Surgery · Medical Literature
Comparative outcomes of unilateral and bilateral drainage in bilateral chronic subdural hematoma: A systematic review and meta-analysis.
Abstract
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.
Clinical relevance
Bilateral chronic subdural hematoma (CSDH) is a common neurosurgical entity disproportionately affecting older adults, yet the optimal operative strategy — unilateral versus bilateral burr-hole drainage in a single setting — has lacked high-quality comparative evidence. This systematic review and meta-analysis of 11 studies and 1,390 patients directly addresses that clinical equipoise, providing the most comprehensive pooled analysis to date. The findings are immediately relevant to practicing neurosurgeons who must make intraoperative decisions about contralateral drainage in this vulnerable population.
Key findings
1. Unilateral drainage was associated with a significantly higher recurrence rate compared with bilateral drainage (8 studies, n = 1,172; OR = 1.45, 95% CI 1.06–1.98, p = 0.02), with mild heterogeneity that resolved on sensitivity analysis (OR = 1.65, 95% CI 1.13–2.16, p = 0.007; I² = 0%). 2. Reoperation was significantly more frequent following unilateral drainage (7 studies, n = 953; OR = 1.73, 95% CI 1.21–2.48, p = 0.003; I² = 0%), indicating a meaningfully higher surgical burden in this group. 3. Among patients initially managed with unilateral drainage, 14.3% subsequently required contralateral treatment (9 studies; 95% CI 9.2%–19.3%), reflecting a clinically important rate of staged reoperation. 4. No statistically significant differences were identified between unilateral and bilateral drainage with respect to mortality, overall postoperative complications, or surgical site infection, suggesting comparable safety profiles. 5. The evidence base comprised one RCT and ten cohort studies (total n = 1,390; 623 unilateral, 767 bilateral), with risk of bias assessed via ROB 2 and the Newcastle-Ottawa Scale; the predominance of observational data represents a limitation. 6. Heterogeneity for the primary recurrence outcome was mild and fully resolved on sensitivity analysis (I² = 0%), strengthening confidence in the pooled effect estimate.
Practice implications
For adult patients presenting with bilateral CSDH requiring surgical intervention, bilateral burr-hole drainage performed in the same operative setting should be favored over unilateral drainage, given significantly lower rates of recurrence (OR 1.45–1.65 favoring bilateral) and reoperation (OR 1.73) without an increase in mortality, complications, or infection. Surgeons adopting a selective unilateral approach must counsel patients and families that approximately 1 in 7 (14.3%) will require subsequent contralateral intervention, adding operative risk, anesthesia exposure, and resource utilization — a particularly relevant consideration in elderly or anticoagulated patients with limited physiologic reserve. Future prospective RCTs should stratify by hematoma volume asymmetry, midline shift, and neurological grade to identify subgroups in whom a staged unilateral strategy may remain appropriate.