Comparative outcomes of unilateral and bilateral drainage in bilateral chronic subdural hematoma: A systematic review...

Background bilateral chronic subdural hematoma (CSDH) is frequently encountered in neurosurgical practice, particularly in older adults. While burr-hole drainage remains the standard treatment, the optimal surgical strategy for bilateral disease is still debated. In daily practice, surgeons often choose between unilateral drainage and bilateral drainage in the same operative setting. Clear evidence to support one approach over the other remains limited. Aim to compare the efficacy and safety of unilateral versus bilateral drainage in patients with bilateral CSDH through a systematic review and meta-analysis. Methods a systematic search of PubMed, Scopus, and Web of Science was conducted from inception to January 2026. Eligible studies included adult patients with bilateral CSDH undergoing unilateral or bilateral drainage. Primary outcome was recurrence. Secondary outcomes included reoperation, mortality, postoperative complications, infection, and the proportion of patients requiring additional contralateral treatment after unilateral drainage. Risk of bias was assessed using ROB 2 for randomized trials and the Newcastle-Ottawa Scale (NOS) for cohort studies. Comparative meta-analyses were performed using RevMan with a fixed-effect model, while single-arm pooling for contralateral retreatment was conducted using OpenMeta. Results eleven studies involving 1390 patients were included (623 unilateral; 767 bilateral), including one RCT and ten cohort studies. Unilateral drainage was associated with a significantly higher recurrence rate compared with bilateral drainage (8 studies, 1172 patients; OR = 1.45, 95% CI 1.06-1.98, p = 0.02), with mild heterogeneity that resolved after sensitivity analysis (OR = 1.65, 95% CI 1.13-2.16, p = 0.007; I² = 0%). Reoperation was also more frequent after unilateral drainage (7 studies, 953 patients; OR = 1.73, 95% CI 1.21-2.48, p = 0.003; I² = 0%). There were no significant differences between groups in mortality, overall complications, or infection. Among unilateral cases, 14.3% required subsequent contralateral treatment (9 studies; 95% CI 9.2%-19.3%), with moderate heterogeneity. Conclusion in bilateral CSDH, bilateral drainage is associated with lower recurrence and reoperation rates compared with unilateral drainage, while safety outcomes appear comparable.