Predictive Value of MRI and US in the Detection of Fetal Posterior Fossa Anomalies

Background: Among all fetal anomalies, the Central Nervous System (CNS) represents one of the most frequently involved structures with an estimated incidence of 1 per 100 births. The Posterior Fossa (PF) malformations are among the most common brain anomalies identified by current fetal imaging techniques. Complete and exact prenatal diagnosis of fetal CNS anomalies as early as possible in pregnancy is essential for correct obstetric management and adequate counseling of the parents. Aim of the Work: To evaluate the accuracy and the predictive values of fetal MRI and US in the detection of PF anomalies comparing their end results with the post delivery scans. Patients and Methods: This study involved 45 pregnant female patients; their ages ranged from 20-35 years with a mean of 28.4 years ±4.8 (mean ± SD). (Gestational Age) GA ranged from 15th to 36th (Weeks Gestation) WG with a mean of 27.5t^h WG ±5.9 (mean ± SD). Cases were referred from Feto-maternal unit in Kasr Al-Aini Hospital, with suspected fetal CNS anomalies. Preliminary US examination was done in all cases using 3.5-5MHz curvilinear 2D transducer, 3D studies were done for selected cases. Fetal MRI was performed in all cases as a complementary examination. Using 1.5 T MR magnet with a multi-channel phased array coil to allow increased coverage of the fetal head. Prenatal results were correlated with postnatal (MRI or CT) imaging. This study was approved by the hospital research ethics committee. All patients were counseled and signed a consent form. Results: The results of this study showed superior diagnostic performance of fetal MRI compared to prenatal US in detection of PF anomalies.