Electroclinical features of MEF2C haploinsufficiency-related epilepsy: A multicenter European study

Federico Raviglione;Sofia Douzgou;Marcello Scala;Alessia Mingarelli;Stefano D'Arrigo;Elena Freri;Francesca Darra;Sabrina Giglio

Membro del Collaboration Group

;Maria C Bonaglia;Chiara Pantaleoni;Massimo Mastrangelo;Roberta Epifanio;Maurizio Elia;Veronica Saletti;Silvia Morlino;Maria Stella Vari;Paola De Liso;Julija Pavaine;Luigina Spaccini;Elisa Cattaneo;Elena Gardella;Rikke S Møller;Francesca Marchese;Clara Colonna;Claudia Gandioli;Giuseppe Gobbi;Dipak Ram;Orazio Palumbo;Massimo Carella;Michele Germano;Davide Tonduti;Diego De Angelis;Davide Caputo;Patrizia Bergonzini;Francesca Novara;Orsetta Zuffardi;Alberto Verrotti;Alessandro Orsini;Alice Bonuccelli;Maria Carmela De Muto;Marina Trivisano;Federico Vigevano;Tiziana Granata;Bernardo Dalla Bernardina;Antonia Tranchina e Pasquale Striano

2021-01-01

---

Abstract

Purpose Epilepsy is a main manifestation in the autosomal dominant mental retardation syndrome caused by heterozygous variants in MEF2C . We aimed to delineate the electro-clinical features and refine the genotype-phenotype correlations in patients with MEF2C haploinsufficiency. Methods We thoroughly investigated 25 patients with genetically confirmed MEF2C -syndrome across 12 different European Genetics and Epilepsy Centers, focusing on the epileptic phenotype. Clinical features (seizure types, onset, evolution, and response to therapy), EEG recordings during waking/sleep, and neuroimaging findings were analyzed. We also performed a detailed literature review using the terms “MEF2C”, “seizures”, and “epilepsy”. Results Epilepsy was diagnosed in 19 out of 25 (∼80%) subjects, with age at onset <30 months. Ten individuals (40%) presented with febrile seizures and myoclonic seizures occurred in ∼50% of patients. Epileptiform abnormalities were observed in 20/25 patients (80%) and hypoplasia/partial agenesis of the corpus callosum was detected in 12/25 patients (∼50%). Nine patients harbored a 5q14.3 deletion encompassing MEF2C and at least one other gene. In 7 out of 10 patients with myoclonic seizures, MIR9-2 and LINC00461 were also deleted, whereas ADGRV1 was involved in 3/4 patients with spasms. Conclusion The epileptic phenotype of MEF2C -syndrome is variable. Febrile and myoclonic seizures are the most frequent, usually associated with a slowing of the background activity and irregular diffuse discharges of frontally dominant, symmetric or asymmetric, slow theta waves with interposed spike-and-waves complexes. The haploinsufficiency of ADGRV1, MIR9-2 , and LINC00461 likely contributes to myoclonic seizures and spasms in patients with MEF2C syndrome.