Central pain in multiple sclerosis--prevalence and clinical characteristics

Trigeminal and Glossopharyngeal Neuralgia

Trigeminal neuralgia and glossopharyngeal neuralgia are craniofacial pain syndromes characterized by recurrent brief shock-like pains in the distributions of their respective cranial nerves. In this article, the authors aim to summarize each condition's characteristics, pathophysiology, and current pharmacotherapeutic and surgical interventions available for managing and treating these conditions.

Neuroprotection by acrolein sequestration through exogenously applied scavengers and endogenous enzymatic enabling strategies in mouse EAE model

We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in MS pathology. In this study, we found that the acrolein scavenger hydralazine (HZ), when applied from the day of induction, can suppress acrolein and alleviate motor and sensory deficits in a mouse experimental autoimmune encephalomyelitis (EAE) model. Furthermore, we also demonstrated that HZ can alleviate motor deficits when applied after the emergence of MS symptoms, making potential anti-acrolein treatment a more clinically relevant strategy. In addition, HZ can reduce both acrolein and MPO, suggesting a connection between acrolein and inflammation. We also found that in addition to HZ, phenelzine (PZ), a structurally distinct acrolein scavenger, can mitigate motor deficits in EAE when applied from the day of induction. This suggests that the likely chief factor of neuroprotection offered by these two structurally distinct acrolein scavengers in EAE is their common feature of acrolein neutralization. Finally, up-and-down regulation of the function of aldehyde dehydrogenase 2 (ALDH2) in EAE mice using either a pharmacological or genetic strategy led to correspondent motor and sensory changes. This data indicates a potential key role of ALDH2 in influencing acrolein levels, oxidative stress, inflammation, and behavior in EAE. These findings further consolidate the critical role of aldehydes in the pathology of EAE and its mechanisms of regulation. This is expected to reinforce and expand the possible therapeutic targets of anti-aldehyde treatment to achieve neuroprotection through both endogenous and exogenous manners.

Risk factors of neuropathic pain in multiple sclerosis: a retrospective case-cohort study

Background

Pain is a common symptom in multiple sclerosis (MS), especially neuropathic pain, which has a significant impact on patients' mental and physical health and quality of life. However, risk factors that related to neuropathic pain, still remain unclear.

Objective

The study aimed to explore the risk factors of neuropathic pain among MS patients.

Materials and methods

This retrospective study examined the consecutive patients diagnosed with MS in the Department of Neurology of Guangdong Provincial Hospital of Chinese Medicine between August 2011 and October 2022. Neuropathic pain was defined as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system". Demographic and clinical features were obtained from the electronic system of the hospital.

Results

Our cohort revealed that the prevalence of patients with neuropathic pain in MS was 34.1%. The results indicated that the longer the spinal lesions, the greater the neuropathic pain risks (2-4: OR, 13.3(2.1-82), >5: OR, 15.2(2.7-86.8), p for tread: 0.037). Meanwhile, multivariate regression analysis showed that cervical and thoracic lesions (OR 4.276, 95% CI 1.366-13.382, P = 0.013), upper thoracic lesions (T1-T6) (OR 3.047, 95% CI 1.018-9.124, P = 0.046) were positively correlated with neuropathic pain, while basal ganglia lesions (OR 0.188, 95% CI 0.044-0.809, P = 0.025) were negatively correlated with neuropathic pain among MS patients.

Conclusion

Extended spinal lesions (≥3 spinal lesions), cervical and thoracic lesions, upper thoracic lesions were independent risk factors of neuropathic pain among MS patients. Furthermore, our study found that the longer the spinal lesions, the greater the neuropathic pain risks.

A systematic review and meta-analysis of neuropathic pain in multiple sclerosis: Prevalence, clinical types, sex dimorphism, and increased depression and anxiety symptoms

Chronic pain is the most disability symptom related to multiple sclerosis (MS) brain lesions and can also generate anxiety and depression. There are no updated reports of the general prevalence of neuropathic pain, MS clinical types, sex dimorphism, and its association with depression and anxiety. The protocol was listed in PROSPERO (CRD42022303571). The article selection resulted in 24 studies with a low risk of bias. The prevalence of neuropathic pain in MS patients was 26.8% with higher levels of depression and anxiety. We also observed that female patients (74.2%) have a higher prevalence of neuropathic pain than males (28.9%). We showed the enhanced prevalence of neuropathic pain using the female and male data (58.9%) compared to the total prevalence (26.8%). In addition, the SPMS (40.3%) presented an increased prevalence of neuropathic pain compared to PPMS (15.6%). Thus, we demonstrated the association between neuropathic pain, depression and anxiety symptoms and the influence of diagnosis, age, disease score, and disease duration in the increased prevalence of neuropathic pain in MS patients.

