# Incidence, predictors, and management of postoperative subdural empyema following chronic subdural hematoma evacuation: a population-based cohort study

## TL;DR

This study examines the risk factors and outcomes of a rare brain infection complication after a common surgical procedure for chronic subdural hematoma.

## Contribution

Identifies new risk factors and optimal treatment strategies for postoperative subdural empyema after chronic subdural hematoma surgery.

## Key findings

- Larger hematoma size and Cloxacillin prophylaxis increase the risk of postoperative subdural empyema.
- Craniotomy is more effective than burr-hole evacuation for managing subdural empyema.
- One-year mortality is not significantly higher in patients who develop subdural empyema.

## Abstract

Subdural empyema (SDE) is a rare but potentially serious complication following chronic subdural hematoma (CSDH) evacuation. This study aimed to establish the incidence of postoperative SDE, identify risk factors for its development, characterize the bacterial pathogens involved, and evaluate optimal surgical management strategies.

Patients aged ≥ 15 years who underwent CSDH evacuation at the Karolinska University Hospital between 2006 and 2022 were retrospectively screened for postoperative SDE. Logistic regression analyses were used to identify predictors of SDE development and treatment failure.

Among 2656 operations for CSDH, 37 (1.4%) resulted in postoperative SDE. Independent predictors of SDE were larger CSDH diameter (odds ratio [OR] 1.12, 95% confidence interval [CI] 1.06 – 1.17, p < 0.001) and Cloxacillin prophylaxis during index CSDH-surgery (OR 4.63, 95% CI 2.19 – 11.0, p < 0.001). Hemiparesis (54%) and wound infection (30%) were the most common SDE symptoms, and fever was frequently absent. Cutibacterium acnes was the most common bacterial isolate, identified in 76% of cases. Craniotomy was more effective than burr-hole evacuation for managing SDE, with the latter showing a higher risk of reoperation (OR 11.5, 95% CI 1.72 – 230, p = 0.032). The median antibiotic treatment duration was 48 days (interquartile range 35–77). One-year mortality did not differ significantly between patients with and without SDE (8.1% vs. 12%, p = 0.618).

A larger CSDH diameter and Cloxacillin prophylaxis significantly increased the risk of postoperative SDE. Craniotomy was more effective than burr-hole evacuation for SDE management, and one-year mortality was not elevated in patients who developed an SDE.