Frontiers in Cell and Developmental Biology (Mar 2024)

Developmental outcome of electroencephalographic findings in SYNGAP1 encephalopathy

  • Juliana Ribeiro-Constante,
  • Alba Tristán-Noguero,
  • Alba Tristán-Noguero,
  • Fernando Francisco Martínez Calvo,
  • Salvador Ibañez-Mico,
  • José Luis Peña Segura,
  • José Miguel Ramos-Fernández,
  • María del Carmen Moyano Chicano,
  • Rafael Camino León,
  • Víctor Soto Insuga,
  • Elena González Alguacil,
  • Carlos Valera Dávila,
  • Alberto Fernández-Jaén,
  • Laura Plans,
  • Ana Camacho,
  • Nuria Visa-Reñé,
  • María del Pilar Martin-Tamayo Blázquez,
  • Fernando Paredes-Carmona,
  • Itxaso Marti-Carrera,
  • Aránzazu Hernández-Fabián,
  • Meritxell Tomas Davi,
  • Merce Casadesus Sanchez,
  • Laura Cuesta Herraiz,
  • Patricia Fuentes Pita,
  • Teresa Bermejo Gonzalez,
  • Mar O'Callaghan,
  • Federico Felipe Iglesias Santa Polonia,
  • María Rosario Cazorla,
  • María Teresa Ferrando Lucas,
  • Antonio González-Meneses,
  • Júlia Sala-Coromina,
  • Alfons Macaya,
  • Amaia Lasa-Aranzasti,
  • Anna Ma Cueto-González,
  • Francisca Valera Párraga,
  • Jaume Campistol Plana,
  • Mercedes Serrano,
  • Xenia Alonso,
  • Diego Del Castillo-Berges,
  • Marc Schwartz-Palleja,
  • Marc Schwartz-Palleja,
  • Marc Schwartz-Palleja,
  • Sofía Illescas,
  • Alia Ramírez Camacho,
  • Oscar Sans Capdevila,
  • Angeles García-Cazorla,
  • Àlex Bayés,
  • Itziar Alonso-Colmenero

DOI
https://doi.org/10.3389/fcell.2024.1321282
Journal volume & issue
Vol. 12

Abstract

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SYNGAP1 haploinsufficiency results in a developmental and epileptic encephalopathy (DEE) causing generalized epilepsies accompanied by a spectrum of neurodevelopmental symptoms. Concerning interictal epileptiform discharges (IEDs) in electroencephalograms (EEG), potential biomarkers have been postulated, including changes in background activity, fixation-off sensitivity (FOS) or eye closure sensitivity (ECS). In this study we clinically evaluate a new cohort of 36 SYNGAP1-DEE individuals. Standardized questionnaires were employed to collect clinical, electroencephalographic and genetic data. We investigated electroencephalographic findings, focusing on the cortical distribution of interictal abnormalities and their changes with age. Among the 36 SYNGAP1-DEE cases 18 presented variants in the SYNGAP1 gene that had never been previously reported. The mean age of diagnosis was 8 years and 8 months, ranging from 2 to 17 years, with 55.9% being male. All subjects had global neurodevelopmental/language delay and behavioral abnormalities; 83.3% had moderate to profound intellectual disability (ID), 91.7% displayed autistic traits, 73% experienced sleep disorders and 86.1% suffered from epileptic seizures, mainly eyelid myoclonia with absences (55.3%). A total of 63 VEEGs were revised, observing a worsening of certain EEG findings with increasing age. A disorganized background was observed in all age ranges, yet this was more common among older cases. The main IEDs were bilateral synchronous and asynchronous posterior discharges, accounting for ≥50% in all age ranges. Generalized alterations with maximum amplitude in the anterior region showed as the second most frequent IED (≥15% in all age ranges) and were also more common with increasing age. Finally, diffuse fast activity was much more prevalent in cases with 6 years or older. To the best of our knowledge, this is the first study to analyze EEG features across different age groups, revealing an increase in interictal abnormalities over infancy and adolescence. Our findings suggest that SYNGAP1 haploinsufficiency has complex effects in human brain development, some of which might unravel at different developmental stages. Furthermore, they highlight the potential of baseline EEG to identify candidate biomarkers and the importance of natural history studies to develop specialized therapies and clinical trials.

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