Systematic review and meta-analysis of isolated posterior fossa malformations on prenatal imaging (part 2): neurodevelopmental outcome

Prenatal Diagnosis and Clinical Outcomes of Isolated Mega Cisterna Magna

Objective: The study aimed to investigate the clinical outcomes of fetuses diagnosed with isolated mega cisterna magna in utero. Methods: A multicenter retrospective cohort study was conducted across 18 university hospitals from 2010 to 2019. Cases diagnosed with isolated mega cisterna magna, defined as a cisterna magna >10 mm with a normal cerebellar vermis and no cystic dilation of the fourth ventricle, were included. Cases with other central nervous system (CNS) anomalies, extra-central nervous system anomalies, chromosomal abnormalities, or congenital infections were excluded. Maternal demographics, prenatal findings, delivery outcomes, and postnatal outcomes were analyzed. Results: The mean gestational age at initial diagnosis was 28.6 ± 3.9 weeks, and the mean anteroposterior diameter of the cisterna magna was 12.5 ± 3.2 mm. Of the 71 cases initially assessed, 48 (67.6%) showed self-regression in utero. Postnatally, 13 cases (18.3%) had persistent isolated mega cisterna magna, whereas 10 cases (14.1%) were diagnosed with other central nervous system anomalies. Among the persistent isolated mega cisterna magna cases, one child exhibited delayed neurodevelopment. There was a higher incidence of isolated mega cisterna magna in male fetuses, which exhibited a significantly larger mean cisterna magna diameter compared with female fetuses (P = .045). Conclusion: Male fetuses exhibited a higher incidence of isolated mega cisterna magna compared with female fetuses and had larger anteroposterior diameters of the cisterna magna. The study demonstrated favorable neurodevelopmental outcomes associated with isolated mega cisterna magna, with self-regression observed in two-thirds of the cases. However, consecutive prenatal and postnatal evaluations for additional central nervous system or extra-central nervous system malformations need to be performed, considering the differences between prenatal and postnatal diagnoses.

Ultrasonographic evaluation of fetal posterior fossa anomalies: Six years experience of a tertiary center

PURPOSE

The aim of this study is to reveal ultrasonographic features, associated anomalies and genetic errors in posterior fossa anomalies. As secondary aim postnatal outcomes of the cases were reviewed.

METHODS

We conducted a retrospective case series from 2018 to 2024 involving fetuses with posterior fossa anomalies (PFA). Terminated cases confirmed by radiologic and postmortem pathologic findings and cases confirmed by postnatal clinical findings were included in the study.

RESULTS

A total of 138 cases were included. In 81 (59%) cases there were multipl anomalies including cranial anomalies other than posterior fossa in 31 (22%) and non-central nerve system anomalies in 69 (50%) cases. Of the 94 cases born, 28 (20%) died within a median of 2 months, within 1.5 years at the latest. Of the 66 (48%) cases still living, 30 (22%) have neurodevelopmental delay in Denver II Turkish standardized test.

CONCLUSIONS

It is crucial to have accurate and standardized prenatal classification and a multidisciplinary approach in fetuses with PFA. Specific ultrasonographic findings may be diagnostic especially where fetal MRI is not always available. We offer "arrow sign" to be tested whether it is accurate to diagnose Joubert syndrome by ultrasonography.

Optimal prenatal genetic diagnostic approach for posterior fossa malformation: karyotyping, copy number variant testing, or whole-exome sequencing?

BACKGROUND

Posterior fossa malformation (PFM) is a relatively uncommon prenatal brain malformation. Genetic diagnostic approaches, including chromosome karyotyping, copy number variant (CNV) testing, and whole-exome sequencing (WES), have been applied in several cases of fetal structural malformations. However, the clinical value of appropriate genetic diagnostic approaches for different types of PFMs has not been confirmed. Therefore, in this study, we aimed to analyze the value of different combined genetic diagnostic approaches for various types of fetal PFMs.

METHODS

This retrospective study was conducted at Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital. Fifty-one pregnant women diagnosed with fetal PFMs who underwent genetic testing in our hospital from January 1, 2017 to December 31, 2022 were enrolled; women with an isolated enlarged cisterna magna were excluded. All participants were categorized into two groups according to the presence of other abnormalities: isolated and non-isolated PFMs groups. Different combined approaches, including karyotype analysis, CNV testing, and trio-based WES, were used for genetic analysis. The detection rates of karyotype analysis, CNV testing, and WES were measured in the isolated and non-isolated groups.

RESULTS

In isolated PFMs, pathogenic/likely pathogenic (P/LP) CNVs were detected in four cases (36.36%, 4/11), whereas G-banding karyotyping and WES showed negative results. In non-isolated PFMs, a sequential genetic approach showed a detection rate of 47.5% (19/40); karyotyping revealed aneuploidies in five cases (16.67%, 5/30), CNV testing showed P/LP CNVs in five cases (16.13%, 5/31), and WES identified P/LP variants (in genes CEP20, TMEM67, OFD1, PTPN11, ARID1A, and SMARCA4) in nine cases (40.91%, 9/22). WES showed a detection rate of 83.33% (5/6) in fetuses with Joubert syndrome. Only six patients (five with Blake's pouch cyst and one with unilateral cerebellar hemisphere dysplasia) survived.

CONCLUSIONS

We recommend CNV testing for fetuses with isolated PFMs. A sequential genetic approach (karyotyping, CNV testing, and WES) may be beneficial in fetuses with non-isolated PFMs. Particularly, we recommend WES as the first-line genetic diagnostic tool for Joubert syndrome.

Advancing fetal diagnosis and prognostication using comprehensive prenatal phenotyping and genetic testing

Prenatal diagnoses of congenital malformations have increased significantly in recent years with use of high-resolution prenatal imaging. Despite more precise radiological diagnoses, discussions with expectant parents remain challenging because congenital malformations are associated with a wide spectrum of outcomes. Comprehensive prenatal genetic testing has become an essential tool that improves the accuracy of prognostication. Testing strategies include chromosomal microarray, exome sequencing, and genome sequencing. The diagnostic yield varies depending on the specific malformations, severity of the abnormalities, and multi-organ involvement. The utility of prenatal genetic diagnosis includes increased diagnostic clarity for clinicians and families, informed pregnancy decision-making, neonatal care planning, and reproductive planning. Turnaround time for results of comprehensive genetic testing remains a barrier, especially for parents that are decision-making, although this has improved over time. Uncertainty inherent to many genetic testing results is a challenge. Appropriate genetic counseling is essential for parents to understand the diagnosis and prognosis and to make informed decisions. Recent research has investigated the yield of exome or genome sequencing in structurally normal fetuses, both with non-invasive screening methods and invasive diagnostic testing; the prenatal diagnostic community must evaluate and analyze the significant ethical considerations associated with this practice prior to generalizing its use. IMPACT: Reviews available genetic testing options during the prenatal period in detail. Discusses the impact of prenatal genetic testing on care using case-based examples. Consolidates the current literature on the yield of genetic testing for prenatal diagnosis of congenital malformations.

Fetal and neonatal outcomes of posterior fossa anomalies: a retrospective cohort study

The primary aim of this study was to estimate the incidence of posterior fossa anomalies (PFA) and assess the associated outcomes in King Abdulaziz Medical City (KAMC), Riyadh. All fetuses diagnosed by prenatal ultrasound with PFA from 2017 to 2021 in KAMC were analyzed retrospectively. PFA included Dandy-Walker malformation (DWM), mega cisterna magna (MCM), Blake's pouch cyst (BPC), and isolated vermian hypoplasia (VH). The 65 cases of PFA were 41.5% DWM, 46.2% MCM, 10.8% VH, and 1.5% BPC. The annual incidence rates were 2.48, 2.64, 4.41, 8.75, and 1.71 per 1000 anatomy scans for 2017, 2018, 2019, 2020, and 2021, respectively. Infants with DWM appeared to have a higher proportion of associated central nervous system (CNS) abnormalities (70.4% vs. 39.5%; p-value = 0.014) and seizures than others (45% vs. 17.9%; p-value = 0.041). Ten patients with abnormal genetic testing showed a single gene mutation causing CNS abnormalities, including a pathogenic variant in MPL, C5orf42, ISPD, PDHA1, PNPLA8, JAM3, COL18A1, and a variant of uncertain significance in the PNPLA8 gene. Our result showed that the most common PFA is DWM and MCM. The autosomal recessive pathogenic mutation is the major cause of genetic disease in Saudi patients diagnosed with PFA.

