Assessment of cerebellar vermis biometry at 18-32 weeks of gestation by three-dimensional ultrasound examination.

Objective: The purpose of this study was to construct reference limits for cerebellar vermis (CV) dimensions measured on images reconstructed from three-dimensional (3D) ultrasonography and to evaluate these measurements reproducibility.

Methods: 3D ultrasound volumes were acquired transabdominally from an axial view of the fetal head in 342 fetuses cross-sectionally studied between 18 to 32 weeks of gestation. Offline analysis of fetal brain midsagittal plane was used to evaluate length and area of CV. The agreement between two-dimensional (2D) and 3D measurements as well as the interobserver variability in 3D measurements were assessed by interclass correlation coefficients (ICC).

Results: Adequate visualization of the midsagittal plane was obtained in 96.7% of the fetuses. CV length (r = 0.89, p < 0.0001) and CV area (r = 0.93, p < 0.0001) showed a significant linear growth with gestation. A good agreement was found between measurements from either 2D or 3D ultrasound views (CV length ICC 0.943, CV area ICC 0.940) as well as between measured obtained by different observers (CV length ICC 0.965, CV area ICC 0.905).

Conclusions: Measurements of the CV can be obtained from the midsagittal plane of fetal brain reconstructed from 3D volumes acquired transabdominally. The constructed nomograms may facilitate the diagnosis of cerebellar abnormalities.