of brain and craniocervical junction to clarify ventricular size, and the presence of CM II.

Enhanced Reclosure of Surgically Induced Spinal Open Neural Tube Defects in Chick Embryos by Injecting Human Bone Marrow Stem Cells Into the Amniotic Cavity

To evaluate the reclosure-promoting capacity of a neural stem cell line (F3) and a human bone marrow stem cell line (B10) injected into the amniotic cavity of spinal open neural tube defects (ONTDs) of chick embryos of Hamburger and Hamilton stage 18 or 19. Fifteen chick embryos that survived the procedure were obtained for each of 4 groups: untreated control, F3-, B10-, and HFF-1 (human foreskin fibroblast)-treated groups. Embryos in the control group underwent ONTD surgery but no cell injection. Compared with the untreated control and HFF-1 groups, the B10 group showed enhanced reclosure at 3, 5, and 7 days after injection, whereas the F3 group did not. B10 cells were not incorporated into reclosed neural tubes but simply covered ONTDs during the process of reclosure. F3 cells did not cover ONTDs. The cell survival of F3 cells exposed to the chick amniotic fluid in vitro for 48 hours was significantly lower than that of B10 cells. The results confirmed that B10 cells enhance reclosure of ONTDs by covering and protecting neural tissues, not by direct cell incorporation. The lack of reclosure capacity in the F3 group may be related to the poor survival of F3 cells in the amniotic fluid.

Commentary to the paper double neural tube defect: a case report and discussions on neural tube development by V. Ravindran

This is a case report of a child with double neural tube defect (NTD) comprising a parietal encephalocoele and an open thoracic myelomeningocoele. The authors use this case to endorse the multi-site neural tube closure theory as aetiology for all multiple NTDs. Proponents of this theory claim that neural tube defects occur at “collision sites” of neural tube closure with opposing closure directions, and because up to five or six of these waves are thought to be operational, there are, accordingly, multiple collision sites. The multi-site closure theory was used originally to explain the different favoured locations of encephalcoeles, and as such, the theory is seductive. At collision sites, the overlying myocutaneous tissues may be potentially weaker and, therefore, susceptible to being stretched but not disrupted by a focal herniation of the alar plates of the already closed cranial neural tube and surrounding meninges. The disorganised gyral development and cortical dysplasia of the herniated brain may be secondary to early tissue distortion. The overlying skin and meninges are intact. Spinal open neural tube defects (ONTD) are due to focal absence of neural plate closure, as shown in numerous, very credible animal experiments. The skin, muscles, neural arches and dura are wide open, and the exposed neural material is an unfused neural plate. This true “closure lesion” is thus fundamentally different from a “collision lesion” exemplified by the encephalocoele. Most spinal ONTDs are terminal lesions involving the end of the primary neural tube, but there are rare examples of segmental lesions in which the “suspended” open neural placode is flanked by normal spinal cord both rostrally and caudally. The incomplete neural plate closure occurs in a square-pulse fashion followed by resumption of normal closure. Three percent of ONTDs in our unit are segmental placodes. Most hemi-myelomeningocoeles associated with split cord malformation (SCM) are segmental lesions. Limited dorsal myeloschisis (LDM), though not technically “open”, is a segmental neural tube closure abnormality, as is dorsal lipoma, a lesion of segmental premature disjunction. If there can be one segmental closure failure, why not two or even three square pulse insults, separated in time, causing in tandem closure lesions resulting in either two segmental ONTDs or one segmental and one terminal ONTD? Other multiple neural tube closure abnormalities, though rare, have been reported, such as double LDMs, double dorsal lipomas and double dermal sinus tracts. Even double SCMs caused by multi-focal gastrulation defects with multiple endomeschymal tracts are well known in the literature. Thus, multiple spinal ONTDs can conceivably occur without invoking the multiple closure-wave theory, which, in the spinal cord will produce a very different lesion. It is not known why there should be abrupt recovery of normal neural tube closure after the square pulse insult. There could conceivably be transient presence of a teratogenic impulse that disturbs certain downstream transcription factors, without a fixed genomic mutation that would perpetuate the developmental error. It is thus the timing of the next transient insult that determines the location of the second neural tube defect, rather than the activities of the colliding zippers.

