Chronic Subdural Hematomas—A Retrospective Analysis of the Internal Architecture and Evaluation of Risk Factors for Recurrences After Surgical Therapy

<b>Background:</b> Chronic subdural hematoma (CSDH) is increasingly common due to the aging population and widespread use of anticoagulant and antiplatelet medications. The objective of this study is to examine the internal composition of CSDH and explore potential risk factors associated with its recurrence. <b>Methods:</b> This retrospective study analyzed data from 189 patients who underwent surgery in our department between 2014 and 2018. Recorded data included demographics, clinical information, details of surgical interventions, computer tomography (CT) scans, neurological assessments, and follow-up data. The outcome was evaluated clinically and through CT follow-up conducted 4-12 weeks post-surgery. CT scans measured various parameters, including hematoma thickness, hyperdense regions, chronic components, and membrane presence. <b>Results:</b> Patients after the evacuation of CSDH were significantly more common males (66.1%, <i>p</i> > 0.001) had a significantly higher BMI (<i>p</i> < 0.001, 61.6%), arterial hypertension (<i>p</i> < 0.001, 68.3%), and the intake of anticoagulant therapy (<i>p</i> < 0.001, 58%). The recurrence rate was 18.6% after 4 weeks and 2.1% after 8-12 weeks. After uni- and multivariable analysis, the initial hemispheric type (<i>p</i> = 0.019, HR: 3.191; <i>p</i> = 0.012, HR: 3.810) and the increasing preoperative midline shift in CT (<i>p</i> = 0.028, HR: 1.114; <i>p</i> = 0.041, HR: 1.107) were found as independent predictors for recurrence. Overall, outcomes were favorable with a modified Rankin scale (mRS) of 0-2 at discharge (72%), after 4 (89.7%) and 12 (87%) weeks. <b>Conclusion:</b> According to our data, increasing midline shift before surgery and initial hemispheric type of hematoma were independent predictors of recurrence. Most patients achieved an excellent outcome with a low-risk profile.