The incidence of postoperative chronic pain after craniotomy is high. Postoperative chronic pain seriously affects patient's quality of life. Compound local scalp nerve block is a good choice for analgesia after craniotomy. However, the scalp nerve block commonly cannot cover the area of suboccipital retrosigmoid approach craniotomy, leading to incomplete block. Superficial cervical plexus block (SCPB) is theoretically promising to solve the analgesia requirements of such surgical approach. At the same time, ultrasound guidance can not only accurately locate, ensure the effect of block and avoid accidental injury during puncture. The purpose of this study is to explore whether ultrasound-guided superficial cervical plexus block can safely and effectively reduce the incidence of chronic pain after craniotomy via suboccipital retrosigmoid approach.

Inclusion Criteria:

1. Elective suboccipital retrosigmoid approach approach craniotomy;
2. Age between 18 and 65 years;
3. American Society of Anesthesiologists (ASA) physical status I-III.

Exclusion Criteria:

1. The patients or legal clients refuse to provide informed consent;
2. Local infection;
3. Preoperative impairment of consciousness and cognitive function;
4. Uncontrolled hypertension;
5. Inability to communicate;
6. Allergies to experimental drugs;
7. History of drug abuse;
8. History of chronic headache;
9. Aphasia and hearing impairment;
10. Patients undergoing second craniotomy;
11. Body mass index < 18.5 kg/m2 or > 35.0 kg/m2;