Sleep deprivation from mid-gestation leads to impaired of motor coordination in young offspring mice with microglia activation in the cerebellar vermis

OBJECTIVE

To investigate the effects of mid-pregnancy sleep deprivation (SD) in C57BL/6 J mice on the motor coordination of the offspring and to explore the potential mechanism of microglia activation in the cerebellar vermis of the offspring involved in the induction of impaired motor coordination development.

METHODS

C57BL/6 J pregnant mice were randomly divided into the SD and control groups. SD was implemented by the multi-platform method from first day of the middle pregnancy (gestation day 8, GD8). At postnatal day 21 (PND21), we measured the development of motor behavior and collected cerebellar vermis tissues to observe the activation of microglia by H&E staining, the expression of microglia-specific markers ionized calcium-binding adaptor molecule-1 (Iba-1) and cluster of differentiation 68 (CD68) by immunohistochemical, and interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor -α (TNF-α) by real-time quantitative PCR (RT-qPCR).

RESULTS

In the offspring of SD group, comparing to the control group, the total time of passage and the reverse crawl distance in the balance beam test, and the frequency of falls from the suspension cord was increased; with lower max rotational speed and shorter duration in the rotarod experiment. Further, we found that the microglia of cerebellar vermis tissues emerged an amoeba-like activation. The mean gray value of Iba-1 was lower, the density of positive cells of CD68 and the expression levels of IL-6 and TNF-α were increased.

CONCLUSIONS

The motor coordination of offspring is impaired, accompanying a SD from mid-pregnancy, and the cerebellar vermis showed microglia activation and pro-inflammatory response. It suggested the adverse effects of SD from mid-gestation on the development of motor coordination through the inflammatory response in the cerebellar vermis of the offspring.

Speech and Language Delays Associated With New-Onset Seizures Revealing Dandy-Walker Variant

Dandy-Walker malformation or syndrome is a rare congenital deformity in which the cerebellar vermis is hypoplastic and upwardly rotated, the fourth ventricle enlarged, and the posterior fossa cystically dilated. It represents the most common type of posterior fossa malformations that are usually diagnosed before the age of one year old. We present a seven-year-old boy with a history of neonatal hypotonia and delayed walking, who presented with speech and language difficulties. His physical examination and cognitive tests were unremarkable. The patient's brain magnetic resonance imaging showed a partial defect of the inferior part of the cerebellar vermis and communication between a normal-sized cisterna magna and the fourth ventricle. There were no other coexisting central nervous system or systemic anomalies. This isolated inferior vermian hypoplasia was compatible with an uncommon variant of the Dandy-Walker syndrome. The aim of this report is to provide insight into the importance of implementing a pediatrician-psychiatrist collaboration in the clinical decision-making process of such developmental delay cases. What makes the present case further interesting are the new-onset unprovoked seizures that developed and recurred in the setting of such isolated and less severe posterior fossa anomaly, raising both diagnostic and therapeutic challenges.

Impact of choroid plexus size in prenatal diagnosis of normal and abnormal closure of fourth ventricle

OBJECTIVE

To assess the role of the choroid plexus (CP) of the fourth ventricle (4V) in fetuses with an open 4V and a normal cerebellar vermis.

METHODS

Two groups of patients were recruited in two fetal medicine referral centers. The prospectively collected control group included singleton pregnancies with a normal sonographic examination after first-trimester combined screening for chromosomal abnormalities and normal outcome, recruited in the period between 2019 and 2022. The study group was selected retrospectively by searching our databases to identify all cases with an isolated open 4V and normal anatomy and size of the cerebellar vermis. The inclusion criteria of the study group were: (1) gestational age between 20 and 22 weeks; (2) a brainstem-vermis angle ≥ 18° in the midsagittal plane with an otherwise normal cerebellum and vermis; (3) 4V-CP visible and seen separately from the vermis; (4) absence of other intra- and extracranial anomalies; and (5) available prenatal and/or postnatal magnetic resonance imaging (MRI) data.

RESULTS

In 169 cases of the control group, the 4V-CP was seen separately from the cerebellar vermis and was noticed to progressively fill the space caudal to the 4V, between the vermis and brainstem. From 12 to 22 weeks, the surface areas of the vermis and medial portion of the 4V-CP increased progressively with advancing gestation (P < 0.0001). Intra- and interobserver correlation analysis showed good reproducibility for the measurements. Among the cases with an open 4V and a normal vermis, it was retrospectively feasible to visualize the 4V-CP separately from the inferior part of the vermis in 41 fetuses. In five of these cases, the open 4V was due to a small CP. In all 41 fetuses, the diagnosis on MRI was isolated upward rotation of the cerebellar vermis, and no additional anomaly was found.

CONCLUSIONS

Closure of the 4V is dependent on the 4V-CP and not only the cerebellar vermis. In fact, a small CP may represent another cause of an open 4V. Therefore, separate visualization of the 4V-CP and cerebellar vermis is crucial to improve discrimination between the different causes of an open 4V at the anomaly scan and its clinical implications. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Modeling fetal cortical development by quantile regression for gestational age and head circumference: a prospective cross sectional study

OBJECTIVES

To develop charts for fetal brain cortical structures following a proposed standardized methodology and using quantile regression.

METHODS

Prospective cross-sectional study including 344 low-risk singleton pregnancies between 19 and 34 weeks of gestation. The depth of Sylvian (SF), Parieto-occipital (POF) and Calcarine fissures (CF) were measured on ultrasound images using a standardized technique and their changes were evaluated by quantile regression as a function of gestational age (GA) interval or head circumference (HC).

RESULTS

The measurements of SF, POF and CF depth significantly increased with gestation. Linear models better described the changes of cortical variables with GA and HC. When the fit of sulci depth with GA and HC were compared, a close relationship was highlighted for the latter variable.

CONCLUSIONS

We provided prospective charts of fetal cortical development using quantile regression and following a strict standardized methodology These new charts may help in better identifying cases at higher risk of abnormal cortical neurodevelopment.

NID1-related autosomal dominant Dandy-Walker malformation with occipital cephalocele in three generations

The combination of Dandy-Walker malformation and occipital cephalocele is a rare autosomal dominant condition, known as ADDWOC, and caused by mutations in NID1 or LAMC1. We present a three-generation family with variable manifestations of Dandy-Walker malformation and occipital cephalocele. They all have normal psychomotor development and lack neurological manifestations. Mutation analysis revealed a likely pathogenic missense variant in NID1 (c.3336T > G, p.Asn1112Lys), affecting an amino acid residue crucial in the nidogen/laminin interaction.

Prenatal diagnosis of ultrasound soft markers in a single medical center of mainland China

BACKGROUND

There are a few studies on the chromosomal aberration of Ultrasound soft markers (USMs). The aim of this study was to determine the detection rate of clinically significant chromosomal abnormalities (CSCA) in fetuses with different USMs.

METHODS

This study included fetuses with USMs who underwent invasive prenatal diagnosis for karyotype and/or chromosomal microarray (CMA) by categorizing into two groups: a single USM (SUSM) and multiple USMs (MUSMs).

