Normal cavum veli interpositi at 14-17 gestational weeks: three-dimensional and Doppler transvaginal neurosonographic study

OBJECTIVES

To provide evidence to support the hypothesis that the midline cyst-like fluid collection that is frequently observed on fetal brain ultrasound (US) imaging during the early second trimester represents a normal transient cavum veli interpositi (CVI).

METHODS

This was a retrospective analysis of 89 three-dimensional normal fetal brain volumes, acquired by transvaginal US imaging in 87 pregnant women between 14 and 17 gestational weeks. The midsagittal view was studied using multiplanar imaging, and the maximum length of the fluid collection located over (dorsal to) the tela choroidea of the third ventricle was measured. We calculated the correlation of the transverse cerebellar diameter (TCD) and of the maximum length of the fluid collection with gestational age according to last menstrual period. Color Doppler images were analyzed to determine the location of the internal cerebral veins with respect to the location of the fluid collection. Reports of the second-trimester anatomy scan at 22-24 weeks were also reviewed.

RESULTS

Interhemispheric fluid collections of various sizes were found in 55% (49/89) of the volumes (mean length, 5 (range, 3.0-7.8) mm). There was a strong correlation between TCD and gestational age (Pearson's correlation, 0.862; P < 0.001). There was no correlation between maximum fluid length and gestational age (Pearson's correlation, -0.442; P = 0.773). Color Doppler images were retrieved in 32 of the 49 fetuses; in 100% of these, the internal cerebral veins coursed within the echogenic roof of the third ventricle. The midline structures were normal at the 22-24-week scan in all cases.

CONCLUSIONS

In approximately half of normal fetuses, during the evolution of the midline structures of the brain, various degrees of fluid accumulate transiently in the velum interpositum, giving rise to a physiologic CVI. Patients should be reassured that this is a normal phenomenon in the early second trimester that, if an isolated finding, has no influence on fetal brain development. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Development of the Neuro-Immune-Vascular Plexus in the Ventricular Zone of the Prenatal Rat Neocortex

Microglial cells make extensive contacts with neural precursor cells (NPCs) and affiliate with vasculature in the developing cerebral cortex. But how vasculature contributes to cortical histogenesis is not yet fully understood. To better understand functional roles of developing vasculature in the embryonic rat cerebral cortex, we investigated the temporal and spatial relationships between vessels, microglia, and NPCs in the ventricular zone. Our results show that endothelial cells in developing cortical vessels extend numerous fine processes that directly contact mitotic NPCs and microglia; that these processes protrude from vessel walls and are distinct from tip cell processes; and that microglia, NPCs, and vessels are highly interconnected near the ventricle. These findings demonstrate the complex environment in which NPCs are embedded in cortical proliferative zones and suggest that developing vasculature represents a source of signaling with the potential to broadly influence cortical development. In summary, cortical histogenesis arises from the interplay among NPCs, microglia, and developing vasculature. Thus, factors that impinge on any single component have the potential to change the trajectory of cortical development and increase susceptibility for altered neurodevelopmental outcomes.

Camel regulates development of the brain ventricular system

Development of the brain ventricular system of vertebrates and the molecular mechanisms involved are not fully understood. The developmental genes expressed in the elements of the brain ventricular system such as the ependyma and circumventricular organs act as molecular determinants of cell adhesion critical for the formation of brain ventricular system. They control brain development and function, including the flow of cerebrospinal fluid. Here, we describe the novel distantly related member of the zebrafish L1-CAM family of genes-camel. Whereas its maternal transcripts distributed uniformly, the zygotic transcripts demonstrate clearly defined expression patterns, in particular in the axial structures: floor plate, hypochord, and roof plate. camel expresses in several other cell lineages with access to the brain ventricular system, including the midbrain roof plate, subcommissural organ, organum vasculosum lamina terminalis, median eminence, paraventricular organ, flexural organ, and inter-rhombomeric boundaries. This expression pattern suggests a role of Camel in neural development. Several isoforms of Camel generated by differential splicing of exons encoding the sixth fibronectin type III domain enhance cell adhesion differentially. The antisense oligomer morpholino-mediated loss-of-function of Camel affects cell adhesion and causes hydrocephalus and scoliosis manifested via the tail curled down phenotype. The subcommissural organ's derivative-the Reissner fiber-participates in the flow of cerebrospinal fluid. The Reissner fiber fails to form upon morpholino-mediated Camel loss-of-function. The Camel mRNA-mediated gain-of-function causes the Reissner fiber misdirection. This study revealed a link between Chl1a/Camel and Reissner fiber formation, and this supports the idea that CHL1 is one of the scoliosis factors.

Trend in ventricle size during pregnancy and its use for prediction of ventriculoperitoneal shunt in fetal open neural tube defect

OBJECTIVES

Fetal surgery for repair of open neural tube defect (ONTD) typically results in decreased need for a ventriculoperitoneal shunt (VPS). Our objectives were to determine the trend in ventricle size (VS) during pregnancy and whether VS and change in VS, as assessed by ultrasound, were predictive of the need for VPS in pregnancy with ONTD.

METHODS

This was a retrospective analysis of prospectively collected data of consecutive pregnancies with ONTD, evaluated in a single center from January 2012 to May 2018. Two groups were identified: the first consisted of pregnancies that underwent in-utero repair (IUR) and the second those that had postnatal repair (PNR). Penalized B splines were used to determine the trend in VS, across 2-week gestational-age (GA) epochs, between 24 and 36 weeks of gestation. VS at each GA epoch and the change in VS between each GA epoch were compared between the IUR and PNR groups. To determine whether VS at any GA was predictive of VPS, receiver-operating-characteristics (ROC) curves were used and the optimal cut-off at each GA epoch was identified. Univariate analysis and multiple logistic regression were used for further analysis.

RESULTS

ONTD was diagnosed in 110 fetuses, of whom 69 underwent IUR and 41 had PNR. Fetuses in the IUR group were more likely to have Chiari II malformation (100.0% vs 82.9%; P < 0.01), lower GA at delivery (34.9 ± 3.2 vs 37.1 ± 2.1 weeks; P < 0.01) and lower rates of VPS within the first year postpartum (36.2% vs 61.0%; P = 0.02) compared with the PNR group. In both groups, VS increased steadily with GA from the initial evaluation to delivery. In the IUR group, there was a significant change in VS between the 24 + 0 to 25 + 6-week and the 26 + 0 to 27 + 6-week epochs (2.3 (95% CI, 0.4-4.1) mm; P = 0.02). There was a positive trend in the change in VS at later GAs, but this was not significant. Although there was no significant change in VS in the PNR group before 30 weeks, there was a positive trend after that time. On multivariate analysis, each week of advancing GA was associated with a mean increase of 0.74 mm in VS (P < 0.0001) in both groups. VS was not associated with the level or type of lesion, but presence of Chiari II malformation was associated with a mean increase of 5.88 mm (P < 0.0001) in VS in both the IUR and PNR groups. VS was modestly predictive of need for VPS in both groups, with area under ROC curves between 0.68 and 0.76 at the different GA epochs. Change in VS between the first and last measurements was also modestly predictive of the need for VPS, with better performance in the PNR group.

CONCLUSIONS

VS increased with advancing GA in all fetuses with ONTD, although in the IUR group this increase occurred immediately after fetal surgery and in the PNR group it occurred after 30 weeks of gestation. In-utero surgery was associated with a decreased rate of VPS and was more predictive of need for VPS than was VS. Postnatal factors resulting in increased need for VPS in the PNR group need to be assessed further. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Outcome of fetuses with prenatal diagnosis of isolated severe bilateral ventriculomegaly: systematic review and meta-analysis

OBJECTIVE

To quantify from the published literature survival and neurodevelopmental outcome of fetuses with prenatally detected isolated severe bilateral ventriculomegaly.

