Subclinical low-grade infection in untreated primary chronic subdural hematoma

OBJECTIVE Chronic subdural hematoma (CSDH), a condition with high recurrence rates, is traditionally attributed to trauma-induced inflammation and angiogenesis. Emerging evidence suggests an association between clinically unapparent low-grade infection and recurrence. The role of subclinical low-grade infection in untreated primary CSDH remains unknown. The aim of this study was to examine intraoperative swab results in de novo CSDH to assess its association with recurrence. METHODS In this prospective study, patients undergoing primary surgical evacuation for CSDH were enrolled and intraoperative swabs were collected for microbiological analysis. Patients were followed up for 6 months after surgery to assess recurrence. The presence or absence of a positive intraoperative swab was used to dichotomize the cohort. Relevant clinical parameters, including preoperative comorbidities, intra- and perioperative management, recurrence rates, and follow-up information were compared between the two groups. RESULTS Eighty patients (60 male, median age 79 years) with CSDH were included in the analysis. Intraoperative swab cultures identified low-grade bacterial colonization, predominantly Cutibacterium acnes (69%), in 40% (32/80) of patients. Recurrence rates were significantly higher in patients with positive bacteria detection (31%, 10/32) compared with patients without bacteria detection (12.5%, 6/48) (OR 3.1, 95% CI 1.02–9.90; p < 0.039). CONCLUSIONS These findings substantiate the hypothesis that subclinical low-grade infection contributes to CSDH origination. Further trials evaluating perioperative antibiotic interventions are warranted.