Frontal bilateral megalencephaly: fetal and autopsy MR evaluation of an unclassified malformation

OBJECTIVE: To describe an unreported brain malformation with in utero onset. METHODS: A 21-weeks-of-gestational-age fetus underwent prenatal MR imaging because of macrocephaly detected by ultrasound. Prenatal MR imaging revealed a complex brain malformation. At 22 weeks of GA, pregnancy was terminated; an MR autopsy study was also performed. RESULTS: MR imaging revealed frontal bilateral megalencephaly and malformation of cortical development, suggesting polymicrogyria. These findings do not fit into any of the known megalencephalic syndromes. CONCLUSIONS: To our knowledge, this is a previously unreported malformation. Fetal and autoptic MR examination have been the best tools in understanding this complex brain pathology, allowing a more complete genetic counseling.