The development of the fetal vermis: an in-utero sonographic evaluation

MRI of fetal and neonatal cerebellar development

In the last few years magnetic resonance imaging (MRI) has expanded its diagnostic capability in the evaluation of fetal brain. Starting from the 18th to 20th gestational weeks, MRI can reliably depict fetal brain anatomy and locate pathology, offering a robust and reliable tool for the assessment of disorders of the fetal central nervous system. In this review quantitative and qualitative in vivo MRI data on fetal cerebellar development are presented. Our normative reference data have been obtained from a database of 580 MR fetal imaging studies. Normal cases were selected within normal MRI fetal brain studies, and all selected cases had a normal clinical evaluation and a normal cranial ultrasound or MR image after birth. Fetal cerebellar development is gradual, steady, and grossly comparable to the development of the supratentorial brain. Archicerebellar (flocculonodular lobe) and paleocerebellar (vermis) structures develop before the neocerebellum (cerebellar hemispheres) that develops more slowly and largely after birth.

Development of the human fetal pons: in utero ultrasonographic study

OBJECTIVES

To examine the ultrasonographic feasibility of imaging the fetal pons and to construct a reference chart for its normal development during gestation.

METHODS

A cross-sectional, prospective study on 293 healthy fetuses of low-risk pregnancies between 19 and 34 weeks was performed. The transfontanel approach, via the abdominal or vaginal routes, was used to evaluate the fetal metencephalon (pons and cerebellum). The anteroposterior diameter of the fetal pons was measured in a mid-sagittal plane. The longitudinal diameter of the cerebellar vermis was measured at the same plane and the vermis-pons ratio (VPR) was established.

RESULTS

One hundred and forty-four fetuses were in vertex position. In 140 (97.2%) satisfactory visualization and measurements of the pons and cerebellar vermis were obtained. One hundred and forty-nine fetuses were breech presentations and measurements were successfully performed in 147 (98.6%). The pons anteroposterior and vermis longitudinal diameters showed a linear correlation with gestational age (GA) (r = 0.95 for both measurements; P < 0.001). The mean VPR was 1.5 (+/-0.1 SD) and did not change in the gestational interval that was considered.

CONCLUSION

By using the transfontanel approach, evaluation of the fetal pons is feasible via the mid-sagittal plane. The nomograms developed and the ratio to fetal vermis provides reference data that may be helpful when evaluating anomalies of the brainstem.