The Efficacy, Adverse Events & Withdrawal Rates of the Pharmacological Management of Chronic Spinal Cord Injury Pain: A Systematic Review & Meta-Analysis

Postoperative Ketamine May be Associated with Venous Thromboembolism in Chronic Opioid Users After Spine Surgery

OBJECTIVE

Venous thromboembolism (VTE) is a serious postoperative adverse event after spine surgery. In patients with pain refractory to typical multimodal analgesia regimens after spine surgery, whom are often chronic opioid users, perioperative ketamine is an alternative analgesic that has grown in popularity. The aim of this study is to assess the risk of VTE in chronic opioid users undergoing spine surgery.

METHODS

We conducted a structured query language search to identify patients with a diagnosis of VTE after spine surgery from 2017 to 2021. structured query language identified patient demographic information and chart review was performed to confirm procedure details, including levels fused and decompressed. Opioid use was identified using the Prescription Drug Monitoring Program for each patient. Chronic opioid users were defined as having >180 days or >9 opioid prescriptions prescribed in the 12 months prior to surgery.

RESULTS

A total of 322 patients were identified with complete Prescription Drug Monitoring Program and postoperative ketamine data, including 29 patients with confirmed VTE after spine surgery. Length of stay (P < 0.001) and Elixhauser comorbidity index (P = 0.008) were significantly greater in the VTE group compared to the no VTE group. Analysis of only chronic opioid users also found a significant association between postoperative ketamine and VTE (P = 0.034).

CONCLUSIONS

Our study found no association between chronic opioid use and VTE occurrence; however, we identified a significant association between ketamine infusion and VTE after spine surgery. Further studies should be conducted to identify the risks associated with ketamine and other newly implemented alternative analgesics.

Cannabis constituents for chronic neuropathic pain; reconciling the clinical and animal evidence

Chronic neuropathic pain is a debilitating pain syndrome caused by damage to the nervous system that is poorly served by current medications. Given these problems, clinical studies have pursued extracts of the plant Cannabis sativa as alternative treatments for this condition. The vast majority of these studies have examined cannabinoids which contain the psychoactive constituent delta-9-tetrahydrocannabinol (THC). While there have been some positive findings, meta-analyses of this clinical work indicates that this effectiveness is limited and hampered by side-effects. This review focuses on how recent preclinical studies have predicted the clinical limitations of THC-containing cannabis extracts, and importantly, point to how they might be improved. This work highlights the importance of targeting channels and receptors other than cannabinoid CB1 receptors which mediate many of the side-effects of cannabis.

Exploring Functional Connectivity in Chronic Spinal Cord Injury Patients With Neuropathic Pain Versus Without Neuropathic Pain

The great majority of spinal cord injury (SCI) patients have debilitating chronic pain. Despite decades of research, these pain pathways of neuropathic pain (NP) are unknown. SCI patients have been shown to have abnormal brain pain pathways. We hypothesize that SCI NP patients' pain matrix is altered compared to SCI patients without NP. This study examines the functional connectivity (FC) in SCI patients with moderate-severe chronic NP compared to SCI patients with mild-no NP. These groups were compared to control subjects. The Neuropathic Pain Questionnaire and neurological evaluation based on the International Standard Neurological Classification of SCI were utilized to define the severity and level of injury. Of the 10 SCI patients, 7 (48.6 ± 17.02 years old, 6 male and 1 female) indicated that they had NP and 3 did not have NP (39.33 ± 8.08 years old, 2 male and 1 female). Ten uninjured neurologically intact participants were used as controls (24.8 ± 4.61 years old, 5 male and 5 female). FC metrics were obtained from the comparisons of resting-state functional magnetic resonance imaging among our various groups (controls, SCI with NP, and SCI without NP). For each comparison, a region-of-interest (ROI)-to-ROI connectivity analysis was pursued, encompassing a total of 175 ROIs based on a customized atlas derived from the AAL3 atlas. The analysis accounted for covariates such as age and sex. To correct for multiple comparisons, a strict Bonferroni correction was applied with a significance level of p < 0.05/NROIs. When comparing SCI patients with moderate-to-severe pain to those with mild-to-no pain, specific thalamic nuclei had altered connections. These nuclei included: medial pulvinar; lateral pulvinar; medial geniculate nucleus; lateral geniculate nucleus; and mediodorsal magnocellular nucleus. There was increased FC between the lateral geniculate nucleus and the anteroventral nucleus in NP post-SCI. Our analysis additionally highlights the relationships between the frontal lobe and temporal lobe with pain. This study successfully identifies thalamic neuroplastic changes that occur in patients with SCI who develop NP. It additionally underscores the pain matrix and involvement of the frontal and temporal lobes as well. Our findings complement that the development of NP post-SCI involves cognitive, emotional, and behavioral influences.