METHODS

MEDLINE, EMBASE and the Cochrane Library were searched electronically. Only cases with a prenatal diagnosis of apparently isolated severe ventriculomegaly and postnatal neurodevelopmental assessment were selected and included. Severe ventriculomegaly was defined as enlargement of the ventricular atria, with a diameter of greater than 15 mm in the transventricular plane. All cases in which the investigators were unable to detect associated structural abnormality, chromosomal abnormality or fetal infection, and in which the ventriculomegaly was therefore regarded as apparently isolated, were included. Those for which the etiology was identified prenatally were excluded, whereas those with postnatal identification of the underlying cause were not excluded, since this information was not available prenatally. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS) for cohort studies. Pregnancy outcomes such as termination, stillbirth, neonatal survival and developmental outcome of the baby, were recorded. The degree of disability was classified as no, mild or severe disability. Statistical assessment was performed by meta-analysis of proportions to combine data, weighting the studies using the inverse variance method and a random-effects model. Proportions and CIs were reported.

RESULTS

Eleven studies including 137 fetuses were found. Twenty-seven pregnancies underwent termination and were excluded. The remaining 110 fetuses with apparently isolated severe ventriculomegaly for which continuation of pregnancy was intended, form the study population. Overall quality assessed using NOS for cohort studies was good. Survival was reported in 95/110 (pooled proportion 87.9% (95% CI, 75.6-96.2%)) cases. In 15/110 (pooled proportion 12.1% (95% CI, 3.8-24.4%)), either stillbirth or neonatal demise was reported. No disability was reported in 41/95 survivors (pooled proportion 42.2% (95% CI, 27.5-57.6%)). However, 17/95 showed mild/moderate disability (pooled proportion 18.6% (95% CI, 7.2-33.8%)) and 37/95 were reported to have severe disability (pooled proportion 39.6% (95% CI, 30.0-50.0%)).

CONCLUSIONS

Four-fifths of fetuses with severe ventriculomegaly survive and, of these, just over two-fifths show normal neurodevelopment. The overall survivors without disability account for more than one third of the total. Given that many cases undergo termination of pregnancy and require longer follow-up in order to detect subtle abnormalities, mortality and prevalence of developmental delay may be even higher than that reported in this paper. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Formation of the calcarine sulcus: a potential marker to predict the progression in utero of isolated mild fetal ventriculomegaly

Our previous study confirmed the negative association between the development of calcarine sulcus and the width of lateral ventricles. The purpose of current study was to evaluate the reliability of calcarine sulcus depth in the 2nd trimester to predict the prenatal enlargement of lateral ventricle in fetuses with isolated mild fetal ventriculomegaly (IMVM).This study used a retrospective cohort study design. A total of 97 pregnant women with IMVM diagnosed between 20 and 26 weeks' gestation returned for a 2nd examination at 30 to 32 weeks. Lateral ventricular size and calcarine sulcus depth were acquired from ultrasonography and magnetic resonance imaging (MRI) scans, respectively. Progression was defined as the process of developing from a lower group toward a higher (<10 mm, 10-12 mm, 13-15 mm, and ≥16 mm).Significant correlation was observed between calcarine sulcus depth and ventricular measurements at the 2nd scan (r = -0.71, P < .0001). Receiver-operating characteristic curves showed that calcarine sulcus depth (area under curve [AUC] = 0.83, 95% confidence interval [CI] = 0.74-0.92) had the best diagnostic performance in predicting the prenatal progression, as compared with lateral ventricle width (AUC = 0.69, 95%CI = 0.54-0.84) and gestational age (AUC = 0.70, 95%CI = 0.57-0.83) at the initial scan. The cutoff value for calcarine sulcus depth was 3.3 mm, with the corresponding sensitivity and specificity were 75.0% and 81.3%, respectively. Multivariate analyses showed that calcarine sulcus depth ≥3.3 mm (odds ratio = 0.09, 95%CI = 0.02-0.38, P = .001) was an independent predictor of the prenatal progression.For IMVM, calcarine sulcus depth might be a powerful marker to identify subjects at higher risk for worse prenatal progression.

Fetal ventriculomegalies during pregnancy course, outcome, and psychomotor development of born children

PURPOSE

The objectives of this study were as follows: to present the course and outcome of pregnancies complicated with fetal ventriculomegaly, determine the association between prenatal ultrasound diagnoses and definitive postnatal diagnosis or diagnoses after autopsy and additional analysis, and to monitor the psychomotor development of children born with ventriculomegaly.

MATERIALS AND METHODS

The survey was designed as retrospective study and included 62 pregnant women who were attending a regular ultrasound examinations at the Department of Gynecology and Obstetrics, Clinical Center of Serbia, or patients who were referred from other institutions in Serbia.

RESULTS

Ventriculomegalies were divided into three groups: mild, moderate, and severe or hydrocephalus. The most common were severe ventriculomegalies, with 34 cases (55%). Of all pregnancies complicated with ventriculomegalies, 61% were terminated. Among those continued, 88% had normal psychomotor development. In 97% ultrasonographic diagnosis was confirmed.

CONCLUSION

Majority of pregnancies complicated with ventriculomegaly were continued and most of the children born with anomalies had normal psychomotor development.

Choroid plexus separation in fetuses without ventriculomegaly: Natural course and postnatal outcome

PURPOSE

To evaluate fetuses with choroid plexus separation without ventriculomegaly in terms of fetal malformations, behavior of the separation during follow-up, and postnatal outcome.

METHODS

In total, 172 fetuses with choroid plexus separation without ventriculomegaly were included in this prospective study. Fetal sonography was performed at 2- to 4-week intervals, and detailed physical and neurologic examinations were performed after their delivery. Fetuses were categorized into normal and abnormal subgroups according to the outcome.

RESULTS

Sixteen fetuses (9.3%) were included in the abnormal-outcome group and 156 fetuses (90.7%) were included in the normal-outcome group. Both the initial mean lateral ventricular diameter (9.3 mm versus 8.6 mm) and the initial mean choroid plexus separation (4.8 mm versus 3.3 mm) were greater in the abnormal group than in the normal group (p < 0.001 for both comparisons). We found that 4.0 mm was the best cutoff point of choroid plexus separation to detect a major anomaly, with 87.5% sensitivity and 93.6% specificity.

CONCLUSIONS

Choroid plexus separation without ventriculomegaly often resolves within the third trimester and does not affect postnatal outcome. It can be associated with various fetal malformations; however, with a comprehensive examination, all fetal malformations can be detected prenatally. Follow-up sonography studies would be useful, especially in the case of suspected corpus callosum agenesis.

The prognostic role of prenatal MRI volumetric assessment in fetuses with isolated ventriculomegaly

In this prospective study, we aimed to establish the value of volumetric assessment by prenatal brain MRI in determining the prognosis of fetuses with isolated VM. A total of 23 fetuses with isolated VM were included in the study. Supratentorial cerebral parenchyma volume (PV) and ventricular volume (VV) were measured, and supratentorial ventricular/parenchymal volume (VV/PV) ratios were calculated. Pregnancy and postnatal neurodevelopmental outcomes up to two years of age were obtained and correlated with the volumetric measurements. VV was found to be strongly and positively correlated with ventricular dimension. There was a statistically significant difference between the VV/ PV ratios of the good and poor prognosis groups into which the cases had been categorized. The fetuses with a poor prognosis had a significantly higher VV/PV ratio. Volumetric parenchymal and ventricular measurements obtained by fetal brain MRI may contribute to future clinical studies concerning the evaluation of fetuses with VM and provide an important indicator in cases where management dilemmas arise.

