CLINICAL ARTICLE J Neurosurg 134:1743–1750, 2021 ABBREVIATIONS AUC = area under the curve; EOR = extent of resection; KPS = Karnofsky Performance Status; ML = machine learning; PROM = patient-reported out- come measure. SUBMITTED February 29, 2020. ACCEPTED April 6, 2020. INCLUDE WHEN CITING Published online June 12, 2020; DOI: 10.3171/2020.4.JNS20643. Development and external validation of a clinical prediction model for functional impairment after intracranial tumor surgery Victor E. Staartjes, BMed, 1,2 Morgan Broggi, MD, PhD, 3 Costanza Maria Zattra, MD, 3 Flavio Vasella, MD, 1 Julia Velz, MD, 1 Silvia Schiavolin, PsyD, 4 Carlo Serra, MD, 1 Jiri Bartek Jr., MD, PhD, 5–7 Alexander Fletcher-Sandersjöö, MD, 5,6 Petter Förander, MD, PhD, 5,6 Darius Kalasauskas, MD, 8 Mirjam Renovanz, MD, 8 Florian Ringel, MD, 8 Konstantin R. Brawanski, MD, 9 Johannes Kerschbaumer, MD, 9 Christian F. Freyschlag, MD, 9 Asgeir S. Jakola, MD, PhD, 10,11 Kristin Sjåvik, MD, PhD, 12 Ole Solheim, MD, PhD, 13 Bawarjan Schatlo, MD, 14 Alexandra Sachkova, MD, 14 Hans Christoph Bock, MD, 14 Abdelhalim Hussein, MD, 14 Veit Rohde, MD, 14 Marike L. D. Broekman, MD, PhD, 15,16 Claudine O. Nogarede, MSc, 15,16 Cynthia M. C. Lemmens, MD, 17 Julius M. Kernbach, MD, 18 Georg Neuloh, MD, 18 Oliver Bozinov, MD, 1 Niklaus Krayenbühl, MD, 1 Johannes Sarnthein, PhD, 1 Paolo Ferroli, MD, 3 Luca Regli, MD, 1 and Martin N. Stienen, MD, FEBNS 1 1 Department of Neurosurgery and Machine Intelligence in Clinical Neuroscience (MICN) Laboratory, Clinical Neuroscience Center, University Hospital Zurich, University of Zurich, Switzerland; 2 Amsterdam UMC, Vrije Universiteit Amsterdam, Neurosurgery, Amsterdam Movement Sciences, Amsterdam, The Netherlands; 3 Department of Neurosurgery, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan; 4 Neurology, Public Health and Disability Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; 5 Department of Neurosurgery, Karolinska University Hospital, Stockholm; 6 Department of Clinical Neuroscience and Medicine, Karolinska Institutet, Stockholm, Sweden; 7 Department of Neurosurgery, Rigshospitalet, Copenhagen, Denmark; 8 Department of Neurosurgery, University Medical Center, Johannes Gutenberg University Mainz, Germany; 9 Department of Neurosurgery, Medical University of Innsbruck, Austria; 10 Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg; 11 Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden; 12 Department of Neurosurgery, University Hospital of North Norway, Tromsö; 13 Department of Neurosurgery, St. Olav’s University Hospital, Trondheim, Norway; 14 Department of Neurosurgery, Georg August University, University Medical Center, Göttingen, Germany; 15 Department of Neurosurgery, Haaglanden Medical Center, The Hague; 16 Department of Neurosurgery, Leiden University Medical Center, Leiden; 17 Department of Neurology, Haaglanden Medical Center, The Hague, The Netherlands; and 18 Department of Neurosurgery, Faculty of Medicine, RWTH Aachen University, Aachen, Germany OBJECTIVE Decision-making for intracranial tumor surgery requires balancing the oncological beneft against the risk for resection-related impairment. Risk estimates are commonly based on subjective experience and generalized num- bers from the literature, but even experienced surgeons overestimate functional outcome after surgery. Today, there is no reliable and objective way to preoperatively predict an individual patient’s risk of experiencing any functional impair- ment. METHODS The authors developed a prediction model for functional impairment at 3 to 6 months after microsurgical resection, defned as a decrease in Karnofsky Performance Status of ≥ 10 points. Two prospective registries in Swit- zerland and Italy were used for development. External validation was performed in 7 cohorts from Sweden, Norway, Germany, Austria, and the Netherlands. Age, sex, prior surgery, tumor histology and maximum diameter, expected major brain vessel or cranial nerve manipulation, resection in eloquent areas and the posterior fossa, and surgical approach were recorded. Discrimination and calibration metrics were evaluated. RESULTS In the development (2437 patients, 48.2% male; mean age ± SD: 55 ± 15 years) and external validation (2427 patients, 42.4% male; mean age ± SD: 58 ± 13 years) cohorts, functional impairment rates were 21.5% and J Neurosurg Volume 134 • June 2021 1743 ©AANS 2021, except where prohibited by US copyright law Unauthenticated | Downloaded 09/05/21 12:35 PM UTC