Factors affecting outcomes following burr hole drainage of chronic subdural hematoma: a single-center retrospective study
Authors: Zolnourian Ardalan , Manivannan Susruta , Edwards Ben , Chua Anne , Arora Mukul , Akhigbe Taiwo , Durnford Andrew , Hempenstall Jonathan , Nader-Sepahi Ali , Bulters Diederik , Sadek Ahmed-Ramadan 
Published: February 2025

OBJECTIVE
Chronic subdural hematoma (CSDH) is among the most common neurosurgical conditions. Patient selection for surgical intervention is often complex and multifactorial. The objective of this study was to examine the predictors of clinical outcomes, complications, and hospital length of stay (LOS) in patients with burr hole drainage of CSDH.

METHODS
A retrospective electronic neurosurgical database search was performed between January 2009 and January 2020 at a single tertiary referral unit. Adult patients treated with burr hole evacuation of CSDH and with extractable outcome data at discharge were eligible for inclusion. Variables including preoperative clinical status, antithrombotic use, surgical factors, clinical outcome, hospital LOS, discharge destination, and complications were extracted.

RESULTS
A total of 1226 patients were eligible for inclusion, with a median age of 79 years (IQR 71–85 years) and predominantly male (n = 885, 72.2%). Most patients were independent at baseline (n = 1019, 83.1%) with a median Karnofsky Performance Status score of 80 (IQR 70–90). The majority of patients underwent unilateral burr hole drainage (n = 1001, 81.6%) with two burr holes (n = 1177, 96.0%) and subdural drain insertion (n = 1087, 88.7%). The majority of patients had favorable outcomes at discharge (Glasgow Outcome Scale scores 4 and 5; n = 975, 79.5%) with a median hospital LOS of 6 days (IQR 4–9 days). Recurrence was observed in 122 patients (10.0%) with an overall postoperative complication rate of 27.2% (n = 334). Age < 80 years, preadmission independence, preoperative Glasgow Coma Scale motor (GCS-M) score of 6, < 5 regular medications, and American Society of Anesthesiologists (ASA) grades I and II were associated with significantly increased odds of a favorable outcome and being discharged home, decreased odds of postoperative complications, and decreased risk of prolonged hospital LOS. Surgical factors including laterality and number of burr holes were not associated with the tested outcomes. The use of a subdural drain was associated with increased odds of favorable outcome and being discharged home but not recurrence or complications. Long-term mortality analysis (n = 1222) demonstrated a median survival of 93 months (95% CI 84–105 months) with a median follow-up of 57 months (IQR 31–88 months). Nonmodifiable baseline variables (age, preadmission independence, GCS-M score, and ASA grade) demonstrated significant differences (p < 0.001) in survival distribution, while surgical factors (drain insertion, symptomatic recurrence, and number of days of bed rest) did not.

CONCLUSIONS
In the largest single-center study of patients managed with burr hole drainage of CSDH, the authors highlight several preoperative factors that may influence short-term outcome. Their findings offer robust criteria for counseling patients and families in situations in which surgical decision-making is not entirely clear.