Cerebellar vermis and cerebral fissure evaluation in fetuses with isolated mega cisterna magna: a retrospective magnetic resonance imaging study.

backgroundTo assess vermian biometry and cerebral fissure depth in fetuses with isolated MCM and to examine postnatal neurodevelopmental outcomes.

methodsFetal cisterna magna, transcerebellar diameter, vermis anterioposterior, vermis cranio-caudal, parieto-occipital fissure and calcarine fissure depth measurements were performed by a radiologist and a perinatologist on fetal magnetic resonance images using our hospital’s Image Archiving and Communication System. The measurements obtained from fetuses with isolated mega cisterna magna (n = 48) and fetuses with normal fetal MRI findings included as a control group (n = 100) were analyzed comparatively. For postnatal neurodevelopmental assessment in the isolated mega cisterna magna group, parents were contacted by telephone using the contact information available in the hospital electronic archive. During these interviews, information was obtained regarding whether the children demonstrated age-appropriate overall development, achieved major developmental milestones on time (particularly independent walking), and had any history of neurodevelopmental or psychiatric diagnoses established by a child psychiatrist. In addition, the need for supportive interventions, including speech therapy or occupational therapy, was also questioned.

resultsVermian cranio-caudal diameters were significantly greater in the isolated mega cisterna magna group than in the control group at 32, 33, and 34 weeks of gestation (p = 0.015, p = 0.028, and p = 0.028, respectively). The parieto-occipital fissure depth was significantly greater in the isolated mega cisterna magna group compared with controls both in the overall analysis (9.6 ± 3.0 mm vs. 8.4 ± 2.5 mm, p = 0.012) and in the gestational week specific analysis at 31 and 34 weeks. No significant differences were observed for the remaining measurements between the groups. With the exception of two cases that resulted in exitus, no neurodevelopmental abnormality was identified in the isolated mega cisterna magna group.

conclusionIsolated fetal mega cisterna magna remains a challenging finding in prenatal practice, especially in terms of counseling expectant parents and fetal monitoring. Therefore, evaluation of fetal vermis in combination with cerebral fissures may provide a more comprehensive view of brain development and help clarify the clinical significance of this finding. Furthermore, postnatal neurodevelopmental outcomes in infants are generally reassuring. We believe that these findings may contribute to the existing literature and support prenatal counseling in isolated cases of mega cisterna magna.