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

Seizure. 2021 May:88:60-72. doi: 10.1016/j.seizure.2021.03.025. Epub 2021 Mar 30.


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.

Keywords: EEG; Electro-clinical phenotype; Epilepsy; MEF2C, ADGRV1; Seizures; Therapy.

Publication types

  • Multicenter Study

MeSH terms

  • Electroencephalography
  • Epilepsies, Myoclonic*
  • Epilepsy* / genetics
  • Haploinsufficiency
  • Humans
  • Intellectual Disability* / genetics
  • MEF2 Transcription Factors* / genetics
  • Seizures


  • MEF2 Transcription Factors
  • MEF2C protein, human