[Morphological changes in ventricular germinal zone and neocortex of the cerebral hemispheres in human fetuses and newborns on weeks 22-40 of prenatal development]

In this study, we investigated the morphology of the ventricular germinal zone and neocortex of the cerebral hemispheres in the projection field no. 4 of the motor area in human fetuses in dynamics from week 22 to 40 of fetal development. Morphological study allowed us to clarify the following patterns of prenatal ontogeny of the human CNS. On weeks 22-27, an intensive formation of the main sulci of the first order, differentiating the brain into lobes, is observed. By weeks 28-32, the formation of all sulci of the first order is completed; and on weeks 33-37, additional sulci characteristic of an individual are formed. The spurt of gyrification of the cortex (weeks 22-27) practically coincides with the completion of neuronal differentiation and formation of the motor neocortex. The structure of the latter is characterized by a clear stratification of cytoarchitectonic layers and modular organization of neurons with their vertical orientation in cell columns (weeks 25-27). In subsequent weeks of prenatal development until birth, no significant changes in the topography and structure of the neocortex are observed. Structural rearrangement of the ventricular germinal zone on weeks 22-40 of prenatal development consists in its gradual reduction and is completed on weeks 37-40. The criteria of physiological reduction of this area are the zonal location of glioblasts and a progressive decrease in its thickness on weeks 33-37 of prenatal development.

Robo1 modulates proliferation and neurogenesis in the developing neocortex

The elaborate cytoarchitecture of the mammalian neocortex requires the timely production of its constituent pyramidal neurons and interneurons and their disposition in appropriate layers. Numerous chemotropic factors present in the forebrain throughout cortical development play important roles in the orchestration of these events. The Roundabout (Robo) family of receptors and their ligands, the Slit proteins, are expressed in the developing forebrain, and are known to play important roles in the generation and migration of cortical interneurons. However, few studies have investigated their function(s) in the development of pyramidal cells. Here, we observed expression of Robo1 and Slit genes (Slit1, Slit2) in cells lining the telencephalic ventricles, and found significant increases in progenitor cells (basal and apical) at embryonic day (E)12.5 and E14.5 in the developing cortex of Robo1(-/-), Slit1(-/-), and Slit1(-/-)/Slit2(-/-), but not in mice lacking the other Robo or Slit genes. Using layer-specific markers, we found that both early- and late-born pyramidal neuron populations were significantly increased in the cortices of Robo1(-/-) mice at the end of corticogenesis (E18.5). The excess number of cortical pyramidal neurons generated prenatally appears to die in early postnatal life. The observed increase in pyramidal neurons was due to prolonged proliferative activity of their progenitors and not due to changes in cell cycle events. This finding, confirmed by in utero electroporation with Robo1 short hairpin RNA (shRNA) or control constructs into progenitors along the ventricular zone as well as in dissociated cortical cell cultures, points to a novel role for Robo1 in regulating the proliferation and generation of pyramidal neurons.

The criterion value of fetal cerebral lateral ventricular atrium width for diagnosis of ventriculomegaly

AIM

To determine the distribution of cerebral lateral ventricular atrium width (LVAW) as established according to gestational weeks, and calculate the criterion value of LVAW that differentiates normal fetuses from abnormal fetuses.

MATERIALS AND METHODS

A total of 832 patients meeting the study's criteria were included in the control group. An additional 43 fetuses with LVAW > ten mm formed the case group.

RESULTS

The criterion value ofLVAW was 9.7 mm. It did not change significantly throughout gestation. In the case group, 23 fetuses were terminated for fetal abnormalities, two fetuses died in utero, and 18 infants were born alive. Most of the abnormal development coincided with LVAW values greater than 12 mm.

CONCLUSION

The authors suggest 9.7 mm as the criterion value, based on receiver operating characteristic (ROC) curve analysis. When the LVAW is between 9.8 and 12 mm without other fetal abnormalities, it may be regarded as a variation of the normal.

Routine sonographic measurement of the near-field lateral ventricle during second-trimester morphologic scans

OBJECTIVES

The purpose of this study was to determine whether measurement of the near-field lateral ventricular diameter can be reliably obtained within a practical time frame during second-trimester obstetric scans by angling the fetal head approximately 30° away from the horizontal image axis such that the posterior aspect of the fetal head lies closer to the transducer.

METHODS

Fifty consecutive singleton pregnancies presenting for a routine-second trimester scan were recruited for this study. The far-field lateral ventricular diameter was measured, followed by the near-field lateral ventricular diameter using the proposed technique. The measurements were repeated by a second operator who was blinded to the first measurement. Both operators recorded the measurements taken and scored the level of visibility of the near-field lateral ventricle. The difference between the two operators' measurements was compared by a κ analysis.

RESULTS

The near-field lateral ventricle was visualized in 49 of 50 cases (98%). There was no statistically significant difference in the measurement of the near-field lateral ventricular diameter by the two operators (P = .34). There was, however, a statistically significant difference in the time it took each operator to obtain the near-field measurement after the far-field measurement (P = .01).

CONCLUSIONS

Manipulating the transducer to position the falx of the fetal head approximately 30° away from the horizontal image axis allows the near-field lateral ventricle to be routinely visualized and measured with a high degree of interoperator agreement and within a practical time frame once the operator is experienced in performing the technique.

[The behaviors of proliferative cells in the subventricular zone during cortical development]

Recent studies revealed that the subventricular zone (SVZ) in the developing mammalian cerebrum is a source of cortical neurons along with the ventricular zone (VZ), and especially in human SVZ, abundant self-renewal stem cells exist and are thought to largely contribute to the development of huge brain. These studies suggested that the regulations of the number of progenitors or stem cells in the SVZ and their stemness are important issues for understanding the final output of the cortical neurons. We previously reported the migratory difference between the direct progeny of the VZ and the further dividing cells in the SVZ in mice. The former population finishes the cell division in the VZ, stays there for more than 10 hours, and then accumulates in the lower SVZ as multipolar cells. The other exits the VZ earlier than former, distributes widely in the SVZ and divides. These observations showed that the SVZ is divided into two regions; the lower postmitotic cell accumulation region and upper dividing cell-rich region. This model provides the framework for understanding the nature of the SVZ.

Diversity of neural precursor cell types in the prenatal macaque cerebral cortex exists largely within the astroglial cell lineage

The germinal zones of the embryonic macaque neocortex comprise the ventricular zone (VZ) and the subventricular zone (SVZ). The mammalian SVZ is subdivided into an inner SVZ and an outer SVZ, with the outer SVZ being particularly large in primates. The existence of distinct precursor cell types in the neocortical proliferative zones was inferred over 100 years ago and recent evidence supports this concept. Precursor cells exhibiting diverse morphologies, patterns of transcription factor expression, and fate potential have been identified in the neocortical proliferative zones. Neurogenic precursor cells are thought to exhibit characteristics of glial cells, but the existence of neurogenic precursor cells that do not share glial specific properties has also been proposed. Therefore, one question that remains is whether neural precursor cells in the prenatal neocortex belong within the astroglial cell class, as they do in neurogenic regions of the adult neocortex, or instead include a diverse collection of precursor cells belonging to distinct cell classes. We examined the expression of astroglial markers by mitotic precursor cells in the telencephalon of prenatal macaque and human. We show that in the dorsal neocortex all mitotic cells at the surface of the ventricle, and all Pax6+ and Tbr2+ mitotic cells in the proliferative zones, express the astroglial marker GFAP. The majority of mitotic cells undergoing division away from the ventricle express GFAP, and many of the GFAP-negative mitoses express markers of cells derived from the ventral telencephalon or extracortical sites. In contrast, a markedly lower proportion of precursor cells express GFAP in the ganglionic eminence. In conclusion, we propose that the heterogeneity of neural precursor cells in the dorsal cerebral cortex develops within the GFAP+ astroglial cell class.

