Female, 24 years old, 22 weeks gestation, twins, with brain abnormalities detected on ultrasound of the male twin. Please note that assessment is limited to fetus1 which is on the maternal right in cephalic presentation.The corpus callosum is absent with an expected colpocephalic pattern of lateral ventricular prominence. In addition, there is a gap of at least 8 mm within the right cerebral hemisphere which allows communication between the extracerebral CSF and the ventricular system. The choroid plexus appears to dangle through this defect. Severe parenchymal thinning or encephalomalacia affects the bilateral paramedian parietal lobes. Frank parenchymal loss is seen in the bilateral occipital lobes, right side more than left.The third and fourth ventricles are within normal limits. The posterior fossa structures are normal. Apart from the above-mentioned parenchymal lesions, the overall pattern of parenchymal development is appropriate for age.
Multiple intracranial abnormalities are identified in fetus 1 (cephalic, maternal right) including agenesis of the corpus callosum, a parenchymal defect in the right cerebral hemisphere which may represent schizencephaly, and bilateral parenchymal defects involving the parietal and occipital lobes. The posterior fossa structures are spared.