NMDA receptor agonists have been used for many years to generate animal models of polymicrogyria, a malformation of cortical development. Fry et al. identify de novo GRIN1 mutations in eleven patients with severe bilateral polymicrogyria. Polymicrogyria-associated GRIN1 mutations cluster in specific protein domains and significantly alter NMDA receptor function.

Although the ketogenic diet (KD) has been widely accepted as a legitimate and successful therapy for epilepsy and other neurological disorders, its mechanism of action remains an enigma. The use of the KD causes major metabolic changes. The most significant of them seems to be the situation of chronic ketosis, but there are others as well, for instance, high level of polyunsaturated fatty acids (PUFAs). These “primary” influences lead to “secondary”, in part adaptive, effects, for instance changes in mitochondrial density and gene expression. Clinically, the influences of the diet are considered as anticonvulsive and neuroprotective, although neuroprotection can also lead to prevention of seizures. Potential clinical implications of these mechanisms are discussed.

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Pathogenic variants in A Disintegrin And Metalloproteinase (ADAM) 22, the postsynaptic cell membrane receptor for the glycoprotein leucine-rich repeat glioma-inactivated protein 1 (LGI1), have been recently associated with recessive developmental and epileptic encephalopathy. However, so far, only two affected individuals have been described and many features of this disorder are unknown. We refine the phenotype and report 19 additional individuals harboring compound heterozygous or homozygous inactivating ADAM22 variants, of whom 18 had clinical data available. Additionally, we provide follow-up data from two previously reported cases. All affected individuals exhibited infantile-onset, treatment-resistant epilepsy. Additional clinical features included moderate to profound global developmental delay/intellectual disability (20/20), hypotonia (12/20), delayed motor development (19/20). Brain MRI findings included cerebral atrophy (13/20), supported by post-mortem histological examination in patient-derived brain tissue, cerebellar vermis atrophy (5/20), and callosal hypoplasia (4/20). Functional studies in transfected cell lines confirmed the deleteriousness of all identified variants and indicated at least three distinct pathological mechanisms: defective cell membrane expression (1), impaired LGI1-binding (2), and/or impaired interaction with the postsynaptic density protein PSD-95 (3). We reveal novel clinical and molecular hallmarks of ADAM22 deficiency and provide knowledge that might inform clinical management and early diagnostics.