The role of the insula in chronic pain following spinal cord injury: A resting-state fMRI study

BACKGROUND AND PURPOSE

Spinal cord injury (SCI) results in the loss of motor and sensory function from disconnections between efferent and afferent pathways. Most SCI patients are affected with chronic neuropathic pain, but there is a paucity of data concerning neuroplastic changes following SCI. Chronic pain disrupts default networks and is associated with abnormal insular connectivity. The posterior insula (PI) is associated with the degree of pain and intensity of pain. The anterior insula (AI) is related to signal changes. Comprehension of SCI pain mechanisms is essential to elucidate effective treatment options.

METHODS

This study examines the insular gyri functional connectivity (FC) of seven (five male, two female) SCI participants with moderate-severe chronic pain compared to 10 (five male, five female) healthy controls (HC). All subjects had 3-Tesla MRI performed and resting-state functional MRI (fMRI) was acquired. FC metrics were obtained from the comparisons of resting-state fMRI among our various groups. A seed-to-voxel analysis was pursued, encompassing six gyri of the insula. For multiple comparisons, a correction was applied with a significance level of p < .05.

RESULTS

There were significant differences in FC of the insula between SCI participants with chronic pain compared with HC. In the SCI participants, there was hyperconnectivity of the AI and PI to the frontal pole. In addition, there was increased FC noted between the PI and the anterior cingulate cortex. Hyperconnectivity was also observed between the AI and the occipital cortex.

CONCLUSIONS

These findings illustrate that there is a complex hyperconnectivity and modulation of pain pathways after traumatic SCI.

Long-Term Safety and Efficacy of Mirogabalin for Central Neuropathic Pain: A Multinational, Phase 3, 52-Week, Open-Label Study in Asia

INTRODUCTION

Central neuropathic pain (CNeP) is difficult to treat and has diverse etiology, including spinal cord injury (CNePSCI), Parkinson's disease (CNePPD), and central post-stroke pain (CPSP). The safety and efficacy of mirogabalin have been demonstrated in short-term trials, including patients with CNePSCI. The objective of our study was to confirm the safety/efficacy of mirogabalin in patients with CNePPD and CPSP, and obtain long-term data for CNePSCI.

METHODS

This 52-week, open-label extension of a previous randomized controlled study was conducted across Japan, Korea, and Taiwan. Patients with CNePSCI, CNePPD, or CPSP received twice daily (BID) 5-10 mg mirogabalin for a 4-week titration period, after which the dosage was maintained for 47 weeks at a maximum of 15 mg BID, followed by a 1-week taper period receiving the same dose but only administered once daily. The primary endpoint was safety, assessed primarily by incidence and severity of treatment-emergent adverse events (TEAEs). Efficacy was assessed in a post hoc analysis of data obtained by the short-form McGill Pain Questionnaire (SF-MPQ).

RESULTS

Of the 210 patients enrolled, 106, 94, and 10 had CNePSCI, CPSP, and CNePPD, respectively. The mean overall age of patients was 62.9 years, and most patients were male and of Japanese ethnicity. TEAEs occurred in 84.8% of patients, the most common being somnolence (16.7%), peripheral edema (12.4%), edema (11.4%), nasopharyngitis (11.0%), and dizziness (7.6%). Most TEAEs were mild. Severe and serious TEAEs occurred in 6.2% and 13.3% of patients, respectively. All patient groups experienced reductions in SF-MPQ visual analog scores for pain: mean ± standard deviation changes from baseline at week 52 were -2.3 ± 21.13 mm (CNePSCI), -17.0 ± 24.99 mm (CPSP), and -17.1 ± 35.32 mm (CNePPD).

