Ultrasound-guided lesser occipital nerve combined with great auricular nerve block for vestibular schwannoma craniotomy via a suboccipital retrosigmoid approach: a prospective, double-blind randomized controlled trial

Abstract

Purpose: This aim of this study was to investigate the analgesic efficacy and safety of lesser occipital nerve combined with great auricular nerve block (LOGAB) for craniotomy via a suboccipital retrosigmoid approach.

Methods: Patients underwent vestibular schwannoma resection via a suboccipital retrosigmoid approach were randomly assigned to receive ultrasound-guided unilateral LOGAB with 5 ml of 0.5% ropivacaine (LOGAB group) or normal saline (NSB group). Numeric rating scale (NRS) scores at rest and motion were recorded within 48 h after surgery. Mean arterial pressure (MAP), heart rate (HR), opioid consumption and other variables were measured secondly.

Results: Among 59 patients who were randomized, 30 patients received ropivacaine, and 29 patients received saline. NRS scores at rest (1.8 ± 0.5 vs. 3.2 ± 0.8, P = 0.002) and at motion (2.2 ± 0.7 vs. 3.2 ± 0.6, P = 0.013) of LOGAB group were lower than those of NSB group within 48 h after surgery. NRS scores of motion were comparable except for 6th and 12th hour (P < 0.05) in the LOGAB group. In LOGAB group, MAP decreased significantly during incision of skin and dura (P < 0.05) and intraoperative opoid consumption was remarkably reduced (P < 0.01). Postoperative remedial analgesia was earlier in the NSB group (P < 0.001). No patients reported any adverse events.

Conclusion: Among patients undergoing craniotomy for vestibular schwannoma via a suboccipital retrosigmoid approach, LOGAB may be a promising treatment for perioperative analgesia and has the potential to maintain intraoperative hemodynamic stability.

Clinical trial registration number: Chictr.org.cn ChiCTR2000038798.

Keywords: Great auricular nerve block; Lesser occipital nerve block; Suboccipital retrosigmoid craniotomy; Ultrasound-guided; Vestibular schwannoma resection.

Fig. 1

Surgical incisions, anatomy of cervical plexus and ultrasound-guided lesser occipital nerve combined with great auricular nerve block. (A) Three types of posterior suboccipital retrosigmoid incisions for vestibular schwannoma craniotomy. The red circle indicates the tumor site, and the blue dashed line indicates the commonly used incisions. (B) Branches of the cervical plexus and placement of the ultrasound probe for the lesser occipital nerve combined with great auricular nerve block. (C) Ultrasound images of lesser occipital nerve and greater auricular nerve. (D) Ultrasound-guided lesser occipital nerve block. (E) Ultrasound-guided greater auricular nerve block. GAN: greater auricular nerve; LON: lesser occipital nerve; SCM: Sternocleidomastoid muscle. The white arrows indicate the shaft of block needle

Fig. 2

Flow of participants through the study. LOGAB: lesser occipital nerve combined with great auricular nerve block; NSB: normal saline block

Fig. 3

Box plots of NRS scores within 48 h after surgery, intraoperative MAP and HR and their increment rates during skin and dural incisions. (A) NRS scores at rest. (B) NRS scores at motion. NRS, Numeric Pain Rating Scales; LOGAB, ultrasound-guided unilateral lesser occipital nerve combined with great auricular nerve block; NSB, normal saline block. T1, extubation; T2, 2 h after surgery; T3, 4 h after surgery; T4, 6 h after surgery; T5, 12 h after surgery; T6, 24 h after surgery; T7, 48 h after surgery. *P < 0.05, **P < 0.01, ***P < 0.001. (C) MAP during skin and dural Incisions. (D) HR during skin and dural Incisions. MAP, mean arterial pressure; HR, heart rate; LOGAB, ultrasound-guided unilateral lesser occipital nerve combined with great auricular nerve block; NSB, normal saline block. T1, 1 min before induction; T2, 1 min after induction; T3, 1 min before skin incision; T4, 1 min after skin incision; T5, 3 min after skin incision; T6, 5 min after skin incision; T7, 10 min after skin incision; T8, 1 min before dural incision; T9, 1 min after dural incision; T10, 3 min after dural incision; T11, 5 min after dural incision; T12, 10 min after dural incision. *P < 0.05. (E) MAP increment (%) during skin and dural Incisions. (F) HR increment (%) during skin and dural Incisions. T1, 1 min after skin incision; T2, 3 min after skin incision; T3, 5 min after skin incision; T4, 10 min after skin incision; T5, 1 min after dural incision; T6, 3 min after dural incision; T7, 5 min after dural incision; T8, 10 min after dural incision. *P < 0.05