P02.16: Diagnosis and clinical attendance on fetuses with Galen's vein aneurysms-Report of two cases

Objective: To describe the possibility of rotation of the vermis as the cause of enlarged posterior fossa in the fetus. Methods: Eight women were referred to our ultrasound unit for evaluation of enlarged posterior fossa with suspected agenesis of the vermis on axial plane. All women underwent thorough ultrasound evaluation, including demonstration of the posterior fossa on midsagittal plane with measurements of the vermis. All patients received a genetic as well as pediatric neurologist consultation. Results: The mean age of the women was 27 (with range of 20–33) years and the mean gestational week at diagnosis was 19.5 (with range of 15–25). On standard axial plane, there was a ‘‘direct communication’’ between the cysterna magna and the 4th ventricle. On mid-sagittal plane, however, the vermis could be very well delineated with slight anterior rotation. Its measurements were within normal limits for gestational age. The normality of the vermis was confirmed in prenatal MRI in 2 cases, on postnatal MRI and/or US in 5 cases and in PM in one case. The 7 alive children are well developed with no neurological sequels after a mean follow-up of 4 years (with range of 1–7.5). Conclusion: The demonstration of the normal vermis on mid-sagittal plane in cases with ‘‘enlarged posterior fossa’’ on standard plane raises the possibility of rotation of the vermis. We suggest that in every case of enlarged posterior fossa or suspected vermian agenesis, the mid-sagittal plane should be utilized and rotation of the normal vermis should be excluded.