CONCLUSION

Mirogabalin was generally safe, well tolerated, and effective for treatment of CNeP in this long-term study.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03901352.

Different Gabapentin and Pregabalin Dosages for Perioperative Pain Control in Patients Undergoing Spine Surgery: A Systematic Review and Network Meta-Analysis

IMPORTANCE

Patients undergoing spine surgery often experience severe pain. The optimal dosage of pregabalin and gabapentin for pain control and safety in these patients has not been well established.

OBJECTIVE

To evaluate the associations of pain, opioid consumption, and adverse events with different dosages of pregabalin and gabapentin in patients undergoing spine surgery.

DATA SOURCES

PubMed/MEDLINE, Embase, Web of Science, Cochrane library, and Scopus databases were searched for articles until August 7, 2021.

STUDY SELECTION

Randomized clinical trials conducted among patients who received pregabalin or gabapentin while undergoing spine surgery were included.

DATA EXTRACTION AND SYNTHESIS

Two investigators independently performed data extraction following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) reporting guideline. The network meta-analysis was conducted from August 2022 to February 2023 using a random-effects model.

MAIN OUTCOMES AND MEASURES

The primary outcome was pain intensity measured using the Visual Analog Scale (VAS), and secondary outcomes included opioid consumption and adverse events.

RESULTS

Twenty-seven randomized clinical trials with 1861 patients (median age, 45.99 years [range, 20.00-70.00 years]; 759 women [40.8%]) were included in the systematic review and network meta-analysis. Compared with placebo, the VAS pain score was lowest with gabapentin 900 mg per day, followed by gabapentin 1200 mg per day, gabapentin 600 mg per day, gabapentin 300 mg per day, pregabalin 300 mg per day, pregabalin 150 mg per day, and pregabalin 75 mg per day. Additionally, gabapentin 900 mg per day was found to be associated with the lowest opioid consumption among all dosages of gabapentin and pregabalin, with a mean difference of -22.07% (95% CI, -33.22% to -10.92%) for the surface under the cumulative ranking curve compared with placebo. There was no statistically significant difference in adverse events (nausea, vomiting, and dizziness) among all treatments. No substantial inconsistency between direct and indirect evidence was detected for all outcomes.

CONCLUSIONS AND RELEVANCE

These findings suggest that gabapentin 900 mg per day before spine surgery is associated with the lowest VAS pain score among all dosages. In addition, no differences in adverse events were noted among all treatments.

Treatment of spasticity

Spasticity is characterized by an enhanced size and reduced threshold for activation of stretch reflexes and is associated with "positive signs" such as clonus and spasms, as well as "negative features" such as paresis and a loss of automatic postural responses. Spasticity develops over time after a lesion and can be associated with reduced speed of movement, cocontraction, abnormal synergies, and pain. Spasticity is caused by a combination of damage to descending tracts, reductions in inhibitory activity within spinal cord circuits, and adaptive changes within motoneurons. Increased tone, hypertonia, can also be caused by changes in passive stiffness due to, for example, increase in connective tissue and reduction in muscle fascicle length. Understanding the cause of hypertonia is important for determining the management strategy as nonneural, passive causes of stiffness will be more amenable to physical rather than pharmacological interventions. The management of spasticity is determined by the views and goals of the patient, family, and carers, which should be integral to the multidisciplinary assessment. An assessment, and treatment, of trigger factors such as infection and skin breakdown should be made especially in people with a recent change in tone. The choice of management strategies for an individual will vary depending on the severity of spasticity, the distribution of spasticity (i.e., whether it affects multiple muscle groups or is more prominent in one or two groups), the type of lesion, and the potential for recovery. Management options include physical therapy, oral agents; focal therapies such as botulinum injections; and peripheral nerve blocks. Intrathecal baclofen can lead to a reduction in required oral antispasticity medications. When spasticity is severe intrathecal phenol may be an option. Surgical interventions, largely used in the pediatric population, include muscle transfers and lengthening and selective dorsal root rhizotomy.