Delayed rotation of the cerebellar vermis: a pitfall in early second-trimester fetal magnetic resonance imaging

J. Pinto, D. Paladini, M. Severino, G. Morana, R. Pais, C. Martinetti, A. Rossi

Research output: Contribution to journalArticlepeer-review


We describe two cases in which delayed rotation of the cerebellar vermis simulated a Dandy–Walker malformation (DWM) on early second-trimester magnetic resonance imaging (MRI). Two pregnant women with suspected fetal posterior fossa anomaly on ultrasound examination underwent fetal MRI at 21 (Case 1) and 19 (Case 2) weeks' gestation. In both cases, upward rotation of the cerebellar vermis was noted; on midsagittal imaging, the brainstem–vermis angle was 28° and 43°, respectively, while cerebellar morphometry showed a reduced vermian anteroposterior diameter compared to reference data. The posterior fossa appeared to be mildly enlarged, while all other findings were normal. Follow-up MRI at 28 + 3 weeks' gestation (Case 1) and at 1 postnatal year (Case 2) showed completely normal findings. Both children had normal psychomotor development and neurological examinations at 1 year of age. Incomplete rotation of the cerebellar vermis can be a physiological finding on early second-trimester fetal MRI examination and can simulate DWM or other forms of cerebellar hypoplasia. Embryologically, delayed permeabilization of Blake's pouch could account for the delayed vermian rotation. Follow-up imaging at a later gestational age is crucial to ensure that this condition is not over-reported and to avoid the potential risk of unnecessary pregnancy interruption.

Original languageEnglish
Pages (from-to)121-124
Number of pages4
JournalUltrasound in Obstetrics and Gynecology
Issue number1
Publication statusPublished - Jul 1 2016


  • Blake's pouch
  • Dandy–Walker malformation
  • fetal MRI
  • posterior fossa malformation
  • vermian hypoplasia

ASJC Scopus subject areas

  • Obstetrics and Gynaecology
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Reproductive Medicine


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