Comparison of efficacy of cranial vs cervical approach of ultrasound guided greater occipital nerve block in patients undergoing posterior fossa craniotomy: A randomized controlled study

COMPARISON OF EFFICACY OF CRANIAL VS CERVICAL APPROACH OF ULTRASOUND GUIDED GREATER OCCIPITAL NERVE BLOCK IN PATIENTS UNDERGOING POSTERIOR FOSSA CRANIOTOMY: A RANDOMISED, CONTROLLED STUDY

INTRODUCTION

Posterior fossa craniotomy is a neurosurgical procedure that is often associated with postoperative headaches, which can significantly impact the quality of life and recovery of patients. Despite advancements in anesthesia and pain management, effective strategies for mitigating postoperative pain in this specific patient population remain a challenge. Greater occipital nerve (GON) block has been used successfully in pediatric patients to treat chronic primary headache disorders and manage postoperative pain after ventricular shunt revision. Ultrasound guidance enhances the precision and safety of nerve block procedures, offering the potential for improved outcomes.

However, the choice between cranial and cervical approaches for greater occipital nerve block in the context of posterior fossa craniotomy remains a topic of debate and limited research. Previous research emphasizes the significance of providing neurosurgical patients with appropriate pain management, with a focus on the possible benefits of regional anaesthesia techniques for improving recovery. However, the finer points of contrasting the cervical and cranial methods for greater occipital nerve block in this context are not fully discussed.

Several studies have investigated the efficacy of greater occipital nerve block in different clinical scenarios, demonstrating varying degrees of success. However, a paucity of research directly comparing the cranial and cervical approaches in the unique context of posterior fossa craniotomy prompts the need for a focused and rigorous investigation. Understanding the anatomy and innervation of the greater occipital nerve in relation to the surgical site is crucial for interpreting the potential efficacy of different approaches.

Pingree MJ et al (2017) conducted a prospective open-label study that demonstrated successful blockade of the GON at the level of C2 using a novel ultrasound-guided technique. The observations from this study provide important preliminary data for future randomized trials involving patients with occipital neuralgia and cervicogenic headache.

Flamer et al (2019) conducted a multicenter, prospective, randomized control trial that compared the accuracy, effectiveness, and safety of these two techniques in patients with chronic migraines (CMs). The primary outcome was the difference in Numerical Rating Score (NRS) for headache intensity at 1 month. Secondary outcomes included effectiveness, performance, and safety-related outcomes. NRS pain scores were significantly reduced at 24 hours and at 1 week post procedure in both cohorts and at 1 and 3 months in the proximal group as compared with the baseline. There was no significant difference in NRS pain scores between the two cohorts at any of the follow-up time points.

This study compared two different US-guided approaches for blocking the GON, demonstrating that both distal and proximal techniques can provide short-term improvements in headache intensity, reduced number of headache days per week, and improved sleep interruption. The proximal GON technique may confer more sustained analgesic benefit compared with the distal approach in patients with chronic migraine headaches.

USG to block the nerves of the scalp is easy and may improve patient safety by reducing the total amounts of LA used and lowering the risk of vascular puncture. Additionally, USG might allow for a more precise nerve location due to numerous variations in nerve foramina or course.

Chowdhary et al (2020) studied 532 articles, 9 open-label and 4 placebo-controlled trials that studied the role of GON block for prevention of CM. Open-label trials reported a reduction of headache severity and frequency in 35–68% of patients, with the beneficial effect of a single block lasting up to 4 weeks. Randomized controlled trials (RCTs) used varied methodology and techniques of GON block, and the outcomes were reported at different time points. A single RCT showed a beneficial effect of the GON block at 1 week, but the GON block was found to be safe and well tolerated.

Muse et al (2021) discussed regional anesthetic techniques that can be used for primary anesthesia and analgesia, or in combination with general anesthesia. Nassar H et al (2023) conducted a prospective randomized controlled study that found that the GON block group was associated with superior quality and duration of postoperative analgesia and better hemodynamic profile compared to standard care.

