Intrauterine myelomeningocele repair reverses preexisting hindbrain herniation

Significant brainstem dysfunction in neonates with myelomeningoceles: a comparison of prenatal versus postnatal closure

OBJECTIVE

The purpose of this study was to compare the incidence of significant brainstem dysfunction (SBD) in neonates with myelomeningocele who have been treated with prenatal versus postnatal closure at a single institution.

METHODS

The records and imaging of all children undergoing either prenatal (n = 27) or postnatal (n = 60) closure of myelomeningocele at the authors' institution from December 2014 through May 2021 were reviewed. SBD, fetal ventricular size, gestational age at fetal imaging and delivery, postnatal ventricular size, need for and type of hydrocephalus treatment, spinal neurological level at birth, anatomical Chiari severity, death, and prenatal or postnatal repair were factors recorded. SBD was defined by need for airway surgery or gastrostomy tube, or endotracheal intubation because of apnea, aspiration, or airway control problems. Comparisons between prenatal and postnatal cohorts and between the cohorts with and without SBD were performed.

RESULTS

SBD occurred in 25% and 0% of neonates who underwent postnatal and prenatal closure, respectively. There were no differences in fetal ventricular size or spinal neurological level between the prenatal and postnatal cohorts or between those with or without SBD. Anatomical severity of the Chiari malformation after birth was worse in the postnatal cohort. Hydrocephalus treatment was required in 70% and 33% of infants who underwent postnatal and prenatal closure, respectively. All three deaths were in the postnatal group from SBD.

CONCLUSIONS

Prenatal closure of myelomeningocele is associated with a significant reduction in SBD.

Fetal open spinal dysraphism repair through a mini-hysterotomy: Influence of gestational age at surgery on the perinatal outcomes and postnatal shunt rates

OBJECTIVE

To analyze the impact of gestational age (GA) at the time of fetal open spinal dysraphism (OSD) repair through a mini-hysterotomy on the perinatal outcomes and the infants' ventriculoperitoneal shunt rates.

METHODS

Retrospective study of cases of fetal OSD correction performed from 2014 and 2019.

RESULTS

One hundred and ninety women underwent fetal surgery for OSD through a mini-hysterotomy, and 176 (176/190:92.6%) have since delivered. Fetal OSD correction performed earlier in the gestational period, ranging from 19.7 to 26.9 weeks, was associated with lower rates of postnatal ventriculoperitoneal shunting (P: .049). Earlier fetal surgeries were associated with shorter surgical times (P: .01), smaller hysterotomy lengths (P < .001), higher frequencies of hindbrain herniation reversal (P: .003), and longer latencies from surgery to delivery (P < .001). Median GA at delivery was 35.3 weeks. Multivariate binary logistic regression showed that both fetal lateral ventricle-to-hemisphere ratio (%; P < .001; OR: 1.14 [95% CI: 1.09-1.21]) and GA at the time of fetal surgery (P: .016; OR: 1.37 [95% CI: 1.07-1.77]) were independent predictors of postnatal ventriculoperitoneal shunting.

CONCLUSION

Fetuses with OSD who were operated on earlier in the gestational interval, which ranged from 19.7 to 26.9 weeks, were less prone to receiving postnatal ventriculoperitoneal shunts.

Antenatal management of fetal neurosurgical diseases

The advance in the imaging tools during the pregnancy (ultrasound and magnetic resonance) allowed the early diagnose of many fetal diseases, including the neurological conditions. This progress brought the neurosurgeons the possibility to propose treatments even before birth. Myelomeningocele is the most recognized disease that can be treated during pregnancy with a high rate of success. Additionally, this field can be extended to other conditions such as hydrocephalus and encephaloceles. However, each one of these diseases has nuances in the diagnostic evaluation that should fit the requirements to perform the fetal procedure and overbalance the benefits to the patients. In this article, the authors aim to review the neurosurgical aspects of the antenatal management of neurosurgical conditions based on the experience of a pediatric neurosurgery center.

Sequential morphological change of Chiari malformation type II following surgical repair of myelomeningocele

PURPOSE

To document long-term morphological changes of Chiari type II malformation (CM-II) following closure of spina bifida manifesta (SBM).

METHODS

We retrospectively evaluated postnatal magnetic resonance images of the CM-II and posterior fossa (PF) in 28 consecutive cases. We measured changes in vertebral level and length of the cerebellar peg (CP), cerebrospinal fluid (CSF) spaces anterior and posterior to the cerebrospinal junction, PF area, and the anteroposterior diameters of the foramen magnum (FM) and C1 vertebra. We examined the morphological differences between the cases with and without ventriculoperitoneal (VP) shunting and derived predicted means by nonlinear mixed-effect modeling.

RESULTS

At birth, there were significant differences in CP length, PF area, and FM and C1 diameters between those who underwent VP shunting and those who did not. In cases with a CP below C1, VP shunting was required in every case but one. In those with visible CSF space at birth, VP shunts were not required. In 17 of 18 cases with a CP below C1, the vertebral level ascended by mean two vertebral levels (range 0-5 levels) within 4-6 months of delivery. In the remaining case, slowly progressive hydrocephalus and delayed CP descent required VP shunting at 8 months. Predicted mean CP length and FM and C1 diameters were greater in those who underwent VP shunting, but there was no difference in predicted mean PF area.

CONCLUSION

The morphology of CM-II and the presence of hydrocephalus influence each other in children who have undergone postnatal SBM repair.

Intraoperative neurophysiological monitoring in patients undergoing tethered cord surgery after fetal myelomeningocele repair

OBJECT

Fetal myelomeningocele closure has been shown to be advantageous in a number of areas. In this study, the authors report on neural function in patients who had previously undergone fetal myelomeningocele repair and returned to the authors' institution for further surgery that included intraoperative neurophysiological monitoring.

METHODS

The authors retrospectively reviewed data obtained in 6 cases involving patients who underwent fetal myelomeningocele repair and later returned to their institution for spinal cord untethering. (In 4 of the 6 cases, the patients also underwent removal of a dermoid cyst [3 cases] or removal of an epidermoid cyst [1 case] during the untethering procedure.) Records and imaging studies were reviewed to identify the anatomical level of the myelomeningocele as well as the functional status of each patient. Stimulated electromyography (EMG) and transcranial motor evoked potential (tcMEP) recordings obtained during surgery were reviewed to assess the functional integrity of the nerve roots and spinal cord.

RESULTS

During reexploration, all patients had reproducible signals at or below their anatomical level on stimulated EMG and tcMEP recordings. Corresponding to these findings, prior to tethering, all patients had antigravity muscle function below their anatomical level.

CONCLUSIONS

All 6 patients had lower-extremity function and neurophysiological monitoring recording signals at or below their anatomical level. These cases provide direct evidence of spinal cord and nerve root conductivity and functionality below the anatomical level of the myelomeningocele, further supporting that neurological status improves with fetal repair.

