Neuroimaging Features of GRIN-Related Epilepsies

N-methyl-D-aspartate receptors (NMDARs) are ionotropic glutamate channels that play a pivotal role in brain development and the regulation of learning and memory processes. De novo pathogenic variants in four genes encoding NMDA receptor subunits (GRIN1, GRIN2A, GRIN2B, and GRIN2D) have been implicated in a broad spectrum of neurodevelopmental disorders, including developmental delay, intellectual disability, autism spectrum disorders, epilepsy, and movement disorders. Mutations in the GRIN1 and GRIN2B genes, which encode the GluN1 and GluN2B subunits, respectively, are strongly associated with malformations of cortical development, including diffuse dysgyria, bilateral polymicrogyria, hippocampal dysplasia, corpus callosum hypoplasia, and other findings such as ventricular enlargement and basal ganglia abnormalities. Conversely, GRIN2A mutations are associated with heterogeneous and less specific neuroimaging patterns. We reviewed the existing literature on the neuroradiological features associated with GRIN gene mutations, also providing pictorial representations from our patient cohort. The analysis revealed a more consistent association of malformations of cortical development with GRIN1 and GRIN2B variants, likely reflecting the critical role of these genes in neuronal migration and proper development of cortical structures. In comparison, GRIN2A mutations are associated with milder brain abnormalities. An integrated assessment of neuroimaging patterns and GRIN gene variants provides valuable insights for differential diagnosis and supports targeted genetic screening in patients presenting with epileptic encephalopathy, global developmental delay, and autism spectrum disorders.