Stern JI, et al (2022) studied 12 RCTs examining the use of greater occipital nerve blocks for migraine, all but one showing efficacy with reduction in headache frequency, intensity, and/or duration compared to placebo. Studies have not demonstrated a difference in clinical outcomes with the use of corticosteroids for nerve blocks compared to blocks with local anesthetic in the treatment of migraine.

Observational studies and case series/reports show that greater occipital nerve block may be effective in prolonged migraine aura, status migraineurs, post-dural puncture headache, and occipital neuralgia. Overall, peripheral nerve blocks are well tolerated, and serious side effects are rare but have been reported, including acute cerebellar syndrome and infection. Peripheral nerve blocks, especially occipital nerve blocks, are a viable treatment option for migraine and may be helpful in cluster headache as a transitional therapy or rescue therapy.

AIMS AND OBJECTIVES

Aim:

·        To compare the efficacy of ultrasound-guided greater occipital nerve block using cranial and cervical approaches in patients undergoing posterior fossa craniotomy.

Objectives:

Primary:

·        To compare the postoperative pain using Numeric Rating Scale (NRS)

Secondary:

·        To compare the hemodynamics in perioperative period

·        To compare the sedation score using Ramsay Sedation Score (RSS)in post operative period

·        To compare the time to first analgesic request, and total analgesic consumption

·        To compare the neurological outcome using Extended Glasgow Outcome Scale (GOSE)

·        To observe the complications

 MATERIAL AND METHODS

Study Settings: The study will be conducted in Department of Anesthesiology, King George’s Medical University, Lucknow.

Study design:  Prospective Randomized Controlled Study

Study duration: 1 year

Sample size: 25 in each group

 Inclusion Criteria:

·        Patients of either sex, and aged between 18 to 60 years

·        Elective posterior fossa craniotomy

·        American Society of Anesthesiologists (ASA) physical status I to II

 Exclusion Criteria:

·        Patient’s Refusal

·        Allergy to local anesthetics

·        Pre-existing neurological or psychiatric conditions

·        History of chronic headache disorders (e.g., migraine, tension-type headache).

·        Pregnancy or Lactation

·        Coagulopathy

·        Previous Craniotomy

·        Participation in other clinical trials concurrently

     STUDY PROTOCOL

Ethical clearance and Written and Informed consent will be taken.The study will be done at **King George Medical University, Lucknow.**Randomization will be performed using computer-generated random numbers to ensure a balanced distribution of potential confounding factors. All participants will be randomly assigned to one of two groups:

·        Cranial Approach Group

·        Cervical Approach Group

The study aims to record demographic data, signs and symptoms, number of surgical accesses, and fixations of patients scheduled for posterior fossa craniotomy. Postoperative headaches are at risk for all patients, and informed consent is required to understand the potential benefits and risks of both cranial and cervical approaches. Procedure details, ultrasound-guided techniques, needle size, and injection volume are specified. Standardized anesthesia protocols are used for both groups to ensure consistency in perioperative care. Postoperative pain is assessed using the objective pain scale (OPS), based on five criteria: systolic arterial blood pressure, crying, movement, agitation, and verbal evaluation. The worst OPS score is 10 if the child is old enough to complain of pain, and 8 if too young. In the ICU, intravenous paracetamol is given and repeated every 6 hours for patients who first complained of pain, while ketorolac is administered every 8 hours for persistent or breakthrough pain. Outcomes include the OPS score at 12 hours postoperatively, duration of analgesia, cumulative intraoperative fentanyl dose, intraoperative heart rate and systolic blood pressure, incidence of postoperative nausea and vomiting, and incidence of nerve-block complications, such as scalp hematoma or inadvertent subarachnoid or intravascular injection of local anesthetic.

Statistical analysis

Statistical analysis was performed by the SPSS version 23rd version. Continuous variables were presented as mean±SD and categorical variables were presented as absolute numbers and percentage. Normally distributed continuous variables and categorical variables were compared using appropriate statistical test. P value less than 0.05 was taken as significant.