Air matters: the role of postoperative intracranial pneumocephalus in recurrence of chronic subdural hematomas evaluated through a multivariate analysis of 460 patients comparing closed drainage versus standard irrigation

OBJECTIVE Chronic subdural hematoma (CSDH) is a common neurosurgical pathology, especially among older patients, with increasing incidence due to aging populations and widespread antithrombotic use. Despite the relatively straightforward nature of its surgical treatment, recurrence remains a major concern, with rates up to 30% reported. Among the factors implicated in recurrence, postoperative pneumocephalus has emerged as a significant and potentially modifiable risk factor. This study aimed to compare the efficacy and safety of a burr hole craniostomy with a closed drainage system (CDS) versus the traditional burr hole with standard irrigation (SI), with a focus on recurrence, pneumocephalus, and patient recovery. METHODS This retrospective, single-center cohort study included 460 patients undergoing surgical evacuation of symptomatic CSDH between 2010 and 2024. Patients were divided into two groups based on surgical technique: CDS (n = 358) and SI (n = 102). Demographics, clinical status, radiological features, and surgical outcomes were analyzed. Univariate and multivariate logistic regression analyses were utilized to assess predictors of 30-day recurrence. Volumetric analysis of hematomas and pneumocephalus was performed using standardized imaging protocols. RESULTS Baseline characteristics were well balanced. Postoperative pneumocephalus was significantly reduced in the CDS group (3.0 ± 1.78 cm 3 ) compared with SI (49.3 ± 11.97 cm 3 ) (p < 0.0001). Recurrence rates were markedly lower in the CDS group (10.1% vs 27.5%, p < 0.001), with CDS also associated with a mean shorter hospital stay (6.8 vs 11.2 days, p < 0.001), faster hematoma reabsorption (2.1 vs 3.2 months, p < 0.001), and lower 30-day mortality (1.1% vs 4.9%, p = 0.042). Multivariate analysis identified postoperative pneumocephalus volume (OR 1.0293 per cm 3 , p < 0.001) and residual hematoma (OR 1.00 per cm 3 , p = 0.046) as the only independent predictors of recurrence, while undergoing SI as opposed to the CDS was associated with a significantly increased risk of recurrence (OR 6.63, 95% CI 1.08–40.74; p = 0.041). No significant association was found between recurrence and antithrombotic therapy. CONCLUSIONS The CDS technique offers a cost-effective, safe, and efficient approach for the treatment of CSDH. By limiting air entry and promoting controlled drainage, it significantly reduces recurrence and improves patient outcomes. Given its simplicity and low resource requirements, the CDS method should be considered as a preferred first-line surgical strategy, particularly in the context of value-based care for an aging population.