MR imaging of the fetal cerebellar vermis: Biometric predictors of adverse neurologic outcome

Purpose: To provide normal biometry of the cerebellar vermis using fetal MR and determine threshold values associated with abnormal neurologic outcome. Materials and Methods: Cerebellar vermis biometry was applied in prospective, cross-sectional evaluation of fetal brains. Vermis length and inferior vermian distance were obtained in mid-sagittal planes using T2-weighted, single-shot sequences with 1.5 Tesla MR. Measurements were compared with reference nomograms from a retrospective review of fetal brains with normal intracranial anatomy. Observed and predicted measurements of the cerebellar vermis were recorded. Neurologic outcome was classified as normal or abnormal. Unpaired t-tests and discriminate analysis were applied to the two measurements and differences between the observed and predicted values. Results: The reference group included 64 fetuses of 13 to 38 weeks gestation. Both vermis length and inferior vermian distance increased linearly with time (r = 0.92, P < 0.001; r = 0.32, P = 0.01). The prospective group included 64 additional fetuses with documented normal (39/64, 61%) and abnormal (25/64, 39%) outcomes. Significant differences were seen in vermis length, inferior vermian distance, and correlation with predicted values based on neurologic outcome (P < 0.001). Vermis length discrepancy ≥ 4 mm or inferior vermian distance ≥ 4 mm were associated with abnormal neurologic outcome. Conclusion: MR measurements of a short, raised vermis characterized by a vermis length discrepancy ≥ 4 mm or an inferior vermian distance ≥ 4 mm is associated with abnormal neurologic, syndromic, and developmental outcomes. J. Magn. Reson. Imaging 2016;44:1284–1292.