Acrania-exencephaly-anencephaly sequence phenotypic characterization using two- and three-dimensional ultrasound between 11 and 13 weeks and 6 days of gestation

Research progress on ultrasound and molecular markers for prenatal diagnosis of neural tube defects

Neural tube defects (NTDs) are severe congenital anomalies that result from the failure of early neural tube closure during fetal neurogenesis. They are the most common and severe congenital malformations of the central nervous system. Identifying reliable prenatal diagnostic ultrasound and molecular markers that can predict NTDs is of paramount importance. Early diagnosis of NTDs allows embryonic treatment and prevention strategies, which are crucial for reducing the disability rate associated with these malformations, reducing the burden on individuals and on society. The purpose of this comprehensive review was to summarize the ultrasound biomarkers between 11 and 13 weeks of gestation and the molecular biomarkers used in the diagnosis of NTDs, providing additional insights into early screening for NTDs.

Fetal acrania diagnosed at 17 weeks of gestation by 2D∕3D ultrasound: a case report and literature review

Acrania is a fetal malformation characterized by complete or partial absence of the calvaria above the orbits and supraciliary ridge. No exact mechanism is demonstrated for this anomaly but disturbances in mesenchymal migration during the fourth week of development are the most documented. The key sonographic features of acrania are absent calvaria and dorsally bulging brain (Mickey Mouse head). Due to the normal process of ossification of cranial bones, the diagnosis can be established only after 11 weeks of gestation. Early detection is extremely important. The prognosis is extremely poor so elective termination of pregnancy is the treatment of choice. In this paper, we discuss the things we know about pathogeny and ultrasonographic features of fetal cranial malformations based on a case diagnosed late during gestation.

'Turkish turban' sign: rare phenotype of acrania-exencephaly-anencephaly sequence

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The Alberta Congenital Anomalies Surveillance System: a 40-year review with prevalence and trends for selected congenital anomalies, 1997-2019

INTRODUCTION

Current published long-term provincial or territorial congenital anomaly data are lacking for Canada. We report on prevalence (per 1000 total births) and trends in 1997-2019, in Alberta, Canada, for selected congenital anomalies. Associated risk factors are also discussed.

METHODS

We used data from the Alberta Congenital Anomalies Surveillance System (ACASS) to calculate the prevalence and perform chi-square linear trend analyses.

RESULTS

From 1997 to 2019, the overall prevalence of neural tube defects was stable, at 0.74 per 1000 total births. The same was true for spina bifida (0.38), orofacial clefts (1.99), more severe CHDs (transposition of the great arteries, 0.38; tetralogy of Fallot, 0.33; and hypoplastic left heart syndrome, 0.32); and gastroschisis (0.38). Anencephaly, cleft palate and anorectal malformation significantly decreased with a prevalence of 0.23, 0.75 and 0.54 per 1000 total births, respectively. Significantly increasing trends were reported for anotia/microtia (0.24), limb reduction anomalies (0.73), omphalocele (0.36) and Down syndrome (2.21) and for hypospadias and undescended testes (4.68 and 5.29, respectively, per 1000 male births).

CONCLUSION

Congenital anomalies are an important public health concern with significant social and societal costs. Surveillance data gathered by ACASS for over 40 years can be used for planning and policy decisions and the evaluation of prevention strategies. Contributing genetic and environmental factors are discussed as is the need for continued surveillance and research.

Prenatal diagnosis of acrania/exencephaly/anencephaly sequence (AEAS): additional structural and genetic anomalies

OBJECTIVES

To analyse additional structural and genetic anomalies in fetuses with acrania/exencephaly/anencephaly sequence (AEAS).

METHODS

A retrospective analysis of 139 fetuses with AEAS diagnosed between 2006 and 2020 in a single tertiary referral ultrasound department.

RESULTS

The median gestational age at diagnosis decreased from 15 weeks in 2006 to 13 weeks in 2020 (- 0.21 per each year; p = 0.009). In 103 fetuses, the defects were limited to the neural tube (NTD) (74.1%), in 36 fetuses (25.9%), there were additional structural non-NTD anomalies. The most common were ventral body wall defects present in 17.8% (23/139), followed by anomalies of the limbs (7.2%; 10/139), face (6.5%; 9/139) and heart (6.5%; 9/139). Genetic anomalies were diagnosed in 7 of the 74 conclusive results (9.5%; 7/74; trisomy 18, n = 5; triploidy, n = 1; duplication of Xq, n = 1). In univariate logistic regression models, male sex, limb anomalies and ventral body wall defects significantly increased the risk of genetic anomalies (OR 12.3; p = 0.024; OR 16.5; p = 0.002 and OR 10.4; p = 0.009, respectively).

