Background: Chronic subdural hematoma (CSDH) is a common condition among older people living with frailty. Outcome after surgery is generally good, but there is a significant proportion of patients who do not benefit from surgery. This study aimed to identify predictors of failure to improve functional outcomes after CSDH surgery.

Methods: This is a post-hoc analysis of the nationwide FINISH trial, which enrolled 589 adult patients undergoing burr-hole drainage for symptomatic CSDH during 2020-22. Functional outcome was assessed using the modified Rankin Scale (mRS). Failure to improve was defined as unchanged or worsened mRS at 6 months compared to preoperative mRS. Multivariable logistic regression was used to identify factors associated with failure to improve.

Results: Of the 568 patients with available mRS data at 6 months, 20% (n = 115) showed no improvement in mRS between the preoperative and 6-month period. Factors associated with failure to improve included pre-existing dementia (OR 2.62, 95% CI 1.21-5.66), use of a walker (OR 3.19, 95% CI 1.64-6.23), smaller hematoma width (OR 0.96, 95% CI 0.93-0.99), and lesser midline shift (OR 0.91, 95% CI 0.86-0.97). Despite this, 88% of patients had stable or improved residence status, and 85% maintained or improved mobility.

Conclusion: A substantial proportion of surgically treated CSDH patients do not improve in functional status. Dementia was a significant predictor of poor outcomes. Future research should focus to better identify patients at risk of poor outcomes in order to avoid overtreatment and explore possible alternative treatment strategies.