In this prospective, randomized, multicenter trial shall patients with chronic subdural hematoma (cSDH) recruited, who were surgically treated. Initially, we would divide the patients randomized into two groups: Patients with supervised blow-maneuver and without. After surgical treatment of cSDH with insertion of a subdural drain, one group would perform a supervised blow maneuver ("Valsalva maneuver") every hour for five minutes from 10:00 to 20:00. In the other group, the standard care would be performed. The subdural drain would be explanted 2days after operation and a postoperative CT scan would routinely be performed. After hospital discharge, the patient would be rechecked in an ambulant setting and would receive CT scan as clinical standard. Recurrence of hematoma is defined as recurrent hematoma which should be reoperated. After 3 and 6 months we would evaluate the outcome of patients.

Inclusion Criteria:

• age over 18 years
• surgically treated cSDH
• patients with an operatively implanted subdural drainage

Exclusion Criteria:

• age under 18 years
• Admission in critical clinical state, e.g. already to light unresponsive pupils for about 2 hours
• conservative treatment of cSDH
• patients without an operatively implanted subdural drainage
• patient cannot be consented
• participation in other clinical trials