A brain disorder caused by biallelic variants in NDE1 that is characterized by extreme microcephaly (typically head circumference of more than 10 standard deviations (SD) below the mean), profound motor and intellectual disability, spasticity, and incomplete cerebral formation. Radiologic studies demonstrate overt microcephaly with cortical dysgenesis ranging from simplification to pachygyria/lissencephaly to hydranencephaly. Agenesis of the corpus callosum as well as hypoplasia of the brainstem and cerebellum are typically present.