Low torcular Herophili position and large brainstem-tentorium angle in fetuses with open spinal dysraphism at 11-13 weeks' gestation

OBJECTIVE

To evaluate whether in fetuses with open spina bifida (OSB) the tentorium can be seen to be displaced downwards and vertically oriented by the time of the 11-13-week scan and whether this is reflected in an alteration of the brainstem-tentorium (BST) angle.

METHODS

The study population was recruited between 2015 and 2020 from three fetal medicine referral centers and comprised a control group and a study group of pregnancies with OSB. The control group was recruited prospectively and included singleton pregnancies with a normal sonographic examination after first-trimester combined screening for chromosomal abnormalities and normal outcome. The study group was selected retrospectively and included all cases with OSB between 2015 and 2020. All cases underwent detailed ultrasound assessment at 11 + 0 to 13 + 6 weeks' gestation. The position of the torcular Herophili (TH) was identified in the midsagittal view of the fetal brain with the use of color Doppler and was considered as a proxy for the insertion of the tentorium on the fetal skull. The BST angle was calculated in the same view and was compared between the two groups.

RESULTS

Sixty normal fetuses were included in the control group and 22 fetuses with OSB in the study group. In both groups, the BST angle was found to be independent of gestational age or crown-rump length (P = 0.8815, R²  = 0.0003861 in the controls, and P = 0.2665, R²  = 0.00978 in the OSB group). The mean BST angle was 48.7 ± 7.8° in controls and 88.1 ± 1.18°, i.e. close to 90°, in fetuses with OSB. Comparison of BST-angle measurements between the control group and cases with OSB showed a statistically significant difference (P = 0.0153). In all fetuses with OSB, the downward displacement of the TH and tentorium was clearly visible at the 11-13-week scan.

CONCLUSIONS

In fetuses with OSB, the BST angle is significantly larger than in normal controls, with the tentorium being almost perpendicular to the brainstem. This sign confirms the inferior displacement of the tentorium cerebelli with respect to its normal insertion on the occipital clivus as early as the first trimester of pregnancy and is useful in the diagnosis of Chiari-II malformation at this early stage. In fetuses with OSB, the low position of the tentorium and TH is clearly visible, even subjectively, at the 11-13-week scan. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal regenerative fetoscopic interventions for congenital anomalies

Fetal intervention has progressed in the past two decades from experimental proof-of-concept to practice-adopted, life saving interventions in human fetuses with congenital anomalies. This progress is informed by advances in innovative research, prenatal diagnosis, and fetal surgical techniques. Invasive open hysterotomy, associated with notable maternal-fetal risks, is steadily replaced by less invasive fetoscopic alternatives. A better understanding of the natural history and pathophysiology of congenital diseases has advanced the prenatal regenerative paradigm. By altering the natural course of disease through regrowth or redevelopment of malformed fetal organs, prenatal regenerative medicine has transformed maternal-fetal care. This review discusses the uses of regenerative medicine in the prenatal diagnosis and management of three congenital diseases: congenital diaphragmatic hernia, lower urinary tract obstruction, and spina bifida.

Myelomeningocele sac associated with worse lower-extremity neurological sequelae: evidence for prenatal neural stretch injury?

OBJECTIVE

To determine whether the presence of a myelomeningocele (MMC) sac and sac size correlate with compromised lower-extremity function in fetuses with open spinal dysraphism.

METHODS

A radiology database search was performed to identify cases of MMC and myeloschisis (MS) diagnosed prenatally in a single center from 2013 to 2017. All cases were evaluated between 18 and 25 weeks. Ultrasound reports were reviewed for talipes and impaired lower-extremity motion. In MMC cases, sac volume was calculated from ultrasound measurements. Magnetic resonance imaging reports were reviewed for hindbrain herniation. The association of presence of a MMC sac and sac size with talipes and impaired lower-extremity motion was assessed. Post-hoc analysis of data from the multicenter Management of Myelomeningocele Study (MOMS) randomized controlled trial was performed to confirm the study findings.

RESULTS

In total, 283 MMC and 121 MS cases were identified. MMC was associated with a lower incidence of hindbrain herniation than was MS (80.9% vs 100%; P < 0.001). Compared with MS cases, MMC cases with hindbrain herniation had a higher rate of talipes (28.4% vs 16.5%, P = 0.02) and of talipes or lower-extremity impairment (34.9% vs 19.0%, P = 0.002). Although there was a higher rate of impaired lower-extremity motion alone in MMC cases with hindbrain herniation than in MS cases, the difference was not statistically significant (6.6% vs 2.5%; P = 0.13). Among MMC cases with hindbrain herniation, mean sac volume was higher in those associated with talipes compared with those without talipes (4.7 ± 4.2 vs 3.0 ± 2.6 mL; P = 0.002). Review of the MOMS data demonstrated similar findings; cases with a sac on baseline imaging had a higher incidence of talipes than did those without a sac (28.2% vs 7.5%; P = 0.007).

