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SYNGAP1 encephalopathy: A distinctive generalized developmental and epileptic encephalopathy
Danique R M Vlaskamp1, Benjamin J Shaw1, Rosemary Burgess1
1From the Epilepsy Research Centre (D.R.M.V., B.J.S., R.B., M.F.B., S.F.B., M.S.H., I.E.S.), Department of Medicine, University of Melbourne, Austin Health, Australia; Departments of Genetics (D.R.M.V., C.M.A.v.R.-A.) and Neurology (D.R.M.V.), University Medical Center Groningen, University of Groningen, the Netherlands; Pediatric Neurology Unit and Laboratories (D.M., M.M.) and Pediatric Neurology (R.G.), Neurogenetics and Neurobiology Unit and Laboratories, A. Meyer Children's Hospital, University of Florence, Italy; Department of Pediatrics and Pediatric Epilepsy Centre (H.X., W.X.W., Y.J.), Peking University First Hospital, Beijing, China; Department of Pediatrics (C.T.M., H.C.M.), Division of Genetic Medicine, University of Washington, Seattle; Population Health and Immunity Division (M.F.B.), Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia; Department of Medical Biology (M.F.B.), University of Melbourne, Australia; Caulfield (D.W.), Melbourne, Australia; Department of Clinical Genetics (S.M.M.), Academic Medical Centre, Amsterdam, the Netherlands; Department of Clinical Genetics (A.S.B., G.M.S.M., I.M.B.H.v.d.L.), Erasmus University Medical Centre, Rotterdam, the Netherlands; Department of Clinical Genetics (J.M.v.H.), VU University Medical Center, Amsterdam, the Netherlands; Tasmanian Health Service (T.L.W.), Women's and Children's Services, Launceston General Hospital, Tasmania, Australia; TY Nelson Department of Neurology and Neurosurgery (R.I.W.) and Institute of Neuroscience and Muscle Research (R.I.W.), Children's Hospital at Westmead, Sydney, Australia; Department of Neurosciences (S.M.), Lady Cilento Children's Hospital, Brisbane, Australia; Department of Anatomical Pathology (R.M.K.), Austin Hospital, Melbourne, Australia; IRCCS Stella Maris Foundation (F.S., R.G.), Pisa, Italy; Klinikum Oldenburg (G.C.K.), Zentrum für Kinder-und Jugendmedizin, Klinik für Neuropädiatrie u. angeborene Stoffwechselerkrankungen, Oldenburg, Germany; Centre of Epilepsy (Y.J.), Beijing Institute for Brain Disorders, China; Department of Paediatrics (I.E.S.), University of Melbourne, Royal Children's Hospital, Australia; and Florey Institute of Neurosciences and Mental Health (I.E.S.), Parkville, Australia.
Syngap1-related disorder is a generalized developmental and epileptic encephalopathy characterized by specific epilepsy syndromes, including eyelid myoclonia with absences and eating-triggered seizures.
Area of Science:
- Genetics
- Neurology
- Epileptology
Background:
- SYNGAP1 gene mutations are associated with a spectrum of neurodevelopmental disorders.
- Epilepsy is a common and significant feature of the SYNGAP1 phenotypic spectrum.
- Understanding the specific epilepsy characteristics is crucial for patient management.
Purpose of the Study:
- To characterize the epileptology in a large cohort of patients with SYNGAP1 variants.
- To define the epilepsy phenotype associated with SYNGAP1 mutations and microdeletions.
- To identify specific seizure types and triggers in this patient population.
Main Methods:
- Retrospective analysis of 57 patients with pathogenic SYNGAP1 variants or microdeletions.
- Phenotypic data collected via standardized epilepsy questionnaires, medical records, EEG, MRI, and seizure videos.
- Detailed analysis of seizure types, onset, triggers, and associated developmental and neurological features.
Main Results:
- 56 out of 57 patients presented with epilepsy, predominantly generalized (55/56).
- A novel drop attack pattern involving eyelid myoclonia was identified.
- Common seizure types included eyelid myoclonia with absences, myoclonic, atypical absences, and atonic seizures, with 25% triggered by eating.
- Developmental delay and intellectual disability were near-universal, often preceding seizure onset and indicative of a developmental and epileptic encephalopathy (DEE).
- Other frequent features included behavioral problems, eating difficulties, hypotonia, sleep disturbances, autism spectrum disorder, and ataxia.
Conclusions:
- SYNGAP1 mutations are a significant cause of generalized developmental and epileptic encephalopathy (DEE).
- The study identified a distinctive epilepsy syndrome associated with SYNGAP1, including eyelid myoclonia with absences and myoclonic-atonic seizures.
- A notable predilection for eating-triggered seizures was observed in this cohort.
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