Imaging the course of a hypoplastic cerebellum in a spina bifida newborn

INTRODUCTION

We report about a spina bifida patient with myelomeningocele at the lumbar level L5, extensive Chiari malformation type II with vermal herniation reaching to C6 with downward pontine shift, and a severe hypoplastic cerebellum. Chromosomal diagnostic tests showed no abnormalities.

CASE REPORT

The infant experienced severe central apneas successfully treated with oxygen therapy and caffeine medication; functional motor level was established at L5 with sparse anal sphincter function.

DISCUSSION

After surgical intervention (myelomeningocele repair and ventriculoperitoneal shunt placement), these abnormalities significantly improved on radiological imaging; the preoperative hypoplastic, almost undetectable, cerebellum developed to a fair sized cerebellum. Apneas disappeared over time and the patient showed further developmental improvement. Herein, we illustrate and discuss the changes of the cerebellar volume before and after neurosurgical intervention.

Primary and secondary management of the Chiari II malformation in children with myelomeningocele

OBJECT

Chiari malformation type II is almost exclusively found in patients with open spinal dysraphism. Etiology and pathophysiology are not yet completely understood, and management guidelines regarding the best follow-up and treatment of this pathological entity do not exist. In order to assess essential management aspects, literature and a series of secondary neurosurgical interventions in Chiari II patients have been reviewed.

METHODS

A literature review regarding etiology, diagnostics, pathophysiology, and management of Chiari malformation type II (CMII) and a retrospective evaluation of a series (2009-2012) of secondary interventions in Chiari II patients have been performed. Inclusion criteria were ICD for myelomeningocele with or without hydrocephalus and ICD for Chiari malformation and neurosurgical OR procedure. Evaluated parameters were: patient demographics, primary management, secondary neurosurgical operations (cranio-cervical decompression, shunt revision, myelolysis) as well as specific findings pre- and postoperatively. Essential results from literature review and patients' series are compiled in order to define management recommendations.

RESULTS

Fifty patients (28 f, 22 m; mean age, 7.1 years (range, 0.5-26 years)) with myelomeningocele-associated Chiari malformation type II were operated on between 2009 and 2012. Twenty-four patients had syringomyelia and scoliosis each, and 12 suffered from both. Orthopedic surgery for scoliosis or kyphosis had been performed in 13 cases. Shunt revision was performed in 38 cases, myelolysis in 17, and decompression of the foramen magnum in 14 (28 %). After a mean follow-up of 1.9 years, syringomyelia decreased from 24 to 16 cases. There was a postoperative reduction of neck pain (one third), sensorimotor (two fifths), and cranial nerve deficits (one half). CSF flow at the foramen magnum did not change visibly after surgery. Ventricular size improved in about half of the patients. Slit-like ventricles were found in nine (6 pre-surgical) and enlarged ventricles in nine (23 pre-surgical). Complication rate was 6 % (3/50) per cases, and no patient died or deteriorated neurologically after surgery.

CONCLUSION

CMII-related management guidelines are not well defined, since clinical constellations and presentations are varying. Often associated findings are syringomyelia, hydrocephalus, and scoliosis, and symptomatic CMII may be triggered by more than one underlying condition. According to literature and clinical experience, management recommendations can be defined. The most important finding is that hydrocephalus is often involved in symptomatic CMII and must always be considered first in any symptomatic patient. Intrinsic brain stem dysfunctions cannot be treated surgically, and monitoring of vital functions is sometimes the only clinical means that can be offered to the patient. Knowledge of the complex background has led to improved follow-up programs for the affected children and thus also improved longtime survival.

Myelomeningocele: the management of the associated hydrocephalus

BACKGROUND

The pathogenesis of the hydrocephalus associated with myelomeningocele (MMC) has been the subject of an extensive number of studies. The contemporary reduction of the incidence of the Chiari II malformation and of the associated active hydrocephalus after closure of the spinal defect in utero is in line with previous studies suggesting a prominent role of the posterior cranial fossa abnormalities, where even the increased venous pressure might be at least mostly a consequence of the constriction of the posterior cranial fossa structures. Pure absorptive abnormalities however coexist, the main ones documented to be abnormal cisternal spaces and peculiar cerebrospinal fluid chemical features.

MATERIALS AND METHODS

We reviewed the pertinent literature concerning the pathogenesis and management of the hydrocephalus associated to MMC. We also reviewed our personal experience in managing the hydrocephalus in such patients through an endoscopic third ventriculostomy.

RESULTS AND CONCLUSIONS

The literature review demonstrated an overall reduction in more recent series of children with MMC needing to be treated for the associated hydrocephalus postnatally, questioning the role of the prenatal care of the disease in this context. Less severe conditions and a more conservative neurosurgical attitude have certainly contributed to the reduction of the reported active postnatal hydrocephalus rate. Long-term cognitive evaluation of the children with MMC that we managed with an endoscopic third ventriculocisternostomy (ETV) as primary as well as secondary procedure did not demonstrate significant differences in the outcome compared with non-complicated extrathecally shunted children, favouring ETV as a valuable option in this subset of patients.

Intrauterine myelomeningocele repair postnatal results and follow-up at 3.5 years of age--initial experience from a single reference service in Brazil

PURPOSE

Present the outcomes of six cases submitted to intrauterine myelomeningocele (MMC) repair.

METHODS

Descriptive observational study of six children submitted to antenatal surgical repair of MMC between 26 and 27 weeks gestation. All deliveries were through cesarean section. The following neonatal variables were assessed: gestational age at delivery, birth weight, Apgar scores, need for intubation, duration of hospital stay and need for postnatal shunt procedures. After 3.5 years, the children were evaluated using the Columbia Mental Maturity Scale or Denver II tests and the Hoffer Ambulation Scale.

RESULTS

All deliveries were preterm at a mean gestational age of 32 + 4 weeks and mean birth weight was 1,942 g. Two infants had Apgar scores <7 at 1 min and 1 at 5 min. Ventricular-peritoneal shunts were placed in two cases. All six children are alive: five have normal cognitive development and one has a neuropsychomotor developmental delay. Two children had normal leg movements, a sacral functional level and are community ambulators. Three children had upper lumbar anatomical level lesions and one had a lower thoracic level lesion at the time of fetal surgery. One child, with an L1-L2 anatomical level lesion, in noambulatory and fully dependent on a wheelchair for mobility.

CONCLUSION

Antenatal surgical repair of MMC reduced the need for postnatal shunt placements. Despite preterm delivery, the cognitive development of most children at 3.5 years was normal. Antenatal surgery seemed to improve lower limb motor function in these cases.

Interobserver reliability and diagnostic performance of Chiari II malformation measures in MR imaging--part 2

PURPOSE

Brain MR imaging is essential in the assessment of Chiari II malformation in clinical and research settings concerning spina bifida. However, the interpretation of MR images of the malformation is not always straightforward. Morphometric analyses of the extent of Chiari II malformation may improve the assessment. In an attempt to select appropriate morphometric measures for this purpose, we investigated the interobserver reliability and diagnostic performance of several morphometric measures of Chiari II malformation on MR images.