CONCLUSIONS

In fetuses with open spinal dysraphism, the presence of a MMC sac was associated with fetal talipes, and this effect was correlated with sac size. The presence of a larger sac in fetuses with open spinal dysraphism may result in additional injury through mechanical stretching of the nerves, suggesting another acquired mechanism of injury to the exposed spinal tissue. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Normal intracranial BS/BSOB ratio values in the first trimester of single gestations with live fetuses in a Korean population

AIM

The purpose of this study was to determine the normal length of the brainstem (BS) in Korean fetuses and to evaluatethe usefulness of the routine measurement of BS size in the first trimester of pregnancy for the early detection of spina bifida.

MATERIAL AND METHODS

A total of 2,621 normal singleton pregnant Korean women at 10+6 to 13+6 weeks of gestation were selected for this retrospective cross-sectional study. Ultrasonography was used to measure the length of the longest vertical depth diameter of the BS and brainstem-occipital bone (BSOB) in order to obtain the BS to BSOB ratio.

RESULTS

The best indicators for spina bifida ranged from 1.00±0.24 mm to 4.70±0.46 mm for the BS and from 2.90±0.36 mm to 8.50±0.92 mm for the BSOB. For the gestational period, BS (R=0.70) and BSOB (R=0.81) values were considered statistically significant (p<.0001). The value of the BS to BSOB ratio was <1.0 in normal fetuses, and was not correlated with the gestational age.

CONCLUSION

Measurement of BS and BSOB diameter in the first trimester is thought to provide the best reference marker for evaluating the posterior brain for diagnosis of spina bifida.

Cryopreserved human umbilical cord patch for in-utero spina bifida repair

OBJECTIVE

To identify a patch system to repair surgically created spina bifida in a sheep model for its efficacy in healing the skin defect, protecting the underlying spinal cord and reducing the Chiari II malformation.

METHODS

Spina bifida was created surgically in 16 fetuses from eight timed-pregnant sheep at gestational age of 75 days. Two fetuses did not survive the procedure. Repeat hysterotomy was performed at 95 days' gestation to cover the defect with either biocellulose film with underwater adhesive (BCF-adhesive) (n = 7) or human umbilical cord with suture (HUC-suture) (n = 7). Three fetuses without formation of the defect served as reference controls. The skin healing was examined by direct visualization after a planned Cesarean section at term, followed by histological analysis using hematoxylin and eosin and Masson's trichrome stains. Mid-sagittal sections of the fetal cranium and upper cervical spine were analyzed by a pediatric neuroradiologist who was blinded to the type of patch received.

RESULTS

Three fetuses that received the BCF-adhesive and six fetuses that received the HUC-suture survived to term for final analysis. As a result of dislodgment of the BCF-adhesive, all spina bifida defects repaired using BCF-adhesive were not healed and showed exposed spinal cord with leakage of cerebrospinal fluid. In contrast, all spinal defects repaired by HUC-suture were healed with complete regrowth of epidermal, dermal and subdermal tissue components, with no exposed spinal cord. The maximal skin wound width was 21 ± 3.6 mm in the BCF-adhesive group but 3 ± 0.8 mm in the HUC-suture group (P < 0.001). The spinal cord area (P = 0.001) and the number of anterior horn cells (P = 0.03) was preserved to a greater degree in the HUC-suture group than in the BCF-adhesive group, whilst psammoma bodies, signifying neuronal degeneration, were only observed in the BCF-adhesive group. Anatomic changes, indicative of Chiari II malformation, were seen in all three fetuses of the BCF-adhesive group but in none of the HUC-suture group (P < 0.01).

CONCLUSION

Cryopreserved umbilical cord graft is a promising regenerative patch for intrauterine repair of spina bifida.

Pentalogy of Cantrell associated with exencephaly and spinal dysraphism: antenatal ultrasonographic diagnosis. Case report

The pentalogy of Cantrell, a rare syndrome, consists of the defects in the anterior diaphragm, diaphragmatic pericardium, lower sternum and supraumbilical abdominal wall, along with congenital cardiac abnormalities. Till date, only few patients with full spectrum of this syndrome have been reported with only 2 cases showing associated exencephaly and spinal dysraphism. We report extremely rare association of complete pentalogy of Cantrell syndrome with exencephaly and spinal dysraphism on antenatal sonogram and autopsy in a 18 weeks fetus of a 19 year-old primi gravida female.

Fetal surgery for myelomeningocele: trials and tribulations. Isabella Forshall Lecture

The rationale for in utero repair of myelomeningocele (MMC) in the context of pathologic observations, animal models, and outcomes from the initial experience with human fetal MMC repair is presented. This has now culminated in a randomized trial, Management of Myelomeningocele Study, the findings of which are listed. The story is focused on the milestone contributions of members of the Center for Fetal Diagnosis and Treatment at the Children's Hospital of Philadelphia on the road to successful fetal surgery for spina bifida. This is now performed in selected patients and presents an additional therapeutic alternative for expectant mothers carrying a fetus with MMC.

