Neuropathic Pain in Neurologic Disorders: A Narrative Review

Exploring the Therapeutic Potential of Mesenchymal Stem Cells-derived conditioned medium: An In-depth Analysis of Pain Alleviation, Spinal CCL2 Levels, and Oxidative Stress

Neuropathic pain, a debilitating condition, remains a significant challenge due to the lack of effective therapeutic solutions. This study aimed to evaluate the potential of mesenchymal stromal cell (MSC)-derived conditioned medium in alleviating neuropathic pain induced by sciatic nerve compression injury in adult male rats. Forty Wistar rats were randomly assigned to four groups: control, nerve injury, nerve injury with intra-neural injection of conditioned medium, and nerve injury with intra-neural injection of culture medium. Following sciatic nerve compression, the respective groups received either 10 µl of conditioned medium from amniotic fluid-derived stem cells or an equal volume of control culture medium. Behavioral tests for cold allodynia, mechanical allodynia, and thermal hyperalgesia were conducted, and the spinal cord was analyzed using Western Blot and oxidative stress assays. The behavioral experiments showed a decrease in mechanical hyperalgesia and cold allodynia in the group receiving conditioned medium compared to the injury group and the control medium group. Western blot data revealed a decrease in the expression of the CCL2 protein and an increase in GAD65. Oxidative stress tests also showed increased levels of SOD and glutathione in conditioned media-treated animals compared to animals with nerve injury. The findings suggest that conditioned medium derived from amniotic fluid-derived stem cells can effectively reduce neuropathic pain, potentially through the provision of supportive factors that mitigate oxidative stress and inflammation in the spinal cord.

Research hotspots and trends of spinal cord stimulation for neuropathic pain: a bibliometric analysis from 2004 to 2023

The purpose of this study is to systematically analyze the development trend, research hotspots, and future development direction on the treatment of neuropathic pain (NP) with spinal cord stimulation through bibliometric method. We extracted the literature related to the treatment of NP with spinal cord stimulation from January 2004 to December 2023 from the Web of Science database. As a result, a total of 264 articles were retrieved. By analyzing the annual published articles, authors, countries, institutions, journals, co-cited literature, and keywords, we found that the count of publication in this field has been experiencing an overall growth, and the publications within the past 5 years accounted for 42% of the total output. Experts from the United States and the UK have made significant contributions in this field and established a stable collaborative team, initially establishing an international cooperation network. Pain is the frequently cited journal in this field. The study on spinal cord stimulation therapy for NP especially the study on spinal cord stimulation therapy for back surgery failure syndrome (FBSS) and its potential mechanisms are the research hotspots in this field, while the study on novel paradigms such as high-frequency spinal cord stimulation and spinal cord burst stimulation represents the future development directions. In short, spinal cord stimulation has been an effective treatment method for NP. The novel paradigms of spinal cord stimulation are the key point of future research in this field.

Impact of pain and adverse health outcomes on long-term US testicular cancer survivors

BACKGROUND

No study has quantified the impact of pain and other adverse health outcomes on global physical and mental health in long-term US testicular cancer survivors or evaluated patient-reported functional impairment due to pain.

METHODS

Testicular cancer survivors given cisplatin-based chemotherapy completed validated surveys, including Patient-Reported Outcomes Measurement Information System v1.2 global physical and mental health, Patient-Reported Outcomes Measurement Information System pain questionnaires, and others. Multivariable linear regression examined relationships between 25 adverse health outcomes with global physical and mental health and pain-interference scores. Adverse health outcomes with a β^  of more than 2 are clinically important and reported below.

RESULTS

Among 358 testicular cancer survivors (median age = 46 years, interquartile range [IQR] = 38-53 years; median time since chemotherapy = 10.7 years, IQR = 7.2-16.0 years), median adverse health outcomes number was 5 (IQR = 3-7). A total of 12% testicular cancer survivors had 10 or more adverse health outcomes, and 19% reported chemotherapy-induced neuropathic pain. Increasing adverse health outcome numbers were associated with decreases in physical and mental health (P < .0001 each). In multivariable analyses, chemotherapy-induced neuropathic pain (β^ = -3.72; P = .001), diabetes (β^ = -4.41; P = .037), obesity (β^ = -2.01; P = .036), and fatigue (β^ = -8.58; P < .0001) were associated with worse global mental health, while being married or living as married benefited global mental health (β^ = 3.63; P = .0006). Risk factors for pain-related functional impairment included lower extremity location (β^ = 2.15; P = .04) and concomitant peripheral artery disease (β^ = 4.68; P < .001). Global physical health score reductions were associated with diabetes (β^ = -3.81; P = .012), balance or equilibrium problems (β^ = -3.82; P = .003), cognitive dysfunction (β^ = -4.43; P < .0001), obesity (β^ = -3.09; P < .0001), peripheral neuropathy score (β^ = -2.12; P < .0001), and depression (β^ = -3.17; P < .0001).