METHODS

Brain MR images of 79 children [26 with open spinal dysraphism, 17 with closed spinal dysraphism, and 36 without spinal dysraphism; mean age 10.6 (SD 3.2; range, 6-16) years] were evaluated. All children had been assessed for Chiari II malformation (defined as cerebellar herniation in combination with open spinal dysraphism; n = 23). Three observers blindly and independently reviewed the MR images for 21 measures of the cerebellum, brainstem, and posterior fossa in three planes. The interobserver reliability was assessed by an agreement index (AI = 1 - RRE) and the diagnostic performance by receiver operating characteristic analyses.

RESULTS

Reliability was good for most measures, except for the degree of herniation of the vermis and tonsil. Most values differed statistically significantly between children with and without Chiari II malformation. The measures mamillopontine distance and cerebellar width showed excellent diagnostic performance.

CONCLUSIONS

Morphometric measures may reliably quantify the morphological distortions of Chiari II malformation on MR images and provide additional tools to assess the severity of Chiari II malformation in clinical and research settings.

Morphometric analysis of posterior fossa after in utero myelomeningocele repair

OBJECT

Myelomeningocele (MMC) is characterized by a defect in caudal neurulation and appears at birth with a constellation of neuroanatomical abnormalities, including Chiari malformation Type II. The authors investigated the effects of antenatal versus postnatal repair of MMC through a quantitative analysis of morphometric changes in the posterior fossa (PF).

METHODS

The authors retrospectively reviewed the records of 29 patients who underwent in utero MMC repair, 24 patients who underwent postnatal repair, and 114 fetal and pediatric controls. Tonsillar displacement, cerebellum length, pons length, clivus-supraocciput (CSO) angle, and PF area were compared in antenatal and postnatal MMC repair groups as well as in controls without neural tube defects by using t-tests and correlation coefficients.

RESULTS

Initially, the in utero CSO angle was significantly more acute in all patients with MMC--prenatally and postnatally repaired--as compared with controls (57.8° vs 75.4°, p < 0.001); however, the angle rapidly changed and became similar to that in controls between 30 and 31 weeks' gestation to approximately 80°, with antenatal repair having little effect. Postnatally, the CSO angle decreased in controls (R = -0.58) and in the antenatal repair group (R = -0.17). The cerebellum and pons length demonstrated no significant differences in any group. Overall, tonsil descent was corrected in the antenatal repair group as compared with postnatal repair (p < 0.001), and the PF area increased in all 3 groups in utero. Growth was less rapid in patients with MMC compared with controls, but this was corrected by antenatal repair (p = 0.015).

CONCLUSIONS

Myelomeningocele was associated with tonsillar herniation and a smaller PF than in control fetuses. Antenatal surgical repair corrected both abnormalities. The CSO angle began significantly more acutely in patients with MMC, but normalized with development regardless of when surgery was performed. Determining the clinical effects of antenatal repair requires further follow-up.

Fetoscopic coverage of experimental myelomeningocele in sheep using a patch with surgical sealant

OBJECTIVE

Assess the feasibility of a fetoscopic patch coverage method for myelomeningocele repair in a sheep model.

STUDY DESIGN

Experimental study. A myelomeningocele-like defect was created in 15 fetal sheep on day 75 of gestation. Six remained untreated, whereas 9 underwent fetoscopic coverage of the defect on day 95 of gestation using an inert patch secured with surgical sealant. Clinical and histological examinations were performed after delivery.

RESULTS

Four valid newborn lambs were obtained in each group. Mean fetoscopic surgical time was 26.9 (SD=7.4)min. All untreated animals had an open lumbar defect with cerebrospinal fluid leakage, paraplegia, urinary incontinence, and Chiari malformation. All treated animals had a closed defect and were able to walk; one had weak bladder control, and another mild Chiari malformation.

CONCLUSION

In a chronic myelomeningocele model in fetal sheep, fetoscopic repair using a sealed patch results in simple, fast, satisfactory neural tube closure and averts neurological damage and Chiari malformation.

Impact of tethered cord release on symptoms of Chiari II malformation in children born with a myelomeningocele

PURPOSE

The role of distal traction in the form of a tethered spinal cord in exacerbating anatomical findings or symptoms of Chiari II malformation (CIIM) has been debated for decades. Despite the association of Chiari II malformation with myelomeningocele, the impact of tethered cord release on CIIM symptoms in patients has not been explored.

METHODS

A retrospective review of 59 patients born with a myelomeningocele was performed. A total of 92 untethering procedures were performed in which symptoms of CIIM were present in 29 cases. In 57 out of 92 cases, the patients did not have symptoms of CIIM prior to untethering. Six cases were excluded because cervicomedullary decompression was performed prior to untethering. The response of CIIM symptoms, syrinx size, and cerebellar tonsil position were examined before and after spinal cord untethering.

RESULTS

Forty-four characteristic signs and symptoms of CIIM were present prior to 29 untetherings. Thirty-three of 44 (75%) symptoms improved following spinal cord untethering, though no symptom resolved completely. Syrinx size and cerebellar tonsil position were unchanged following untethering.

CONCLUSION

The authors conclude that mild to moderate symptoms of CIIM may respond positively to spinal cord untethering, potentially by normalization cerebrospinal fluid flow dynamics. Symptom improvement occurs despite the lack of radiographic evidence of CIIM resolution.

Anomalous development of brain structure and function in spina bifida myelomeningocele

Spina bifida myelomeningocele (SBM) is a specific type of neural tube defect whereby the open neural tube at the level of the spinal cord alters brain development during early stages of gestation. Some structural anomalies are virtually unique to individuals with SBM, including a complex pattern of cerebellar dysplasia known as the Chiari II malformation. Other structural anomalies are not necessarily unique to SBM, including altered development of the corpus callosum and posterior fossa. Within SBM, tremendous heterogeneity is reflected in the degree to which brain structures are atypical in qualitative appearance and quantitative measures of morphometry. Hallmark structural features of SBM include overall reductions in posterior fossa and cerebellum size and volume. Studies of the corpus callosum have shown complex patterns of agenesis or hypoplasia along its rostral-caudal axis, with rostrum and splenium regions particularly susceptible to agenesis. Studies of cortical regions have demonstrated complex patterns of thickening, thinning, and gyrification. Diffusion tensor imaging studies have reported compromised integrity of some specific white matter pathways. Given equally complex ocular motor, motor, and cognitive phenotypes consisting of relative strengths and weaknesses that seem to align with altered structural development, studies of SBM provide new insights to our current understanding of brain structure-function associations.

Cervical spinal dysraphism

OBJECTIVE

Cervical spinal dysraphism is a rare congenital spinal pathology. The results obtained from our series are compared with the results obtained from other series of studies in the literature.

