Prenatal MRI features of fetal complete agenesis of the corpus callosum associated with unilateral hemispheric cortical malformation: a retrospective study

Introduction To explore the prenatal MRI features of fetal complete agenesis of the corpus callosum (cACC) associated with unilateral hemispheric cortical malformation. Methods A retrospective analysis was conducted on 101 cases diagnosed with cACC via prenatal MRI. Among them, 16 cases were found to be associated with unilateral hemispheric cortical malformation. The imaging characteristics of this specific malformation were analyzed, and its associations with fetal gender and gestational age were investigated. Results In this group of 16 cases of cACC with unilateral cortical malformation, 13 fetuses were male and 3 were female. The gestational age at diagnosis ranged from 23 weeks to 27 weeks and 2 days. The malformation was located in the left hemisphere in 7 cases and in the right hemisphere in 9 cases. Type I (C1 type: extensive cortical twisting/folding) was observed in 11 cases, all of which exhibited the “rake sign” and “garland sign”. The “rake sign” manifests as abnormally folded dysplastic cortex resembling a rake on axial or coronal views, while the “garland sign” appears as abnormally folded dysplastic cortex resembling a garland on sagittal views. Type II (C4 type: transcortical cleft formation) was observed in 1 case, and Type III (C5 type: focal cortical indentation or serrated changes) was observed in 4 cases. The unilateral cortical malformation involved the frontal lobe in 16 cases, the parietal lobe in 10 cases, and the occipital lobe in 8 cases, with no involvement of the temporal lobe. Discussion Fetal agenesis of the corpus callosum has a relatively high probability of being associated with unilateral cortical malformation. This malformation occurs more frequently in males, is mostly detected during the mid-trimester, and most commonly involves the frontal lobe. The “rake sign” and “garland sign” are its characteristic imaging features. Prenatal definitive diagnosis aids in the perinatal management of this malformation. Prenatal MRI is a crucial supplementary examination for fetal cACC diagnosed by prenatal ultrasound, as it can accurately detect associated unilateral hemispheric cortical malformations that are easily missed by ultrasound, and thus is essential for optimizing perinatal management and parental genetic counseling.