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"cerebellar vermis" AND "fetal MRI" AND hypoplasia

Here is a full, plain-language interpretation of this fetal brain MRI report:

Fetal Brain MRI - Plain Language Interpretation

Patient: Rita Shrestha, 25 years old Date: June 29, 2026 Scan type: MRI of fetal brain (no contrast), 3.0T scanner Fetal age at scan: 20 weeks + 4 days

What Was Measured and What It Means

The Good News - Most Things Are Normal

What was checkedResultStatus
Transverse cerebellar diameter2.0 cm (5th percentile = 1.77 cm)✅ Normal
Vermis AP dimension7.7 mm (5th percentile = 5.9 mm)✅ Normal
Vermis area0.7 cm² (expected 0.7 ± 0.3 cm²)✅ Normal
Tegmento-vermian angle8° (normal < 10°)✅ Normal
4th ventricle coverage by vermisComplete✅ Normal
4th ventricle sizeNormal✅ Normal
BrainstemNormal morphology✅ Normal
Corpus callosumPresent, normal✅ Normal
Cerebral hemispheresSymmetric, normal sulcation for GA✅ Normal
VentriclesNormal size and configuration✅ Normal
Placenta locationAnterior wall✅ Normal

The One Borderline Finding

  • Cerebellar vermis height = 9.8 mm - slightly below the 5th percentile (which is 10.69 mm for this gestational age)
The cerebellar vermis is a small worm-shaped structure in the middle of the cerebellum (the back part of the brain that controls coordination and balance). Its height is just marginally smaller than expected.

The Key Point: What Does This Mean?

The radiologist's impression is reassuring but cautious, for three important reasons:
  1. The tegmento-vermian angle is only 8° (normal is < 10°). This is the single most important angle measured. It effectively rules out true vermian hypoplasia and Dandy-Walker malformation, both of which cause a rotated, upwardly displaced vermis with angles > 18-45°.
  2. The vermis completely covers the 4th ventricle, and there is no communication between the 4th ventricle and the cisterna magna. This rules out Blake's pouch cyst and Dandy-Walker spectrum disorders.
  3. All other measurements are normal, so this isolated borderline height could simply be a normal anatomic variation - the baby may just naturally have a slightly smaller vermis that will grow normally.
The radiologist's conclusion is:
"This could represent mild vermian hypoplasia OR normal anatomic variation. This can only be separated by strict follow-up with imaging."

What Is the Follow-Up Plan?

The radiologist recommends:
  1. Weekly or biweekly ultrasound - to measure transverse cerebellar diameter, vermian height, and AP dimension and track growth
  2. Repeat fetal brain MRI at 24-26 weeks - if ultrasound shows no growth or any new abnormality
This is a sensible, evidence-based approach. A 2025 meta-analysis on isolated fetal posterior fossa anomalies supports the practice of follow-up imaging for borderline findings, as outcomes for isolated mild findings are often favorable. Similarly, a 2025 single-center study on isolated vermian hypoplasia found that neurodevelopmental outcomes in truly isolated cases can be normal to mildly affected, emphasizing the importance of distinguishing isolated from non-isolated cases.

Bottom Line Summary

  • The overall fetal brain MRI is largely reassuring
  • The only concern is the cerebellar vermis height being just below the 5th percentile, but all the critical measurements that distinguish serious malformations (angle, coverage, 4th ventricle) are completely normal
  • This is a borderline finding - not a diagnosis of a malformation, but it needs to be watched
  • You must follow up with your obstetrician and the referring doctor (Dr. Anita Shrestha) who will coordinate serial ultrasounds and potentially a repeat MRI at 24-26 weeks
  • Do not panic - the radiologist has explicitly stated this may simply be a normal variation for this baby
⚠️ Disclaimer: This is an educational interpretation only. Please discuss all findings and the follow-up plan with your obstetrician or maternal-fetal medicine specialist, who has full clinical context including your pregnancy history and ultrasound results.
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