Prenatal diagnosis of posterior fossa anomalies: Additional value of chromosomal microarray analysis in fetuses with cerebellar hypoplasia.

Objective: To elucidate the relationship between copy number variations (CNVs) detected by high-resolution chromosomal microarray analysis (CMA) and the type of prenatal posterior fossa anomalies (PFAs), especially cerebellar hypoplasia (CH).

Methods: This study involved 77 pregnancies with PFAs who underwent CMA.

Results: Chromosomal aberrations including pathogenic CNVs and variants of unknown significance were detected in 31.2% (24/77) of all cases by CMA and in 18.5% (12/65) in fetuses with normal karyotypes. The high detection rate of clinically significant CNVs was evident in fetuses with cerebellar hypoplasia (54.6%, 6/11), vermis hypoplasia (33.3%, 1/3), and Dandy-Walker malformation (25.0%, 3/12). Compare with fetuses without other anomalies, cases with CH and additional malformations had the higher CMA detection rate (33.3% vs 88.9%). Three cases of isolated unilateral CH with intact vermis and normal CMA result had normal outcomes. The deletion of 5p15, 6q terminal deletion, and X chromosome aberrations were the most frequent genetic defects associated with cerebellar hypoplasia.

Conclusion: Among fetuses with PFA, those with cerebellar hypoplasia, vermis hypoplasia, or Dandy-Walker malformation are at the highest risk of clinically significant CNVs. Chromosomal microarray analysis revealed the most frequent chromosomal aberrations associated with CH.