Inclusion Criteria:

• Adult patients (≥ 18 years).
• Patients with symptomatic CSDH confirmed on brain CT- or magnetic resonance imaging (MRI), admitted to a Danish neurosurgical department for surgical treatment.
• Patients undergoing a single burr-hole evacuation.
• Informed written and oral consent is taken prior to surgery.

Exclusion Criteria:

• Patients who are mentally incapacitated
• Patients with known abnormalities in their cerebrospinal fluid (protein and glucose levels, cell count, and type)
• Patients with changes or abnormalities in their normal cerebrospinal fluid dynamics, e.g., obstructive hydrocephalus, normal pressure hydrocephalus, intracranial hypotension, and ventricular peritoneal shunt.
• Patients with additional/previously intracranial pathology that requires/has required neurosurgical treatment (e.g., brain tumor, vascular malformation, abscess).
• Patients with recurrent CSDH or with previous craniotomy or other transcranial surgery (for any reason)
• Patients unable to give consent prior to surgery