Risk Factors for Contralateral Progression after Unilateral Burr-Hole Evacuation of Bilateral Chronic Subdural Hematoma

Abstract Purpose Contralateral hematoma progression (CHP) is a common condition among bilateral chronic subdural hematoma (bCSDH) patients after the unilateral evacuation. Investigations focusing on this topic are limited. The author aims to identify risk factors correlated with the CHP. Methods 82 patients with bCSDH who underwent the unilateral evacuation in Beijing Tiantan Hospital from 2011 to 2021 were included in this retrospective study. Clinical information and radiological features of these patients were collected and analyzed. Chi Square test, Student t test and Mann-Whitney test was performed to find variables which were statistically significant (p < 0.05), then multivariate analysis was applied to identify the independent risk factors. Results In our research, the progression rate was up to 13.41% (11/82). The mean age of CHP patients was significantly higher than non-CHP patients (72.45 ± 12.78 vs 62.85 ± 13.91, p = 0.025). Contralateral hematoma locating on the curved side was more likely to progress (p = 0.007). The other risk factors including pre- and post-operative volume of hematoma in the non-surgical side and the wide type of contralateral hematoma. The multivariate analysis demonstrated that the wide type of contralateral hematoma was one of the independent risk factors for CHP (OR = 8.769, p = 0.020, 95%CI 1.410-54.545). Moreover, the opposite hematoma locating on the curved side was also associated with the contralateral progression independently (OR = 7.103, p = 0.033, 95%CI 1.168–43.213). Conclusion For bCSDH patients, wide contralateral hematoma may increase the risk of CHP. Moreover, non-operative hematoma which locates on the curved side of skull is also an independent risk factor for the enlargement of opposite hematoma. Patients with such radiological characteristic may need additional medical treatment and rigorous follow-up to prevent the progression of contralateral hematoma.