Prenatal evaluation of the position of the fetal conus medullaris

OBJECTIVES

To determine the position of the fetal conus medullaris during pregnancy in relation to the last vertebral body and to examine its use in detecting skin-covered spinal dysraphism.

METHODS

This was a retrospective study involving 300 consecutive ultrasound examinations between 15 weeks of gestation and term. Two operators independently assessed images of the spine to determine whether the conus medullaris and the last vertebral body could be visualized in a single image in a midsagittal plane. The distance between these two landmarks (the conus distance) was measured twice by both operators who were not aware of any previous measurements. Intra- and interobserver variability was assessed by 95% limits of agreement. Linear regression analysis was used to determine the relevant contributors to the conus distance and a normal range was computed based on the best-fit model. The normal results were compared with five cases of prenatally detected skin-covered spinal dysraphism.

RESULTS

In 84.7% of the 300 cases, both operators were able to visualize the conus medullaris and the last vertebral body. Ninety-five percent limits of agreement for the intraobserver variability in measurement of conus distance were ± 1.9 mm. For the interobserver variability, they were - 3.7 and 2.5 mm. We found a linear relationship between conus distance and gestational age, biparietal diameter and abdominal circumference. The strongest relationship was observed for femur length (conus distance = - 8.2 + femur length (mm)). In the five abnormal cases, conus distance was well below the 5(th) percentile.

CONCLUSIONS

Determination of conus distance allows for an objective and feasible assessment of the conus medullaris position. This parameter promises to be useful in the prenatal detection of skin-covered spinal dysraphism.

MRI of closed spinal dysraphisms

We present a pictorial review of MRI features of various closed spinal dysraphisms based on previously described clinicoradiological classification of spinal dysraphisms proposed. The defining imaging features of each dysraphism type are highlighted and a diagnostic algorithm for closed spinal dysraphisms is suggested.

Frontomaxillary facial angle in fetuses with spina bifida at 11-13 weeks' gestation

OBJECTIVE

To determine whether in fetuses with open spina bifida at 11-13 weeks' gestation the frontomaxillary facial angle is decreased.

METHODS

The frontomaxillary facial angle was measured in 20 fetuses with open spina bifida and in 100 normal controls matched for crown-rump length (CRL) at 11 + 0 to 13 + 6 weeks and the values in the two groups were compared.

RESULTS

In the control group the frontomaxillary facial angle decreased significantly with CRL from a mean of 84.0 degrees at a CRL of 45 mm to 76.5 degrees at a CRL of 84 mm (SD, 3.26 degrees). In the spina bifida group the mean frontomaxillary facial angle, corrected for CRL, was 9.9 degrees lower than in the controls and it was below the 5(th) centile in 18 (90%) of the cases (P < 0.0001).

CONCLUSIONS

In fetuses with open spina bifida at 11-13 weeks' gestation the frontomaxillary facial angle is decreased and this measurement may be useful in early screening for this abnormality.

Role of prenatal ultrasound in predicting survival and mental and motor functioning in children with spina bifida

OBJECTIVE

To determine which prenatal ultrasound findings can predict survival and mental and motor functioning in children with spina bifida.

METHODS

Prenatal ultrasound examinations of all liveborn children who were prenatally diagnosed with spina bifida between 1997 and 2002 at the University Medical Centre, Utrecht (n = 41) were retrospectively reviewed for lesion level, head circumference, ventriculomegaly, scoliosis and talipes. These measures were correlated with postnatal anatomical (as assessed by magnetic resonance imaging (MRI)) and functional lesion levels, survival and motor and mental outcome at 5 years of age. The capacity of prenatal ultrasonography to determine lesion level was also assessed in all fetuses diagnosed with spina bifida from 2006-2007 (n = 18).

RESULTS

Nineteen infants died before the age of 5 years. Multivariate regression analysis showed that higher lesion level and head circumference > or = the 90th percentile on prenatal ultrasound examination were independent predictors of demise (P < 0.05 and P = 0.01, respectively). None of the ultrasound features was a predictor of motor or mental functioning. Ultrasound predicted anatomical lesion level within one level of the postnatal findings in 50% of the first cohort and 89% of the second cohort (P < 0.01). The level of the anatomical lesion as assessed by postnatal MRI differed from the functional lesion by as many as six vertebral levels.

CONCLUSIONS

Lesion level and head circumference on prenatal ultrasound are predictive of survival in children with spina bifida. No predictors were found for mental or motor function at the age of 5 years.

Developmental toxicity assessment of d,l-methylphenidate and d-methylphenidate in rats and rabbits

BACKGROUND

Previous investigations reported no teratogenicity for methylphenidate (MPH). These studies investigated potential teratogenicity of d-MPH and d,l-MPH as commitments to the FDA.

