Quantitative diagnostic advantages of three-dimensional ultrasound volume imaging for fetal posterior fossa anomalies: Preliminary establishment of a prediction model.

Objectives: To quantitatively assess prenatal diagnostic performance of three-dimensional ultrasound (3D-US) for posterior fossa anomalies (PFA) and establish a preliminarily 3D-US prediction model.

Methods: Sixty singleton fetuses suspected of PFA by 2D-US presented their detailed 3D-US evaluation. The surface area of vermis (SAV), brainstem-vermis, and brainstem-tentorium angles were measured by 3D-US. The good prognosis was defined as normal neurodevelopmental outcome. MRI and autopsy were the diagnostic reference standard.

Results: There was a significant difference between 2D-US (60.0%, 36/60) and 3D-US (94.8%, 55/58) for the diagnostic accuracy (P < .01). Prenatal 3D-US prediction model was established with observed/expected SAV as the main predictor (area under the curve [AUC]: 0.901; 95% CI, 0.810-0.992, P < .001). When it was more than 107.5%, the prognosis seemed to be good (sensitivity: 96.4%, specificity: 26.7%), which led to consideration of mega cisterna magna, Blake pouch cyst, or small arachnoid cyst. The prognosis appeared to be poor when it was less than 73% (sensitivity: 71.4%, specificity: 100%), and the diagnosis tended to be a Dandy-Walker malformation, vermian hypoplasia, and cerebellar hypoplasia. Brainstem-vermis and brainstem-tentorium angles were the secondary indicators (AUC: 0.689 vs 0.761; 95% CI, 0.541-0.836 vs 0.624-0.897, P = .014 vs.001).

Conclusions: It seems that the exact types of PFA can be effectively diagnosed by quantitative indicators of 3D-US.