Expression of neuronal antigens and related ventral and dorsal proteins in the normal spinal cord and a surgically induced open neural tube defect of the spine in chick embryos: an immunohistochemical study

The aims of this study were to elucidate the processes of neuronal differentiation and ventrodorsal patterning in the spinal cord of the chick embryo from embryonic day (E) 3 to E17 and to study the effect of a prenatal spinal open neural tube defect (ONTD) on these processes. Expression patterns of neuronal antigens (neuronal nuclear antigen, neurofilament-associated protein (NAP), and synaptophysin) and related ventral markers [sonic hedgehog, paired box gene (PAX)6, and islet-1], and dorsal markers (bone morphogenetic protein, Notch homolog 1, and PAX7) were investigated in the normal spinal cord and in a surgically induced spinal ONTD in chick embryos. Four normal and ONTD chick embryos were used for each antigen group. There were no differences in the expression of neuronal and ventrodorsal markers between the control and ONTD groups. NAP and synaptophysin were useful for identifying dorsal structures in the distorted anatomy of the ONTD chicks.

P30.03: Value of fetal magnetic resonance imaging in fetuses diagnosed prenatally with CNS abnormalities in ultrasound

We evaluated whether fetal magnetic resonance imaging (MRI) could provide useful clinical information to diagnose the CNS abnormalities prenatally and assessed whether fetal MRI could affect the obstetric counseling with the parents or the plan of management. A retrospective study of all cases of prenatally detected CNS abnormalities was performed in 20 patients in Kangnam St. Mary's Hospital, the Catholic University of Korea, from May 2002 to December 2006. Associated abnormalities, pregnancy outcome and infant follow-up were recorded. Indications of fetal MRI included Dandy walker malformation (n = 4), ventriculomegaly combined with additional CNS anomaly (n = 3), megacisterna magna (n = 3), macrocephaly (n = 3), isolated ventriculomegaly (n = 2), arachnoid cyst (n = 2), agenesis of corpus callosum (n = 1), arnold-chiari malformation (n = 1), and spinal open neural tube defect (n = 1). The results of MRI were in agreement with ultrasound in 13 cases. Among those MRI provided more additional information in eight cases, incorrect diagnosis in one case with ventriculomegaly which was proven to be an agenesis of corpus callosum. In one case with Arnold-chiari malformation, ultrasound provided more clinical information than MRI. MRI changed the diagnosis in seven cases. Among those there was an error in the diagnosis of one fetus with isolated marked ventriculomegaly, which had been diagnosed as an ACC. Five parents decided to terminate their pregnancies because of ACC, Dandy-walker malformation, severe ventriculomegaly, Arnold-chiari malformation, and meningomyelocele. Fetal MRI is a useful complementary examination when prenatal ultrasound is inadequate or doubtful. MRI is also valuable in the evaluation of the fetal anatomy for planning delivery and management.

Reclosure of surgically induced spinal open neural tube defects by the intraamniotic injection of human embryonic stem cells in chick embryos 24 hours after lesion induction