RESULTS

Of the 358 cases with USMs, CSCA occurred in 3.09% (8/259) and 8.08% (8/99) of the SUSM and MUSM groups, respectively (P < 0.05). Of 16 cases identified with CSCA, theoretically 68.75% (11/16) could be detected by karyotype, while 31.25% (5/16) could be recognized only by CMA. Among CSCA cases, the most frequent USM was an absent or hypoplastic nasal bone (62.5%, 10/16). In cases with negative karyotypes and/or CMA, follow-up results were available in 307 cases, including 292 term deliveries, 6 preterm deliveries, 8 terminations of pregnancy due to USMs, and 1 still birth.

CONCLUSION

MUSMs increased the risk of chromosomal abnormalities. An absent or hypoplastic nasal bone was the most clinically significant marker either alone or in combination with other USMs. Most of SUSM had a good prognosis.

Relative prevalence and outcome of fetal posterior fossa abnormality

AIM

To find out the relative incidence and outcome of posterior fossa abnormality (PFA) in terms of survival at birth until 2 years of age.

METHODS

We conducted a prospective study; all fetuses diagnosed with posterior fossa abnormality were followed-up. The outcome was observed with respect to survival, the presence of associated anomalies, the existence of developmental delay after a telephonic interview.

RESULTS

Out of 2703 children with congenital anomalies, 921 (34.1%) had a central nervous system defect; 76 cases of PFA were fully followed. Dandy-Walker malformation (DWM) was present in 50% (38/76), mega cisterna magna 18.4% (14/76), Blake pouch cyst 13.2% (10/76), vermian hypoplasia (VH) 13.2% (10/76) and arachnoid cyst 5.2% (4/76). The diagnosis was possible before 20 weeks in only 12 (15.8%) cases. The mean gestational age at delivery was 34.7 ± 6.7 weeks. Associated anomalies were seen in 35/76 (46.1%) cases. A total of 35/76 (46.1%) survived after 2 years; there was developmental delay in 9.2% of cases.

CONCLUSION

There is a large variation in the outcome of PFA depending upon the type of anomaly. Associated anomalies are common in VH and DWM, making their prognosis worse.

Fetal Neurology: From Prenatal Counseling to Postnatal Follow-Up

Brain abnormalities detected in fetal life are being increasingly recognized. Child neurologists are often involved in fetal consultations, and specific fetal neurology training has been implemented in many countries. Pediatric neurologists are asked to examine the data available and to contribute to the definition of the long-term outcomes. Ventriculomegaly, posterior fossa malformations, and agenesis/dysgenesis of corpus callosum are among the most common reasons for antenatal neurological consultations. Fetuses with central nervous system and extra-CNS anomalies should ideally be managed in secondary/tertiary hospitals where obstetricians who are experts in fetal medicine and pediatric specialists are available. Obstetricians play a critical role in screening, performing detailed neurosonography, and referring to other specialists for additional investigations. Clinical geneticists are frequently asked to propose diagnostic tests and counsel complex fetal malformations whose phenotypes may differ from those during postnatal life. Advances in fetal MRI and genetic investigations can support the specialists involved in counseling. Nevertheless, data interpretation can be challenging, and it requires a high level of expertise in a multidisciplinary setting. Postnatally, child neurologists should be part of an integrated multidisciplinary follow-up, together with neonatologists and pediatricians. The neurodevelopmental outcomes should be assessed at least up to school age. Children should be evaluated with formal tests of their gross motor, cognitive, language, fine motor/visuo-perceptual skills, and their behavior. In this perspective, fetal neurology can be regarded as the beginning of a long journey which continues with a prolonged, structured follow-up, support to the families, and transition to adult life. A review of the most common conditions is presented, along with the long-term outcomes and a proposal of the neurodevelopmental follow-up of children with CNS malformation which are diagnosed in uterus.

Should 3D volume assessment of the corpus callosum and cerebellar vermis be a part of a routine second trimester screening?

BACKGROUND

The majority of fetal structural defects can be detected in the second trimester, thus this is the main time for screening for structural defects. 3D imaging of the fetal brain does not create a common part of this screening.

METHODS

This prospective observational study was conducted at the Fetal Medicine Center of The Gynecological-Obstetrical Department of the University Hospital Olomouc in years 2017-2020. The study sample was 451 consecutively scanned morphologically normal fetuses attending for routine second trimester anatomical survey at 20-22 weeks of pregnancy. A transabdominal 3D ultrasound volume acquisition of fetal brain was obtained from an axial and sagittal plane using skull sutures as an acoustic window.

RESULTS

Both the corpus callosum (CC) and the vermis (VC) were detected in 51.7% of examinations in the sagittal plane, and in 31.7% in the axial plane. In 61.9% of the examinations, there was at least partial detection in both planes. Maternal BMI was found to be the only significant predictor of the quality of imaging in both planes.

CONCLUSION

3D acquisition of fetal brain images in the sagittal plane followed by manipulation of acquired volume was valuable in assessment of corpus callosum and cerebellar vermis. This allows reconstruction of the sagittal plane that can be difficult to obtain in 2D imaging.

Fetal Brain Development: Regulating Processes and Related Malformations

This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic–fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.

The Brainstem-Vermis and Brainstem-Tentorium Angles in the Fetus: A Study of Their Reproducibility by Fetal Magnetic Resonance Imaging and Their Evolution Along the Gestation

Aim

To assess the reproducibility of brainstem-vermis (BV) and brainstem-tentorium (BT) angles measured by fetal Magnetic Resonance Imaging (MRI) during second half of pregnancy in normal and abnormal fetuses. Secondly, to assess reproducibility of two alternative methodologies to measure the brainstem-tentorium angle (BT1 and BT2) proposed by our group that could be more reliable in fetuses with posterior fossa fluid collection (PFFC) anomalies. Finally, to describe the evolution of BV and BT angles along gestation in normal fetuses.

Methods

We conducted a cross-sectional study of BV and BT angles obtained by MRI performed at our center, in 22 fetuses with PFFC and 8 fetuses without PFFC to calculate both angles’ reproducibility and the correlation between them and the gestational age.

Results

We found good interobserver reproducibility for the BV, BT1 and BT2 angles (Intraclass correlation coefficient: 0.98; 0.89 and 0.88 for each of these angles, with p &lt; 0.001). In patients with PFFC the BT angle could not always be measured. BT angle presented a positive relationship with gestational age (p = 0.002) but BV angle stayed stable. The measurements of BV, BT1, and BT2 angles can be reliably performed by MRI with good interobserver reproducibility.

Conclusion

BV angle stays stable during pregnancy, whereas BT angle tends to augment with gestational age.

Regional brain development in fetuses with Dandy-Walker malformation: A volumetric fetal brain magnetic resonance imaging study

Dandy-Walker malformation (DWM) is a common prenatally diagnosed cerebellar malformation, characterized by cystic dilatation of the fourth ventricle, upward rotation of the hypoplastic vermis, and posterior fossa enlargement with torcular elevation. DWM is associated with a broad spectrum of neurodevelopmental abnormalities such as cognitive, motor, and behavioral impairments, which cannot be explained solely by cerebellar malformations. Notably, the pathogenesis of these symptoms remains poorly understood. This study investigated whether fetal structural developmental abnormalities in DWM extended beyond the posterior fossa to the cerebrum even in fetuses without apparent cerebral anomalies. Post-acquisition volumetric fetal magnetic resonance imaging (MRI) analysis was performed in 12 fetuses with DWM and 14 control fetuses. Growth trajectories of the volumes of the cortical plate, subcortical parenchyma, cerebellar hemispheres, and vermis between 18 and 33 weeks of gestation were compared. The median (interquartile range) gestational ages at the time of MRI were 22.4 (19.4-24.0) and 23.9 (20.6-29.2) weeks in the DWM and control groups, respectively (p = 0.269). Eight of the 12 fetuses with DWM presented with associated cerebral anomalies, including hydrocephalus (n = 3), cerebral ventriculomegaly (n = 3), and complete (n = 2) and partial (n = 2) agenesis of the corpus callosum (ACC); 7 presented with extracerebral abnormalities. Chromosomal abnormalities were detected by microarray analysis in 4 of 11 fetuses with DWM, using amniocentesis. Volumetric analysis revealed that the cortical plate was significantly larger in fetuses with DWM than in controls (p = 0.040). Even without ACC, the subcortical parenchyma, whole cerebrum, cerebellar hemispheres, and whole brain were significantly larger in fetuses with DWM (n = 8) than in controls (p = 0.004, 0.025, 0.033, and 0.026, respectively). In conclusion, volumetric fetal MRI analysis demonstrated that the development of DWM extends throughout the brain during the fetal period, even without apparent cerebral anomalies.