CONCLUSIONS

Testicular cancer survivors suffer adverse health outcomes that negatively impact long-term global mental health, global physical health, and pain-related functional status. Clinically important factors associated with worse physical and mental health identify testicular cancer survivors requiring closer monitoring, counseling, and interventions. Chemotherapy-induced neuropathic pain must be addressed, given its detrimental impact on patient-reported functional status and mental health 10 or more years after treatment.

NLRs and inflammasome signaling in opioid-induced hyperalgesia and tolerance

We investigated the role that innate immunological signaling pathways, principally nod-like receptors (NLRs) and inflammasomes, in the manifestation of the contradictory outcomes associated with opioids, namely hyperalgesia, and tolerance. The utilization of opioids for pain management is prevalent; nonetheless, it frequently leads to an increased sensitivity to pain (hyperalgesia) and reduced efficacy of the medication (tolerance) over an extended period. This, therefore, represents a major challenge in the area of chronic pain treatment. Recent studies indicate that the aforementioned negative consequences are partially influenced by the stimulation of NLRs, specifically the NLRP3 inflammasome, and the subsequent assembly of the inflammasome. This process ultimately results in the generation of inflammatory cytokines and the occurrence of neuroinflammation and the pathogenesis of hyperalgesia. We also explored the putative downstream signaling cascades activated by NOD-like receptors (NLRs) and inflammasomes in response to opioid stimuli. Furthermore, we probed potential therapeutic targets for modifying opioid-induced hyperalgesia, with explicit emphasis on the activation of the NLRP3 inflammasome. Ultimately, our findings underscore the significance of conducting additional research in this area that includes an examination of the involvement of various NLRs, immune cells, and genetic variables in the development of opioid-induced hyperalgesia and tolerance. The present review provides substantial insight into the possible pathways contributing to the occurrence of hyperalgesia and tolerance in individuals taking opioids.

Effectiveness of Botulinum Toxin in the Treatment of Neuropathic Pain: A Literature Review

Neuralgia is characterized by chronic pain resulting from damage or diseases in the somatosensory system, including nerves responsible for transmitting sensory information. Current treatments for neuropathic pain, which is a type of neuralgia, have limited success rates and can cause unwanted side effects. Since 1989, botulinum toxin-A (BTX-A), derived from the potent neurotoxin Clostridium botulinum, has been used to treat neuropathic pain in humans. BTX-A has shown analgesic effects by inhibiting the release of neurotransmitters involved in pain transmission. This review aims to evaluate the effectiveness of BTX-A in various types of neuralgia. The research question guiding this review is whether BTX-A is safe and effective in reducing pain in different types of neuralgias. To conduct this review, a literature search was performed using the PubMed, Medline, and PubMed Central databases. The search strategy included relevant keywords related to BTX-A, neuralgia, and neuropathic pain. After screening titles, abstracts, and full texts, a total of 30 articles were included in the review. These studies examined the efficacy of BTX-A in various conditions such as postherpetic neuralgia (PHN), auriculotemporal neuralgia (ATN), occipital neuralgia (ON), leprosy-induced neuropathic pain (LIN), focal painful neuropathies, complex regional pain syndrome (CRPS), trigeminal neuralgia (TN), and neuropathic pain associated with spinal cord injury. However, further research is needed to enhance our understanding of the optimal use of BTX-A in specific neuralgias. It is important to acknowledge the limitations of the included studies. Nevertheless, BTX-A might be considered a viable treatment option for neuralgia.

Clinical characteristics of ankylosing spondylitis patients depending on neuropathic pain

Introduction

Neuropathic pain (NP) in ankylosing spondylitis (AS) is an important factor that complicates patients' everyday activities and leads to a decrease of life quality. Detection and diagnosis of NP can be facilitated by the use of screening instruments, and the comparative assessment of the sensitivity of different scales is important for improving the diagnosis and personalizing the treatment of AS.The aim of the study was to analyze prevalence of NP in patients with AS and clinical features of AS patients depending on the presence of NP.

Material and methods

We examined 94 patients with NP and 48 patients without pain in AS using the following questionnaires: LANSS, DN4, StEP, BASFI, BASMI, BASDAI, HAQ, ASAS HI/EF and BAS-G.