Long-lasting pain and somatosensory disturbances in children with myelin oligodendrocyte glycoprotein antibody-associated disease

Myelin oligodendrocyte glycoprotein antibody (MOG-Ab) is an autoantibody associated with acquired demyelinating syndrome (ADS) in childhood and adults. The pathogenic roles of MOG-Ab and long-term outcomes of children with MOG-Ab-associated disease (MOGAD) remain elusive. We investigated the clinical features of children with ADS during follow-up in our institute. Clinical data were retrospectively analyzed using medical charts of patients managed in Kyushu University Hospital from January 1st, 2001, to March 31st, 2022. Participants were children of < 18 years of age when they received a diagnosis of ADS in our hospital. Cell-based assays were used to detect MOG-Ab in serum or cerebrospinal fluid at the onset or recurrence of ADS. The clinical and neuroimaging data of MOG-Ab-positive and MOG-Ab-negative patients were statistically analyzed. Among 31 patients enrolled in this study, 22 (13 females, 59%) received tests for MOG antibodies. Thirteen cases (59%) were MOG-Ab-positive and were therefore defined as MOGAD; 9 (41%) were MOG-Ab-negative. There were no differences between MOGAD and MOG-Ab-negative patients in age at onset, sex, diagnostic subcategories, or duration of follow-up. MOGAD patients experienced headache and/or somatosensory symptoms more frequently than MOG-Ab-negative patients (12/13 (92%) vs. 3/9 (22%); p = 0.0066). Somatosensory problems included persistent pain with hyperesthesia in the left toe, perineal dysesthesia, and facial hypesthesia. No specific neuroimaging findings were associated with MOGAD or the presence of somatosensory symptoms.

CONCLUSIONS

Long-lasting somatosensory disturbances are prominent comorbidities in children with MOGAD. Prospective cohorts are required to identify molecular and immunogenetic profiles associated with somatosensory problems in MOGAD.

WHAT IS KNOWN

• Recurrence of demyelinating events occurs in a group of children with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).

WHAT IS NEW

• Long-lasting headache and somatosensory problems are frequent comorbidities with pediatric MOGAD. Pain and somatosensory problems may persist for more than 5 years. • Neuroimaging data do not indicate specific findings in children with somatic disturbances.

The evaluation of small fibers in multiple sclerosis

BACKGROUND

Dysesthetic or ongoing extremity pain is a common symptom in all multiple sclerosis (MS) types. Although the pathology of the disease is the demyelination of central neurons, the patients may also complain of neuropathic pain in distal extremities that is generally related to A-delta and C fiber dysfunction. It is not known whether thinly myelinated and unmyelinated fibers are affected in MS patients. We aim to investigate the small fiber loss and its length dependency.

METHODS

We evaluated the skin biopsy taken from proximal and distal leg of MS patients with neuropathic pain. Six patients with primary progressive MS (PPMS), seven with relapsing-remitting MS (RRMS), seven with secondary progressive MS (SPMS) and as a control group ten age and sex-matched healthy controls were included. Neurological examination, electrophysiological evaluation and DN4 questionnaire were performed. Subsequently, skin punch biopsy from 10 cm above the lateral malleolus and proximal thigh were done. The biopsy samples were stained with PGP9.5 antibody and intraepidermal nerve fiber density (IENFD) was determined.

RESULTS

The mean proximal IENFD was 8.58±3.58 fibers/mm among MS patients and 14.72±2.89 fiber/mm among healthy controls (p=0.001). However, the mean distal IENFD did not differ between MS patients and healthy controls (9.26±3.24 and 9.75±1.6 fiber/mm respectively. Although proximal and distal IENFD tends to be lower in MS patients with neuropathic pain, there was no statistically significant difference between MS patients with and without neuropathic pain CONCLUSION: Although MS is a demyelinating disease, unmyelinated fibers can also be affected. Our findings suggest non-length dependent small fiber neuropathy in MS patients.

Pain in patients with multiple sclerosis

Objectives

This study aims to identify the factors associated with pain and neuropathic pain (NP) in patients with multiple sclerosis (MS) and to determine the relationship between pain and NP with disability, functionality, activities of daily living, fatigue, mood, and quality of life (QoL).

Patients and methods

Between July 2017 and October 2017, a total of 100 adult patients with MS (18 males, 82 females; mean age: 35.3±9.9 years; range, 19 to 71 years) were included. All patients were evaluated in terms of pain and NP. Patients with and without pain, and patients with and without NP were compared in terms of sociodemographic characteristics, disease data, disability, functionality, daily living activities, fatigue severity, mood, and QoL using various scales.

