Meeting report of the 20th International Congress of Neuropathology (ICN) 2023 in Berlin

Exactly 62 years to the month after the 4th International Congress of Neuropathology (ICN) took place from September 4th to 8th 1961 at the Ludwig Maximilian University of Munich, the global neuropathological community—or, more accurately, its neuropathological children and grandchildren—returned back to the 20th ICN, that is, ICN2023, in Berlin/Germany (12–16 September 2023). The archives of the International Society of Neuropathology (ISN), gainfully groomed by Maria Thom at University College, London/UK, provided extensive information on the scope, frame, and content of the earlier Munich ICN, which enabled a quick and insightful glimpse into the evolution of ICN between these two events, then and now. In 1961, the documents of the 4th ICN were primarily produced in German and only secondly in English. Abstracts could only be submitted for oral presentations, as posters had not been "invented" but the submission languages were quite diverse, with abstracts in English, German, French, Italian, and Spanish. However, whether the multilingual presentations were delivered in the language as their titles suggested, remains unknown. Around 230 presentations were listed in the program and were held in two parallel sessions covering main topics according to different methodological techniques: "Histochemistry, " "Electron microscopy" and "Tissue culture" as well as "Free Communication" the entire content of which was subsequently published as "Proceedings" by Thieme Publishing Company 1. The President of the International Committee of Neuropathology, Webb Haymaker from the United States, delivered a lengthy and solemn welcome opening address, presenting "perspectives on Neuropathology. " Following this, the local organizer and host of ICN1961, Willibald Scholz from Munich/Germany, and Hans Jacob, the General Secretary of ICN1961 from Marburg/Germany, addressed the audience. Recognition and merit awards were then presented to Armano Ferraro from New York City and Ludo van Bogaert from Antwerp. The presumably quite elaborate opening ceremony of ICN1961 was commented with a handwritten "Amen" in the archival papers by an unidentified critical reader. Two exhibitions, one with neuropathological slides and photographs, one with historical aspects of German Neuropathology, completed the scientific part of ICN1961. Socially, the participants were feasted to receptions hosted by the Bavarian State Government, the Mayor of Munich, a special opera performance of "Cosi fan tutte" at the Cuvillies Theater, and a gala banquet at the luxury hotel "Bayerischer Hof, " for a 15/20 registration fee and 5 for the banquet. A separate "Ladies' Program" encompassed a city tour, a visit to an antique collection, and a day tour to the tourist attraction "Wies-Kirche. " Finally, a post congress trip via Venice to the International Congress of Neurology in Rome was offered. In 2016, at the European Congress of Neuropathology in Bordeaux, France, the ISN Council assigned the 20th ICN to Frank Heppner and his Institute of Neuropathology in Berlin/Germany, ahead of its competitor Toronto. The 20th ICN was scheduled for 2022, 4 years after the ICN2018 in Tokyo. The general societal paralysis caused by the coronavirus pandemic and associated re-scheduling of the European Congress of Neuropathology in Odense, Denmark, for 2021 led to ICN2022 being postponed by 1 year to 2023. The uncertain pandemic situation during the planning phase of ICN2023 further compelled the organizers to offer a hybrid meeting that allowed both physical and virtual participation. Professor David Capper, Berlin, became the President and Professor Frank Heppner, Berlin, became the Vice president of ICN2023. They were supported by a local organizing committee, a program committee and a supporting scientific committee (refer to Supplementary Table 1 for individual members). The primary role of the supporting scientific committee was to screen and evaluate the submitted abstracts for the topic categories: "Neurooncology, " "Neurodegeneration, " "Epilepsy, " "Neuroimmunology, " "Muscle and Nerve, " and "Other fields of Neuropathology or method development. " A secondary role of this committee was to nominate outstanding scientific contributions during the conference, which were honored during the awarding ceremony. The Langenbeck-Virchow-Haus, located opposite the Charité Berlin hospital complex and named after Bernhard von Langenbeck (1810–1887), a well-known Charité surgeon and Rudolf Virchow (1821–1902), a highly reputed pathologist at the Charité, was selected as the local venue for ICN2023. The building is currently owned by the German Surgical Society and the Berlin Medical Association. During the times of the German Democratic Republic the Langenbeck-Virchow-Haus served as the East German parliament, and its first president, Wilhelm Pieck, was elected