Abstract / Summary
Abstract Background Postoperative chronic subdural hematoma (CSDH) thickness ≥ 10 mm has been used as an outcome measure in clinical trials. However, the relevance of this radiological threshold for patient outcome and reoperation risk remains uncertain. Methods In this post hoc study of the nationwide, multicenter, randomized FINISH trial, we stratified patients who underwent burr-hole drainage for CSDH according to postoperative hematoma thickness at 6 weeks (< 10 mm vs. ≥ 10 mm). We identified optimal thickness thresholds and evaluated their associations with functional outcome (modified Rankin Scale [mRS]), mortality, and reoperation at 6 weeks and 6 months. Results Median age of the 581 patients was 78 years (IQR 72–85). Postoperative hematoma thickness was ≥ 10 mm in 283 patients (49%). All evaluated thickness thresholds demonstrated poor discriminatory performance when used alone, and the relationship between the poor functional outcome and hematoma thickness was linear. After adjustment for baseline characteristics, patients with ≥ 10 mm thickness had worse functional outcomes (mRS) at both 6 weeks (adjusted odds ratio [aOR] 1.6, 95% CI 1.2–2.2, p = 0.004) and at 6 months (aOR 1.4, 95% CI 1.0–1.8, p = 0.049). There was no difference in dichotomized unfavorable outcome (6-month mRS 4–6: aOR 1.3, 95% CI 0.7–2.4, p = 0.48). Ninety-one patients (16%) were reoperated within 6 months and 50 (55%) within 6 weeks. Patients with ≥ 10 mm hematomas had markedly higher reoperation rates (32% vs. 0.7%, aOR 75.6, 95% CI 18.0–316.8, p < 0.001). Conclusion Postoperative CSDH thickness ≥ 10 mm at 6 weeks is associated with worse functional outcome and higher risk of reoperation. However, the relationship between functional outcome and hematoma thickness seems to be linear, making any single cut-off arbitrary. These findings suggest that although a 10 mm radiological threshold may serve as a surrogate endpoint in CSDH trials, it should complement rather than replace patient-centered outcomes.