Vermian Agenesis or Hypoplasia with Mega Cisterna Magna

Diagnostic Approach

The American College of Radiology recommends performing a detailed multiplanar ultrasound examination, including sagittal views, to distinguish true vermian agenesis from benign vermian rotation when vermian agenesis or hypoplasia with mega cisterna magna is suspected on routine axial ultrasound 1
Morphometric analysis is necessary to determine vermian size, as visual assessment alone may miss true hypoplasia 2

The American Heart Association, as published in Circulation, recommends genetic evaluation for all fetuses with vermian agenesis or hypoplasia with mega cisterna magna, as this finding is associated with multiple genetic syndromes and chromosomal abnormalities 3
Offer amniocentesis or chorionic villus sampling for karyotype analysis and chromosomal microarray, as genetically transmitted disorders account for approximately one-third of cases with multiple anomalies 3

The American Academy of Pediatrics recommends obtaining postnatal brain MRI with diffusion-weighted imaging to characterize the specific pattern and identify associated malformations that may not have been apparent on prenatal imaging 2
Implement developmental surveillance and screening using standardized tools at regular intervals, as children with cerebellar anomalies are at increased risk for developmental disabilities 2

The American College of Radiology recommends performing serial ultrasound examinations for growth monitoring, assessment of progression, and delivery planning if the pregnancy is continued 1
Schedule follow-up ultrasound at 32 weeks gestation to reassess the finding and evaluate for development of additional anomalies 1