METHODS

Rabbits received 15, 50, 150 mg/kg/day (mkd) d-MPH or 20, 60, 200, 300 mkd d,l-MPH on gestation days 7-20. Rats received 2.5, 10, 40 mkd d-MPH, or 7, 25, 75, 80 mkd d,l-MPH on gestation days 6-17.

RESULTS

d-MPH-In rabbits, mortality occurred at 150 mkd. Dilated pupils, increased activity, biting/chewing, respiration, and salivation occurred at >or=15 mkd in rabbits and >or=10 mkd in rats. Decreased food consumption occurred at 40 mkd in rats. Decreased body weight parameters occurred at 150 mkd in rabbits and >or=10 mkd in rats. There were no fetal findings in rabbits. In rats, skeletal variations occurred at 40 mkd. d,l-MPH-In rabbits, mortality occurred at >or=200 mkd. Dilated pupils, increased activity, biting/chewing, respiration, and salivation occurred at >or=20 mkd in rabbits and >or=25 mkd in rats. Decreased food consumption occurred at >or=200 mkd in rabbits and >or=25 mkd in rats. Decreased body weight parameters occurred at >or=200 mkd in rabbits and >or=25 mkd in rats. In rabbits, two fetuses (separate litters) had spina bifida and malrotated hindlimbs at 200 mkd. In rats, skeletal variations occurred at >or=75 mkd.

CONCLUSIONS

There was no teratogenicity with d-MPH. There was a low teratogenic risk with d,l-MPH in only the rabbit. Higher C(max) may explain differences in results from previous studies.

3D ultrasound in fetal spina bifida

3D ultrasound can be used to study the fetal spine, but skeletal mode can be inconclusive for the diagnosis of fetal spina bifida. We illustrate a diagnostic approach using 2D and 3D ultrasound and indicate possible pitfalls.

Physical and biochemical characteristics of the human dysraphic spinal cord

The spinal cords were removed from 29 infants between 17 and 46 weeks gestation, all with various forms of spinal dysraphia. The spinal cords were assessed for weight, length, thickness, size and number of cells, and myelination, and then were compared with 86 control spinal cords. The strongest characteristic of the dysraphic cords was a reduced degree of myelination. Cell size and number generally were appropriate for the weight of the cords. There was a tendency for cord weight, length and thickness to be reduced, though in part this was a reflection of poor over-all bodily growth. In a small group of infants these measurements were increased in comparison with the controls.

The embryogenesis of trypan-blue induced spina bifida aperta and short tail in the rat

The study of litters from 140 Wistar-derived rats injected with trypan blue during gestation leads to conclusion that a myelocele can result from faulty closure of the neural plate and that this is accompanied in many cases by blebs in the paraxial mesoderm. Haematomata usually underlie the open neural plate at an early stage and they form by extravasation of blood from the dorsal aortae into the blebs. Local ventral deflection of the notochord beneath a myelocele probably results from delayed separation of the notochord from the hindgut. Complete failure of separation and abnormality induced in the tail-bud could result in sacral agenesis and/or a short tail. All these malformations may result from varying severity of the action of the trypan blue at different developmental stages.

Embryology of neural tube defects: information provided by associated malformations

OBJECTIVES

To get information about embryologic mechanisms of neural tube defects (NTD), by studying the associated malformations.

METHODS

Eighty three cases of NTD, seen at the prenatal diagnosis unit of Rennes University Hospital (France) between May 1999 and December 2002, were retrospectively studied. Cases with chromosomal anomalies (5/83), cases without available karyotype or pathologic examination were excluded. 24 spina bifida, and 27 cephalic forms (anencephalies, exencephalies, and encephaloceles) were thus analyzed.

RESULTS

Only 22/51 cases (43%) were strictly isolated NTD. Anomalies of tissues arising from neural crests were noted in 8/51 fetuses (16%), midline or lateralization anomalies in 12/51 (24%), and anomalies of mesoblastic tissues in 17/51 (33%). An already known syndrome was found in 4/51 cases (8%).

CONCLUSION

NDT are more extensive congenital damages that would suggest the restrictive terminology. That prompts to assess cautiously prenatal diagnosis of NTD, and to get detailed pathological examination after termination of pregnancy.

