Utility of indirect sonographic signs (including cavum septum pellucidum ratio) in midgestational screening for partial agenesis of corpus callosum

PURPOSE: This study was undertaken to evaluate the performance of indirect sonographic signs in detecting partial agenesis of the corpus callosum (pACC) at midgestation, focusing on the cavum septum pellucidum (CSP) ratio. METHODS: A retrospective case-controlled study of singleton pregnancies was conducted, examining fetuses diagnosed with isolated pACC and normal controls. At midgestational age, fetal head volumes were imaged with 3D US and stored for the evaluation of indirect sonographic findings in axial planes. RESULTS: Fifteen normal and 15 abnormal fetuses (with pACC) were analyzed. Based on a CSP ratio < 1.5, detection of pACC increased from 66.7% (10/15) to 80% (12/15). All indirect signs proved highly suspicious for pACC (risk ratios > 1). CONCLUSION: Use of indirect sonographic signs to screen for pACC at midgestation is challenging. However, a low CSP ratio may improve the detection rate, serving as a new indirect sign.