there twice. The building offers a large auditorium, actually the former parliament hall, and several smaller rooms on five floors for parallel sessions. Five large electronic poster-viewing stations were available for poster sessions and individual poster viewing, while printed posters were not on display due to limited space in the Langenbeck-Virchow-Haus and the incompatibility of printed posters and hybrid participation. This arrangement allowed participants to be housed in a single building for all scientific and poster sessions as well as coffee and lunch breaks and the welcome reception on Wednesday evening. A total of 58 distinguished speakers from the global ISN community were invited and an additional 110 speakers were selected from the submitted abstracts. To coordinate the sessions and discussions, 57 session chairs were selected from around the world. ICN2023 was scheduled to last for 4 days, with the first and the last days being ½ conference days. The conference was preceded by an "Education Day" and a half-day "EVEREST Pre-Congress Symposium" on low-grade glial and glioneuronal tumors. In total, 619 participants (305 males, 294 females, 1 non-binary, 19 missing data) from 55 countries registered for ICN2023 of whom 106 participated virtually (Figure 1A). From a total of approximately 350 submitted abstracts, the supporting scientific committee selected 333 abstracts for ICN2023: 139 for neurooncology, 85 for neurodegeneration, 35 for neuroimmunology, 25 for epilepsy, 23 for muscle by the Toronto group (abstract S19-ND-A147) on the specific dysregulation of iron hemostasis in the human brain; by the Mayo Clinic/Florida group (abstract S28-ND-A156) on the correlation between amyloid deposits, incl. "coarse-grained plaques" and tangles and glial activation in Alzheimer's disease; again by the Toronto group (abstract eP-ND-A223) on the molecular subtyping of progressive supranuclear palsy. In the neuroinflammation sessions, a comprehensive scientific cross-section was presented, encompassing also neuroinflammatory aspects in Neurodegeneration and Epilepsy. The sessions were not only limited to classical diseases such as multiple sclerosis, but also incorporated emerging entities characterized by autoantibodies. Romana Höftberger from Vienna greatly summarized these highlights in the cross-fields welcoming session; those who were not already fans of neuroimmunology will have become so by then at the latest. Noteworthy throughout the sessions was the seamless collaboration of speakers, bridging the expertise of neuropathologists, neurobiologists, and neurologists. This interdisciplinary approach aptly mirrors the dynamic nature of the current scientific landscape in this field. In addition, the abstract submission process clearly reflected the diverse interests of the participants. Although a specific session on the neurobiology of SARS-CoV-2 was not initially planned, the sheer volume of high-quality abstracts submitted necessitated the creation of a separate session specifically on SARS-CoV-2. This additional session demonstrated the unexpectedly high level of interest and contribution from our scientific community to this timely and crucial topic. This synergy between disciplines was also evident in the field of epileptic diseases. Both epilepsy session at ICN2023 made it clear that neuropathological research does not stand alone but rather represents an indispensable part of the complex puzzle of neuroscience. This holistic perspective strengthens the interconnectedness of various disciplines and underlines the central role of neuropathological findings in advancing our understanding of neurological disorders. The audience agreed emphatically and cast their votes with their feet. Despite the simultaneous occurrence of highly relevant Neurooncology sessions, the session on epilepsy with Ingmar Blümcke from Erlangen, Germany, and Eleonora Aronica from Amsterdam (Netherlands) attracted such a large crowd that the lectures were streamed in a second room. Highlights on the topic of Muscle and Nerve were: a prion study on necrotizing myopathy in murine muscle by Reimann et al. (abstract S13-MN-A267) ; a microvascular study in muscle on Long/post-Covid patients by Aschman et al. (abstract S21-NI-A238) ; a 3D demonstration of a neuromuscular junction in seronegative Myasthenia gravis by Dittmayer et al. (abstract S14-MN-A275) ; the myopathology in an SMA patient leading to genetic clarification by Meinhardt et al. (abstract eP-MN-A277) ; the myopathology in Ku myositis by Preusse et al. (abstract S14-MN-A276) ; and a presentation of the immunopathology in neuropathies by Vallat (separate review in this issue 2). Several groups seized the opportunity presented by ICN2023 and arranged in-person closed or open meetings. Figure 3, for example, illustrates a group photo taken during the closed meeting of the steering committee of cIMPACT-NOW, which convened during ICN2023 to discuss