Antenatal counselling for prospective parents whose fetus has a neurological anomaly: part 2, risks of adverse outcome in common anomalies

After diagnosis of a fetal neurological anomaly, prospective parents want to know the best and worst-case scenarios and an estimation of the risk to their infant of having an atypical developmental outcome. The literature on developmental outcomes for fetal neurological anomalies is poor: studies are characterized by retrospective design, small sample size, often no standardized assessment of development, and differing definitions of anomalies. This review provides an aide-memoir on the risks of adverse neurodevelopmental outcome for ventriculomegaly, cortical anomalies, microcephaly, macrocephaly, agenesis of the corpus callosum, posterior fossa anomalies, and myelomeningocele, to assist healthcare professionals in counselling. The data in this review should be used alongside recommendations on counselling and service design described in part 1 to provide antenatal counselling.

Role of prenatal magnetic resonance imaging in fetuses with isolated anomalies of corpus callosum: multinational study

OBJECTIVE

To assess the performance of fetal magnetic resonance imaging (MRI) in detecting associated anomalies in fetuses diagnosed with isolated corpus callosal (CC) anomaly on multiplanar ultrasound evaluation of the fetal brain (neurosonography).

METHODS

This was a multicenter, retrospective cohort study involving 14 fetal medicine centers in Italy, UK, Portugal, Canada, Austria and Spain. Inclusion criteria were fetuses with an apparently isolated CC anomaly, defined as an anomaly of the CC and no other additional central nervous system (CNS) or extra-CNS abnormality detected on expert ultrasound, including multiplanar neurosonography; normal karyotype; maternal age ≥ 18 years; and gestational age at diagnosis ≥ 18 weeks. The primary outcome was the rate of additional CNS abnormalities detected exclusively on fetal MRI within 2 weeks following neurosonography. The secondary outcomes were the rate of additional abnormalities according to the type of CC abnormality (complete (cACC) or partial (pACC) agenesis of the CC) and the rate of additional anomalies detected only on postnatal imaging or at postmortem examination.

RESULTS

A total of 269 fetuses with a sonographic prenatal diagnosis of apparently isolated CC anomalies (207 with cACC and 62 with pACC) were included in the analysis. Additional structural anomalies of the CNS were detected exclusively on prenatal MRI in 11.2% (30/269) of cases, with malformations of cortical development representing the most common type of anomaly. When stratifying the analysis according to the type of CC anomaly, the rate of associated anomalies detected exclusively on MRI was 11.6% (24/207) in cACC cases and 9.7% (6/62) in pACC cases. On multivariate logistic regression analysis, only maternal body mass index was associated independently with the likelihood of detecting associated anomalies on MRI (odds ratio, 1.07 (95% CI, 1.01-1.14); P = 0.03). Associated anomalies were detected exclusively after delivery and were missed on both types of prenatal imaging in 3.9% (8/205) of fetuses with prenatal diagnosis of isolated anomaly of the CC.

CONCLUSION

In fetuses with isolated anomaly of the CC diagnosed on antenatal neurosonography, MRI can identify a small proportion of additional anomalies, mainly malformations of cortical development, which are not detected on ultrasound. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Taenia-tela choroidea complex and choroid plexus location help distinguish Dandy-Walker malformation and Blake pouch cysts

BACKGROUND

Dandy-Walker malformation and Blake pouch cysts can have overlapping imaging features. The choroid plexus and associated taenia-tela choroidea complex are displaced inferolaterally in Dandy-Walker malformation and below the vermis in Blake pouch cysts.

OBJECTIVE

To determine the normal fetal and postnatal MR appearance of the choroid plexus and taenia-tela choroidea complex, and whether their location can help distinguish Dandy-Walker malformation from Blake pouch cysts.

MATERIALS AND METHODS

In this retrospective study, we evaluated brain MR exams from normal-appearing fetuses (gestational age 19-38 weeks) and infants, fetal and postnatal exams in Blake pouch cysts and Dandy-Walker malformation, and ambiguous cases equivocal for mild Dandy-Walker malformation and Blake pouch cysts. We documented choroid plexus and the taenia-tela choroidea complex location and axial and sagittal angles in each case. Then we contrasted and compared the original and updated fetal diagnoses based on taenia-tela choroidea complex and choroid plexus positions.

RESULTS

The choroid plexus location and the taenia-tela choroidea complex location and angles varied significantly among normal exams, Blake pouch cyst exams and Dandy-Walker malformation exams (P<0.01). Dandy-Walker malformation showed inferolateral displacement of the taenia-tela choroidea complex and choroid plexus distant from the vermis. Adding the taenia-tela choroidea complex and choroid plexus into the assessment improved diagnostic accuracy, especially in ambiguous cases.

CONCLUSION

The location of the taenia-tela choroidea complex and choroid plexus provided additional diagnostic neuroimaging clues that could be used in conjunction with other conventional findings to distinguish Dandy-Walker malformation and Blake pouch cysts. Normal, Blake pouch cyst, and Dandy-Walker malformation cases differed with regard to taenia-tela choroidea complex and choroid plexus position. Inferolateral taenia-tela choroidea complex displacement distant from the vermian margin was characteristic of Dandy-Walker malformation.

Chromosomal Microarray Analysis in Pregnancies With Corpus Callosum or Posterior Fossa Anomalies

OBJECTIVE

We investigated the detection rate of clinically significant chromosomal microarray analysis (CMA) results in pregnancies with sonographic diagnosis of fetal corpus callosum anomalies (CCA) or posterior fossa anomalies (PFA).

METHODS

All CMA tests in pregnancies with CCA or PFA performed between January 2015 and June 2020 were retrospectively evaluated from the Israeli Ministry of Health database. The rate of CMA with clinically significant (pathogenic or likely pathogenic) findings was calculated and compared to a local Israeli cohort of 5,541 pregnancies with normal ultrasound.

RESULTS

One hundred eighty-two pregnancies were enrolled: 102 cases with CCA and 89 with PFA (9 cases had both). Clinically significant CMA results were found in 7/102 of CCA (6.9%) and in 7/89 of PFA (7.9%) cases. The CMA detection rate in pregnancies with isolated CCA (2/57, 3.5%) or PFA (2/50, 4.0%) was lower than in nonisolated cases, including additional CNS and/or extra-CNS sonographic anomalies (CCA-5/45, 11.1%; PFA-5/39, 12.8%), but this was not statistically significant. However, the rate among pregnancies that had extra-CNS anomalies, with or without additional CNS involvement (CCA-5/24, 20.8%; PFA-5/29, 17.2%), was significantly higher compared to all other cases (p = 0.0075 for CCA; p = 0.035 for PFA). Risk of CMA with clinically significant results for all and nonisolated CCA or PFA pregnancies was higher compared to the background risk reported in the control cohort (p < 0.001), but was not significant for isolated cases.

CONCLUSIONS

Our findings suggest that CMA testing is beneficial for the genetic workup of pregnancies with CCA or PFA, and is probably most informative when additional extra-CNS anomalies are observed.