METHODS

Seven patients with cervical myelomeningocele and meningocele who underwent surgery between January 1996 and March 2009 at the YYU Faculty of Medicine in the Department of Neurosurgery were retrospectively studied.

RESULTS

The referral ages of the patients (6 females and 1 male) varied between 4 days and 4 months (median 1 month). A stalk lesion covered with a dysplastic skin formed as a sac and located at the cervical midline was demonstrated in all of the patients. Cervical myelomeningocele was present in 4 patients, while cervical meningocele was present in 3 patients; however, Chiari type II malformation and hydrocephaly were present in 3 patients with myelomeningoceles. Diastematomyelia and a filum terminal lipoma were present in 1 of the patients.

CONCLUSION

In this series, in contrast to the literature, we noted that the number of girls with spinal dysraphism with a cervical myelomeningocele and meningocele was greater than the number of boys. Chiari type II malformation, hydrocephaly and motor weakness in patients with cervical spinal dysraphism are less frequent when compared to patients with caudal spinal dysraphism. The structure of the sac is also more durable and, accordingly, a cerebrospinal fluid leakage is uncommon.

Postnatal ascent of the cerebellar tonsils in Chiari malformation Type II following surgical repair of myelomeningocele

OBJECT

Postnatal improvement in Chiari malformation type II (CM-II) following surgical repair of myelomeningocele was evaluated.

METHODS

The authors reviewed data obtained in 20 cases in which patients underwent postnatal myelomeningocele repair within the first 48 hours after birth between October 2002 and September 2006. In 14 patients (Group 1), myelomeningocele was diagnosed in utero and the infants were delivered by cesarean section at 35-39 weeks' gestation (mean 36.4). The 6 infants in Group 2 were born after full-term gestation (39-41 weeks), and their myelomeningoceles were diagnosed postnatally. In all 20 patients, the myelomeningoceles were surgically repaired postnatally. Dynamic change of the herniated cerebellar tonsils in CM-II before and after the myelomeningocele repair, associated hydrocephalus, and symptomatic CM-II were analyzed.

RESULTS

In Group 1, the CM-II was confirmed before myelomeningocele repair in 13 cases (93%). The spinal level of the caudal end of the cerebellar tonsils ranged from C-2 to C-7. Ascent of the cerebellar tonsils was observed in 11 patients (range 1-4 spinal levels, mean 2 levels) and continued even after ventriculoperitoneal (VP) shunt placement in most patients. A VP shunt was required for the treatment of hydrocephalus in 12 patients (86%). Symptomatic CM-II developed in 8 of 13 patients (61%), 3 of whom required surgical decompression. In Group 2, CM-II was confirmed in 5 infants (83%), with the cerebellar tonsils at a spinal level of C-2 to C-4 or C-5. Ascent of the cerebellar tonsils was observed in 4 patients (range 1-1.5 spinal levels, average 1.1 levels), and no patient had symptomatic CM-II. A VP shunt was placed in 5 patients (83%). No patient was lost to follow-up during the 18-month follow-up period. The only statistically significant difference between the 2 groups was the presence of symptomatic CM-II in Group 2 (p = 0.02).

CONCLUSIONS

Patients showed ascent of the cerebellar tonsils after postnatal myelomeningocele repair. Placement of a VP shunt helped promote the ascent. However, postnatal myelomeningocele repair in the patients in Group 1 failed to consistently prevent development of symptomatic CM-II. This limited experience suggests that postnatal repair of myelomeningocele can partially reverse the anatomical CM-II, but symptomatic CM-II cannot be prevented in some patients when the repair is performed after 36 weeks' gestation.

Vascular and apoptotic changes in the placode of myelomeningocele mice during the final stages of in utero development

OBJECT

Myelomeningocele (MMC) is a primary neurulation defect that is associated with devastating neurological disabilities in affected newborns. To better characterize the in utero neurodegenerative process of MMC, the authors investigated the changes in vascular organization, apoptosis, and the presence of inflammatory cells during gestation by using a mutant mouse model of MMC.

METHODS

The curly tail/loop tail (ct/lp) mutant mouse model of MMC was chosen to obtain fetuses at different stages of gestation. Mouse fetuses harboring MMC were harvested by caesarean section at embryonic Days 14.5, 16.5, and 18.5 (complete mouse gestation at 19 days, 6 mice/group); littermate fetuses with the same gestational age but without an MMC were used as controls. Samples of the MMC placode or normal spinal cord were stained for immunocytochemical labeling with caveolin antibody (endothelium marker) and activated caspase-3 antibody (apoptosis marker). Samples were morphometrically analyzed with a computer-assisted image analyzer.

RESULTS

The MMC mice presented with an increase in vascular density from embryonic Days 16.5-18.5 and an enhanced number of apoptotic cells at embryonic Day 18.5, compared with controls. There were scarce signals of an inflammatory reaction in the MMC placode, as a few infiltrating neutrophils were seen only at embryonic Day 18.5.

CONCLUSIONS

Fetal placodes in MMC mice showed evidence of increased vascular density since embryonic Day 16.5 and increased apoptosis at embryonic Day 18.5. These new data support the view that in utero changes of the MMC placode, occurring during the last stages of gestation, contribute to the neuropathological manifestations in full-term newborns with MMC.

The old and the new: supratentorial MR findings in Chiari II malformation

OBJECTIVE

The objective of this study was to use magnetic resonance imaging to develop an improved morphological understanding of the abnormalities of the forebrain in Chiari II malformation.

MATERIALS AND METHODS

Seventy-four patients with Chiari II malformations investigated between 1999 and 2007 were enrolled. Imaging was retrospectively reviewed by two pediatric neuroradiologists, with special attention given to diencephalon, midline commissures, hemispheric white matter, and cortex.

RESULTS

An abnormal gray matter structure that we called hypothalamic adhesion across the anterior-inferior portion of the third ventricle was noted in 48.6%. The anterior commissure was in a low position in the lamina terminalis in 38%. Gross abnormalities of the corpus callosum/hippocampal commissure were found in 57%; they were, however, different from the abnormalities seen in classical commissural agenesis. An abnormal bundle of white matter forming a callosal ridge was noted on the dorsal callosal surface in 60%; it is believed to represent the aberrant cingular bundle recently identified using diffusion tensor imaging. Hemispheric white matter could be considered as normal in 48%, deficient posteriorly in 55%, and globally in 10%. Cortical posterior medial stenogyria was observed in 72%. Gray matter heterotopias were found in 19%. The posterior limbic cortex was thin and dysplastic in 46%. Hippocampi were commonly abnormal (85%), with atypical sulcation of the adjacent temporo-mesial cortex (93%).

CONCLUSION

Major structural abnormalities were common in Chiari II malformation and were probably not related to hydrocephalus. Important anatomical structures involved in neurocognitive function should be considered as factors in the prognostic assessment of Chiari II patients.

