Citation: Hamed, M.; Lampmann, T.; Salemdawod, A.; Asoglu, H.; Houedjissin, N.; Thudium, M.; Asadeh, L.; Schmeel, F.C.; Schuch, F.; Vatter, H.; et al. Correlation between Blood Type 0 and Risk of Chronic Subdural Hematoma Recurrence: A Single Center Retrospective Cohort Study. Brain Sci. 2023, 13, 567. https://doi.org/10.3390/ brainsci13040567 Academic Editor: Woon-Man Kung Received: 9 March 2023 Revised: 22 March 2023 Accepted: 24 March 2023 Published: 28 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). brain sciences Communication Correlation between Blood Type 0 and Risk of Chronic Subdural Hematoma Recurrence: A Single Center Retrospective Cohort Study Motaz Hamed 1 , Tim Lampmann 1 , Abdallah Salemdawod 1,2 , Harun Asoglu 1 , Naomi Houedjissin 1 , Marcus Thudium 3 , Lakghomi Asadeh 4 , Frederic Carsten Schmeel 4 , Fabiane Schuch 5 , Hartmut Vatter 1 and Mohammed Banat 1, * 1 Department of Neurosurgery, University Hospital Bonn, 53127 Bonn, Germany; motaz.hamed@ukbonn.de (M.H.); tim.lampmann@ukbonn.de (T.L.); abdallah.salemdawod@ukbonn.de (A.S.); harun.asoglu@ukbonn.de (H.A.); naomi.houedjissin@ukbonn.de (N.H.); hartmut.vatter@ukbonn.de (H.V.) 2 Center for Advanced Imaging Research, Department of Diagnostic Radiology and Nuclear Medicine, Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland, Baltimore, MD 20742, USA 3 Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, 53127 Bonn, Germany; marcus.thudium@ukbonn.de 4 Department of Neuroradiology, University Hospital Bonn, 53127 Bonn, Germany; asadeh.lakghomi@ukbonn.de (L.A.); carsten.schmeel@ukbonn.de (F.C.S.) 5 Department of Neurology, University Hospital Bonn, 53127 Bonn, Germany; fabiane.schuch@ukbonn.de * Correspondence: mohammed.banat@ukbonn.de Abstract: Chronic subdural hematoma (cSDH) is a common disease in the neurological and neuro- surgical world. The recommended treatment for cSDH patients with moderate or severe neurological symptoms is surgical evacuation, but cSDH frequently recurs. The patient’s ABO blood type may influence the outcome. This study aims to evaluate the correlation between cSDH recurrence and blood type O. We performed a retrospective analysis of the data of patients with cSDH who were surgically treated. Recurrence was defined as the need for re-operation within the first 12 weeks after the initial surgery. We analyzed standard demographic data, duration and type of surgery, ABO blood types, and the re-operation rate. Univariate and multivariate analyses were conducted. A total of 229 patients were included. The recurrence of hematoma was identified in 20.5% of patients. Blood type O was found to be significantly associated with cSDH recurrence leading to re-operation within 12 weeks (p = 0.02, OR 1.9, 95% CI 1.1–3.5). Thrombocyte aggregation inhibition and oral anticoagulants were not predictors of cSDH recurrence. Patients with blood type O in our cohort were identified to be at higher risk of cSDH recurrence and may, therefore, be a more vulnerable patient group. This finding needs further evaluation in larger cohorts. Keywords: chronic subdural hematoma; ABO blood type; minor head trauma 1. Introduction Chronic subdural hematoma (cSDH) is a common disease in the neurological and neurosurgical world. The incidence of cSDH increases with age [1]. This incidence in the population can be expected to increase over the next decades [2]. In addition to age, risk factors for cSDH include anticoagulation therapy, cerebral atrophy, alcoholism, and minor head injuries [3,4]. The clinical signs of cSDH vary between headaches and vomiting as a sign of raised intracranial pressure to hemispheric symptoms such as limb weakness, speech impairment, and gait disturbances or falls [5]. Surgical evacuation is the recommended treatment for patients with cSDH with relevant neurological symptoms, preferably by burr hole drainage and opening the dura to release the hematoma [6]. Brain Sci. 2023, 13, 567. https://doi.org/10.3390/brainsci13040567 https://www.mdpi.com/journal/brainsci