Fetal MRI assessment of posterior fossa anomalies: A review

Prenatal ultrasound (US) is the first prenatal imaging tool for screening and evaluation of posterior fossa malformations since it is noninvasive, widely available, and safe for both mother and child. Fetal MRI is a widely used secondary technique to confirm, correct, or complement questionable US findings and plays an essential role in evaluating fetuses with suspected US findings and /or positive family history. The main sequences of fetal MRI consist of T2-weighted (T2w) ultrafast, single-shot sequences. Axial, coronal, and sagittal images are typically acquired allowing for a detailed evaluation of the posterior fossa contents. Also, various complimentary sequences, such as T1w, T2*w gradient sequences, or advanced techniques, including diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy, may provide additional information based on the studied malformation. Inclusion of these techniques should be done with careful risk-benefit analysis. The use of fetal MRI also aims to evaluate for associated anomalies. In addition, prenatal diagnosis of posterior fossa malformations is still a challenge but advances in knowledge in human developmental anatomy, genetic, and imaging recognition patterns have enabled us to shed some light on prognostic information that will help with the counseling of families. Finally, high-resolution late third trimester fetal MRI offers a safe alternative to early postnatal MR imaging, basically taking advantage of the uterine environment as a kind of "maternal incubator." Our goal is to discuss the spectrum of prenatal posterior fossa pathologies that can be studied by fetal MRI and their key neuroimaging features.

The Role of Fetal MRI for Suspected Anomalies of the Posterior Fossa

BACKGROUND

Posterior fossa anomalies can be diagnostic dilemmas during the fetal period. The prognosis for different diagnoses of the posterior fossa varies widely. We investigated whether fetal magnetic resonance imaging (MRI) and prenatal neurology consultation led to an alternate prognosis for fetuses referred due to concern for a fetal posterior fossa anomaly and concordance between pre- and postnatal diagnoses.

METHODS

This is a retrospective study of cases referred to the Prenatal Pediatrics Institute at Children's National Hospital from January 2012 to June 2018 due to concern for posterior fossa anomaly. Each encounter was scored for change in prognosis based upon clinical and fetal MRI report. Postnatal imaging was compared with prenatal imaging when available.

RESULTS

In total, 180 cases were referred for fetal posterior fossa anomalies based on outside obstetric ultrasound and had both fetal MRI and a neurology consultation. Fetal MRI and neurology consultation resulted in a change in fetal prognosis in 70% of cases. The most common referral diagnosis in our cohort was Dandy-Walker continuum, but it was not often confirmed by fetal MRI. In complex cases, posterior fossa diagnosis and prognosis determined by fetal MRI impacted choices regarding pregnancy management. Postnatal imaging was obtained in 57 (47%) live-born infants. Fetal and postnatal prognoses were similar in 60%.

CONCLUSIONS

Fetal diagnosis affects pregnancy management decisions. The fetal-postnatal imaging agreement of 60% highlights the conundrum of balancing the timing of fetal MRI to provide the most accurate diagnosis of the posterior fossa abnormalities in time to make pregnancy management decisions.

Blake's pouch cyst: Prenatal diagnosis and management

Objective:

This study aimed to present the characteristic features of 19 patients who were diagnosed as having Blake’s pouch cyst (BPC) at our center.

Materials and Methods:

Nineteen patients diagnosed as BPC between 2015 and 2019 were included in this retrospective study. Follow-up examinations were performed using ultrasonography (US) every three weeks up to 35 weeks of gestation. Prenatal magnetic resonance imaging (MRI) was performed at the time of diagnosis or during follow-up in 13 patients. MRI or transfontanellar US was performed to confirm the diagnosis of BPC after delivery. Karyotype results of eight patients were recorded.

Results:

Isolated BPC was observed in 9 (47%) patients, and associated anomalies were detected in 10 (53%) patients, including seven (36%) with the central nervous system and four (21%) with cardiac anomalies. Two fetuses had abnormal karyotype analysis as trisomy 21 and 13. The MRI report of eight patients was “differential diagnosis required for Dandy-Walker complex” and only in five (26%) patients, it was reported to be compatible with BPC. Spontaneous resolution was seen in four patients. Postnatal MRI was performed in five patients, and transfontanellar US in two patients, and all MRI and US results were consistent with BPC. During the neonatal period, abnormal neurologic development was observed in four (21%) patients, and one (5%) died.

Conclusion:

Although the prognosis of isolated BPC is very good with healthy neurologic development until advanced ages, death in the early neonatal period and abnormal neurologic development may be observed depending on the condition of the associated anomalies.

Pediatric cerebellar malformations: magnetic resonance diagnostic merits and correlation with neurodevelopmental outcome

Background

In spite of having many classifications for pediatric cerebellar malformations (PCMs), no broadly accepted classification is recommended. Associated neurodevelopmental outcomes in children with PCMs remain poorly defined. Neuroimaging is compulsory for the diagnosis of cerebellar malformation and their associated abnormalities. This article emphasizes on the clinical and radiological traits of PCMs. It proposes a radiological classification and a diagnostic approach and assesses whether specific neuroimaging features in patients with PCM correlate with their neurodevelopmental outcomes.

Results

Fifty-eight pediatric patients were classified as follows: The majority of about 51 cases (88%) showed cerebellar hypoplasia and the remaining 7 cases (12%) showed cerebellar dysplasia. Twenty-six patients (45%) remained undiagnosed, while 32 patients (55%) were having a final diagnosis (24% Dandy-Walker malformation (DWM) (n = 14), 7% isolated vermian hypoplasia (n = 4), 7% congenital disorder of glycosylation (CDG) (n = 4), 5% congenital muscular dystrophy (n = 3), 5% congenital cytomegalovirus (CMV) infection (n = 30), 3% rhombencephalosynapsis (n = 2), 2% Lhermitte-Duclos syndrome (n = 1), and 2% DWM with Joubert syndrome (n = 1)). Overall, for the neurodevelopmental outcome, the majority of patients 90% (52/58) had a global developmental delay (GDD) which is a delay in two or more developmental domains. Both motor and language delay represented about 72% (37/58), intellectual disability was present in 59% (34/58), epilepsy in 53% (31/58), ataxic gait in 57% (33/58), attention deficit hyperactivity disorder (ADHD) in 19% (11/58), autism spectrum disorder (ASD) in 17% (10/58), nystagmus and tremors in 15% (9/58), and behavioral changes in 7% (6/58). Most of the children with cerebellar hypoplasia, about 93%, had GDD. Also, patients with PCH associated with a severe GDD, 75% had a language delay, 50% had intellectual and motor delay, and about 25% had epilepsy. However, we observed mild GDD in half of the vermian hypoplasia cases and half of them had a mild fine motor delay.

Conclusions

Magnetic resonance imaging (MRI) of the pediatric brain provides key information to categorize and classify cerebellar malformations. A neurodevelopmental deficit is highly associated with different types of PCMs. Severe GDD was associated with cerebellar and brain stem involvement. However, children with vermis mal-development were likely to have mild GDD. Familiarity with their diagnostic criteria is mandatory for correct diagnosis and prognosis for patients.

Are fetal gender and gestational age related to the size of cisterna magna?

OBJECTIVES

The purpose of this article was to explore whether the gestational age(GA)and gender could affect the size of the cisterna magna (CM).

METHODS

This study that included pregnant women who were between 20 ∼ 39⁺⁶. The recorded included BPD, HC, anteroposterior diameter of CM and gender. The fetuses were divided into normal and isolated enlargement of the CM (IECM)group for statistical analysis.

RESULTS

Seven hundred ninety six fetuses with normal CM, 412 cases were boys and 384 cases were girls. 73 fetuses with IECM, 59 cases were boys and 14 cases were girls. The anteroposterior diameter of the CM increased with GA during 20-26⁺⁶weeks. After 27 weeks, the anteroposterior diameter of CM became stable. In the IECM group, the mean anteroposterior of male and female fetuses were 1.31 ± 0.18 cm and 1.24 ± 0.15 cm, respectively. The IECM fetus accounted for 8.4% of the total number of fetuses, male IECM accounted for 14.3% of normal male fetus, and female fetus was 3.6%, which showed that male fetus had a higher rate of IECM than female (χ2 = 21.6, p<.001).

CONCLUSIONS

There is a gender difference between normal fetuses and IECM fetuses. Based on our finding, it is reasonable to establish the normal value of CM according to the gender difference.

