Objective: To investigate whether administration of dexamethasone affects postoperative cognitive dysfunction.Methods: Ninety-nine patients with facial spasm who were scheduled to receive microvascular decompression (MVD) were randomly divided into three groups: Dex-0 (n=34), Dex-1 (n=31) and Dex-2 (n=34), respectively administrate normal sodium, dexamethasone 0.1mg/kg and 0.2mg/kg.The patients, anesthesiologists, nurses, and research coordinators were blinded to the study arms.Exclusion criteria included: a history ofneurologic or mental disease, serum creatinine in excess of 177umol/L, active liver disease, cardiac dysfunction, pulmonary dysfunction, endocrine disease, metabolic disease, peptic ulcer disease, a history of surgery, fewer than 6 years of school, inability to complete neuropsychological testing, vision dysfunction, and auditory dysfunction.Propofol and sufentanil were used for anesthesia induction, propofol and remifentanil were used for maintenance of anesthesia.A battery of 9 neuropsychological was administered pre-operatively and 5 days after surgery.A postoperative deficit was defined as a post-op decrement to pre-op score greater than one standard deviation on any test.Patients who experienced 2 or more deficits were deemed to have early postoperative cognitive dysfunction.Results: Eighty-eight patients completed both pre-and post-operative neuropsychological testing.Thirty of the 88 patients belonged to the Dex-0 group, 27 belonged to Dex-1 group and 31 belonged to Dex-2 group.Postoperative cognitive dysfunction occurred in 7 patients (23.3 %) in the Dex-0 group, in 8 patients (29.6%) in the Dex-1 group, and 9 patients (29.0%) in the Dex-2 group.There were no statistically significant differences among groups in early postoperative cognitive dysfunction (P=0.836, Chi-square).Conclusion: Administration adaptable dose of dexamethasone didnt affect the incidence of postoperative cognitive dysfunction in the early postoperative period after microvacular decompression.