Posterior Fossa Anomalies: A Detailed Review of Prenatal Findings and Management from a Tertiary Care Center
Tanisha Gupta1, K Aparna Sharma2, Vatsla Dadhwal1
1Department of Obstetrics and Gynecology, All India Institute of Medical Sciences, New Delhi, India.
Insights
Posterior fossa anomalies (PFAs) have varied outcomes, requiring detailed prenatal diagnosis and genetic testing. The Medical Termination of Pregnancy Act facilitated terminations for severe cases, impacting pregnancy outcomes.
Area of Science:
- Neuroscience
- Medical Genetics
- Prenatal Diagnosis
Background:
- Posterior fossa anomalies (PFAs) are a group of congenital central nervous system malformations.
- These anomalies affect critical structures like the cerebellum and brainstem.
- Understanding their prenatal diagnosis, genetic basis, and outcomes is crucial for clinical management.
Purpose of the Study:
- To evaluate the prenatal diagnosis and genetic findings of PFAs.
- To analyze pregnancy outcomes, including termination and neonatal survival.
- To assess the role of genetic testing and the impact of the Medical Termination of Pregnancy (MTP) Act.
Main Methods:
- Retrospective analysis of 35 PFAs cases diagnosed via ultrasound and fetal MRI.
- Classification of anomalies and genetic testing (karyotype, CMA, WES).
- Documentation of pregnancy outcomes and short-term neurodevelopmental follow-up.
Main Results:
- Common PFAs included Vermian Agenesis/Hypoplasia and Cerebellar Hypoplasia.
- 62.85% of cases had additional anomalies; genetic variants found in 5.71%.
- 65.71% of pregnancies were terminated; 2/9 live births died neonatally, 6 showed normal development at 6 months.
Conclusions:
- PFAs have diverse prognostic implications requiring comprehensive evaluation.
- Detailed imaging and genetic assessment are essential for individualized counseling.
- The MTP Amendment Act facilitated termination for severe PFAs with poor prognoses.
Introduction:
Posterior fossa anomalies (PFAs) encompass a spectrum of central nervous system malformations affecting the cerebellum, brainstem, and surrounding cerebrospinal fluid spaces. This study evaluates the prenatal diagnosis, genetic findings, and pregnancy outcomes of PFAs in a tertiary care setting in India.
Methods:
A retrospective analysis was conducted on 35 cases of PFAs diagnosed via prenatal ultrasound and fetal MRI between January 2023 and May 2024. Anomalies were classified based on standard criteria, and genetic testing (karyotype, chromosomal microarray analysis, and whole-exome sequencing) was offered. Pregnancy outcomes, including termination, live birth, and neonatal survival, were documented, with short-term neurodevelopmental follow-up conducted via telephonic inquiries.
Results:
The most common PFAs identified were vermian agenesis/hypoplasia (VH) and cerebellar hypoplasia, each accounting for 25.71% of cases, followed by Dandy-Walker malformation (20%). Isolated PFAs were observed in 37.14% of cases, while 62.85% had additional anomalies. Genetic testing was performed in 74.2% of cases, revealing variants in 5.71%. Karyotyping was performed in all tested cases and yielded normal results, while additional molecular testing with chromosomal microarray analysis (5 cases) and whole-exome sequencing (3 cases) detected clinically relevant variants in selected fetuses with PFAs. Among the 35 pregnancies, 65.71% opted for termination, facilitated by the Medical Termination of Pregnancy (MTP) Act, particularly for cases diagnosed beyond 24 weeks of gestation. Of the 9 live births, 2 neonates with VH (5.71%) died within 1 month, while 6 (17.14%) had normal developmental milestones at 6 months including 6 babies with mega cisterna magna and one with an arachnoid cyst. One infant exhibited delayed milestones.
Conclusion:
PFAs are present with diverse prognostic implications, necessitating detailed imaging, genetic evaluation, and individualized counseling. The MTP Amendment Act played a crucial role in providing extended access to termination in pregnancies with severe PFAs and poor prognoses.
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