Massive posterior cranial vault erosion and its reconstruction: A peculiar presentation of "mega cisterna magna"

Dandy-Walker (DW) complex is a rare central nervous system malformation, commonly associated with complex non-neurological conditions, defined by four variants with characteristic anatomic features, still inadequately known for its etiological aspects. "Mega Cisterna Magna" (MCM) is a type of DW complex which is represented by an enlarged posterior cranial fossa. Though reduction cranioplasty has been reported in enlarged posterior cranial fossa malformations, however we report a peculiar case of MCM with massive posterior cranial bone erosion, presenting completely asymptomatic at an age of 8 years, without any associated co-morbidities till date, nor with any evident occipital mass at birth. Survival of the child till this age is an exception in itself, but this can probably be explained by the presence of the giant defect of the posterior cranial bone, which must have acted like a vent and prevented the elevation of the ICP. Hence no symptoms were observed till date. Ventriculo-peritoneal (VP) shunting was done to drain the accumulated fluid, followed by massive cranioplasty, which was challenging and was performed with autologous cranial and fibular bone grafts, along with alloplastic titanium mesh, and thus achieving marked aesthetic improvement with satisfactory bone healing at a 3-year follow-up.

International standards for fetal brain structures based on serial ultrasound measurements from Fetal Growth Longitudinal Study of INTERGROWTH-21st Project

OBJECTIVE

To create prescriptive growth standards for five fetal brain structures, measured using ultrasound, in healthy, well-nourished women at low risk of impaired fetal growth and poor perinatal outcome, taking part in the Fetal Growth Longitudinal Study (FGLS) of the INTERGROWTH-21^st Project.

METHODS

This was a complementary analysis of a large, population-based, multicenter, longitudinal study. The sample analyzed was selected randomly from the overall FGLS population, ensuring an equal distribution among the eight diverse participating sites and of three-dimensional (3D) ultrasound volumes across pregnancy (range: 15-36 weeks' gestation). We measured, in planes reconstructed from 3D ultrasound volumes of the fetal head at different timepoints in pregnancy, the size of the parieto-occipital fissure (POF), Sylvian fissure (SF), anterior horn of the lateral ventricle, atrium of the posterior horn of the lateral ventricle (PV) and cisterna magna (CM). Fractional polynomials were used to construct the standards. Growth and development of the infants were assessed at 1 and 2 years of age to confirm their adequacy for constructing international standards.

RESULTS

From the entire FGLS cohort of 4321 women, 451 (10.4%) were selected at random. After exclusions, 3D ultrasound volumes from 442 fetuses born without a congenital malformation were used to create the charts. The fetal brain structures of interest were identified in 90% of cases. All structures, except the PV, showed increasing size with gestational age, and the size of the POF, SF, PV and CM showed increasing variability. The 3^rd , 5^th , 50^th , 95^th and 97^th smoothed centiles are presented. The 5^th centiles for the POF and SF were 3.1 mm and 4.7 mm at 22 weeks' gestation and 4.6 mm and 9.9 mm at 32 weeks, respectively. The 95^th centiles for the PV and CM were 8.5 mm and 7.5 mm at 22 weeks and 8.6 mm and 9.5 mm at 32 weeks, respectively.

CONCLUSIONS

We have produced prescriptive size standards for fetal brain structures based on prospectively enrolled pregnancies at low risk of abnormal outcome. We recommend these as international standards for the assessment of measurements obtained using ultrasound from fetal brain structures. © 2020 Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal visualisation of the torcular herophili by means of a Doppler technology highly sensitive for low-velocity flow in the expert assessment of the posterior fossa: a prospective study

OBJECTIVE

To evaluate the usefulness of a Doppler technology highly sensitive for low-velocity flow in the antenatal imaging of the torcular herophili (TH) in the second trimester of pregnancy.

DESIGN

Prospective study.

SETTING

Referral Fetal Medicine Unit.

POPULATION

Non-consecutive series of singleton pregnancies submitted to antenatal neurosonogram between 20 and 28 weeks of gestation.

METHODS

A midsagittal section of the fetal brain was obtained by insonating through the anterior fontanelle, then the MV-Flow™ and LumiFlow™ presets were selected to visualise the TH as the posterior confluence of the superior sagittal sinus and the straight sinus.

MAIN OUTCOME MEASURES

Evaluation of the anatomic relationship of the TH with the 'transpalatal line' joining the upper bony palate to the fetal skull.

RESULTS

A total of 99 pregnant women were recruited, including one fetus with open spina bifida, one with Dandy-Walker malformation (DWM) and two with Blake's pouch cysts. In normal fetuses, the TH appeared to lie on or just below the 'transpalatal line'. In the cases of Blake's pouch cyst, the position of the TH appeared normal if compared with controls, whereas in DWM a supra-elevated position of the TH in respect of the transpalatal line was demonstrated. Finally, in the fetus with Chiari II malformation the TH was identified below the 'transpalatal plane'.

CONCLUSIONS

Prenatal ultrasound visualisation of the TH by means of newly developed Doppler technologies characterised by high sensitivity for low-velocity flow is feasible and allows the indirect evaluation of the insertion of cerebellar tentorium in the second trimester.

TWEETABLE ABSTRACT

Prenatal imaging of the torcular herophili using a Doppler technology highly sensitive for low-velocity flow.

Quantitative fetal magnetic resonance imaging assessment of cystic posterior fossa malformations

OBJECTIVE

Normal cognitive development usually requires a structurally intact and complete cerebellar vermis. The aim of this study was to evaluate whether quantification by fetal magnetic resonance imaging (MRI) of vermis- and brainstem-specific imaging markers improves the definition of cystic posterior fossa malformations (cPFM).

METHODS

Fetuses diagnosed with cPFM that had an available midsagittal plane on T2-weighted MRI were identified retrospectively and compared with gestational-age (GA) matched brain-normal controls. Fetuses with cPFM were assigned to three groups, according to standard criteria (vermian size and brainstem-vermis (BV) angle): normal vermian area and BV angle < 25° (Group 1); reduced vermian area and/or BV angle of 25-45° (Group 2); and reduced vermian area and BV angle > 45° (Group 3; Dandy-Walker malformation (DWM) group). The number of differentiable vermian lobules and the areas of the vermis, mesencephalon, pons and medulla oblongata were quantified, correlated with and controlled for GA, and compared between the study groups.

RESULTS

In total, 142 cases of cPFM were included, with a mean GA of 25.20 ± 5.11 weeks. Cases comprised Blake's pouch cyst (n = 46), arachnoid cyst (n = 12), inferior vermian hypoplasia (n = 5), megacisterna magna (n = 35) and classic DWM (n = 44). In the control group, 148 fetuses were included, with a mean GA of 25.26 ± 4.12 weeks. All quantified areas and the number of differentiable vermian lobules had a significant positive correlation with GA. The number of vermian lobules and the areas of all quantified regions, except for that of the medulla oblongata, differed significantly between the study groups (P ≤ 0.015 for all). The control group had the highest number of differentiable vermian lobules and the DWM group had the lowest (P < 0.01).

CONCLUSIONS

Prenatal MRI assessment of vermian lobules is a useful addition to standard neuroradiological and neurosonographic techniques. The quantification of vermian lobules using fetal MRI allows further differentiation of cPFM into subgroups and thereby improves the classification of hindbrain malformations. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal magnetic resonance imaging within the 26th week of gestation may predict the fate of isolated upward rotation of the cerebellar vermis: insights from a multicentre study

OBJECTIVES

We investigated whether prenatal magnetic resonance imaging (MRI) within 26 weeks of gestation (GW) may predict the fate of isolated upward rotation of the cerebellar vermis (URCV).