The authors previously reported that human embryonic stem cells (hESCs) injected into the amniotic cavity of chick embryos immediately after neural tube incision in a surgically induced spinal open neural tube defect (ONTD) model promote the reclosure capacity of neural tubes. To simulate more closely the clinical situation of human ONTDs, in which a substantial time period elapses before the prenatal diagnosis of spinal ONTDs, the authors investigated whether this reclosure capacity remains enhanced by the intraamniotic injection of hESCs at 24 hours after ONTD induction. One hundred twenty-two chick embryos with ONTDs were randomly assigned to two groups: the control group (59 embryos) and the hESC-injection group (hESC group, 63 embryos). After the neural tubes of both groups had been opened, the hESC group underwent direct intraamniotic injection with hESCs marked with an enhanced green fluorescent protein at 24 hours after ONTD induction. The lengths of the remnant ONTDs were measured and the presence of hESCs was determined at 4, 6, and 8 days after ONTD induction. No difference in survival rates was observed between the two groups. The mean length of the ONTDs, adjusted for body length at the time of death and initial lesion length, was significantly shorter in the hESC group than in the control group (p < 0.001). No hESCs were found within reclosed neural tubes; rather, they covered the defect area during the reclosure process. The authors demonstrate that hESCs injected into the amniotic cavity at 24 hours after ONTD induction enhance reclosure ability in chick embryos.

Enhancement of re-closure capacity by the intra-amniotic injection of human embryonic stem cells in surgically induced spinal open neural tube defects in chick embryos

To evaluate the re-closure promoting capacity of human embryonic stem (hES) cells injected into the amniotic cavity on spinal open neural tube defects (ONTDs) of chick embryos, neural tubes were opened at Hamburger and Hamilton stage 18 or 19 and the embryos were divided into three groups: a control group (no injection), a vehicle group, and a hES cell group (injection of 20,000 hES cells immediately after neural tube incision). On postoperative days 3, 5, and 7, ONTDs were significantly more re-closed in the hES cell group than in the other two groups. hES cells were present at the area in the process of re-closure, and covered ONTDs, but were not found in the re-closed area, suggesting indirect effects rather than cell replacement on the neural tissue.

Skin graft on the surgically induced spinal open neural tube defects does not induce lipomatous malformation but enhances re-closure to the normal state in chick embryos

To determine the effect of skin allograft on open neural tube defects (ONTDs), the neural tube was incised open using Hamburger and Hamilton stage 18 or 19 chick embryos for a length of six somites. Embryos were divided into two groups: graft and control (with and without skin allograft). On postoperative day 5, closure of ONTDs was more frequent in the graft group than in the control group (9/15 versus 0/15), and healing was nearly complete. However, typical lipomatous features were not observed. These results suggest that simple mechanical attachment of skin allograft on ONTDs does not lead to lipomatous malformation in chick embryos. On the other hand, our results support a potential role of skin allograft in the management of prenatal spinal ONTDs.

Chronological changes of re-closure capacity in surgically induced spinal open neural tube defects of chick embryos

To investigate the re-closure capacity of surgically induced spinal open neural tube defects (ONTD) and its correlation to the cell proliferation activity in embryonic stages, longitudinal incisions of 3- or 6-somite lengths were made in neural tubes of chick embryos at Hamburger and Hamilton stage 18-19, and the length of the ONTDs was measured on postoperative days 2, 3, 5, 7, and 10. The results demonstrated that re-closure occurred more actively when the incision length was shorter. The chronological changes in the re-closure capacity of the ONTDs paralleled the proliferative activity of the neural tube. We conclude that surgically induced spinal ONTDs may be remodeled in early chick embryos and that manipulation of cell dynamics can enhance the re-closure process in the embryonic spinal cord tissue.

Cell kinetics of surgically induced spinal open neural tube defect in chick embryos

In an attempt to understand cell kinetics of open neural tube defects (ONTDs) in the embryonic stages, chronological changes of cell proliferation and cell death patterns in the surgically induced spinal ONTDs of chick embryos were investigated using proliferating cell nuclear antigen (PCNA) staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) method. ONTDs were induced at Hamburger and Hamilton stages 17–19. Compared with the control group, the surgery group showed a lower PCNA labeling index for 5 days after surgery and demonstrated more TUNEL-positive cells at 6 h, 3 and 5 days after surgery. Decreased cell proliferation and enhanced apoptosis were seen in the ventral as well as in the dorsal spinal cord. These results partly explain the functional deficits of ONTDs.