Comparative assessments of the effects of alcohol exposure on fetal brain development using optical coherence tomography and ultrasound imaging

The developing fetal brain is vulnerable to a variety of environmental agents including maternal ethanol consumption. Preclinical studies on the development and amelioration of fetal teratology would be significantly facilitated by the application of high resolution imaging technologies like optical coherence tomography (OCT) and high-frequency ultrasound (US). This study investigates the ability of these imaging technologies to measure the effects of maternal ethanol exposure on brain development, ex vivo, in fetal mice. Pregnant mice at gestational day 12.5 were administered ethanol (3 g/Kg b.wt.) or water by intragastric gavage, twice daily for three consecutive days. On gestational day 14.5, fetuses were collected and imaged. Three-dimensional images of the mice fetus brains were obtained by OCT and high-resolution US, and the volumes of the left and right ventricles of the brain were measured. Ethanol-exposed fetuses exhibited a statistically significant, 2-fold increase in average left and right ventricular volumes compared with the ventricular volume of control fetuses, with OCT-derived measures of 0.38 and 0.18 mm3, respectively, whereas the boundaries of the fetal mouse lateral ventricles were not clearly definable with US imaging. Our results indicate that OCT is a useful technology for assessing ventriculomegaly accompanying alcohol-induced developmental delay. This study clearly demonstrated advantages of using OCT for quantitative assessment of embryonic development compared with US imaging.

Methods to culture, differentiate, and characterize neural stem cells from the adult and embryonic mouse central nervous system

Since the discovery of neural stem cells (NSC) in the embryonic and adult mammalian central nervous system (CNS), there have been a growing numbers of tissue culture media and protocols to study and functionally characterize NSCs and its progeny in vitro. One of these culture systems introduced in 1992 is referred to as the Neurosphere Assay, and it has been widely used to isolate, expand, differentiate and even quantify NSC populations. Several years later because its application as a quantitative in vitro assay for measuring NSC frequency was limited, a new single-step semisolid based assay, the Neural Colony Forming Cell (NCFC) assay was developed to accurately measure NSC numbers. The NCFC assay allows the discrimination between NSCs and progenitors by the size of colonies they produce (i.e., their proliferative potential). The evolution and continued improvements made to these tissue culture tools will facilitate further advances in the promising application of NSCs for therapeutic use.

Cerebral ventricular system in fetuses with open spina bifida at 11-13 weeks' gestation

OBJECTIVE

To determine if in fetuses with open spina bifida at 11-13 weeks' gestation there are alterations in the cerebral ventricular system.

METHODS

In this study we selected 10 cases of open spina bifida and 410 normal singleton pregnancies which subsequently resulted in the delivery of phenotypically normal neonates. In all cases transvaginal sonography was carried out at 11-13 weeks' gestation and three-dimensional (3D) brain volumes were acquired. The fetal head was systematically assessed in a series of transverse views and measurements were obtained of the area of the lateral ventricles, the diameter of the roof of the third ventricle, the diameter of the aqueduct of Sylvius and the diameter of the fourth ventricle. The measurements obtained on the normal and affected fetuses were compared.

RESULTS

In normal fetuses the area of the lateral ventricles and the diameter of the roof of the third ventricle increased, the diameter of the aqueduct of Sylvius decreased and the diameter of the fourth ventricle did not change significantly with biparietal diameter (BPD). In fetuses with open spina bifida, compared with normal fetuses, the measurements of the lateral ventricle area, the diameter of the roof of the third ventricle, the diameter of the aqueduct of Sylvius and the diameter of the fourth ventricle were significantly decreased (P < 0.01).

CONCLUSION

In fetuses with open spina bifida at 11-13 weeks' gestation the intracranial collection of cerebrospinal fluid is substantially reduced.

An evolutionary recent neuroepithelial cell adhesion function of huntingtin implicates ADAM10-Ncadherin

The Huntington's disease gene product, huntingtin, is indispensable for neural tube formation, but its role is obscure. We studied neurulation in htt-null embryonic stem cells and htt-morpholino zebrafish embryos and found a previously unknown, evolutionarily recent function for this ancient protein. We found that htt was essential for homotypic interactions between neuroepithelial cells; it permitted neurulation and rosette formation by regulating metalloprotease ADAM10 activity and Ncadherin cleavage. This function was embedded in the N terminus of htt and was phenocopied by treatment of htt knockdown zebrafish with an ADAM10 inhibitor. Notably, in htt-null cells, reversion of the rosetteless phenotype occurred only with expression of evolutionarily recent htt heterologues from deuterostome organisms. Conversely, all of the heterologues that we tested, including htt from Drosophila melanogaster and Dictyostelium discoideum, exhibited anti-apoptotic activity. Thus, anti-apoptosis may have been one of htt’s ancestral function(s), but, in deuterostomes, htt evolved to acquire a unique regulatory activity for controlling neural adhesion via ADAM10-Ncadherin, with implications for brain evolution and development.

Abnormal or delayed development of the posterior membranous area of the brain: anatomy, ultrasound diagnosis, natural history and outcome of Blake's pouch cyst in the fetus

OBJECTIVES

To review the normal and pathological development of the posterior membranous area (PMA) in the fetal brain, to define sonographic criteria with which to diagnose a Blake's pouch cyst (BPC) in the fetus and to review the ultrasound features, associations and outcome of 19 cases of BPC seen at our center over the last 5 years.

METHODS

We conducted a MEDLINE search using the terms 'Blake's pouch', with or without 'fourth ventricle' or '4(th) ventricle', with or without 'roof' and identified articles describing normal and/or abnormal development of the PMA, whether or not they were cited in the limited clinical literature on BPC. A description of the normal and abnormal development of BPC was derived by collating these articles. The clinical retrospective study included 19 cases of posterior fossa anomalies with a final diagnosis of BPC seen at our institution. The following variables were assessed: referral indication, gestational age at diagnosis, ultrasound and magnetic resonance imaging (MRI) findings, associated anomalies, natural history and pregnancy and neonatal outcome. A transvaginal three-dimensional (3D) ultrasound examination was performed in all cases and 15 cases underwent MRI. To confirm the diagnosis, postnatal MRI, transfontanellar ultrasound or autopsy were available in all cases.

RESULTS

Among the 19 cases reviewed, referral indications were: suspicion of vermian abnormality in 11 (58%) cases and other non-central nervous system anomaly in eight (42%) cases. Sonographically, all cases showed the following three signs: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. On 3D ultrasound, the upper wall of the cyst was clearly visible in 11/19 cases, with choroid plexuses on the superolateral margin of the cyst roof. On follow-up, the BPC had disappeared by 24-26 gestational weeks in six of the 11 cases which did not undergo termination of pregnancy (TOP), and remained unaltered until birth in the other five cases. There were associated anomalies in eight (42%) cases, in five of which this consisted of or included congenital heart disease. Karyotype was available in 14 cases, two of which were abnormal (both trisomy 21). Regarding pregnancy outcome, there were eight (42%) TOPs, two (10%) neonatal deaths and nine (48%) survivors. One neonate, in whom the BPC had disappeared by the time of birth, had obstructive hydrocephaly confirmed. Another neonate was diagnosed with Down syndrome after birth. Excluding the Down syndrome baby, neurodevelopmental outcome was normal at the time of writing in all eight cases.

CONCLUSIONS

Based on our analysis of ultrasound features, we propose that for BPC to be diagnosed in a fetus the following three criteria should be fulfilled: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. Furthermore, we found that BPC can undergo delayed fenestration at 24-26 weeks in more than 50% of cases. Finally, it seems that BPC shows a risk of association with extracardiac anomalies (heart defects in particular) and, to a lesser extent, trisomy 21.

