Chronic subdural hematoma (cSDH) is a very common disease, primarily affecting older people, and is associated with significant morbidity and mortality. The incidence described in the literature is approximately 5 per 100,000/year, but it occurs more frequently in the elderly, with up to 58 per 100,000/year. The recurrence rate is high and is described in the literature as 10 to 27%. Consequently, various studies have evaluated potential risk factors for hematoma recurrence, such as age, brain atrophy, mixed HU density in CCT, increased body mass index, and bilateral hematomas. The pathomechanism of recurrence is currently unknown.

The mechanism of development after minor trauma and the progression of the hematoma to a symptomatic form remain unclear. A recent retrospective investigation submitted for publication by the applicant, regarding the occurrence of a low-grade infection in patients with recurrent hematomas, examined this as a possible cause. In this study, microbiological swabs were taken from the subdural space after hematoma evacuation. It was shown that a low-grade infection could be detected in approximately 30% of all hematoma recurrences. This is previously unknown in the neurosurgical literature. This raises the question of whether a low-grade infection is already present in the primary chronic subdural hematoma.

Inclusion Criteria:

• >18 years of age
• surgical treatment of chronic subdural hematoma

Exclusion Criteria:

• prior or current antibiotic treatment
• infection
• recurrent chronic subdural hematoma
• conservatively treated chronic subdural hematoma