Two-Dimensional Ultrasound Evaluation of the Fetal Cerebral Aqueduct: Improving the Antenatal Diagnosis and Counseling of Aqueductal Stenosis

Objective: To describe a technique for the visualization and measurement of cerebral aqueduct diameter through a 2D sagittal median plane, and to report its aspect and measurement in fetuses with aqueductal stenosis (AS). Methods: This was a cross-sectional study of 207 morphologically normal fetuses in low-risk pregnancies between 20 and 36 weeks of gestation. The cerebral aqueduct was visualized transvaginally in a midsagittal plane, and measurements of its greatest diameter (ampulla) were taken independently by an expert and a nonexpert sonographer. In addition, the aqueduct morphology from 7 fetuses with AS and complete follow-up were compared to the reference range. Results: Aqueductal measurements were obtained in 206 of 207 normal fetuses. Aqueductal growth occurred linearly with gestational age. Our method demonstrated excellent interobserver reproducibility. Among the 7 fetuses with AS, the aqueductal lumen could not be identified in 6 and had a funneling aspect in 1. Discussion: Our study demonstrated that it is possible to visualize and measure the cerebral aqueduct directly through a 2D ultrasound median plane. In fetuses with severe ventriculomegaly, the morphology and width of this structure could represent a relevant tool in improving AS diagnosis, differentiating it from other causes of significant ventricular dilation that carry a different outcome.