{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T09:53:43Z","timestamp":1791280423921,"version":"4.1.0"},"reference-count":15,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Epilepsia"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This study was undertaken to establish expert consensus clinical and diagnostic criteria for ring chromosome 20 syndrome using a modified electronic Delphi process.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this modified two\u2010round electronic Delphi consensus study, international experts rated candidate statements using a 9\u2010point Likert scale. Consensus was predefined as at least 70% agreement. A disagreement index assessing rating dispersion was calculated for each statement. The international expert consensus study was conducted remotely using Research Electronic Data Capture. Thirteen international experts with clinical and\/or research expertise in ring chromosome 20 syndrome were invited; 12 completed Round 1, and 11 completed Round 2. Experts evaluated statements developed by a steering committee across clinical and diagnostic domains, including age at onset, seizure phenotype, comorbidities, treatment response, laboratory testing, neuroimaging, electroencephalographic findings, and genetic\/genomic testing. Statements not reaching consensus after Round 1 were revised and redistributed in Round 2. Proportion of statements achieving consensus agreement was determined, and high\u2010agreement statements were synthesized into key diagnostic criteria.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Consensus was achieved for 25 clinical statements and 19 diagnostic statements, with agreement ranging from 73% to 100%. Clinical consensus emphasized normal early development before seizure onset, seizure onset most commonly between ages 4 and 8\u2009years in mosaic cases, rapid progression to drug resistance, and recurrent nonconvulsive status epilepticus with fluctuating cognitive impairment. Diagnostic consensus highlighted the limited utility of routine laboratory testing and neuroimaging, while strongly endorsing a characteristic electroencephalographic pattern of prolonged rhythmic theta activity over frontal and temporal regions. Participants unanimously agreed that karyotype analysis is required for diagnosis and that next generation sequencing modalities cannot reliably establish diagnosis in mosaic cases.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Significance<\/jats:title>\n                    <jats:p>This study establishes the first internationally accepted consensus clinical and diagnostic criteria for ring chromosome 20 syndrome. These criteria provide a framework to improve recognition of this underdiagnosed epilepsy syndrome and reinforce the continued importance of cytogenetic testing in childhood onset drug\u2010resistant epilepsy.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/epi.70525","type":"journal-article","created":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T09:17:09Z","timestamp":1791278229000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Establishing consensus diagnostic criteria for ring chromosome 20 syndrome: A modified electronic Delphi consensus study"],"prefix":"10.1002","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-9375-7674","authenticated-orcid":false,"given":"Abizairie","family":"S\u00e1nchez\u2010Feliciano","sequence":"first","affiliation":[{"name":"Department of Dermatology Brigham and Women's Hospital  Boston Massachusetts USA"},{"name":"Case Western Reserve University School of Medicine  Cleveland Ohio USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-6006-0856","authenticated-orcid":false,"given":"William D.","family":"James","sequence":"additional","affiliation":[{"name":"Department of Dermatology Perelman School of Medicine at the University of Pennsylvania  Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7121-0705","authenticated-orcid":false,"given":"Mark P.","family":"Fitzgerald","sequence":"additional","affiliation":[{"name":"Division of Neurology, Children's Hospital of Philadelphia Epilepsy Neurogenetics Initiative, Perelman School of Medicine at University of Pennsylvania  Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7201-9710","authenticated-orcid":false,"given":"Allison","family":"Watson","sequence":"additional","affiliation":[{"name":"Ring 20 Research &amp; Support  Dorset UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1769-6548","authenticated-orcid":false,"given":"Angela","family":"Peron","sequence":"additional","affiliation":[{"name":"Department of Experimental and Clinical Biomedical Sciences Mario Serio University of Florence  Florence Italy"},{"name":"Division of Medical Genetics Meyer Children's Hospital Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)  Florence Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4515-0793","authenticated-orcid":false,"given":"Antonio","family":"Gil\u2010Nagel","sequence":"additional","affiliation":[{"name":"Epilepsy Unit, Department of Neurology Ruber International Hospital  Madrid Spain"},{"name":"Fundaci\u00f3n Iniciativa para las Neurociencias (Fundaci\u00f3n INCE)  Madrid Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7831-4593","authenticated-orcid":false,"given":"Kenneth A.","family":"Myers","sequence":"additional","affiliation":[{"name":"Division of Neurology, Department of Pediatrics, Montreal Children's Hospital McGill University Health Centre  Montreal Quebec Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2502-5496","authenticated-orcid":false,"given":"Kentaro","family":"Tokumoto","sequence":"additional","affiliation":[{"name":"National Epilepsy Center National Hospital Organization Shizuoka Institute of Epilepsy and Neurological Disorders  Shizuoka Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7118-0139","authenticated-orcid":false,"given":"Lieven","family":"Lagae","sequence":"additional","affiliation":[{"name":"Section of Pediatric Neurology, Department of Development and Regeneration University Hospitals KU Leuven, member of European Reference Network EPICARE  Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8109-3648","authenticated-orcid":false,"given":"Nancy B.","family":"Spinner","sequence":"additional","affiliation":[{"name":"Department of Pathology and Laboratory Medicine Northwell Health  New Hyde Park New York USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2062-8623","authenticated-orcid":false,"given":"Rhys H.","family":"Thomas","sequence":"additional","affiliation":[{"name":"Faculty of Medical Sciences Newcastle University  Newcastle Upon Tyne UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-1811-3187","authenticated-orcid":false,"given":"Rudolf R.","family":"Roth","sequence":"additional","affiliation":[{"name":"Department of Dermatology Perelman School of Medicine at the University of Pennsylvania  Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0170-1987","authenticated-orcid":false,"given":"Sarah","family":"Woodson","sequence":"additional","affiliation":[{"name":"Department of Neurology University of Maryland School of Medicine  Baltimore Maryland USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-7685-1768","authenticated-orcid":false,"given":"Tim","family":"Buckinx","sequence":"additional","affiliation":[{"name":"Ring 20 Research &amp; 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