Temporal and spatial regulation of interneuron distribution in the developing cerebral cortex--an in vitro study

GABAergic interneurons are local circuit cells that control the excitatory balance in most regions of the nervous system, particularly the cerebral cortex. Because they are integrated in every cortical module, we posed the question whether interneuronal precursors would display some topographic specificity between their origin at the ventral telencephalon and their cortical location after migration. If this was true, GABAergic cells would have to be provided with intrinsic features that would make them able to perform specific functional roles in each specific module. On the other hand, if no topography was found, one would conclude that inhibitory precursors would be functionally naive, being able to integrate anywhere in the cortex, with equal capacity of performing their functions. This issue was approached by use of organotypic cultures of wild mice embryonic slices, into which fragments of the ganglionic eminence taken from enhanced green fluorescent protein (eGFP) mice were implanted, observing the topographic location of both the implant and its destination. Despite the existence of different genetic domains in the ventricular zone of the medial ganglionic eminences (MGE), we found that cells originating in different regions spread in vitro all over the mediolateral axis of the developing cortical wall, independently of their sites of origin. Results favor the hypothesis that GABAergic precursors are functionally naive, integrating into modules irrespective of which cortical area they belong to.

Deficiency of mDia, an actin nucleator, disrupts integrity of neuroepithelium and causes periventricular dysplasia

During development of the central nervous system, the apical-basal polarity of neuroepithelial cells is critical for homeostasis of proliferation and differentiation of neural stem cells. While adherens junctions at the apical surface of neuroepithelial cells are important for maintaining the polarity, the molecular mechanism regulating integrity of these adherens junctions remains largely unknown. Given the importance of actin cytoskeleton in adherens junctions, we have analyzed the role of mDia, an actin nucleator and a Rho effector, in the integrity of the apical adherens junction. Here we show that mDia1 and mDia3 are expressed in the developing brain, and that mDia3 is concentrated in the apical surface of neuroepithelium. Mice deficient in both mDia1 and mDia3 develop periventricular dysplastic mass widespread throughout the developing brain, where neuroepithelial cell polarity is impaired with attenuated apical actin belts and loss of apical adherens junctions. In addition, electron microscopic analysis revealed abnormal shrinkage and apical membrane bulging of neuroepithelial cells in the remaining areas. Furthermore, perturbation of Rho, but not that of ROCK, causes loss of the apical actin belt and adherens junctions similarly to mDia-deficient mice. These results suggest that actin cytoskeleton regulated by Rho-mDia pathway is critical for the integrity of the adherens junctions and the polarity of neuroepithelial cells, and that loss of this signaling induces aberrant, ectopic proliferation and differentiation of neural stem cells.

[Outcome and prognosis of isolated mild fetal ventriculomegaly in uterus]

OBJECTIVE

To investigate outcome and prognosis of isolated mild fetal ventriculomegaly (IMV) of fetus in uterus.

METHODS

From Jan. 2006 to Dec. 2009, 18 200 singleton pregnancy women from 20 weeks gestation underwent prenatal ultrasonography examination in Department of Obstetrics and Gynecology, Second Affiliated Hospital of Wenzhou Medical College. One hundred and forty-eight women with IMV (transverse diameter of the atrium of the lateral ventricle measuring between 10 and 15 mm with no other abnormalities) were studied prospectively, which were divided into two groups: 99 women with transverse diameter of the lateral ventricle of 10 - 11 mm in group A and 49 women with transverse diameter lateral ventricle of 12 - 15 mm in group B. The changes of ventriculomegaly and the associated intracranial and extracranial anomalies were observed regularly every 2 or 4 weeks until delivery. The development of neurological system was also followed up.

RESULTS

(1) The overall incidence of IMV was 0.08% (148/18 200). The rate of bilateral ventriculomegaly were 20% (20/99) in group A and 51% (25/49) in group B, which reached statistical difference (P < 0.05). (2) Prognosis of fetus: 139 cases with 2 or more ultrasonographic examinations, IMV resolved throughout pregnancy in 41.7% (58/139), regressed in 7.9% (11/139), remained stable in 36.7% (51/139) and progressed in 13.7% (19/139). Five cases in group A and 11 cases in group B present progress, which reached significantly difference (P < 0.05). (3) One hundred and eleven cases infant were followed up for 5-12 months, the rate of psycho-motor developmental delay was 5.4% (6/111). The rate of neuro-developmental delay in progressed group (3/15) was higher than 2.5% (1/40) in resolved group, 0 (0/8) in regressed group and 4.2% (2/48) in remained stable group, which reached significantly difference (P < 0.05).

CONCLUSIONS

About 85% of cases of IMV resolved, regressed or remained stable in utero would exhibited good prognosis. IMV with a transverse atrial size ≥ 12 mm or progression in utero was usually associated with a poor prognosis, which should be observed carefully.

[Pathomorphology of congenital ventriculomegaly]

The paper gives the results of a morphological investigation using ventricular system embedding, organometry, light and electron microscopies, histostereometry and immunohistohemistry of brains from 50 fetuses and neonatal infants of 22-27 weeks gestation. The comprehensive investigations revealed the morphological features of intrauterinally acquired ventriculomegaly, which reflect tissue immaturity of the parenchyma and the vascular component of the brain.

Heterogeneity in ventricular zone neural precursors contributes to neuronal fate diversity in the postnatal neocortex

The recent discovery of short neural precursors (SNPs) in the murine neocortical ventricular zone (VZ) challenges the widely held view that radial glial cells (RGCs) are the sole occupants of this germinal compartment and suggests that precursor variety is an important factor of brain development. Here, we use in utero electroporation and genetic fate mapping to show that SNPs and RGCs cohabit the VZ but display different cell cycle kinetics and generate phenotypically different progeny. In addition, we find that RGC progeny undergo additional rounds of cell division as intermediate progenitor cells (IPCs), whereas SNP progeny generally produce postmitotic neurons directly from the VZ. By clearly defining SNPs as bona fide VZ residents, separate from both RGCs and IPCs, and uncovering their unique proliferative and lineage properties, these results demonstrate how individual neural precursor groups in the embryonic rodent VZ create diversity in the overlying neocortex.

Counseling in isolated mild fetal ventriculomegaly

In this Review we aim to provide up-to-date and evidence-based answers to the common questions regarding the diagnosis of isolated mild fetal ventriculomegaly (VM). A literature search was performed to identify all reports of antenatal VM in the English language literature. In addition, reference lists of articles identified using the search were scrutinized to further identify relevant articles. Fetal mild VM is commonly defined as a ventricular atrial width of 10.0-15.0 mm, and it is considered isolated if there are no associated ultrasound abnormalities. There is no good evidence to suggest that the width of the ventricular atria contributes to the risk of neurodevelopmental outcome in fetuses with mild VM. The most important prognostic factors are the association with other abnormalities that escape early detection and the progression of ventricular dilatation, which are reported to occur in about 13% and 16% of cases, respectively. Most infants with a prenatal diagnosis of isolated mild VM have normal neurological development at least in infancy. The rate of abnormal or delayed neurodevelopment in infancy is about 11%, and it is unclear whether this is higher than in the general population. Furthermore, the number of infants that develop a real handicap is unknown. There are limitations of existing studies of mild VM. Although they address many of the relevant questions regarding the prognosis and management of fetal isolated mild VM, there is a lack of good-quality postnatal follow-up studies. The resulting uncertainties make antenatal counseling for this abnormality difficult.

