Perioperative pain is caused by a variety of harmful factors through multiple mechanisms, therefore, reasonable postoperative analgesia should be combined with drugs or measures of different mechanism , which is called multimodal analgesia. Multimodal analgesia could minimize side effects and achieve a better analgesic effect. Commonly used strategies of multimodal analgesia are oral analgesic drug, nerve block, patient controlled analgesia and so on. This study will observe the effect of multimodal analgesia on postoperative pain in patients with microvascular decompression and record side effects. Finally, it will provide technical support for the guidance of postoperative analgesia in patients of trigeminal neuralgia.

The investigators will collect 90 cases which will be divided into 3 groups. Patients in Group A will receive scalp nerve block and patient-controlled analgesia which contains sufentanil and ondansetron. In Group B, patient-controlled analgesia which contains sufentanil, ondansetron and ketamine will be applied. In Group C, patient-controlled analgesia which contains sufentanil and ondansetron will be applied.

Inclusion Criteria:

1. Patients of trigeminal neuralgia plan to receive microvascular decompression
2. Age between 18 and 70, ASA classification between Ⅰ～Ⅲ
3. No severe liver and kidney disease, no blood coagulation dysfunction
4. No history of long-term opioid drugs usage, no drug addiction history
5. Patients are fully conscious, cooperation, understanding and voluntarily signed informed consent

Exclusion Criteria:

1. More than 20% of the total blood volume is lost in operation
2. Intracranial hematoma happens within 24 h after surgery
3. Secondary surgery patients