CONCLUSIONS

A significant number of fetuses with AEAS have additional structural non-NTD anomalies, which are mostly consistent with limb body wall complex. Genetic abnormalities are diagnosed in almost 10% of affected fetuses and trisomy 18 is the most common aberration. Factors that significantly increased the odds of genetic anomalies in fetuses with AEAS comprise male sex, limb anomalies and ventral body wall defects.

Antenatal imaging: A pictorial review

Today, in parallel with the use of imaging modalities increases in all fields, the use of imaging methods in pregnant women is increasing. Imaging has become an integral component of routine pregnancy follow-up. Imaging provides parents with an early opportunity to learn about the current situation, including prenatal detection of anomalies or diseases, etiology, prognosis, and the availability of prenatal or postnatal treatments. Various imaging modalities, especially ultrasonography, are frequently used for imaging both maternal and fetal imaging. The goal of this review was to address imaging modalities in terms of usefulness and safety, as well as to provide demonstrative examples for disorders. And this review provides current information on selecting a safe imaging modality to evaluate the pregnant and the fetus, the safety of contrast medium use, and summarizes major pathological situations with demonstrative sonographic images to assist radiologists and obstetricians in everyday practice.

Accuracy of ultrasonography in diagnosis of fetal central nervous system malformation

BACKGROUND

Prenatal examination is an important measure for the screening and diagnosis of fetal malformations.

AIM

To investigate the accuracy of ultrasonography in the diagnosis of fetal central nervous system (CNS) malformations.

METHODS

One hundred and thirteen pregnant women suspected of having fetal CNS malformations were examined at our hospital from December 2018 to October 2020 using two-dimensional ultrasonography and three-dimensional ultrasonography, respectively.

RESULTS

According to the pathological results, there were 79 cases of CNS malformations and 34 cases of non-CNS malformations among the 113 pregnant women suspected of having fetal CNS malformation. Fifty-one cases of CNS malformation and 26 cases of non-CNS malformation were detected by two-dimensional ultrasonography, and 73 cases of CNS malformation and 30 cases of non-CNS malformation were detected by three-dimensional ultrasonography. The diagnostic sensitivity (92.41%) and accuracy (91.15%) of three-dimensional ultrasonography were higher than those of two-dimensional ultrasonography (64.56% and 68.14%, respectively) (P = 0.000). The specificity of three-dimensional ultrasonography (88.24%) was higher than that of two-dimensional ultrasonography (76.47%); however, the difference was not significant (P = 0.203).

CONCLUSION

Three-dimensional ultrasonography has high application value in the diagnosis of fetal CNS malformations. In addition, the image quality is clear, and the diagnostic sensitivity and accuracy are high.

Further insights into unusual acrania-exencephaly-anencephaly sequence caused by amniotic band – first trimester fetoscopic correlation with two- and three-dimensional ultrasound

Objectives

Antenatal detection of acrania-exencephaly-anencephaly (AEA) sequence beyond 10 completed weeks of gestation is usually straight-forward. An earlier detection and classification of the causative conditions prior to disaggregation of exposed dysplastic brain tissue remains challenging.

Case presentation

We present two- and three-dimensional ultrasound correlated with fetoscopic findings of an unusual type of neural tube defect at 11 gestational weeks caused by an amniotic constriction ring resulting in cystic degeneration of the developing skull.

Conclusions

By giving further illustrative insights into early defective brain development, this report confirms recent findings of an unusual subtype of acrania-exencephaly-anencephaly sequence suggesting early disruption of the developing brain, following an amniotic entrapment of the skull.

Ultrasound Appearances of the Acrania-Anencephaly Sequence at 10 to 14 Weeks' Gestation

OBJECTIVES

The acrania-anencephaly sequence is a lethal condition with a high detection rate in experienced hands after 10 weeks' gestation. However, earlier in gestation, many cases remain undetected. Different phenotypic appearances have been described and might help increase the detection rate in less experienced hands and also earlier in gestation. The purpose of this study was to assess interobserver reliability in classifying cases of the acrania-anencephaly sequence during first trimester in 6 different subtypes according to their ultrasound appearances.

METHODS

This was a retrospective descriptive cohort study at 3 centers for fetal imaging. Each case was classified according to its phenotypic appearance by 2 independent operators as "bilobular," "cystic," "elongated," "irregular," "foreshortened," or "overhanging." Frequencies of each type are described, and interoperator agreement was assessed with the intraclass correlation coefficient.

RESULTS

From the 88 included cases, the frequencies of the different subtypes classified as overhanging, elongated, bilobular, cystic, foreshortened, and irregular were 31%, 25%, 19%, 11%, 8%, and 6%, respectively. The interoperator reliability was good, with an intraclass correlation coefficient of 0.903 (95% confidence interval, 0.853-0.937; P < .001).