High-frequency chirp ultrasound imaging with an annular array for ophthalmologic and small-animal imaging

High-frequency ultrasound (HFU, >20 MHz) is an attractive means of obtaining fine-resolution images of biological tissues for ophthalmologic, dermatological and small-animal imaging applications. Even with current improvements in circuit designs and high-frequency equipment, HFU has two inherent limitations. First, HFU images have a limited depth-of-field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU is usually limited to shallow imaging because of the significant attenuation in most tissues. In a previous study, a five-element annular array with a 17-MHz center frequency was excited using chirp-coded signals, and a synthetic-focusing algorithm was used to extend the DOF and increase penetration depth. In the present study, a similar approach with two different five-element annular arrays operating near a center frequency of 35 MHz is implemented and validated. Following validation studies, the chirp-imaging methods were applied to imaging vitreous-hemorrhage-mimicking phantoms and mouse embryos. Images of the vitreous phantom showed increased sensitivity using the chirp method compared with a standard monocycle imaging method, and blood droplets could be visualized 4mm deeper into the phantom. Three-dimensional datasets of 12.5-day-old mouse embryo heads were acquired in utero using chirp and conventional excitations. Images were formed and brain ventricles were segmented and reconstructed in three dimensions. The brain ventricle volumes for the monocycle excitation exhibited artifacts that were not apparent on the chirp-based dataset reconstruction.

Normal sonographic development of the central nervous system from the second trimester onwards using 2D, 3D and transvaginal sonography

The developmental changes of the fetal central nervous system (CNS) during the second and third trimesters, specifically the brain, relate mostly to changes in size. However, other changes do occur in the fetal brain during the second and third trimester such as: the union of the cerebellar hemispheres, development of the corpus callosum (CC), and increasing complexity of the cerebral cortex. These changes follow a well-defined developmental timeline recognizable by sonography. The fetal neuroscan can be divided into a 'basic scan' which is performed transabdominally and a 'targeted Exam or neurosonogram' which uses a multiplanar approach, which preferably should be performed transvaginally. During the 'basic scan', several brain structures are imaged in addition to obtaining important biometric measurements. The 'neurosonogram' is a more extensive or detailed fetal study during which the emphasis is on the addition of coronal and sagittal planes. The easiest way to obtain these planes, if the fetus is in a cephalic presentation, is the transvaginal route. Three-dimensional (3D) sonography should, if possible, be performed transvaginally using the multiplanar approach. An added benefit of 3D sonography is the ability to display and render the volume in a variety of ways which may enhance the detection of pathology.

Fetal cerebral ventricular pointing as a marker of spina bifida: incidence and observational agreement

OBJECTIVE

Occipital cerebral ventricular pointing is a promising intracranial marker for spina bifida. We sought to determine (1) the incidence of pointing in fetuses with and without spina bifida and (2) inter-observer and intraobserver agreement for visualizing pointing.

METHODS

Second-trimester transverse axial images of the lateral cerebral ventricles from an equal number of affected and unaffected fetuses were independently reviewed in a blinded fashion by 2 examiners.

RESULTS

Sixty-two fetuses (31 with isolated spina bifida and 31 without) had sonographic examinations at 19.2+/-1.3 weeks (mean+/-SD). Pointing was present in 77.3% of fetuses with spina bifida and 15% of those without by the first examiner and in 78.3% of fetuses with spina bifida and 10% of those without by the second examiner. Interobserver and intraobserver agreement were substantial (kappa=0.69 and 0.78, respectively).

CONCLUSIONS

Ventricular pointing is a highly agreed-on finding that is substantially associated with but not pathognomonic for fetal spina bifida.

Navigating neocortical neurogenesis and neuronal specification: a positional information system encoded by neurogenetic gradients

The projection neurons of the neocortex are produced in the pseudostratified ventricular epithelium (PVE) lining the embryonic lateral ventricles. Over a 7 d period in mouse, these neurons arise in an overlapping layer VI-to-II sequence and in an anterolateral to posteromedial gradient [the transverse neurogenetic gradient (TNG)]. At any time in the 7 d neurogenetic interval, a given PVE cell must know what class of precursor cell or neuron to form next. How this information is encoded in the PVE is not known. With comparative experiments in wild-type and double-transgenic mice, overexpressing the cell cycle inhibitor p27(Kip1), we show that a gradient of expression of Lhx2 (inferred from its mRNA levels), a LIM homeodomain transcription factor, together with a gradient in duration of the G1 phase of the cell cycle (T(G1)), are sufficient to specify a positional mapping system that informs the PVE cell what class of neuron to produce next. Lhx2 likely is representative of an entire class of transcription factors expressed along the TNG. This mapping system consisting of a combination of signals from two different sources is a novel perspective on the source of positional information for neuronal specification in the developing CNS.

Delineation of multiple subpallial progenitor domains by the combinatorial expression of transcriptional codes

The mammalian telencephalon is considered the most complex of all biological structures. It comprises a large number of functionally and morphologically distinct types of neurons that coordinately control most aspects of cognition and behavior. The subpallium, for example, not only gives rise to multiple neuronal types that form the basal ganglia and parts of the amygdala and septum but also is the origin of an astonishing diversity of cortical interneurons. Despite our detailed knowledge on the molecular, morphological, and physiological properties of most of these neuronal populations, the mechanisms underlying their generation are still poorly understood. Here, we comprehensively analyzed the expression patterns of several transcription factors in the ventricular zone of the developing subpallium in the mouse to generate a detailed molecular map of the different progenitor domains present in this region. Our study demonstrates that the ventricular zone of the mouse subpallium contains at least 18 domains that are uniquely defined by the combinatorial expression of several transcription factors. Furthermore, the results of microtransplantation experiments in vivo corroborate that anatomically defined regions of the mouse subpallium, such as the medial ganglionic eminence, can be subdivided into functionally distinct domains.

Subventricular zone stem cells are heterogeneous with respect to their embryonic origins and neurogenic fates in the adult olfactory bulb

We determined the embryonic origins of adult forebrain subventricular zone (SVZ) stem cells by Cre-lox fate mapping in transgenic mice. We found that all parts of the telencephalic neuroepithelium, including the medial ganglionic eminence and lateral ganglionic eminence (LGE) and the cerebral cortex, contribute multipotent, self-renewing stem cells to the adult SVZ. Descendants of the embryonic LGE and cortex settle in ventral and dorsal aspects of the dorsolateral SVZ, respectively. Both populations contribute new (5-bromo-2'-deoxyuridine-labeled) tyrosine hydroxylase- and calretinin-positive interneurons to the adult olfactory bulb. However, calbindin-positive interneurons in the olfactory glomeruli were generated exclusively by LGE-derived stem cells. Thus, different SVZ stem cells have different embryonic origins, colonize different parts of the SVZ, and generate different neuronal progeny, suggesting that some aspects of embryonic patterning are preserved in the adult SVZ. This could have important implications for the design of endogenous stem cell-based therapies in the future.

Changes in echogenicity in the fetal brain: a prevalence study in fetuses at risk for preterm delivery

OBJECTIVES

To study the incidence of echodensities in the periventricular white matter, ventricular system, basal ganglia and thalamus of the brain in fetuses at risk for preterm delivery.

METHODS

This was a prospective study of 124 fetuses with a gestational age between 26 and 34 weeks in pregnancies affected by either pregnancy-induced hypertensive disorders or preterm labor. Transvaginal ultrasound examination of the fetal brain in coronal and sagittal planes was performed weekly until delivery and the neonatal brain was examined within 24 h after delivery.

RESULTS

In 66% of all fetuses, echodensities were found in one or more areas of the brain. They were present in the periventricular area in 52% of cases, the intraventricular area in 18% and in the basal ganglia and thalamus area in 28%. Changes in echogenicity were seen throughout the entire gestational-age period studied. Of the periventricular echodensities that exceeded in echodensity that of the choroid plexus, at least 50% persisted after delivery; at least 38% of the intraventricular echodensities and at least 32% of the basal ganglia and thalamus echodensities persisted after delivery.

CONCLUSIONS

In high-risk fetuses, echodensities are a frequent finding in several areas in the brain. How far these echodensities are related to future outcome of the infant needs to be investigated.

