ABSTRACTwhile craniotomy is used as a second-tier treatment (16). Both TDC and BHC can be performed in setting of local anesthesia, and TDC can even be performed at bedside (7). Most neurosurgeons tend to use BHC as the procedure of choice to treat patients with initial CSDH (3). With a smaller diameter of skin incision and skull opening, TDC is less invasive than BHC, which theoretically favors its use in elderly patients who usually have comorbidities. Previous studies comparing therapeutic effects of TDC and BHC concluded controversial results (6)(7)(8)17). Here, we conducted a prospective cohort █ INTRODUCTION C hronic subdural hematoma (CSDH) is a neurological disorder that predominantly affects elderly people and causes serious morbidity and mortality (1,2). Surgical treatment plays an important role in the treatment of patients with symptomatic CSDH. Twist drill craniostomy (TDC), burr hole craniostomy (BHC), and craniotomy are three commonly used procedures in current clinical practice. Among them, TDC and BHC are recognized as first-tier surgical treatment AIm: This study aims to compare clinical outcomes in patients with chronic subdural hematoma (CSDH) following twist drill craniostomy (TDC) or burr hole craniostomy (BHC). mATERIAl and mEThODS: A prospective cohort study was conducted in the patients who suffered from symptomatic CSDH and received surgical treatment in our department from Jan 2011 to Dec 2013. Each patient was followed 3 months after the surgery.RESUlTS: Thirty-eight and 45 patients received TDC and BHC treatment, respectively. There was no significant difference in age, gender, head trauma, diabetes mellitus, hypertension, antiplatelet usage, clinical manifestation, the Glasgow Coma Scale score and preoperative radiographic characteristics between the two groups. Patients in TDC had a significantly shorter operating time, but a longer draining time than those in BHC (16.9 ± 6.3 min vs. 44.4 ± 7.1 min, p< 0.001; 3.1 ± 1.0 d vs. 2.5 ± 0.9 d, p= 0.003; respectively). A smaller degree of midline shift reversal was observed in patients after TDC than those after BHC (2.6 ± 2.5 mm vs. 3.9 ± 2.8, p=0.030). Seven patients (18.4%) in TDC and 5 patients (11.1%) in BHC experienced CSDH recurrence. There was no significant difference in the recurrence rate, in-hospital complications, and neurological outcomes between the two groups.CONClUSION: This study indicates that TDC and BHC have similar clinical outcomes in the treatment of patients with CSDH. A shorter operating time, but a smaller midline shift reversal and a longer draining time may be expected in patients after TDC than after BHC.