METHODS

This retrospective multicentre observational study included foetuses diagnosed with isolated URCV in prenatal MRI performed within 26 GW. Isolated URCV was defined by a brainstem-vermis angle (BVA) ≥ 12° in the MR midline sagittal view without abnormalities of the supratentorial structures, brainstem, or cerebellum hemispheres. The assessments included the BVA, clival-supraoccipital angle, transverse diameter of the posterior cranial fossa, tentorial angle, width of the cisterna magna (WCM), ventricular width, vermian diameters, hypointense stripes, and cerebellar tail sign. Late prenatal or postnatal MRI was used as a reference standard to assess the final vermian fate (rotated/de-rotated).

RESULTS

Forty-five foetuses (mean GW at prenatal MRI = 21.5 ± 1.4 weeks) were included. In the reference standard, the vermis was de-rotated in 26 cases (57.7%). At least two of the following criteria were used to predict the persistence of URCV at imaging follow-up: BVA ≥ 23°, WCM ≥ 9 mm, and the cerebellar tail sign. The results were a sensitivity of 84.21% (95% CI, 60.4-96.6%), specificity of 80.8% (95% CI, 60.6-93.4%), positive predictive value of 76% (95% CI, 58.7-87.8%), and negative predictive value of 87.5% (95% CI, 70.9-95.2%).

CONCLUSIONS

MRI within 26 GW on foetuses diagnosed with isolated URCV may predict delayed cerebellar vermis de-rotation, which is associated with good neurodevelopmental outcome in most cases.

KEY POINTS

• Foetal MRI is a valuable tool in predicting the fate of isolated upward-rotated cerebellar vermis. • A wider angle between the brainstem and vermis is associated with higher risk of persistence of vermian rotation. • The presence of ≥ 2 factors among a brainstem-to-vermis angle ≥ 23°, width of the cisterna magna ≥ 9 mm, and the presence of the "cerebellar tail sign" has a sensitivity of 84.21% (95% CI, 60.4-96.6%) and specificity of 80.8% (95% CI, 60.6-93.4%) in predicting the persistence of the vermian rotation at imaging follow-up.

Quantitative diagnostic advantages of three-dimensional ultrasound volume imaging for fetal posterior fossa anomalies: Preliminary establishment of a prediction model

OBJECTIVES

To quantitatively assess prenatal diagnostic performance of three-dimensional ultrasound (3D-US) for posterior fossa anomalies (PFA) and establish a preliminarily 3D-US prediction model.

METHODS

Sixty singleton fetuses suspected of PFA by 2D-US presented their detailed 3D-US evaluation. The surface area of vermis (SAV), brainstem-vermis, and brainstem-tentorium angles were measured by 3D-US. The good prognosis was defined as normal neurodevelopmental outcome. MRI and autopsy were the diagnostic reference standard.

RESULTS

There was a significant difference between 2D-US (60.0%, 36/60) and 3D-US (94.8%, 55/58) for the diagnostic accuracy (P < .01). Prenatal 3D-US prediction model was established with observed/expected SAV as the main predictor (area under the curve [AUC]: 0.901; 95% CI, 0.810-0.992, P < .001). When it was more than 107.5%, the prognosis seemed to be good (sensitivity: 96.4%, specificity: 26.7%), which led to consideration of mega cisterna magna, Blake pouch cyst, or small arachnoid cyst. The prognosis appeared to be poor when it was less than 73% (sensitivity: 71.4%, specificity: 100%), and the diagnosis tended to be a Dandy-Walker malformation, vermian hypoplasia, and cerebellar hypoplasia. Brainstem-vermis and brainstem-tentorium angles were the secondary indicators (AUC: 0.689 vs 0.761; 95% CI, 0.541-0.836 vs 0.624-0.897, P = .014 vs.001).

CONCLUSIONS

It seems that the exact types of PFA can be effectively diagnosed by quantitative indicators of 3D-US.

Differential Diagnoses and Their Implications of Dandy-Walker Malformation or Isolated Cisterna Magna, a Case Study: Baby V

We explore the outcome of a fetus with a posterior fossa abnormality thought to be a Dandy-Walker malformation based on prenatal ultrasound imaging. The infant was later diagnosed by magnetic resonance imaging (MRI) as having an isolated cisterna magna. When assessing brain abnormalities, there is increased accuracy of prenatal MRI versus prenatal ultrasound. Accurate diagnosis of an infant is paramount so that an inheritance pattern, risk of recurrence, involvement of other systems, and a prognosis can be determined. Communicating with the family and supporting them with the correct information is then enhanced. It should be standard protocol to obtain a fetal MRI if an abnormal prenatal ultrasound of the brain is detected. Further research is needed to assess the accuracy of using MRI versus ultrasonography prenatally to diagnose posterior brain abnormalities.

Delayed fenestration of Blake's pouch with or without vermian hypoplasia: fetal MRI at 3 tesla versus 1.5 tesla

Background

Fetal magnetic resonance imaging (MRI), mainly performed at standard field strength, plays a role in the classification of posterior fossa malformations. In the context of early second-trimester screening, upward rotation of the cerebellar vermis per se is usually compatible with a more favorable outcome than Dandy-Walker malformation and profound vermian hypoplasia. Delayed fenestration of Blake’s pouch may either mimic vermian hypoplasia by compression or be associated with it in individual cases. To increase specificity, there is a growing interest in the use of high-field MRI which is believed to be safe as long as the specific absorption rate is kept within accepted limits. We aim to illustrate its added value during the second and third trimester.

Case presentation

In the first case, fetal MRI at 1.5 Tesla was performed at 21 and 27 weeks’ gestation with sonographic follow up postnataly. In the second case, 3 Tesla MR images were acquired at 21 and 34 weeks’ gestation as well as in the neonatal period.

Conclusions

This pictorial case vignette supports the suggestion that mid-gestational MRI at 3 Tesla has the potential to exclude pronounced vermian hypoplasia with higher confidence than at 1.5 Tesla. However, the discrimination of mild hypoplasia from slight deformation of the cerebellar vermis will likely remain challenging.

Developmental outcomes in children with congenital cerebellar malformations

AIM

Neurodevelopmental outcomes in children with congenital cerebellar malformations (CCMs) remain poorly defined. We aimed to assess whether specific neuroimaging features in CCM patients correlate with neurodevelopmental outcomes.

METHOD

Hospital records and neuroimaging of 67 children with CCMs were systematically reviewed. Logistic regression analyses were used to assess associations between specific imaging features and neurodevelopmental outcomes.

RESULTS

CCM categories were distributed as follows: 28 percent isolated vermis hypoplasia (n=19), 28 percent global cerebellar hypoplasia (n=19), 15 percent Dandy-Walker malformation (n=10), 13 percent pontocerebellar hypoplasia (PCH, n=9), 9 percent molar tooth malformation (n=6), 3 percent rhombencephalosynapsis (n=2), and 3 percent unilateral cerebellar malformation (n=2). Overall, 85 percent (55/65) of the cohort had global developmental delay (GDD). Intellectual disability was present in 61 percent (27/43) and autism spectrum disorder (ASD) in 12 percent (6/52). Adjusting for supratentorial malformations and presence of genetic findings, severe GDD was associated with cerebellar hypoplasia (p=0.049) and PCH (p=0.030), whereas children with vermis hypoplasia were less likely to have severe GDD (p=0.003). Presence of supratentorial abnormalities was not significantly associated with worse neurodevelopmental outcome but was associated with epilepsy.

INTERPRETATION

Children with CCMs have high prevalence of neurodevelopmental deficits. Specific features on imaging can aid prognostication and establish early intervention strategies.

WHAT THIS PAPER ADDS

Atypical long-term neurodevelopmental outcome is very common in patients with congenital cerebellar malformations (CCMs). Involvement of the brainstem and cerebellar hemispheres predicts more severe neurodevelopmental disability. Most patients with vermis hypoplasia have language delay but are verbal. Supratentorial abnormalities are not significantly associated with worse neurodevelopmental outcome but are associated with epilepsy. Comorbidities are common in CCMs, especially ophthalmological issues in cerebellar hypoplasia and sensorineural hearing loss in pontocerebellar hypoplasia.

