The incidence of postoperative pain after craniotomy is high. Severe postoperative pain can lead to a series of complications that are detrimental to the recovery of craniotomy patients. 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 requirement of analgesic drugs and 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;