Toward reducing shunt placement rates in patients with myelomeningocele

OBJECT

The prevalence of shunt-dependent hydrocephalus in patients with myelomeningocele has been reported to be in the region of 85%, and shunt-related complications are a significant cause of morbidity and mortality in these patients. Since 1997 the authors have adopted a stringent policy with respect to shunt placement in patients with myelomeningocele, reserving this treatment for those with symptomatic hydrocephalus, severe ventricular dilation at the time of presentation, and/or unequivocal progressive ventriculomegaly after primary closure. They report their experience.

METHODS

The authors reviewed all cases of myelomeningocele involving patients who presented to their institution over a 10-year period. They excluded cases in which the primary closure was carried out at another institution or in which there was not at least 12 months of clinical and imaging follow-up. Data regarding shunt insertion shunt-related complications, and clinical outcome were obtained from a review of the clinical records and analyzed.

RESULTS

Fifty-four cases satisfied the inclusion criteria for this study. Shunt insertion was performed in 28 of these cases (51.9%).

CONCLUSIONS

Applying more stringent guidelines for shunt placement, permitting moderate ventricular dilation, and accepting some mild increase in ventricular size after myelomeningocele closure has resulted in a reduced rate of shunt placement compared with previous series. The rate is comparable to that reported following in utero closure of myelomeningocele.

Fetal spina bifida repair--current trends and prospects of intrauterine neurosurgery

Myelomeningocele is a common dysraphic defect leading to severe impairment throughout the patient's lifetime. Although surgical closure of this anomaly is usually performed in the early postnatal period, an estimated 330 cases of intrauterine repair have been performed in a few specialized centers worldwide. It was hoped prenatal intervention would improve the prognosis of affected patients, and preliminary findings suggest a reduced incidence of shunt-dependent hydrocephalus, as well as an improvement in hindbrain herniation. However, the expectations for improved neurological outcome have not been fulfilled and not all patients benefit from fetal surgery in the same way. Therefore, a multicenter randomized controlled trial was initiated in the USA to compare intrauterine with conventional postnatal care, in order to establish the procedure-related benefits and risks. The primary study endpoints include the need for shunt at 1 year of age, and fetal and infant mortality. No data from the trial will be published before the final analysis has been completed in 2008, and until then, the number of centers offering intrauterine MMC repair in the USA is limited to 3 in order to prevent the uncontrolled proliferation of new centers offering this procedure. In future, refined, risk-reduced surgical techniques and new treatment options for preterm labor and preterm rupture of the membranes are likely to reduce associated maternal and fetal risks and improve outcome, but further research will be needed.

Intrauterine surgery in myelomeningocele

Intrauterine surgery for repair of fetal myelomeningocele has been performed since 1994. Open repair through a hysterotomy has been performed since 1997. Although much has been published about diagnosis, counseling, case selection, pre-, intra-, and postoperative management, delivery and long-term sequelae for both mother and baby, and associated ethical issues, several questions have yet to be openly discussed in a public forum.

In utero topographic analysis of astrocytes and neuronal cells in the spinal cord of mutant mice with myelomeningocele

OBJECT

Myelomeningocele (MMC) is the most severe form of spina bifida causing severe neurological deficits. Injury to the placode has been attributed to in utero aggression. In this study, glial and neuronal cell changes in both number and topography in mice with MMC were investigated during gestation.

METHODS

The curly tail/loop-tail mice model of MMC was used, and fetuses were harvested using caesarean surgery at Days 14.5, 16.5, and 18.5 (full gestation at 19 days). Immunohistochemical analyses of the MMC placodes and the normal spinal cords from the control group were performed using anti-glial fibrillary acidic protein (astrocytes) and mouse anti-neuronal nuclear (neurons) antibodies. Light microscopy was used along with computer-assisted morphometric evaluation. Progressive increases in astrocytes in the spinal cord of all mouse fetuses were found between Days 14.5 and 18.5 of gestation. This increase was significantly higher in the placodes of mice with MMC than in those of normal mice, particularly in the posterior region. Neuronal labeling at Day 14.5 of gestation was similar between mice with MMC and control mice. At Day 16.5 of gestation there was a deterioration of neural tissue in MMC fetuses, mainly in the posterior region, progressing until the end of gestation with a marked loss of neurons in the entire MMC placode.

CONCLUSIONS

This study delineated the quantitative changes in astrocytes and neurons associated with MMC development during the late stages of gestation. The detailed topographic analysis of the MMC defines the timing of the intrauterine insult and how the placode lesions progress. This study supports the current concept of placode protection through in utero surgery for fetuses with MMC.

Fetal spina bifida in a mouse model: loss of neural function in utero

OBJECT

The devastating neurological deficit associated with myelomeningocele has previously been assumed to be a direct and inevitable consequence of the primary malformation-failure of neural tube closure. An alternative view is that secondary damage to the pathologically exposed spinal cord tissue in utero is responsible for the neurological deficiency. If the latter mechanism were shown to be correct, it would provide an objective rationale for the performance of in utero surgery for myelomeningocele, because coverage of the exposed spinal cord could be expected to alleviate or perhaps prevent neurodegeneration. To examine this question, the authors studied the development of neuronal connections and neurological function of mice during fetal and neonatal stages in a genetic model of exposed lumbosacral spina bifida.

METHODS

The persistently exposed spinal cord of mouse fetuses carrying both curly tail and loop-tail mutations exhibited essentially normal anatomical and functional hallmarks of development during early gestation (embryonic Days 13.5-16.5), including sensory and motor projections to and from the cord. A significant proportion of fetuses with spina bifida at early gestation exhibited sensorimotor function identical to that seen in age-matched healthy controls. However, at later gestational stages, increasing neurodegeneration within the spina bifida lesion was detected, which was paralleled by a progressive loss of neurological function.

CONCLUSIONS

These findings provide support for the hypothesis that neurological deficit in human myelomeningocele arises following secondary neural tissue destruction and loss of function during pregnancy.

Fetal Posterior Fossa Volume: Assessment with MR Imaging

PURPOSE

To retrospectively determine the relationship between posterior fossa volume (PFV) and estimated gestational age (EGA) and/or femur length (FL) during pregnancy for the purpose of developing a normal growth curve.

MATERIALS AND METHODS

Advance institutional review board approval was obtained for this HIPAA-compliant study, and the need for parent informed consent was waived. A cross-sectional retrospective study was performed to measure PFV on in vivo magnetic resonance (MR) images obtained in 76 fetuses of 18-36 weeks gestation who had a morphologically normal CNS. Because this was a retrospective series, MR imaging techniques varied slightly, but all fetuses underwent imaging at contiguous 3-5-mm intervals in at least two orthogonal planes, with repetition time msec/echo time msec, 5-12/62-95; number of signals acquired, one; flip angle, 150 degrees -180 degrees; and matrix, 128-192 x 256. Posterior fossa areas were manually traced on half-Fourier rapid acquisition with relaxation enhancement in utero fetal MR images by one observer. PFVs were then calculated by manually summing areas from the contiguous sections and multiplying the total area by the section thickness. An average PFV (APFV) across orthogonal planes was calculated for each fetus, and the relationship between APFV and EGA was mathematically modeled. Coronal, transverse, and sagittal views were compared with correlations and Bland-Altman plots. Two additional observers repeated the measurements for a small subset of fetuses (n = 5). Paired t test analyses were also performed to determine significant differences between sagittal, transverse, and coronal measurements, as well as to determine preliminary intraobserver and interobserver variability of measurements in a subset of cases.