Neural plate morphogenesis during mouse neurulation is regulated by antagonism of Bmp signalling

Dorsolateral bending of the neural plate, an undifferentiated pseudostratified epithelium, is essential for neural tube closure in the mouse spinal region. If dorsolateral bending fails, spina bifida results. In the present study, we investigated the molecular signals that regulate the formation of dorsolateral hinge points (DLHPs). We show that Bmp2expression correlates with upper spinal neurulation (in which DLHPs are absent); that Bmp2-null embryos exhibit premature, exaggerated DLHPs;and that the local release of Bmp2 inhibits neural fold bending. Therefore,Bmp signalling is necessary and sufficient to inhibit DLHPs. By contrast, the Bmp antagonist noggin is expressed dorsally in neural folds containing DLHPs,noggin-null embryos show markedly reduced dorsolateral bending and local release of noggin stimulates bending. Hence, Bmp antagonism is both necessary and sufficient to induce dorsolateral bending. The local release of Shh suppresses dorsal noggin expression, explaining the absence of DLHPs at high spinal levels, where notochordal expression of Shh is strong. DLHPs`break through' at low spinal levels, where Shh expression is weaker. Zic2 mutant embryos fail to express Bmp antagonists dorsally and lack DLHPs, developing severe spina bifida. Our findings reveal a molecular mechanism based on antagonism of Bmp signalling that underlies the regulation of DLHP formation during mouse spinal neural tube closure.

Abnormal folate metabolism in foetuses affected by neural tube defects

Folic acid supplementation can prevent many cases of neural tube defects (NTDs), whereas suboptimal maternal folate status is a risk factor, suggesting that folate metabolism is a key determinant of susceptibility to NTDs. Despite extensive genetic analysis of folate cycle enzymes, and quantification of metabolites in maternal blood, neither the protective mechanism nor the relationship between maternal folate status and susceptibility are understood in most cases. In order to investigate potential abnormalities in folate metabolism in the embryo itself, we derived primary fibroblastic cell lines from foetuses affected by NTDs and subjected them to the dU suppression test, a sensitive metabolic test of folate metabolism. Significantly, a subset of NTD cases exhibited low scores in this test, indicative of abnormalities in folate cycling that may be causally linked to the defect. Susceptibility to NTDs may be increased by suppression of the methylation cycle, which is interlinked with the folate cycle. However, reduced efficacy in the dU suppression test was not associated with altered abundance of the methylation cycle intermediates, s-adenosylmethionine and s-adenosylhomocysteine, suggesting that a methylation cycle defect is unlikely to be responsible for the observed abnormality of folate metabolism. Genotyping of samples for known polymorphisms in genes encoding folate-associated enzymes did not reveal any correlation between specific genotypes and the observed abnormalities in folate metabolism. These data suggest that as yet unrecognized genetic variants result in embryonic abnormalities of folate cycling that may be causally related to NTDs.

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.

Prenatal diagnosis of open and closed spina bifida

OBJECTIVE

To identify criteria useful for differentiating closed from open spina bifida antenatally.

PATIENTS AND METHODS

A retrospective study of cases of spina bifida diagnosed in a referral center between 1997 and 2004.

RESULTS

Of 66 cases of fetal spina bifida diagnosed at a median gestational age of 21 (range, 16-34) weeks, detailed follow-up was available for 57. Of these, open defects were found in 53 (93.0%) and closed defects in four (7.0%). Closed spina bifida was associated in two cases with a posterior cystic mass with thick walls and a complex appearance, while in two cases the spinal lesion could not be clearly differentiated from an open defect, particularly at mid-gestation. Open spina bifida was always associated with typical alterations of cranial anatomy, including the so-called 'banana' and 'lemon' signs, while in closed spina bifida the cranium was unremarkable. When the data were available, levels of amniotic fluid alpha-fetoprotein were always abnormally elevated with open spina bifida and within normal limits with closed forms.

CONCLUSION

In this study 7% of cases of spina bifida diagnosed in utero were closed. The differentiation between open and closed forms is best shown by the sonographic demonstration of abnormal or normal cranial anatomy.

Obstetrician-gynecologists' practice and knowledge regarding spina bifida

The purpose was to assess practicing obstetrician-gynecologists' knowledge about the prenatal diagnosis and postnatal prognosis of spina bifida. Written questionnaires designed to assess practicing obstetrician-gynecologists' knowledge of spina bifida were mailed to 1000 randomly selected American College of Obstetricians and Gynecologists Fellows. More than 50% did not identify many of the sonographic features indicative of an open neural tube defect in the fetus and more than one third overestimated the risks of stillbirth, whereas more than two thirds overestimated the risk for premature delivery in a pregnancy complicated by fetal spina bifida. Just more than 50% correctly estimated the 1-year survival rate and just less than 50% correctly estimated survival at 6 years. Sixty-six percent overestimated the incidence of mental retardation associated with spina bifida. Maternal-fetal medicine specialists returning the survey exhibited a much better understanding of the prenatal issues and prognostic and outcome factors related to spina bifida. There are gaps in obstetrician-gynecologists' knowledge about the diagnostic features of and prognosis for fetal spina bifida. It is important for them to take advantage of continuing medical education opportunities to learn more about the management of pregnancies complicated by fetal spina bifida and about the prognosis for affected individuals.