Foetal brain development in offspring of women with psychosis

Cerebral ventricular enlargement and reduced cortical volume are correlates of chronic schizophrenia. We investigated whether genetic risk for psychosis related to differences in foetal brain development as measured by prenatal ultrasonography. Routine foetal cerebral measures at 19-23 weeks of gestation were compared between the offspring of 35 women with a history of psychosis and 105 control women matched for gestational age. Overall, no significant differences were found between the high-risk and control groups. There was a non-significant trend in the adjusted analysis towards increased lateral ventricular width in the offspring of mothers with psychosis.

Cell migration: catapulting neurons from the ventricular zone?

In the developing vertebrate brain, newly born neurons migrate away from the proliferative zones. A new paper suggests that the initial phase of this migration may be propelled by the mechanical properties of the new neurons' processes rather than more conventional mechanisms of cell migration.

[Clinical study on fetal encephalic fluid]

OBJECTIVE

To discuss the clinical significance of fetal encephalic accumulated fluid revealed by prenatal ultrasonography.

METHODS

Prenatal ultrasonography was performed on 8426 women at more than 20 weeks' gestation. Totally 150 women with fetal encephalic accumulated fluid more than 5 mm were included in this study. The changes of fetal encephalic accumulated fluid and the associated anomalies were observed regularly every 2 weeks until delivery. The live infants were followed up regularly.

RESULTS

The incidence of fetal encephalic fluid was 1.8%, including 72 cases with fluid in the fetal anterior or posterior cornu of unilateral ventricle, 46 cases with accumulated fluid in fetal posterior fossa, 32 cases with fluid in more than 2 sites. Generally, the accumulated fluid in fetal encephalus was first diagnosed at 17 - 40 gestational weeks, with a median of (26 +/- 5) weeks. Most of them were found between 29 - 32 gestational weeks (63 cases, 42.0%), and the maximum amount of accumulated fluid was also found between 29 - 32 weeks (70 cases, 46.7%). Spontaneous regression of intracranial fluid could be seen in 111 fetuses (74.0%). The period of fluid regression ranged from 29 to 40 weeks of gestation, of which the average gestational week was (36 +/- 2) weeks. Additionally, the most frequent period of regression was in the first two thirds of the three trimesters of pregnancy. The incidence of defected infants was 3.8%, 10.2% and 67.4%, respectively, when the amount of accumulated fluid was less than 10 mm, 10 - 14 mm and more than 15 mm. And the accumulated fluid in more than 2 sites was also a risk factor of defected fetuses, with an incidence of 60.0%.

CONCLUSIONS

Most cases could be diagnosed between 29 - 32 gestational weeks, and the maximum amount of accumulated fluid is also observed in this period. The more fluid in fetal encephalus, the more sites the fluid distributed in, the more defected fetuses or infants would be observed. So in cases of more than 15 mm of fluid, or accumulated fluid in more than 2 sites, anomalies should be observed extremely carefully.

Fetal intracranial hemorrhage (fetal stroke): report of four antenatally diagnosed cases and review of the literature

OBJECTIVE

Neonatal intracranial hemorrhage (ICH) has been estimated to be high in premature infants, occurring in approximately 40% of infants of less than 32 weeks' gestation. However, the true incidence of ICH in utero has not been determined. We present our experience with four cases of fetal ICH (fetal stroke), which was detected prenatally by ultrasonography (US).

MATERIALS AND METHODS

Four cases of fetal ICH were identified over a 2-year period at the prenatal unit of Taichung Veterans General Hospital, Taiwan. Prenatal and neonatal sonograms, computed tomography (CT) scan or magnetic resonance imaging (MRI), medical records, and the clinical course were assessed retrospectively. In each case, a series of initial and follow-up obstetric sonograms were available. Fetal stroke was recognized by several sonographic features: irregular echogenic brain mass, intraventricular echogenic foci or periventricular echodensities; ventriculomegaly; and posthemorrhagic hydrocephalus (PHH). A detailed investigation for possible etiology of fetal ICH was performed in all cases.

RESULTS

Transabdominal US showed hyperechoic lesions in the lateral ventricle and ventriculomegaly in three of the four fetuses, and a massive intraparenchymal hemorrhage in the remaining one. Three fetuses were born vaginally and one by cesarean section due to an enlarged head circumference. Abnormal nonstress tests and abnormal flow velocity waveforms in the umbilical and middle cerebral arteries were present in two cases. Intrapartum fetal death and neonatal death occurred in the first two cases associated with maternal preeclampsia at 31 and 27 weeks, respectively. In the remaining two infants, the one in case 3 underwent ventriculoperitoneal shunting, which developed normally at the age of 18 months. The other infant in case 4 had PHH after suspicious choroids plexus hemorrhage, and the detailed information regarding the cause of neonatal death was not available.

CONCLUSION

This small series demonstrate that an antenatal diagnosis of fetal stroke with intraventricular hemorrhage Grades III and IV or with brain parenchymal involvement appears to be associated with poor neurologic outcome. Due to the significant neonatal neurologic impairment and potential medicolegal implications of antepartum fetal ICH, it follows that obstetricians and sonographers should be familiar with predisposing factors and typical diagnostic imaging findings of rare in utero ICH events.

MRI of the foetal brain

Ultrasound examinations for foetal brain abnormalities have been a part of the routine antenatal screening programme in the UK for many years. In utero brain magnetic resonance imaging (MRI) is now being used increasingly successfully to clarify abnormal ultrasound findings, often resulting in a change of diagnosis or treatment plan. Interpretation requires an understanding of foetal brain development, malformations and acquired diseases. In this paper we will outline the technique of foetal MRI, relevant aspects of brain development and provide illustrated examples of foetal brain pathology.

Prenatal diagnosis of Dandy-Walker malformation associated with distal limb deficiencies

We report the perinatal findings of a 23 gestational-week fetus with Dandy-Walker malformation (DWM), ventriculomegaly, symmetrical transverse limb deficiencies, hypertelorism, frontal bossing, low-set ears, and a depressed nasal bridge. The karyotype was 46,XX. We believe that this combination is significant. Concomitant DWM and symmetrical distal limb deficiencies may represent a new entity that awaits more new cases for further delineation.

Are routine cranial ultrasounds necessary in premature infants greater than 30 weeks gestation?

The purpose of this study was to validate the recommendation of the American Academy of Neurology and the Child Neurology Society that screening cranial ultrasonography be performed routinely on all infants of less than 30 weeks gestation at 7 to 14 days of age and again between 36 and 40 weeks postmenstrual age, and, by using this practice parameter, to determine the number of babies with a clinically significant abnormal screening cranial ultrasound (US) who would otherwise have been missed. A retrospective study of 486 infants of 30 to 33 weeks gestation born January 1, 1999 to June 30, 2004 was done. All had screening cranial ultrasounds. Grade III and/or grade IV intraventricular hemorrhage (IVH) occurred in 4 (0.8%) infants of 30 to 31 weeks gestation. Infants with significant IVH had either risk factors for brain injury or symptoms that would eventually warrant US during their hospitalization. Seven (1.4%) infants had periventricular leukomalacia (PVL). All infants with a final diagnosis of PVL had pre- and/or perinatal risk factors associated with PVL. There was a significant trend toward fewer abnormal cranial ultrasounds from 30 to 33 weeks gestation (p=0.04). Our study supports the recommendation by the American Academy of Neurology and the Child Neurology Society that screening US can be limited but suggests that the gestational age cut off should be 30 weeks or less.

In utero magnetic resonance of non-isolated ventriculomegaly: Does ventricular size or morphology reflect pathology?

AIM

To confirm whether ventricular size or morphology reflects the underlying pathology in foetuses referred with a diagnosis of possible ventriculomegaly (Vm) and central nervous system (CNS) pathology.

