Inclusion Criteria:  Patients who undergo elective microvascular decompression surgery American Society of Anesthesiologists grade 1 or 2 19 - 65 years old  Exclusion Criteria:  Refuse to participate to the study Refuse to use Patient-controlled analgesia Body Mass Index < 18.5 kg/m2 or > 35 kg/m2 history of craniotomy or chemotheraphy Patients who used preoperative antiemetics within 24h before surgery Severe renal or hepatic dysfunction Pregnant