Examining the newborn with an open spinal dysraphism

Spinal dysraphism includes a constellation of frequent and potentially complex malformations of the spine and spinal cord. Open spinal dysraphisms, the majority of which are myelomeningoceles, have a number of associated morbidities that require both immediate and lifelong medical care. The role of the neonatal nurse includes the immediate stabilization of the affected infant, systematic examination of the malformation, and implementation of evidence-based protocols to ameliorate the associated medical problems. Coordination of care and communication and support of the family are essential aspects of care. This article reviews the embryology of open spinal dysraphisms and the steps needed to stabilize and evaluate affected infants.

Antenatal ultrasound and magnetic resonance imaging in localizing the level of lesion in spina bifida and correlation with postnatal outcome

OBJECTIVE

To compare prenatal ultrasonography and magnetic resonance imaging (MRI) in the diagnosis of spina bifida with postnatal MRI/surgical findings and to study the postnatal outcome in relation to the level of lesion and head signs on antenatal imaging.

METHODS

A retrospective study of babies referred to a tertiary neurosurgical unit with a diagnosis of spina bifida in the years 2000-2002 was performed. The levels of lesions and head signs diagnosed using antenatal ultrasonography and MRI were compared with postnatal MRI and operative findings. The levels of lesions and head signs diagnosed pre- and postnatally were used to study the correlation with neurological outcome at a mean follow-up period of 12 months.

RESULTS

Twelve antenatally diagnosed and five postnatally diagnosed cases of spina bifida were seen. The level of lesion as identified by antenatal ultrasound correlated with that observed postnatally in 8/12 cases and the antenatal ultrasound diagnosis of ventriculomegaly was confirmed postnatally in all cases. The level of lesion as identified by antenatal MRI correlated with that observed postnatally in 4/8 cases (50%) and the antenatal MRI diagnosis of ventriculomegaly was confirmed postnatally in 5/8 (63%) cases. 12/17 babies were found to have residuals in the immediate postnatal urodynamic studies, of which 83% (n = 10) required intermittent catheterization of the bladder at 12 months of age. Low spinal lesions were associated with increased bladder morbidity when compared to high spinal lesions (8/10 vs. 4/7, P < 0.05) (odds ratio (OR) = 10.0; 95% CI, 1.05-95.01). The level of spinal lesion and the presence of ventriculomegaly did not have any statistically significant correlation with motor functions, morbidity and developmental milestones.

CONCLUSIONS

Antenatal ultrasonography is a good tool in the diagnosis of spina bifida. We could not demonstrate any advantage of antenatal MRI over ultrasonography. There is better correlation of ultrasonography than MRI with postnatal MRI/operative findings in terms of level of lesion and head signs. Low spinal lesions appear to be associated with increased bladder morbidity.

[Spina bifida--retrospective analysis of fetuses diagnosed in the department of obstetrics & gynecology of the postgraduate center of medical education between 1997 & 2004]

OBJECTIVES

Our objectives were to determine the kind and localisation of the spina bifida and if open neural tube defects are associated with other anomalies and ventriculomegaly.

DESIGN

We retrospectively studied ultrasound reports of the fetuses with open neural tube defects.

MATERIALS AND METHODS

We analyzed 178 cases diagnosed during the last seven years in our center. All fetuses underwent a detailed ultrasonographic survey. We also analyzed gestational age at the first examination.

RESULTS

Associated anomalies were detected in 78 cases, in 100 cases spina bifida was the only anomaly. Lumbo-sacral and sacral localisation was presented in 88% of spina bifida not related with other anomalies and in 50% of cases with associated anomalies. In 94.4% of cases the malformation was myelomeningocoele. Ventriculomegaly was present in 89.1%. The median gestational age at the first examination was 26 weeks. Before 24 week only 34.3% of examinations was done.

CONCLUSIONS

In fetuses with spina bifida detailed ultrasonographic survey should be performed. Measurement of the lateral ventricules should be done in each examination. Furthermore patient with fetus with spina bifida should be diagnosed as early as possible in the referral center.

Embryology of the spine and associated congenital abnormalities

BACKGROUND CONTEXT

The spine is a complex and vital structure. Its function includes not only structural support of the body as a whole, but it also serves as a conduit for safe passage of the neural elements while allowing proper interaction with the brain. Anatomically, a variety of tissue types are represented in the spine. Embryologically, a detailed cascade of events must occur to result in the proper formation of both the musculoskeletal and neural elements of the spine. Alterations in these embryologic steps can result in one or more congenital abnormalities of the spine. Other body systems forming at the same time embryologically can be affected as well, resulting in associated defects in the cardiopulmonary system and the gastrointestinal and genitourinary tracts.

PURPOSE

This article is to serve as a review of the basic embryonic development of the spine. We will discuss the common congenital anomalies of the spine, including their clinical presentation, as examples of errors of this basic embryologic process.

STUDY DESIGN/SETTING

Review of the current literature on the embryology of the spine and associated congenital abnormalities.

METHODS

A literature search was performed on the embryology of the spine and associated congenital abnormalities.

