Diagnostic efficacy and comparison of fetal MR morphometry and volumetry methods in posterior fossa malformations

Introduction and AimCystic malformation of the posterior fossa include; Dandy-Walker malformation(DWM), Dandy-Walker variant(DWV), megacisterna magna and posterior fossa arachnoid cyst. The advent of fetal magnetic resonance(MR) has provided a new tool in the imaging armamentarium, DWM, DWV and mega cisterna magna are currently belived to represent a continuum of development anomalies on a spectrum that has been termed the Dandy Walker complex.The outcomes are base on the degree of vermian hypoplasia/dysplasia, plus the presence of associated abnormalities.The aim of this study is to measure cerebellar volume, lineer dimensions and local surface area of vermis in a normal and abnormal groups and evaluate the better diagnostic parameters.Materials and MethodsThe study has been carried out between january 2006 and June 2011 on cases detected or suspected fetal anomaly on prenatal ultrasound examination or refered to Department of Radiology of DEUMF for the fetal MRI. The study population included 41 normal and abnormal fetuses. MR images of 41 fetuses were evaluated retrospectively and divided into six groups; DWM, DWV, posterior fossa arachnoid cyst/mega cisterna magna(PFAC/MCM), cerebellar hypoplasia, rhombencephalosynapsis and normal by experienced pediatric radiologist. For each group, vermis height, vermis anteroposterior diameter, surface of the vermis, the transverse cerebellar diameter, tegmento-vermian angle, biparietal diameter, posterior fossa volume, cerebellar volume, vermian diameter/biparietal diameter x 100 ratio(VD/BPDx100) were measured.Statistical analysis was performed using the SPSS 15 package for Windows. Non-parametric statistics, including Bonferroni corrected Kruskal-Wallis test and the Mann-Whitney U test, were employed to assess differences in means.ResultsThe study population included 41 normal and abnormal fetuses. MR images of 41 fetuses were evaluated retrospectively and divided into six groups; DWM, DWV, posterior fossa arachnoid cyst/mega cisterna magna, cerebellar hypoplasia, rhombencephalosynapsis and normal by experienced pediatric radiologist. In nine cases of the pathologic group diagnosis was confirmed at autopsy and only twelve cases of the all study group diagnosis was confirmed by postnatally MRI, CT or US.All groups compared with Mann Whitney U test.The comparison between normal and DWM group, vermis height, tegmento-vermian angle, surface of the vermis, cerebellar volume, VD/BPDx100 ratio were found statistically significant.The comparison between normal and DWV group, vermis height, tegmento-vermian angle and VD/BPDx100 ratio were were found statistically significant.The comparison between PFAC/MCM and normal group, the transverse cerebellar diameter, posterior fossa volume were found statistically significant.The comparison between cerebellar hypoplasia and normal group, all parameters except tegmento-vermian angle were found statisticaly significant.The comparison between DWM and PFAC/MCM group, vermis height, the transverse cerebellar diameter, tegmento-vermian angle, surface area of the vermis, cerebellar volume, VD/BPDx100 ratio were found statistically significant.The comparison between DWV and PFAC/MCM group, vermis height, tegmento-vermain angle, VD/BPDx100 ratio were found statistically significant.Discussion and ConclusionThe main aim of this study is to demostrate differential diagnostic biometric parameters and compare them with each other. In the literature some investigation are present associated with cerebellar and posterior fossa volume in normal fetüses. In our study different from the literature, normal and abnormal groups were compared and found that vermis height, tegmento-vermian angle, surface area of vermis, cerebellar volume, posterior fossa volume, VD/BPDx100 ratio were statistically significant.Cerebellar volume was found more reliable parameter than posterior fossa volume in DWM and normal group comparison.The further studies may be based on the relationship between morbidity and mortality with DWM and DWV group?s cerebellar volume.