Objective: Our purpose was to evaluate the ventricular atria and cisterna magna in fetuses with and without suspected central nervous system (CNS) anomalies by magnetic resonance (MR).
Study design: Measurements of the right and left ventricular atria and cisterna magna were obtained by MR in two groups: those with and without CNS anomalies. Published mean ultrasound measurements of the far field atrium were compared with MR.
Results: MR measurements were obtained in 23 fetuses without and 37 fetuses with CNS anomalies. Atrial measurements were independent of gestational age in healthy subjects. MR atrial widths were larger in abnormal compared with normal subjects (P <.05). The atrial cutoff value derived by 2 SDs above the mean with MR is 10 mm. MR cisterna magna measurements increased with gestational age (P =.005).
Conclusion: The cutoff value for ventriculomegaly on MR is >10 mm. MR cisterna magna measurements are dependent on gestational age. Both ventricular atria and cisterna magna are readily measured with MR.