RESULTS

The relationship between APFV (in cubic centimeters) and EGA (in weeks) was well described by a single exponential function [APFV = 0.689 exp(EGA/9.10)]. APFV doubling time was 6.31 weeks. Root-mean-square variation of values around the model line was 1.63 cm(3). There was no statistically significant intra- or interobserver variation (P > .16 for all fetuses) at preliminary analysis. No correlation between APFV and FL could be found.

CONCLUSION

The normal fetal PFV growth curve generated in this study may have potential as a model for clinical application.

Percutaneous Fetoscopic Patch Coverage of Spina Bifida Aperta in the Human – Early Clinical Experience and Potential

OBJECTIVE

The current operative approach for fetal repair of spina bifida aperta requires maternal laparotomy and hysterotomy. Following technical feasibility studies in sheep, we performed percutaneous fetoscopic patch coverage of this lesion in 3 human fetuses between 23 + 4 and 25 + 3 weeks of gestation.

METHODS AND RESULTS

Whereas the patch detached in the first case 3 weeks after the procedure, it covered the exposed neural tissue in the 2 other fetuses beyond their delivery. Two of the three children survived, but 1 unexpectedly died from a ventilation problem in its 3rd week of life. In 1 of the 2 survivors, ventriculoperitoneal shunt insertion was delayed.

CONCLUSIONS

Percutaneous fetoscopic patch coverage of spina bifida aperta is feasible in human fetuses and offers a substantial reduction of maternal trauma compared to open fetal repair. Further clinical experience is now required before the efficacy of the new approach to protect the exposed neural tissue from mechanical and chemical damage and to improve hindbrain herniation can be evaluated.

Impact of maternal-fetal surgery for myelomeningocele on the progression of ventriculomegaly in utero

OBJECTIVE

Intrauterine myelomeningocele (MMC) repair decreases hindbrain herniation and the need for postnatal ventriculoperitoneal shunting. We examined the impact of intrauterine repair on the progression of ventriculomegaly in utero.

STUDY DESIGN

Fetuses with MMC were identified through computerized databases from June 1988 to April 2003. A retrospective cohort design was used to evaluate the impact of intrauterine repair on ventricular progression with a multivariate linear regression model that included baseline ventricle measurement, gestational age, level of lesion, and gender.

RESULTS

Fourteen fetuses with intrauterine repair and 39 fetuses with postnatal repair were identified. The natural history of progression of ventricular diameter increased in a linear fashion throughout gestation (0.57 mm/week). After adjusting for confounding variables, no transient or sustained difference was observed in the rate progression of ventriculomegaly between intrauterine and postnatal repair (0.27 +/- 0.35 mm/week; P=.45).

CONCLUSION

Intrauterine MMC repair does not impact the progression of ventriculomegaly.

Spina bifida

Spina bifida results from failure of fusion of the caudal neural tube, and is one of the most common malformations of human structure. The causes of this disorder are heterogeneous and include chromosome abnormalities, single gene disorders, and teratogenic exposures. However, the cause is not known in most cases. Up to 70% of spina bifida cases can be prevented by maternal, periconceptional folic acid supplementation. The mechanism underlying this protective effect is unknown, but it is likely to include genes that regulate folate transport and metabolism. Individuals with spina bifida need both surgical and medical management. Although surgical closure of the malformation is generally done in the neonatal period, a randomised clinical trial to assess in utero closure of spina bifida has been initiated in the USA. Medical management is a lifelong necessity for individuals with spina bifida, and should be provided by a multidisciplinary team.

Cerebellum-small brain but large confusion: a review of selected cerebellar malformations and disruptions

Defining and classifying congenital disorders of the cerebellum can be difficult and confusing. One reason is that some abnormalities called "malformations" are not truly (primary) developmental malformations. This applies to Chiari I "malformations" as well as to Chiari II "malformations." The latter results mainly from a prenatal cerebrospinal fluid (CSF) leak. Also disruptive cerebellar lesions are not uncommon, examples being the "vanishing cerebellum" in myelomeningocele, cerebellar lesions in very low birth weight prematurely born infants, unilateral cerebellar hypoplasia/aplasia, and probably some instances of cerebellar agenesis (CA). The cerebellar hypoplasias consist of a heterogeneous group of inherited and prenatally acquired conditions. The concept of pontocerebellar hypoplasias will need to be expanded beyond the two main types (PCH-1 and PCH-2), and demonstrate that a classification system of cerebellar malformations cannot be based on neuroimaging criteria only. Additional studies are expected to show that this also applies to the molar tooth sign, which was initially described in Joubert syndrome (JS). The JS is the prototype of midhindbrain malformation, but its delineation is still unsolved. JS may well be an overdiagnosed entity; many cases likely not having JS are on record. Rhombencephalosynapsis (RS) has been increasingly diagnosed with the advent of neuroimaging. No familial cases have been observed. Although many affected individuals have variable impairments, RS can be found in children with normal cognitive function. In this review, some of the cerebellar anomalies are briefly discussed.

Current controversies in perinatal care: fetal versus neonatal surgery

Fetal surgery has become a viable option for many parents whose unborn infants have congenital anomalies. However, this approach is best suited to specific circumstances and specific babies. Careful prenatal care and early diagnosis ensure that this option is available to those who can benefit from the intervention.

MRI of the fetal spine

Magnetic resonance imaging of the fetal spine is a vital complement to fetal sonographic examination. Assessing the wide spectrum of spinal dysraphism, as well as spinal neoplasia, allows for more correct prenatal diagnoses, patient care planning, and patient counselling. Proper appraisal of the value of experimental procedures, such as fetal myelomeningocoele repair, requires a high level of diagnostic accuracy for the selection and follow-up of appropriate candidates.

Recent advances in fetal surgery

Fetal surgery is now an accepted modality for treatment of a variety of lethal and non-lethal congenital conditions. It represents a new, fast-moving frontier of medicine in which cooperative mulitdisciplinary effort and input are required to assure both fetal and maternal welfare. A wide range of therapeutic strategies from percutaneous to open invasive techniques has led to a complex list of different procedures for different diseases. This review identifies the most common disease entities managed by fetal intervention, examines the evolution in development of techniques to those currently used, and describes the prospective, randomized trials presently underway that are designed to establish the safety and determine true efficacy of treatment. Fetal surgery as a (multi)discipline continues to strive to minimize maternal and fetal risk. Undoubtedly, as tocolytic therapy and neonatal intensive efforts improve, fetal therapy will expand.

