Craniotelencephalic dysplasia is an extremely rare, genetic developmental defect during embryogenesis syndrome characterized by craniosynostosis with frontal encephalocele and various additional brain anomalies (severe hydrocephalus, agenesis of the corpus callosum, lissencephaly and polymicrogyria, parenchymal cysts, septo-optic dysplasia) resulting in marked cerebral dysfunction, seizures and very severe psychomotor delay. There have been no further descriptions in the literature since 1983. The disease is Monarch Disease Ontology identifier MONDO_0009042 (craniotelencephalic dysplasia).