Good interobserver and intraobserver agreement in the evaluation of the new ILAE classification of focal cortical dysplasias

Coras R, De Boer OJ, Armstrong D, Becker A, Jacques TS, Miyata H, Thom M, Vinters HV, Spreafico R, Oz B, Marucci G, Pimentel J, Muehlebner A, Zamecnik J, Buccoliero AM, Rogerio F, Streichenberger N, Arai N, Bugiani M, Vogelgesang S, Macaulay R, Salon C, Hans V, Polivka M, Giangaspero F, Fauziah D, Kim JH, Liu L, Dandan W, Gao J, Lindeboom B, Bluemcke I, Aronica E (2012)

Publication Type: Journal article, Review article

Publication year: 2012


Book Volume: 53

Pages Range: 1341-1348

Journal Issue: 8

DOI: 10.1111/j.1528-1167.2012.03508.x


Summary Purpose: An International League Against Epilepsy (ILAE) consensus classification system for focal cortical dysplasias (FCDs) has been published in 2011 specifying clinicopathologic FCD variants. The aim of the present work was to microscopically assess interobserver agreement and intraobserver reproducibility for FCD categories among an international group of neuropathologists with different levels of experience and access to epilepsy surgery tissue. Methods: Surgical FCD specimens covering a broad histopathology spectrum were retrieved from 22 patients with epilepsy. Three surgical nonepilepsy specimens served as controls. A total of 188 slides with routine or immunohistochemical stainings were digitalized with a slide scanner to allow Internet-based microscopy review. Nine experienced neuropathologists were invited to review these cases twice at a time gap of 3 months and different orders of case presentation. The 2011 ILAE FCD consensus classification served as instruction. Kappa analysis was calculated to estimate interobserver and intraobserver agreement levels. In a third evaluation round, 21 additional neuropathologists with different experience and access to epilepsy surgery reviewed the same case series. Key Findings: Interobserver agreement was good (ΰ = 0.6360), with 84% consensus of diagnoses during the first evaluation (21 of 25 cases). Kappa values increased to 0.6532 after reevaluation, and consensus was obtained in 24 (96%) of 25 cases. Overall intraobserver reproducibility was also good (ΰ = 0.7824, ranging from 0.4991 to 1.000). Fewest changes in the classification were made in the FCD type II group (2.2% of 225 original diagnoses), whereas the majority of changes occurred in FCD type III (13.7% of 225 original diagnoses). In the third evaluation round, interobserver agreement was reflected by the level of experience of each neuropathologist, with ΰ values ranging from moderate (0.5056; high level of experience >40 cases/year) to low (0.3265; low level of experience <10 cases/year). Significance: Our study achieved a good and reliable interobserver agreement among the group of expert neuropathologists originally involved in the ILAE FCD consensus classification system. Intraobserver reproducibility in this group was even more robust. These results showed considerable improvement compared to a previous study evaluating the 2004 Palmini FCD classification. Agreement levels were lower in our second group of neuropathologists and were related to their level of access and experience with epilepsy surgery specimens. These results suggested that the more precise ILAE definition of FCD histopathology patterns improves operational procedures in the diagnosis of FCDs. On the other hand, microscopic assessment of FCD is a challenge and requires sustained experience and teaching. The virtual slide review system allowed testing of this hypothesis and reached a widespread group of participating colleagues from different centers all over the world. We propose to further use this tool as a teaching device and also to address other epilepsy-associated entities still difficult to classify such as hippocampal sclerosis, long-term epilepsy-associated tumors, or mild malformations of cortical development (mMCDs), which were not yet covered by current ILAE classification systems. © 2012 International League Against Epilepsy.

Authors with CRIS profile

Involved external institutions

Ajou University KR Korea, Republic of (KR) IRCCS Istituto Neurologico Mediterraneo Neuromed IT Italy (IT) Hôpitaux Universitaires Saint-Louis, Lariboisière, Fernand-Widal FR France (FR) Tsinghua University CN China (CN) Foundation of the Carlo Besta Neurological Institute (IRCCS) IT Italy (IT) Airlangga University / Universitas Airlangga ID Indonesia (ID) Università degli Studi di Firenze / University of Florence IT Italy (IT) University of Amsterdam NL Netherlands (NL) Evangelisches Krankenhaus Bielefeld DE Germany (DE) Université Claude Bernard Lyon 1 (UCB) FR France (FR) Universitätsklinikum Bonn DE Germany (DE) Houston Texas Medical Center US United States (USA) (US) University College London (UCL) GB United Kingdom (GB) Great Ormond Street Hospital (GOSH) GB United Kingdom (GB) University of Tokyo JP Japan (JP) Universität Greifswald DE Germany (DE) University of California Los Angeles (UCLA) US United States (USA) (US) Univerzita Karlova v Praze / Charles University in Prague CZ Czech Republic (CZ) Hospital de Santa Maria PT Portugal (PT) Vrije Universiteit Amsterdam (VU) / University Amsterdam NL Netherlands (NL) Universidade Estadual de Campinas (UNICAMP) / University of Campinas BR Brazil (BR) Medizinische Universität Wien AT Austria (AT) University of Bologna / Università di Bologna IT Italy (IT) Akita Research Institute of Brain and Blood Vessels / 秋田県立脳血管研究センター JP Japan (JP) Capital University of Medical Sciences / 首都医科大学 CN China (CN) Dalhousie University CA Canada (CA) Grenoble University Hospital Centre / Centre Hospitalier Universitaire de Grenoble (CHUG) FR France (FR) Peking Union Medical College / 北京协和医学院 CN China (CN) Istanbul University / İstanbul Üniversitesi TR Turkey (TR)

How to cite


Coras, R., De Boer, O.J., Armstrong, D., Becker, A., Jacques, T.S., Miyata, H.,... Aronica, E. (2012). Good interobserver and intraobserver agreement in the evaluation of the new ILAE classification of focal cortical dysplasias. Epilepsia, 53(8), 1341-1348.


Coras, Roland, et al. "Good interobserver and intraobserver agreement in the evaluation of the new ILAE classification of focal cortical dysplasias." Epilepsia 53.8 (2012): 1341-1348.

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