Intrauterine repair of spina bifida: preoperative predictors of shunt-dependent hydrocephalus

OBJECTIVE

The objective of this study was to determine which factors that are present at the time of intrauterine repair of spina bifida could predict the need for ventriculoperitoneal shunt for hydrocephalus during the first year of life.

STUDY DESIGN

One hundred seventy-eight fetuses have undergone intrauterine repair of spina bifida at Vanderbilt University Medical Center since 1997. Among these, 116 fetuses had a postnatal follow-up period of at least 12 months. The primary outcome of the study was the need for a ventriculoperitoneal shunt for hydrocephalus during the first year of life. The following variables were analyzed: maternal demographics (age, race, gravidity, and parity), gestational age at the time of surgery, ventricular size, degree of hindbrain herniation (determined by magnetic resonance imaging in 33 cases), type of defect (myelomeningocele vs myeloschisis), upper level of the lesion, presence of talipes, and intraoperative use of a lumbar drain. Statistical analysis was performed with logistic regression (to test the association of fetal and maternal factors and the need for ventriculoperitoneal shunting), 2-sample t-tests for comparison of means, and receiver operating curves with the use of the probabilities that were generated by the logistic regression for both continuous and categoric versions of the factors.

RESULTS

Sixty-one of 116 of the fetuses (54%) who underwent operation in utero required the placement of a ventriculoperitoneal shunt before the age of 1 year. The upper level of the lesion was the strongest predictor of shunt requirement (adjusted odds ratio per 1 level increase with the use of continuous variables [S1 through T10], 1.73 [95% CI, 1.22- 2.44]; adjusted odds ratio with the use of upper lesion level >or=L3 vs <L3 as a categorized variable, 5.7 [95% CI, 2.18- 14.7]), followed by gestational age at the time of surgery (adjusted odds ratio per 1 week increase with the use of continuous variables, 1.37 [95% CI, 1.06-1.77]; adjusted odds ratio with the use of gestational age <or=25 weeks vs >25 weeks as a categorized variable, 3.3 [95% CI, 1.28-8.24]), and preoperative ventricular size (adjusted odds ratio per 1 unit increase with the use of continuous variables, 1.17 [95% CI, 1.01-1.36]; adjusted odds ratio with the use of ventricular size >or=14 mm vs <14 mm as a categorized variable, 3.5 [95% CI, 1.08-11.16]). Receiver operating curves with the use of the probabilities that were generated by the logistic regression analyses for both the continuous and categoric versions of the factors were compared. The area under the curve was approximately 0.81 for both methods. Thirty-eight of 48 of the fetuses (79%) with an upper level of the lesion >or=L3 required placement of a ventriculoperitoneal shunt, although 25 of 68 of the fetuses (37%) with lesions <or=L4 did not (P < .0001). Eighty-four percent of the fetuses with a preoperative ventricular size >or=14 mm (27/32 fetuses) needed a shunt compared with 41% of the fetuses (34/81 fetuses) with smaller ventricles (P=.03). Seventy-one percent of the fetuses who underwent operation at >25 weeks of gestation also required shunt placement (37/52 fetuses); 39% of the fetuses (24/61 fetuses) who were treated <or=25 weeks of gestation did not (P=.01). Thirty-five fetuses had a lesion level <or=L4 and a ventricular size <14 mm and underwent operation at <or=25 weeks of gestation. Among these, 8 fetuses (23%) required a ventriculoperitoneal shunt during the first year of life.

CONCLUSION

This study suggests that, among fetuses who underwent operation in utero for spina bifida, fetuses with a ventricular size of <14 mm at the time of surgery, fetuses who had surgery at <or=25 weeks of gestation, and fetuses with defects that were located at <or=L4 were less likely to require ventriculoperitoneal shunting for hydrocephalus during the first year of life.

Recent developments in fetal medicine

Several advances have been made in the field of fetal medicine since the last BMJ review on the subject. This review covers advances in prenatal screening, imaging techniques, management of multiple pregnancies, and fetal therapy

Chiari Type II malformation: past, present, and future

OBJECT

The Chiari Type II malformation (CM II) is a unique hindbrain herniation found only in patients with myelomeningocele and is the leading cause of death in these individuals younger than 2 years of age. Several theories exist as to its embryological evolution and recently new theories are emerging as to its treatment and possible prevention. A thorough understanding of the embryology, anatomy, symptomatology, and surgical treatment is necessary to care optimally for children with myelomeningocele and prevent significant morbidity and mortality.

METHODS

A review of the literature was used to summarize the clinically pertinent features of the CM II, with particular attention to pitfalls in diagnosis and surgical treatment.

CONCLUSIONS

Any child with CM II can present as a neurosurgical emergency. Expeditious and knowledgeable evaluation and prompt surgical decompression of the hindbrain can prevent serious morbidity and mortality in the patient with myelomeningocele, especially those younger than 2 years old. Symptomatic CM II in the older child often presents with more subtle findings but rarely in acute crisis. Understanding of CM II continues to change as innovative techniques are applied to this challenging patient population.

Intrauterine closure of myelomeningocele: an update

Preliminary evidence suggests that intrauterine myelomeningocele repair may benefit patients by reducing the both incidence of hydrocephalus and the severity of the Chiari malformation; however, this benefit remains unproved. Furthermore, the procedure entails substantial risks not associated with conventional therapy. A randomized controlled trial of intrauterine and conventional therapies is underway. This study should definitively establish the procedure-related risks and benefits. Regardless of the outcome, it is clear that the risks of intrauterine intervention need to be reduced before myelomeningocele, or other congenital malformations, can be effectively treated prior to birth. To that end, studies are being conducted to assess the potential advantages of applying state-of-the-art endoscopic techniques to intrauterine therapy. If benefit can be proven and risks reduced, intrauterine myelomeningocele repair has the potential to become the preferred therapy for patients suffering from this debilitating disease.

Intrauterine myelomeningocele repair

Preliminary studies have suggested that IUMR reduces the incidence of shunt-dependent hydrocephalus and the severity of the Chiari malformation. An RCT is in progress to confirm these results. Future efforts will revolve around refinement of the procedure with the goal of reducing risk. Robot-assisted surgery holds the promise of achieving this goal. If it is successful. IUMR might well become the standard therapy for myelomeningocele, resulting in a significant reduction in the devastating morbidity associated with this disease.