the forthcoming guidelines regarding "Clarifications of WHO 2021, " "Meningioma classification, " "Implementation of DNA methylation testing, " and "New entities. " An example of an open meeting attached to ICN2023 was the NATON (German National Autopsy Network) workshop. The revived interest in autopsy research sparked by the coronavirus pandemic has led to the formation of international autopsy registries. The workshop was highly productive, and all participants agreed that modern, well-curated, and electronically connected autopsy registries will continue to provide valuable neuropathological insights 3. Social activities included the breaks between scientific sessions, the welcome reception held on the ground floor of Langenbeck-Virchow-Haus, and a congress dinner in the restaurant "HABEL am Reichstag" within walkable distance from the conference venue. During the congress registration, attendees had the option to contribute funds for a "congress dinner solidarity ticket, " intended for students, neuropathology residents, or participants from countries with developing economies to apply for. A total of 800€ was donated, allowing to raffle off 16 tickets. The congress dinner offered a splendid selection of vegetarian German cuisine with tastefully modernized classics and savory new interpretations. The several rooms of the restaurant further allowed the opportunity for extensive conversation as well as dance and music, with the band Caramel Club from Hamburg playing their last encore at around 1: 00 AM. At the end of ICN2023, 10 awards were presented for outstanding scientific contributions in the main topic categories: 3 in neurodegeneration, 3 in neurooncology, 1 in "muscle & nerve, " 1 in neuroimmunology, 1 in epilepsy, 1 in "other fields of Neuropathology. " The awards ceremony was followed by a video "Welcome Address" from Colin Smith, the president of ICN2027 in Edinburgh, UK. Then, after 4 1/2 days of exciting science, the ICN2023 congress was officially closed on Saturday at 12: 30 PM by the congress president David Capper. Wer vieles bringt, wird manchem etwas bringen, und jeder geht zufrieden aus dem Haus. (Faust, J. W. Goethe) Who offers much will offer some to all, and everybody leaves the (Langenbeck-Virchow) house content. After the congress, participants were invited to complete a digital evaluation, and a total of 95 attendees responded. Supplementary Material 1 contains the compiled results of the evaluation. Overall, the feedback from participants on ICN2023 aligned with the post-congress motto, reflecting an overwhelmingly positive response. There was particularly high praise for neurooncology and its subtopics, including pediatric brain tumors, glial and non-glial neoplasms, as well as epilepsy and neurodegeneration. Notably, "Muscle and Nerve" received only marginal attention in the evaluation. Importantly, almost 90% of participants expressed their intention to attend ICN again. A suggestion for future improvement was to reintroduce a real-life poster exhibition to promote personal interaction between poster visitors and presenters. This was challenging at ICN2023 due to the hybrid organization format. Another suggestion was to permit virtual participation for the Education Day, a modification that the local organizing committee would also recommend following the rapid sale of education day tickets. Participants also positively highlighted more general and cross-disciplinary topics, such as the audience debate on "artificial intelligence in Neuropathology" and presentations on the future of publishing by various Neuropathology journal editors. HHG wrote the first manuscript draft, all authors approved the final manuscript version. The local organizing committee expresses its gratitude to all members of the program committee and the supporting scientific committee for their invaluable contributions. Additionally, we extend our thanks to the dedicated employees of the Institute of Neuropathology at Charité Berlin for their unwavering support and to Philipp Jurmeister for assistance with creating the tSNE of Figure 2B. ICN was partly funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) —Projektnummer 529570353. Additional support was provided by the International Society of Neuropathology (ISN), the German Society of Neuropathology and Neuroanatomy (DGNN) and the Deutsche Gesellschaft für Muskelkranke e. V. (DGM). Special appreciation is extended to Marlene Oberwahrenbrock as well as Dorothee Gröninger and Dirk Eichelberger (the latter two from Conventus Congressmanagement & Marketing GmbH) for their exceptional organizational efforts. Data sharing is not applicable to this article as no new data were created or analyzed in this study. Supplementary Material 1. Supporting information. Supplementary Table 1. Members of local organizing committee, program committee and supporting scientific committee. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.