Results

The prevalence of NP according to LANSS was 51.7% in women and 32.7% in men (p = 0.048); according to DN4 - 58.6% and 32.7%, respectively (p = 0.010). Disease activity and functional disability of the patients were higher in the group of patients with NP than in the group of patients without NP according to the BASDAI, BASFI, BASMI, HAQ, ASAS HI/EF and BAS-G. Significance of differences between groups was at the level of p < 0.01.

Conclusions

The prevalence of NP in AS is alarmingly high. Even with low scores on screening scales, patients showed signs of NP, which may indicate higher prevalence of NP. Neuropathic pain is more associated with the activity of the disease, greater loss of functional capacity and a decrease in indicators of the general state of health, which allows it to be considered as an aggravating factor regarding these manifestations.

Assessment of intraepidermal nerve fiber density and neurophysiological studies in patients with idiopathic polyneuropathy

Background

Idiopathic polyneuropathy is an asymmetrical, length-dependent neuropathy in which neurophysiology demonstrates axonal damage involving large fibers, along with insidious onset and slow progression over 6 months, with no identified etiology in spite of thorough investigations. This study aimed to evaluate the diagnostic role of clinical, electrophysiological, and histopathological studies in patients with idiopathic polyneuropathy.

Methods

Case–control study included 20 patients with clinical and neurophysiological evidence of sensory or sensory–motor neuropathy with no apparent etiology after laboratory investigation were recruited from 127 patients with sensory–motor neuropathy of unknown etiology (the patients group). Twenty apparently healthy individuals, age- and sex-matched, with no neuropathy symptoms (the control group), were recruited from the Neurology Clinic of Al-Azhar University, Assuit.

Results

Age of onset of patients with idiopathic polyneuropathy (44–70) years, duration of illness (1–6) years, 60% had painful neuropathy, diagnostic neuropathic pain questioner (DN4 score) (5–7), abnormal pin brick (80%), abnormal vibration (90%), abnormal fine touch (75%), distal weakness (70%), and lost ankle reflex (90%). In the control group, there were substantial differences with respect to prolonged latency, diminished sympathetic skin response amplitude, and significant intraepidermal nerve fiber density reduction in skin biopsy cases. In diagnosing idiopathic polyneuropathy, the specificity and sensitivity of sympathetic skin response were (80–86)% and (81–89.5)%, respectively, whereas those of diminished intraepidermal nerve fiber density were (92.5%) and (97.5%), respectively.

Conclusion

The assessment of intraepidermal nerve fiber density had an important good diagnostic role in cases presented with polyneuropathy.

Testosterone and long pulse width stimulation (TLPS) for denervated muscles after spinal cord injury: a study protocol of randomised clinical trial

INTRODUCTION

Long pulse width stimulation (LPWS; 120-150 ms) has the potential to stimulate denervated muscles and to restore muscle size in denervated people with spinal cord injury (SCI). We will determine if testosterone treatment (TT)+LPWS would increase skeletal muscle size, leg lean mass and improve overall metabolic health in persons with SCI with denervation. We hypothesise that the 1-year TT+LPWS will upregulate protein synthesis pathways, downregulate protein degradation pathways and increase overall mitochondrial health.

METHODS AND ANALYSIS

Twenty-four male participants (aged 18-70 years with chronic SCI) with denervation of both knee extensor muscles and tolerance to the LPWS paradigm will be randomised into either TT+neuromuscular electrical stimulation via telehealth or TT+LPWS. The training sessions will be twice weekly for 1 year. Measurements will be conducted 1 week prior training (baseline; week 0), 6 months following training (postintervention 1) and 1 week after the end of 1 year of training (postintervention 2). Measurements will include body composition assessment using anthropometry, dual X-ray absorptiometry and MRI to measure size of different muscle groups. Metabolic profile will include measuring of basal metabolic rate, followed by blood drawn to measure fasting biomarkers similar to hemoglobin A1c, lipid panels, C reactive protein, interleukin-6 and free fatty acids and then intravenous glucose tolerance test to test for insulin sensitivity and glucose effectiveness. Finally, muscle biopsy will be captured to measure protein expression and intracellular signalling; and mitochondrial electron transport chain function. The participants will fill out 3 days dietary record to monitor their energy intake on a weekly basis.

ETHICS AND DISSEMINATION

The study was approved by Institutional Review Board of the McGuire Research Institute (ID # 02189). Dissemination plans will include the Veteran Health Administration and its practitioners, the national SCI/D services office, the general healthcare community and the veteran population, as well as the entire SCI community via submitting quarterly letters or peer-review articles.

TRIAL REGISTRATION NUMBER

NCT03345576.