Effectiveness of Intermediate Cervical Plexus Block in Whiplash-Associated Disorder: A Prospective Observational Trial in Fifty Patients.

BACKGROUND: Whiplash trauma can result in a range of symptoms, including chronic neck pain, headache, facial pain, upper back pain, and tinnitus, which comprises whiplash-associated disorder (WAD). Intermediate cervical plexus block (iCPB) is a novel intervention that targets the upper cervical nerves and anecdotal reports suggest benefits in WAD. OBJECTIVES: We hypothesized that the cervical plexus may have a role in the pathogenesis of WAD and blocking the cervical plexus may provide analgesia. STUDY DESIGN: Prospective observational trial. SETTING: Tertiary pain medicine unit at a university teaching hospital. METHODS: Adult patients who presented with refractory chronic neck pain following whiplash were included in a prospective observational trial. The pragmatic trial studied the effectiveness of 2 sequential cervical plexus blocks (iCPB with local anesthetic [iCPB-LA] and iCPB with steroid and LA mixture [iCPB-Steroid]) in refractory chronic neck pain following whiplash. Patients who reported < 50% relief at 12 weeks after iCPB-LA were offered iCPB-Steroid. Primary outcome was "neck pain at its worst in the last 24 hours" at 12 weeks. Secondary outcomes included change in neck disability index, employment status, and mood. RESULTS: After excluding cervical zygapophyseal joint dysfunction, 50 patients underwent the iCPB-LA between June 2020 and August 2022. Five patients reported > 50% relief (durable relief) at 12 weeks and 3 patients were lost to follow-up. Forty-two patients received iCPB-Steroid. iCPB-Steroid was associated with significant reduction in neck pain, neck disability, and improvement in mood at 12 weeks when compared to the block with LA. In addition, iCPB-Steroid was associated with significant reduction in neck pain and disability at 24 weeks. Due to functional improvement, 34 patients (34/50, 78%) were able to maintain employment. LIMITATIONS: This is an open-label, observational, single-center study in a limited cohort under a single physician. Cervical facet joint dysfunction was ruled out clinically and radiologically. CONCLUSIONS: Cervical plexus may play a central role in the pathogenesis of WAD. iCPB could potentially be a treatment option in this cohort.

Risk of infection within 4 weeks of corticosteroid injection (CSI) in the management of chronic pain during a pandemic: a cohort study in 216 patients.

OBJECTIVES: Targeted corticosteroid injections (CSI) are one of the treatments that can provide pain relief and thereby, enhance quality of life in patients with chronic pain. Corticosteroids (CS) are known to impair immune response. The objective was to evaluate the risk of developing post-procedural infection within 4 weeks of receiving depot CSI for chronic pain as part of on going quality improvement project. We hypothesised that interventional treatment with depot steroids will not cause a significant increase in clinical infection in the first 4 weeks. METHODS: Telephone follow-up was performed as a part of prospective longitudinal audit in a cohort of patients who received interventional treatment for chronic pain at a multidisciplinary pain medicine centre based at a university teaching hospital. Patients who received interventional treatment in the management of chronic pain under a single physician between October 2019 and December 2020 were followed up over telephone as part of on going longitudinal audits. Data was collected on any infection within 4 and 12 weeks of receiving the intervention. Outcomes collected included type of intervention, dose of depot steroids and pain relief obtained at 12 weeks following intervention. RESULTS: Over a 15 month period, 261 patients received pain interventions with depot CS. There was no loss to follow-up. Nine patients reported an infection within 4 weeks of receiving depot steroids (9/261, 3.4%). None of the patients tested positive for Covid-19. Eight patients (8/261, 3%) reported an infection between 5 and 12 weeks following the corticosteroid intervention. Although none of the patients tested positive for Covid-19, two patients presented with clinical and radiological features suggestive of Covid-19. Durable analgesia was reported by 51% (133/261) and clinically significant analgesia by 30% (78/261) at 12 weeks following the intervention. Failure rate was 19% (50/261). CONCLUSIONS: Pain medicine interventions with depot steroids do not appear to overtly increase the risk for Covid-19 infection in the midst of a pandemic.

Systematic review and meta-analysis of cannabinoids, cannabis-based medicines, and endocannabinoid system modulators tested for antinociceptive effects in animal models of injury-related or pathological persistent pain.

ABSTRACT: We report a systematic review and meta-analysis of studies that assessed the antinociceptive efficacy of cannabinoids, cannabis-based medicines, and endocannabinoid system modulators on pain-associated behavioural outcomes in animal models of pathological or injury-related persistent pain. In April 2019, we systematically searched 3 online databases and used crowd science and machine learning to identify studies for inclusion. We calculated a standardised mean difference effect size for each comparison and performed a random-effects meta-analysis. We assessed the impact of study design characteristics and reporting of mitigations to reduce the risk of bias. We meta-analysed 374 studies in which 171 interventions were assessed for antinociceptive efficacy in rodent models of pathological or injury-related pain. Most experiments were conducted in male animals (86%). Antinociceptive efficacy was most frequently measured by attenuation of hypersensitivity to evoked limb withdrawal. Selective cannabinoid type 1, cannabinoid type 2, nonselective cannabinoid receptor agonists (including delta-9-tetrahydrocannabinol) and peroxisome proliferator-activated receptor-alpha agonists (predominantly palmitoylethanolamide) significantly attenuated pain-associated behaviours in a broad range of inflammatory and neuropathic pain models. Fatty acid amide hydrolase inhibitors, monoacylglycerol lipase inhibitors, and cannabidiol significantly attenuated pain-associated behaviours in neuropathic pain models but yielded mixed results in inflammatory pain models. The reporting of criteria to reduce the risk of bias was low; therefore, the studies have an unclear risk of bias. The value of future studies could be enhanced by improving the reporting of methodological criteria, the clinical relevance of the models, and behavioural assessments. Notwithstanding, the evidence supports the hypothesis of cannabinoid-induced analgesia.

Intermediate Cervical Plexus Block: A Novel Intervention in the Management of Refractory Chronic Neck and Upper Back Pain Following Whiplash Injury: A Case Report.

Chronic neck and upper back pain occurs in 40%-60% of patients that suffer whiplash injury. Increasing evidence points to a dysfunction of the cervical and thoracic muscles as the predominant cause of persistent pain in this cohort. Response to standard management including physiotherapy, psychotherapy, medications, and acupuncture are often inadequate. As a result, there is significant functional impairment leading to excessive health care costs. The authors present a novel treatment, intermediate cervical plexus block with depot steroids, in 3 patients presenting with refractory chronic neck and upper back pain from whiplash injury that produced durable analgesia and enabled return to employment.

Basic Opioid Pharmacology - An Update.

Opioids are a group of analgesic agents commonly used in clinical practice. The three classical opioid receptors are MOP, DOP and KOP. The NOP (N/OFQ) receptor is considered to be a non-opioid branch of the opioid receptor family. Opioid receptors are G-protein-coupled receptors which cause cellular hyperpolarisation when bound to opioid agonists. Opioids may be classified according to their mode of synthesis into alkaloids, semi-synthetic and synthetic compounds. Opioid use disorder (OUD) is an emerging issue and important lessons can be learnt from the United States where opioid epidemic was declared as a national emergency in 2017.