Antenatal diagnosis of the absent inferior cerebellar vermis – is there any clinical significance?

Objective: The clinical significance of antenatal ultrasound diagnosis of the absent inferior cerebellar vermis (AICV), whether isolated or associated with other ultrasound findings, has not been well-understood with limited research previously. Because of its association with some syndromes, e.g. Dandy–Walker or Walker–Warburg syndromes, we aim to study the outcome for the purpose of counseling of parents when this is diagnosed antenatally. Methods: A single-center, prospective observational study of screening scans of a low risk population was conducted from 1 October 1996 to 30 September 2000. Cases of AICV diagnosed were followed up postnatally for up to 4 years with cranial ultrasound and developmental assessments. Results: There were 56 746 screening scans on 64 225 babies delivered during this period. Twenty-eight cases of AICV were diagnosed between 19 and 34 weeks. Six had isolated AICV and all occurred in women less than 35 years old. All had normal outcome and developmental assessment on follow up. The other 22 were associated with other ultrasound findings like echogenic bowel, structural heart defects or Dandy–Walker malformation. Four of them occurred in mothers 35 years and older with three (75%) having abnormal karyotype. Five occurred in mothers aged 30–34 years with two (40%) having abnormal karyotype. Of the remaining 13 in those less than 30 years, five (38%) had abnormal karyotype. These include trisomy 13 and 18, Turner and Goldenhar syndrome. Conclusion: The antenatal diagnosis of the isolated AICV is associated with low risk of chromosomal abnormalities and thus, does not require further karyotypic analysis. However, if other ultrasound findings are also seen, an abnormal karyotype can be expected in up to 38% of the patients (in our series), and even more (75%) if the maternal age is 35 years and above. Karyotyping should be offered in these cases. [ABSTRACT FROM AUTHOR]