RESULTS

Development of the spine is a complex event involving genes, signaling pathways and numerous metabolic processes. Various abnormalities are associated with errors in this process.

CONCLUSION

Physicians treating patients with congenital spinal deformities should have an understanding of normal embryologic development as well as common associated abnormalities.

Imaging in spine and spinal cord malformations

Spinal and spinal cord malformations are collectively named spinal dysraphisms. They arise from defects occurring in the early embryological stages of gastrulation (weeks 2-3), primary neurulation (weeks 3-4), and secondary neurulation (weeks 5-6). Spinal dysraphisms are categorized into open spinal dysraphisms (OSDs), in which there is exposure of abnormal nervous tissues through a skin defect, and closed spinal dysraphisms (CSD), in which there is a continuous skin coverage to the underlying malformation. Open spinal dysraphisms basically include myelomeningocele and other rare abnormalities such as myelocele and hemimyelo(meningo)cele. Closed spinal dysraphisms are further categorized based on the association with low-back subcutaneous masses. Closed spinal dysraphisms with mass are represented by lipomyelocele, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise simple dysraphic states (tight filum terminale, filar and intradural lipomas, persistent terminal ventricle, and dermal sinuses) and complex dysraphic states. The latter category further comprises defects of midline notochordal integration (basically represented by diastematomyelia) and defects of segmental notochordal formation (represented by caudal agenesis and spinal segmental dysgenesis). Magnetic resonance imaging (MRI) is the preferred modality for imaging these complex abnormalities. The use of the aforementioned classification scheme is greatly helpful to make the diagnosis.

Effect of valproic acid on fetal and maternal organs in the mouse: a morphological study

Valproic acid (VPA) is an antiepileptic drug used clinically. Because of its known teratogenic properties VPA is not recommended for women of child bearing age. The present study was designed to assess the effects of VPA on both fetal and maternal organs. Randomized groups of pregnant mice were treated as follows: Group 1 (n = 10) 500 mg/kg VPA/day on gestation days 8-11; Group 2 (n = 10) 600 mg/kg VPA/day on gestation days 8-11; and Group 3 (n = 4) saline-injected controls. On gestation day 18, the pregnant mice were euthanized, fetuses collected and prepared for scanning electron microscopy. In addition, fetal and maternal organs were processed for routine histology, immunohistochemistry for growth factors (TGF alpha, beta-1, beta-2 and EGF) and transmission electron microscopy. Scanning microscopy revealed specific lesions induced by VPA in the fetus, namely spina bifida occulta, exencephaly, and exophthalmia. On the other hand, there were no detectable morphological changes in fetal or maternal organs by routine histology, immunohistochemistry or electron microscopy. The data suggest that the lesions present in the fetus are due to a direct effect by VPA on retinoic acid, a ubiquitous compound that has a role in normal development, rather than the lack of transport of sufficient nutrients to the fetus as a result of placental insufficiency due to VPA-induced toxicity.

Spinal dysraphism: MR imaging rationale

Spinal cord development occurs through the three consecutive periods of gastrulation (weeks 2-3), primary neurulation (weeks 3-4), and secondary neurulation (weeks 5-6). Spinal cord malformations derive from defects in these early embryonic stages, and are collectively called spinal dysraphisms. Spinal dysraphisms may be categorized clinically into open and closed, based on whether the abnormal nervous tissue is exposed to the environment or covered by skin. Open spinal dysraphisms include myelomeningocele and other rare abnormalities such as myelocele, hemimyelomeningocele, and hemimyelocele, and are always associated with a Chiari II malformation. Closed spinal dysraphisms are further divided into two subsets based on whether a subcutaneous mass is present in the low back. Closed spinal dysraphisms with mass comprise lipomyelocele, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise simple dysraphic states (tight filum terminale, filar and intradural lipomas, persistent terminal ventricle, and dermal sinuses) and complex dysraphic states. The latter category involves abnormal notochordal development, either in the form of failed midline integration (ranging from complete dorsal enteric fistula to neurenteric cysts and diastematomyelia) or of segmental agenesis (caudal agenesis and spinal segmental dysgenesis). Magnetic resonance imaging is the imaging modality of choice for evaluation of this complex group of disorders.

Prenatal and postnatal findings of acrania

INTRODUCTION

Acrania is a rare congenital anomaly in which the flat bones of the cranial vault are partial or complete absent with complete but abnormal development of the cerebral hemispheres.

CASE REPORT

We report two cases, diagnosed prenatally by ultrasound and followed by medical pregnancy termination, one with isolated acrania and one with associated cleft lip and palate and spina bifida.

DISCUSSION

The acrania pathogenesis is unknown and differential diagnosis should be made with other conditions like anencephaly and acalvaria. Genetic counselling is not easy because there is no evidence for a specific genetic origin, but the extreme rarity and sporadic nature suggests a low recurrence risk.

