mostly liquefied CSDH. Conversely, craniotomy is generally accepted as the optimal approach for reaccumulation of a CSDH, existence of a solid hematoma, failure of brain reexpansion, or marked swelling subjacent to the hematoma 5,14) . The purpose of this study was to analyze the efficacy of small or large craniotomy with membranectomy as the initial treatment for CSDH. MATERIALS AND METHODSA retrospective study was performed using the medical records retained by our hospital. computed tomography (CT) scans were the primary imaging method for the evaluation of CSDH in all patients. The technique of a burr-hole with closed system drainage for 24 to 72 hours was chosen for cases of nonseptated and mostly liquefied CSDH. However, on the basis of CT and/or magnetic resonance imaging (MRI) findings, cases of CSDH demonstrating either mixed density or hyperdense lesions ( Fig. 1), intrahematomal membranes or web-like structures (Fig. 2), or an organized/calcified CSDHs (Fig. 3) were selected for craniotomy. We classified 317 patients with CSDH into three groups according to the extent of surgery required : group I, burr hole with drainage (n=259); group II, small crani- INTRODUCTIONChronic subdural hematoma (CSDH) represents one of the most frequent intracranial hemorrhages encountered in neurosurgical department, with elderly citizens being more frequently affected. The reasons why this type of hematoma occurs frequently among the elderly include an increase in antithrombotic medications, venous fragility, augmentation of the subdural space, and an increased exposure to traumatic injury resulting from frequent falls 1) . For the initial management of CSDH, numerous surgical treatments have been proposed 5,14,15,18,21) . However, the extent of surgical treatment required for CSDH is still controversial 2,24) , and the optimal treatment for CSDH is not well defined 16) . The choice of surgical technique for CSDH must be dictated by the degrees of organization of the hematoma. Burr-hole with drainage is mandatory for non-septated and Department of Neurosurgery, Seoul Medical Center, Seoul, KoreaObjective : There are few studies comparing small and large craniotomies for the initial treatment of chronic subdural hematoma (CSDH) which had non-liquefied hematoma, multilayer intrahematomal loculations, or organization/calcification on computed tomography and magnetic resonance imaging. These procedures were compared to determine which would produce superior postoperative results. Methods : Between 2001 and 2009, 317 consecutive patients were surgically treated for CSDH at our institution. Of these, 16 patients underwent a small craniotomy with partial membranectomy and 42 patients underwent a large craniotomy with extended membranectomy as the initial treatment. A retrospective review was performed to compare the postoperative outcomes of these two techniques, focusing on improvement of neurological status, complications, reoperation rate, and days of post-operative hospitalization. Results : The mean ages were 69.4±12.1 a...