The chronic subdural hematoma (HSDC) is a common disease in the population over 60 years. The incidence is 7 / 100000 in patients over 70 years. This condition occurs readily after a minor head injury. Bleeding secondary to cerebral concussion and vascular fragility from a cortico-dural vein. It is favored in most cases by taking anti-platelet or other blood thinners. The hematoma formed and causes a local inflammatory reaction. This reaction tends to partition the collection by the formation of a membrane whose pathological vessels weakened by inflammation, causing bleeding iterative low abundance. A vicious circle is established by a combination of these phenomena and causes a progressive worsening clinical and radiological.Because of the importance of recurrence (15 to 25% at 6 months) and the high rate of mortality at one year (10 to 15%), but also supposed pathophysiological mechanisms (inflammation, formation of membrane self-sustaining blood collection ), a postoperative treatment with corticosteroids was introduced in secondary prevention by some teams (about 20% in France). However, this practice has never been a prospective study on clinical and radiological interest.The aim of this prospective multicenter randomized, double blind, is to evaluate in patients with chronic subdural hematoma, compared with placebo, the efficacy of postoperative corticosteroid treatment orally for approximately 2 months on the rate of clinical recurrence and / or radiological subdural hematoma 6 months after surgery (primary endpoint).The secondary endpoints are the rate of mortality at one year, and the 6 month follow-up of clinical and radiological evolution, neurological status (Markwalder scale), quality of life (health scale perceptual Nottingham), autonomy (Karnofsky scale), the state of consciousness (Glasgow scale), and size of the hematoma on CT scan without injection.340 adult patients of the 2 sexes who received surgical treatment for a chronic subdural hematoma unilateral or bilateral primary diagnosis (hematoma hypodense or isodense with a blade of at least 3 mm thick axial CT scan on brain) will be included in the study on 5 centers (services of Neurosurgery Hospital of Montpellier, Marseille, Nice, Perpignan and Lyon).Patients enrolled will be assigned to one of two treatment groups (active treatment or placebo) by lot. Active treatment is prednisone establishment within 72 hours after the end of surgery at the dose of 1 mg / kg (rounded to the nearest 10 mg) once daily orally for one week . The daily dose then decreases in increments of 10 mg weekly, by the second week. Once the level of 10 mg / day reached the daily dose by one level lower than 5 mg weekly. Treatment is stopped after this week to 5 mg / day .. The placebo was similar in all respects to active treatment and is administered in the same way that the active treatment. Additional treatment will be administered to all patients throughout the duration of the experimental treatment. It is a vitamin and calcium supplementation in preventing the risk of osteoporosis.Medical monitoring of patients will be over a period of six months with visits scheduled in the various departments of Neurosurgery at 1 month, 3 months and 6 months after surgery. Each visit is a consultation with a neurosurgical team physician including a review of clinical research with the recurrence of subdural hematoma and the collection of adverse events. This physician, independent of the investigative team, will also collect scores Markwalder, Nottingham, Karnofsky and Glasgow. Analysis of the CT scan will be centralized. A blood sample will be performed at the visit at 1 month, to establish a biological monitoring in relation to the potential electrolyte disturbances related to steroids.The mortality survey will take place 1 year after surgery by telephone interview between an investigator and the patient or his entourage.The overall duration of the study is about 6 years including 4 years of clinical phase.Given the extensive use of corticosteroids in the treatment of chronic subdural hematomas and absence of solid data on the subject, our research should clarify the role of corticosteroids in secondary prevention and improve the overall management of patients.