The Arnold-Chiari type II malformation at midgestation

The Arnold-Chiari malformation type II (ACMII) is reported to be reversible after closure of a myelomeningocele at midgestation. To elucidate the developmental state of the ACMII malformation at the approximate time fetal surgery is performed, the ACMII of a 20-week human fetus was investigated in vitro using high-field magnetic resonance microscopy at 9.4 T and compared with the hindbrain of a neurologically intact fetus of the same gestational age. Up to 20 weeks of gestation, the developmental failures caused by the early embryonic herniation of the posterior fossa contents are the dominant feature of fetal ACMII, but after 20 weeks, the accelerated and disproportionate growth of the cerebellum dominates. As midgestational surgery stops the leakage of cerebrospinal fluid, the posterior fossa will expand in time to allow further normal growth of both the cerebellum and brain stem. Some early developmental anomalies already present in the primitive rhombencephalon due to early embryonic hindbrain herniation as well as some intra-axial anomalies are probably not reversible.

Diagnosis, outcome, and management of fetal abnormalities: fetal hydrocephalus

INTRODUCTION

It has been recognized that the morphological fetal CNS findings detected in early development are not always the final features: occasionally they may not be determined in diagnosis and may change developmentally or chronologically during the fetal life in utero.

DISCUSSION

Certain factors of the fetal chronology of CNS anomalies can cause irreversible changes during fetal life. These include: significant delay in the neuronal maturation process in fetal hydrocephalus developed in clinico-embryological stage II of the Perspective Classification of Congenital Hydrocephalus (PCCH), secondary neural injury in the intactly developing spinal cord above the neural placode in fetuses with spina bifida aperta (myeloschisis), histological "evolution" of tumors or dysgenetic CNS, and deformity of the normally developed intracranial or intraspinal CNS structures. Considering the current status of fetal surgery in general and technical advances promising improved outcomes, fetal neurosurgery can also be applied to the above-mentioned progressive pathology or pathophysiology in the fetal CNS. However, since the failure of the first trial of fetal neurosurgery in the 1980s, the prerequisites have still not been clarified. In order to use advanced neurosurgery techniques in the management of fetal CNS anomalies, these prerequisites have to be established.

Myelomeningocele: prenatal evaluation--comparison between transabdominal US and MR imaging

PURPOSE

To compare transabdominal ultrasonography (US) with fetal magnetic resonance (MR) imaging in the prenatal evaluation of myelomeningocele lesion level.

MATERIALS AND METHODS

Prenatal US images, pre- and postnatal MR images, and postnatal spinal radiographs obtained in the first 100 fetuses who underwent intrauterine myelomeningocele repair were the basis for this study. Each image was used to assign a lesion level. The assigned levels were compared by means of the kappa statistic, as an index of agreement.

RESULTS

All fetuses underwent prenatal US. Sixty-one fetuses underwent prenatal MR imaging. Fifty fetuses underwent both postnatal spinal radiography and postnatal MR imaging, and an additional 34 fetuses underwent one postnatal study but not the other. When findings on prenatal US images were compared with those on postnatal radiographs, the findings agreed within one spinal level in 79% (55 of 70, kappa = 0.60) of cases. When findings on prenatal MR images were compared with those on postnatal radiographs, the findings agreed in 82% (31 of 38, kappa = 0.63) of cases. Findings on postnatal MR images and those on postnatal spinal radiographs agreed within one spinal level in 100% (50 of 50, kappa = 1.0) of cases.

CONCLUSION

Findings at prenatal MR imaging and prenatal US are equally accurate for the assignment of a lesion level in a fetus with myelomeningocele. Given that findings with both modalities will lead to misdiagnosis of the spinal level by two or more segments in at least 20% of cases, care should be exercised when neurologic outcome is predicted on the basis of these studies alone.

In vitro high-field magnetic resonance imaging-documented anatomy of a fetal myelomeningocele at 20 weeks' gestation. A contribution to the rationale of intrauterine surgical repair of spina bifida

OBJECT

It remains uncertain if closure of a myelomeningocele at midgestation changes the neurological condition at birth in an infant born with spina bifida. The authors conducted a study to provide a detailed analysis of the morphology of the spinal cord with the myelomeningocele at the time fetal surgery usually is performed.

METHODS

The myelomeningocele of a 20-week-gestation-age fetus was examined, and data were compared with those obtained in a neurologically intact specimen of the same age. In vitro high-field 9.4-tesla magnetic resonance (MR) microscopy was used to examine the fetal material. High-field MR spectroscopy provided images in the three orthogonal planes with a resolution comparable with low-power optical microscopy. The authors observed that the fetal cord of the myelomeningocele specimen was tapered and tethered at S3-4 while the conus medullaris in the normal fetus reaches L-4. No neurulation defects were noted. The axial MR images clearly revealed the nonfusion of the mesodermal structures. The absence of neurulation defects suggests that at least in some cases of spina bifida the spinal cord initially is well developed but is damaged later on chemically and mechanically. This might be an argument in favor of intrauterine myelomeningocele repair. By 20 weeks' gestation, however, the deformation of the cord inside the myelomeningocele is severe. An optimization of the preoperative assessment by means of MR imaging therefore might be considered a valuable contribution to intrauterine surgery. The in vitro high-field MR microscopic findings of this study could be used as references for clinical intrauterine MR imaging.

CONCLUSIONS

The detailed in vitro high-field MR analysis of a 20-week-gestation-age fetus with spina bifida demonstrated that an improvement of the preoperative intrauterine imaging should be pursued to detect those cases without neurulation defects and with minimal deformation of the spinal cord.

The effect of intrauterine myelomeningocele repair on the incidence of shunt-dependent hydrocephalus

BACKGROUND

Intrauterine myelomeningocele repair (IUMR) was first successfully performed in 1997. Preliminary reports suggest that this procedure reduces the incidence of shunt-dependent hydrocephalus when compared to conventional postnatal therapy. However, the existing cohort of IUMR patients has not yet been systematically compared to a comparable group of conventionally treated controls.

METHODS

Patients 1 year old or greater who had undergone IUMR at either Vanderbilt University or the Children's Hospital of Philadelphia (CHOP) were compared to a group of conventionally treated historical controls treated and followed at CHOP. In order to measure any differences between the groups, patients were stratified according to the level of the myelomeningocele lesion and the gestational age at the time of IUMR.

RESULTS

One hundred and four IUMR patients were compared to 189 conventionally treated controls. IUMR resulted in statistically significant reductions in the incidence of shunt-dependent hydrocephalus at both lumbar and sacral lesion levels. When lumbar lesion levels were further stratified, from L1 to L5, it appeared that the benefit of IUMR was statistically significant only at levels below L2. Other factors with a significant impact on hydrocephalus were estimated gestational age and ventricular size at the time of surgery. In particular, statistically significant differences compared to controls were seen in the younger (< or =25 weeks) group but not in the older (>25 weeks) group.

CONCLUSIONS

IUMR appears to substantially reduce the incidence of shunt-dependent hydrocephalus when compared to conventional treatment even when lesion level is taken into account. Patients with lesions above L3 may not share in this benefit. IUMR cannot be justified in fetuses older than 25 weeks of gestation. Additional improvements might be obtained by further reducing the average age at which fetuses are operated upon. It remains to be determined whether this benefit outweighs the potential risks of intrauterine surgery.