Evaluation of vermian lobulation is essential in assessment of the vermian maturity. MRI is a useful tool in assessment of the fetal posterior fossa.
Normal vermian lobulation by weeks 1:
- by 21 weeks: the prepyramidal fissure can be seen between the tuber and pyramis
- 21 to 22 weeks: the preculminate fissure can be seen in between the central lobule and culmen.
- 24 weeks: the secondary fissure can be seen between the pyramis and uvula
- from 27 weeks: all vermian lobules and fissures become visible