Fetal skeletal deformities - the diagnostic accuracy of prenatal ultrasonography and fetal magnetic resonance imaging

OBJECTIVE

To evaluate the diagnostic accuracy of prenatal ultrasonography and fetal magnetic resonance imaging (MRI) in fetuses with skeletal deformities (SD).

METHODS

Fourteen pregnant women of 21 - 34 weeks of gestation whose fetuses had SD on prenatal ultrasound (seven fetuses with spina bifida, four with complex malformation syndrome, two with scoliosis, and one with chondrodysplasia) were additionally investigated by fetal MRI using a 1.5T superconducting system with T1-and T2-weighted sequences in three section-planes. Main outcome measures were diagnostic accuracy, potential effect on parental counselling and influence on perinatal management of the additional investigation with fetal MRI.

RESULTS

In 10 cases ultrasound had a better diagnostic accuracy than MRI concerning the diagnosis of SD. In four cases with spina bifida MRI provided additional information towards preoperative evaluation for neurosurgery. In five cases parental counselling was improved. There was no influence on perinatal management.

CONCLUSION

MRI may provide additional information to ultrasound scan in fetuses with spina bifida and consecutive neurosurgery; in fetuses with other skeletal deformities additional information may be expected only in rare cases.

Chromosomal abnormalities in fetuses with open neural tube defects: prenatal identification with ultrasound

OBJECTIVES

To determine the prevalence of chromosomal abnormalities in fetuses with open neural tube defects (NTD) undergoing prenatal chromosome analysis. The role of prenatal ultrasound in detecting those with an underlying chromosomal abnormality was also investigated.

METHODS

Over a 6-year period, 144 fetuses with open NTD underwent prenatal chromosome analysis between 12 and 37 weeks of gestation, as part of a prospective, multicenter prenatal diagnosis and counseling program in Chile. This population included 66 fetuses with spina bifida, 46 with acrania/anencephaly, 21 with cephalocele and 11 with iniencephaly. A confident prenatal diagnosis was made in 143 fetuses (99%) and confirmed postnatally in all cases.

RESULTS

An underlying chromosomal abnormality was diagnosed in 10 fetuses (7%), six with spina bifida, three with cephalocele and one with craniorachischisis. The prevalence of chromosomal abnormality varied according to the defect present in the fetus, with a 14% (3/21) prevalence among those with cephalocele, 9% (6/66) among those with spina bifida and 2% (1/57) among those with lethal defects such as acrania, anencephaly or iniencephaly. Karyotype results revealed trisomy 18 in seven cases, trisomy 13 in two and mosaicism for a marker chromosome in one. Prenatal ultrasound before the procedure showed that all chromosomally abnormal fetuses had additional findings. The prevalence of chromosomal abnormality in fetuses with spina bifida and cephalocele was higher when chromosome analysis was performed at or before 24 weeks of gestation in comparison to those performed after 24 weeks (5/31 (16%) vs. 4/56 (7%), respectively). However, this difference did not reach statistical significance, probably due to the small number of cases.

CONCLUSIONS

A significant number of fetuses with open NTD are chromosomally abnormal. Although prenatal chromosome analysis should be considered in all cases, prenatal ultrasound seems effective in identifying those fetuses with an underlying chromosomal abnormality.

Foetal surgery for spina bifida

In utero repair of open spina bifida or myelomeningocele (MMC) is now performed in selected patients and presents an additional alternative to obstetricians and neonatologists counselling expectant mothers carrying a foetus with MMC. Early foetal intervention may improve neurologic outcomes and reduce the hindbrain herniation associated with the Arnold-Chiari II malformation in open spina bifida. These changes may improve long-term neurologic function and limit requirements for shunt placements and other surgical interventions. Further research is needed to better understand the pathophysiology of MMC, the ideal timing and technique of repair, and the long-term impact of in utero intervention. A prospective, randomized clinical trial is planned comparing prenatal MMC repair with postnatal repair.

[Embryonic mechanisms in development of spina bifida in humans]

The study of 86 human embryos and fetuses beginning from 23rdday of development up to 18th week after fecundation has detected 23 cases of pathologic development which correspond to the modern definition of spina bifida (SB). It is shown that the cause of various forms of the anomaly is the disturbance or temporary delay of a movement of caudal neurulation wave forming the spinal cord. The anomaly size and type are determined by the time and duration of a pathogenic action on neurulation. Postnatal or the 1st type of SB develops in neurulation wave disturbance not longer than 4-6 hours. Anomaly consequence may be compensated surgically. The 2nd or fetal type of SB arises when neurulation delay is from 6 to 20 hours. If the delay occurs on the 22-24th day of development, embryos die by the neurulation end. If the delay takes place on the 26-28th day embryos may survive till the late fetal period. In embryonal or type III of SB embryos die by the end of the 8th week and do not enter the medical statistics. Their death is associated with delayed movement of the caudal neurulation wave for 24 hours and longer. This results in a spontaneous abortion.