Vermian maturity assessment (approach)

Radiological evaluation of the posterior fossa is an essential part of the routine fetal assessment, including vermian maturity assessment.

Radiographic features

Ultrasonography is a readily available diagnostic tool in the assessment of the fetal posterior fossa but is sometimes limited due to a variety of pathologies that can look similar and even identical on standard axial ultrasonography. Also, true sagittal and coronal views of the posterior fossa are difficult to achieve, leading to false positive vermian pathologies ¹. The use of fetal MRI is extremely useful in difficult cases.

MRI

The role of MRI includes ^2:

• documentation of the normal MRI landmarks of developing fetal posterior fossa
• prediction of poor neurological prognosis by assessment of the degree of lobulation
• diagnostic strategy in difficult cases, e.g. Dandy-Walker continuum, vermian hypoplasia, mega cisterna magna, posterior fossa arachnoid cyst

MRI assessment of vermian maturity includes ³:

• vermian lobulation
• tegmento-vermian angle
• craniocaudal diameter of vermis
• ratio of vermian tissue above and below the fastigial point