A lissencephaly spectrum disorder that manifests as posterior predominant pachygyria (ranging from mild severity to classic lissencephaly) and brainstem malformations which include brainstem dysplasia (typically with reduced anteroposterior thickness and transverse broadening of the pons/medulla) and midline crossing defects (anterior commissure, transverse pontine fibers, pyramidal tract, callosum hypoplasia). [ https://www.clinicalgenome.org/affiliation/40020/ ]