To ensure our findings were not simply due to differences in the interpretation of radiology we reviewed MRI brain images from four previous non-polymicrogyria patients with GRIN1 mutations (p.Asp552Glu, p.Met641Ile, p.Gly815Arg and p.Gly827Arg) (Ohba et al., 2015; Lemke et al., 2016). This evidence concerns the gene GRIN1 and polymicrogyria.