Fetal and neonatal neurogenetics

Disorders of the developing nervous system may be of genetic origin, comprising congenital malformations of spine and brain as well as metabolic or vascular disorders that affect normal brain development. Acquired causes include congenital infections, hypoxic-ischemic or traumatic brain injury, and a number of rare neoplasms. This chapter focuses on the clinical presentation and workup of neurogenetic disorders presenting in the fetal or neonatal period. After a summary of the most frequent clinical presentations, clues from history taking and clinical examination are illustrated with short case reports. This is followed by a discussion of the different tools available for the workup of neurogenetic disorders, including the various genetic techniques with their advantages and disadvantages. The implications of a molecular genetic diagnosis for the patient and family are addressed in the section on counseling. The chapter concludes with a proposed workflow that may help the clinician when confronted with a potential neurogenetic disorder in the fetal or neonatal period.

Prenatal imaging of posterior fossa disorders. A review

With advances in fetal imaging, prenatal diagnosis of posterior fossa anomalies has been greatly improved. Based on the anatomical approach proposed by Guibaud and Desportes in 2006, the main anomalies depicted according to the algorithm includes: (1) increased "fluid-filled" space of the posterior fossa, (2) abnormal biometry of the cerebellum, and (3) abnormal cerebellar anatomy. In this review, the spectrum of PF anomalies is covered in an attempt to update this approach in the light of both our experience, more than a decade since this algorithm was published, and the latest data in the literature.

Three-dimensional volumetric study with VOCAL in normal and abnormal posterior fossa fetuses

Purpose: The aim of this study was to compare volumetric parameters in the abnormal and normal posterior fossa using the Virtual Organ Computer-aided AnaLysis (VOCAL™) technique to determine whether fetuses with an abnormal posterior fossa have different volumes.Methods: A prospective study was conducted on 17 fetuses with an abnormal posterior fossa including, Dandy Walker malformation (DWM) (n = 6), vermian hypoplasia (VH) (n = 3), mega cisterna magna (MCM) (n = 8), and 99 healthy control fetuses from 20 to 34 weeks' gestation. Measurement of the fetal cisterna magna and cerebellar volume was performed in the standard transcerebellar plane through the VOCAL™ method. To establish the correlation of volumes with gestational age, polynomial regression analysis was performed. For comparison between groups, univariate ANCOVA was performed using gestational age as a covariate. The reliability was analyzed by the intraclass correlation coefficient (ICC).Results: Cerebellar volume and cisterna magna volume were correlated with gestational age. Posterior fossa volume was significantly larger in DWM (p < .0001) and MCM (p < .0001) in comparison to the control group. In VH group, cisterna magna volume does not seem to expand (p = .298). Cerebellar volume does not seem to change in subgroups when the influence of gestational age is discarded (p = .09). The ratio of cerebellar volume to the cisterna magna volume decreases significantly in abnormal fetuses (p < .0001). Good intraobserver and interobserver reliabilities were found for both cerebellum and cisterna magna measurements.Conclusions: Volume analysis may have a role in discrimination of different posterior fossa pathologies.

Establishment of normative values for the fetal posterior fossa by magnetic resonance imaging

OBJECTIVE

Suspected Dandy-Walker continuum anomalies constitute a significant percentage of prenatal cases evaluated by magnetic resonance imaging (MRI). To unify the description of posterior fossa malformations, we sought to establish objective measurements for the posterior fossa in normal fetuses between 18 and 37 weeks gestation.

METHODS

T2-weighted images of normal fetal brains in sagittal projection were obtained from fetal magnetic resonance (MR) studies of normal brains performed from 2009 to 2017.121 fetal brains were included in the analysis. Three radiologists reviewed images and recorded the following for each case: superior posterior fossa angle (SPFA), posterior fossa perimeter, and tegmento-vermian angle (TVA).

RESULTS

For each feature, the mean of the measurements, the percentage of absolute difference of the reader measurement compared with mean measurement, and the interclass correlation (ICC) were calculated. Values are reported as mean ± standard deviation. Perimeter increases linearly with age, whereas the SPFA and the TVA are independent of gestational age. For all included cases, the SPFA averaged 100.9° ± 8° and the TVA averaged 2.5° ± 2.3°.

CONCLUSION

The superior posterior fossa angle, a novel measurement, and the posterior fossa perimeter can be used for establishing the expected size of the posterior fossa in second- and third-trimester fetuses by MRI.

Fetal cerebellar disorders

The embryologic development of the cerebellum extends over a long time period, thus making it vulnerable to a broad spectrum of malformations and disruptions. Knowledge of the main steps of fetal posterior fossa development; the normal imaging patterns at different stages of embryogenesis; the large spectrum of cerebellar malformations; and their clinical presentations enables diagnosis and precise counseling of parents. Sonography is the most important imaging method for the screening of cerebellar malformations since it is noninvasive, widely available, and safe for both mother and child. The ultrasonographic approach for the evaluation of the fetal posterior fossa is based on the classic transabdominal visualization of axial planes with addition when indicated of a more comprehensive, multiplanar transvaginal or transfundal approach, including coronal and sagittal imaging planes. Fetal magnetic resonance imaging (MRI) has become an adjunct to prenatal ultrasound since the 1980s. Good-quality images have been obtained thanks to the implementation of fast and ultrafast MRI sequences. Fetal MRI has higher-contrast resolution than prenatal sonography and may contribute to the differentiation of normal from abnormal tissue. Both prenatal neurosonography and fetal MRI enable accurate prenatal diagnosis of most posterior fossa anomalies.

Chromosomal aneuploidies and copy number variations in posterior fossa abnormalities diagnosed by prenatal ultrasonography

OBJECTIVE

To explore the genetic aetiology of fetal posterior fossa abnormalities (PFAs).

METHODS

This study involved cases of PFAs that were identified by prenatal ultrasonographic screening and confirmed postnatally between January 2012 and January 2016. Conventional cytogenetic analyses and chromosomal microarray analysis were performed, and chromosomal aneuploidies and copy number variations (CNVs) were identified.

RESULTS

Among 74 cases included in this study, 8 were of Blake's pouch cyst; 7, Dandy-Walker malformation; 11, vermian hypoplasia; 32, enlarged cisterna magna; and 16, cerebellar hypoplasia. The rates of nonbenign chromosomal aberrations (including chromosomal aneuploidies, pathogenic CNVs, and variants of unknown significance) were 2/8 (25.0%), 2/7 (28.5%), 8/11 (72.7%), 7/32 (21.9%), and 6/16 (37.5%), respectively. Cases were also classified as isolated PFAs (30/74), PFAs with other central nervous system (CNS) abnormalities (13/74), or PFAs with extra-CNS structural abnormalities (31/74). No fetuses with isolated PFAs or PFAs accompanied by other CNS abnormalities exhibited chromosomal aneuploidies or pathogenic CNVs. The rate of pathogenic chromosomal aberrations in the remaining fetuses was 17/31 (22.9%).

CONCLUSION

The combined use of chromosomal microarray analysis and karyotype analysis might assist the prenatal diagnosis and management of PFAs, with extra-CNS structural abnormalities being detected by ultrasonography.

Evaluation of the fetal cerebellum by magnetic resonance imaging

Obstetric protocols dictate that the fetal cerebellum should always be assessed during sonograms during pregnancy. For various reasons, including technical limitations or inconclusive sonographic findings, suspicion of cerebellar abnormalities is one of the most common indications for prenatal magnetic resonance imaging (MRI). Although sonography is the imaging technique of choice to assess the cerebellum, MRI shows the anatomy of the posterior fossa and abnormalities in the development of the fetal cerebellum in greater detail and thus enables a more accurate prenatal diagnosis. We describe and illustrate the normal anatomy of the fetal cerebellum on MRI as well as the different diseases that can affect its development. Moreover, we review the most appropriate terminology to define developmental abnormalities, their differential diagnoses, and the role of MRI in the prenatal evaluation of the posterior fossa.