METHODS

Retrospective analysis of 40 in utero magnetic resonance (MR) examinations was undertaken. Ventricular size was measured on axial sections by two observers, and morphology was agreed by consensus. Results were analysed according to gestational age at referral, degree of Vm (mild 10-15 mm, moderate/severe >15 mm) and morphology.

RESULTS

Nine cases had no Vm (mean gestational age 23.6 weeks, range 19-33), 17 had mild Vm (mean age 23.9 weeks, range 20-31), and 14 had moderate/severe Vm (mean age 25.9 weeks, range 20-35). All groups had a mix of morphology and pathology. Eighteen suspected cases of spina bifida were referred and 17 confirmed (mean age 22.6 weeks, range 19-30) using MR. The morphology was mixed, five cases (27.8%) had an angular appearance (this morphology was only seen in cases with spina bifida). Fourteen cases (77.8%) had Vm (eight mild, six severe). Of the thirteen cases of agenesis of the corpus callosum (ACC) suspected on ultrasound, seven were confirmed using MR (mean age 26.5 weeks, range 20-35). Of those seven cases with ACC confirmed on MR, and three additional cases only detected by in utero MR, five had colpocephaly, seven had Vm (four mild, three severe).

CONCLUSION

Severity of Vm did not reflect the type, or presence, of underlying pathology. Morphology appears an indicator of pathology. Angular ventricles should initiate a search for spinal defects. Colpocephaly may indicate ACC.

40-MHz annular array imaging of mouse embryos

Ultrasound biomicroscopy (UBM) has emerged as an important in vivo imaging approach for analyzing normal and genetically engineered mouse embryos. Current UBM systems use fixed-focus transducers, which are limited in depth-of-focus. Depending on the gestational age of the embryo, regions-of-interest in the image can extend well beyond the depth-of-focus for a fixed-focus transducer. This shortcoming makes it particularly problematic to analyze 3-D data sets and to generate accurate volumetric renderings of the mouse embryonic anatomy. To address this problem, we have developed a five-element, 40-MHz annular array transducer and a computer-controlled system to acquire and reconstruct fixed- and array-focused images of mouse embryos. Both qualitative and quantitative comparisons showed significant improvement with array-focusing, including an increase of 3 to 9 dB in signal-to-noise ratio and an increase of at least 2.5 mm in depth-of-focus. Volumetric-rendered images of brain ventricles demonstrated the clear superiority of array-focusing for 3-D analysis of mouse embryonic anatomy.

Fetal Head Biometry Assessed by Fetal Magnetic Resonance Imaging following in utero Myelomeningocele Repair

OBJECTIVE

To examine the impact of fetal myelomeningocele (MMC) repair on fetal head biometry and cerebrospinal fluid (CSF) spaces assessed by magnetic resonance imaging (MR) studies.

STUDY DESIGN

Axial measurements of intracranial structures were taken at defined anatomical landmarks. Pre- and postnatal head biometry data and CSF spaces obtained from in utero repaired MMC fetuses (n = 22) were compared to the pre- and postnatal measurements of MMC patients that underwent standard neurosurgical MMC repair after birth (n = 16) and a cohort of age-matched control patients (prenatal, n = 52; postnatal, n = 9).

RESULTS

In fetuses with MMC, initial MR scans showed an almost complete absence of supratentorial and posterior fossa CSF spaces. No differences in postnatal CSF spaces were found between controls and prenatally repaired MMC newborns. In fetuses with postnatal MMC repair, CSF spaces remained significantly reduced (p < 0.0001). The mean ventricular diameter (VD) increase in the postnatal repaired MMC group was significantly higher compared to the mean percentage of VD increase in the fetal repaired MMC group (6.4 vs. 4.2 mm; p = 0.02). Pre- and postnatal brain thickness measurements were significantly reduced in both MMC populations compared to age-matched normal values (p < 0.0001). In contrast to postnatally repaired patients, in utero repair fetuses showed significant reversal of hindbrain herniation and normalization of the posterior fossa CSF spaces.

CONCLUSION

Mid-gestational repair of MMC promotes normalization of extra-axial CSF spaces. Due to progressive ventriculomegaly, brain thickness remains decreased in both prenatal repaired and age-matched non-repaired MMC patients when compared to age-matched normal values. Restoration of CSF volume in the posterior fossa after in utero repair is indicative of reversal of hindbrain herniation.

The amygdaloid complex and the medial and lateral ventricular eminences in staged human embryos

The amygdaloid complex was investigated in 36 serially sectioned staged human embryos, including 20 impregnated with silver. This is the first such account based on graphic reconstructions, 28 of which were prepared. Significant findings in the human include the following. (1) The medial (first) and (then) lateral ventricular eminences arise independently at stages 14 and 15, and unite only at stage 18 to form the floor of the lateral ventricle. (2) The future amygdaloid region is discernible at stage 14 and the amygdaloid primordium at stage 15. (3) The anterior amygdaloid area and the corticomedial and basolateral complexes appear at stage 16. (4) These three major divisions arise initially from the medial ventricular eminence, which is diencephalic. (5) Individual nuclei begin to be detectable at stages 17-21, the central nucleus at stage 23 and the lateral nucleus shortly thereafter. (6) The ontogenetic findings in the human embryonic period accord best with the classification used by Humphrey. (7) The lateral eminence, which is telencephalic, contributes to the cortical nucleus at stage 18. (8) The primordial plexiform layer develops independently of the cortical nucleus. (9) Spatial changes of the nuclei within the amygdaloid complex and of the complex as a whole begin in the embryonic period and continue during the fetal period, during the early part of which the definitive amygdaloid topography in relation to the corpus striatum is attained. (10) The developing amygdaloid nuclei are closely related to the medial forebrain bundle, which has already appeared in stage 15. (11) Fibre connections develop successively between the amygdaloid nuclei and the septal, hippocampal and diencephalic formations, constituting the beginning of the limbic system before the end of the embryonic period. Although the nucleus accumbens also appears relatively early (stage 19), connections between it and the amygdaloid complex are not evident during the embryonic period. (12) Influence of the olfactory bulb and tubercle on initial amygdaloid development, as postulated for rodents, is unlikely in the human. The findings exemplify the necessity of beginning developmental studies with the embryonic period proper.

Cortical Ventricular Zone Progenitors and Their Progeny Maintain Spatial Relationships and Radial Patterning during Preplate Development Indicating an Early Protomap

The graded expression of transcription factors by progenitors in the ventricular zone (VZ) confers positional or area identity that is inherited by subplate (SP) neurons and governs their expression of guidance molecules for thalamocortical axons and other properties required for cortical area specification. This mechanism would be most efficient if VZ progenitors and their SP neuronal progeny maintain neighbor relationships during the generation of the preplate (PP), the precursor of the SP. Therefore, a major goal of this study is to determine whether progenitors in the cortical VZ and their progeny maintain neighbor relationships during the genesis of the neocortical PP. We used time-lapse video microscopy to follow the movements of VZ progenitors and the radial movement of their progeny and distribution in the PP in whole-mount or slice cortical explants from embryonic rats at stages when PP neurons are generated. We show that labeled VZ cells proliferate and have a strong tendency to retain neighbor relationships within the VZ and that their neuronal progeny move superficially along a radial column to form the overlying PP; during this process, their neuronal progeny also retain neighbor relationships and thereby form the PP in spatial register with the VZ progenitors that generate them. This behavior differs from that reported at later stages of cortical development, when cortical plate (CP) neurons are generated, and considerable dispersion is evident among both cells within the VZ and neuronal progeny as they migrate from the VZ to the CP. However, our findings show that at the early stage of cortical development, when PP/SP neurons are generated, the VZ is, at a cellular level, a "protomap" of the PP/SP.