CONCLUSIONS

Using different subtypes may improve the detection of the acrania-anencephaly sequence. An accurate early diagnosis could lead to timely, less traumatic, and safer management of affected pregnancies.

The role of the "beret" sign and other markers in ultrasound diagnostic of the acrania-exencephaly-anencephaly sequence stages

INTRODUCTION

Neural tube defects (NTDs) are a group of heterogeneous congenital anomalies of the central nervous system (CNS). Acrania is a non-NTD congenital disorder related to the CNS. It can transform into anencephaly through the acrania-exencephaly-anencephaly sequence (AEAS). In AEAS, the cerebral tissue is not protected and is gradually destroyed due to exposure to the harmful effect of amniotic fluid and mechanical injuries. These lead to exencephaly and then into anencephaly. In contrast to primary anencephaly (NTDs), this type of anencephaly authors suggests calling secondary anencephaly.

OBJECTIVE

Analysis of the known prenatal ultrasonography (US) signs associated with AEAS. Simultaneously, the authors propose a new sign in the differentiation of acrania from exencephaly and anencephaly, called the "beret" sign.

METHODS

It is a two-centre retrospective observational study. As part of the study, 4060 US scans were analyzed.

RESULTS

In 10 cases, the absence of calvarium was diagnosed, allowing recognition of either AEAS stages or primary anencephaly. In 5 cases, cerebral structures were enclosed by an inertial rippled thin membrane, with a smooth outer contour. Between the described membrane and the brain structures, a thin anechoic space corresponding to cerebrospinal fluid was observed. This sign was defined as the "beret" sign. In these cases, acrania was diagnosed. In three cases calvarium was missing. The brain structures had an irregular appearance, did not wave and remained motionless. The outer contour was unequal as if divided into lobes. Amniotic fluid was anechoic. Exencephaly was diagnosed in these cases. In two cases calvarium, brain structures, and meninges were missing. The "frog eyes" sign and slightly echogenic amniotic fluid were visible. In this case, anencephaly was diagnosed.

CONCLUSIONS

The "beret" sign seems to be a promising tool in the diagnosis of acrania. Furthermore, echogenicity of amniotic fluid could be useful during differentiation between primary and secondary anencephaly.

An Unusual First-Trimester Ultrasound Presentation of the Acrania-Anencephaly Sequence: The "Turkish Turban" Sign

A previously unrecognized first-trimester presentation of the acrania-anencephaly sequence is described. Ultrasound features included a constriction ring around the external base of the developing skull and an enlarged globular head, resembling a Turkish turban, with large cystic spaces replacing the brain. This constellation of findings was noted in 3 first-trimester fetuses. In 2 of them, it was possible to identify the amniotic membrane attached to the constriction ring. One case presented with anencephaly and fetal demise at 16 weeks. The other 2 women terminated the pregnancies and aborted anencephalic fetuses. This subtype of the acrania-anencephaly sequence could represent an earlier segmental rupture of the amnion, which subsequently entraps the developing fetal skull.

The etiopathogenic and morphological spectrum of anencephaly: a comprehensive review of literature

Anencephaly is a severe malformation of the central nervous system (CNS), being one of the most common types of neural tube defects. It is defined as total or partial absence of the calvarium, with absence of the brain. Anencephaly has an incidence of 1 to 5 in every 1000 births, and the mortality rate is 100% during intrauterine life or within hours or days after birth. The etiology of anencephaly remains unclear, but various maternal-related environmental and genetic risk factors have been reported, which include diabetes, obesity, exposure to different drugs or toxins, genetic polymorphisms and mutations, as well as positive family history for neural tube defects. One of the most important nutritional factors in the development of anencephaly is folate deficiency. Methylenetetrahydrofolate reductase (MTHFR) gene codes the enzyme involved in the intracellular metabolism of folic acid; the 677C-T polymorphism of this gene causes the thermolability of the enzyme and decreased enzymatic activity, which is also dependent of folate plasmatic level. Etiopathogenesis of anencephaly includes several mutations in various other genes, such as: platelet-derived growth factor receptor alpha (PDGFRA), cadherin epidermal growth factor (EGF) laminin G (LAG) seven-pass G-type receptor 1 (CELSR1), Vang-like 1 (VANGL1) and Vang-like 2 (VANGL2), the last two being involved in the process of neurulation. Screening tests include maternal serum alpha-fetoprotein level and ultrasound (US) examination. During the first trimester US screening, anencephaly is now detected in all cases, but in order to decrease the complication rate of pregnancy termination, the diagnosis should be established as soon as possible, during the pregnancy confirmation US. We conclude that given that anencephaly is a severe malformation of the CNS, morphological characterization could improve the screening by US that is mandatory in the first trimester in order to plan the best, safe and early management.