Risk factors for the development of chronic subdural hematoma in patients with subdural hygroma

Objective: Patients with subdural hygroma (SDG) are at increased risk of developing chronic subdural hematoma (CSDH). However, the factors that increase the risk of conversion are not fully understood. This study was to assess the risk factors of SDG conversion to CSDH. Methods: We reviewed the literature and retrospectively studied a series of cases in which CSDH was preceded by SDG to understand the natural history. We reviewed 45 cases of SDG from our hospital between 2015 and 2018. The cases were divided into two groups according to whether SDG converted into CSDH. Data were collected clinical presentation, imaging findings et al. Univariate and multivariate logistic regression analyses were performed to identify factors associated with SDG conversion. Results: Univariate analysis showed that the SDG thickness (p = .009), SDG location (p = .026), and bilateral SDG (p = .042) were significantly associated with CSDH development. Multivariate analysis revealed that SDG thickness (odds ratio, 1.6; 95% confidence interval, 1.111-2.324; p = .012) and bilateral SDG (odds ratio, 27.6; 95% confidence interval 2.889-263.548; p = .004) were independent risk factors for SDG development. Receiver operating characteristic curve analysis revealed that SDG thickness was a significant variable for predicting SDG development. A thickness >11.37 mm was an appropriate cutoff value, and the possibility of SDG conversion had a sensitivity 50.0% and specificity of 87.0%. Conclusions: Bilateral SDG and SDG thickness were independent risk factors for SDG progression into CSDH. An SDG thickness >11.37 mm had a high risk of SDG conversion.