Second trimester fetal MRI features in a fetus with TUBB3 gene mutation

Tubulinopathies are a heterogeneous group of complex cortical malformations that are associated with mutations in tubulin genes. TUBB3 gene mutation is associated with a broader spectrum of central nervous system malformations and constitutes about 10% of all tubulinopathies. The diagnosis may not be immediately apparent on imaging, though the differential diagnosis may be narrowed based on imaging findings and allow for more directed genetic testing. We report a 22-year-old gravida-1 nulliparous female whose routine second trimester fetal ultrasound revealed ventriculomegaly and possible agenesis of the corpus callosum. Fetal magnetic resonance imaging showed severe lateral and third ventriculomegaly and a dysplastic, z-shaped brainstem without any evidence of ocular abnormalities. Genetic testing revealed a pathogenic mutation in TUBB3.