Results

A total of 62% of the patients had pain. Pain was found to be associated with low education level (p=0.014), increased fatigue (p<0.001), depressive mood (p<0.001) and lower QoL (p<0.001). A total of 29.03% of patients with pain had NP. Patients with NP had a greater pain intensity (p<0.001) and fatigue (p=0.002) and lower QoL (p=0.011). The number of patients who received the correct treatment for their symptoms was low.

Conclusion

Pain and NP should be better investigated and treated by physicians, as these symptoms are common in MS and adversely affect the QoL and social relations of affected patients and reduce their productivity.

The Assessment of the Prevalence and Disability Severity of Musculoskeletal Pain in Patients With Multiple Sclerosis in Saudi Arabia

Background Multiple sclerosis (MS) is an autoimmune disease of the nervous system that causes chronic demyelination over time and may lead to physical disability. MS-related pain may be musculoskeletal, paroxysmal, or persistently neurogenic in nature. The most common type of pain is musculoskeletal discomfort, which is typically brought on by muscle weakening, stiffness, and generalized imbalance as the condition progresses. Pain often manifests after prolonged immobilization of muscles, tendons, and ligaments. Aim We aimed to evaluate the prevalence and severity of musculoskeletal pain (MSP) among MS patients in Saudi Arabia. Methodology A quantitative cross-sectional study was conducted. Patients with confirmed MS in Saudi Arabia were invited to participate in the study during the duration from April 2022 to May 2022. Data were collected using an electronic collection tool. The study tool was checked to ensure the content validity and clarity of the Arabic and English versions. Results A total of 360 MS patients were included. Patients' ages ranged from 18 to 65 years with a mean age of 34.9±13.2 years old. Exactly 229 (63.6%) patients were females. A total of 104 (28.9%) patients complained of relapsing-remitting MS, 34 (9.4%) complained of primary progressive MS, and 16 (4.4%) complained of secondary progressive MS. A total of 138 (38.3%) patients had the disease for less than five years, and 14 (3.9%) had the disease for more than 21 years. Exactly 124 (34.4%) MS patients complained of high disability due to MSP, while 236 (65.6%) had low disability. Conclusions This study demonstrates that one out of each three patients with MS complained of pain with high disability associated with pain. Old age, comorbidities, long disease duration, and a family history of MS were significant determinants of associated disability severity.

Systematic review of participant characteristics in theory-based behavior change interventions for physical activity in multiple sclerosis: are we missing those with the greatest potential for lifelong benefits?

PURPOSE

This study examined participant characteristics, particularly disease duration, in theory-based physical activity behavior change trials in multiple sclerosis (MS) and summarized theoretical frameworks and changes in physical activity outcomes.

MATERIALS AND METHODS

PubMed, CINAHL, Embase, and Scopus were searched to identify potential trials. One reviewer screened titles and abstracts, and two reviewers then independently screened full-text articles based on predetermined eligibility criteria. Data were extracted by one reviewer and checked by a second reviewer.

RESULTS

Among 33 trials reviewed, only one trial reported a mean disease duration of less than five years (i.e., 4.5 years) for the sample. The remaining trials included samples with a mean disease duration of 6.7 years or longer. The most common theories used were Social Cognitive Theory, Trans-theoretical Model, and Motivational Interviewing. The effects on physical activity were heterogeneous; device-measured outcomes increased in 41.4% of studies, self-reported outcomes improved in 72.4%. Adherence (≥80%) was reported in 34.5% of studies.

CONCLUSIONS

There is little focus on persons with MS in the early disease course in physical activity behavior change interventions. Future research should include comprehensive theoretical approaches for more homogeneous effects across outcome measures when targeting those in the early stage and all MS populations.IMPLICATIONS FOR REHABILITATIONTheory-based physical activity behavior change interventions have not included persons with multiple sclerosis (MS) in the early disease course (<5 years since diagnosis).Disease duration has not been a criterion used to include or exclude participants in the reviewed theory-based behavior change interventions for physical activity in people with MS.The theory-based behavior change interventions in this review positively affected short-term physical activity levels in people with MS.

Ultrasound-Guided Injections and Proprioceptive Neuromuscular Facilitation as Shoulder Rehabilitation for Multiple Sclerosis and Neuropathic Pain

Multiple sclerosis (MS) represents a major cause of chronic neurological disability in young adults and can result in upper limb sensorimotor impairment with a huge impact on manual dexterity and activities of daily living. Moreover, pain is common in MS and a large proportion of patients suffer from central neuropathic pain. To date, no rehabilitative treatment has been described as useful for these patients. A 46-year-old woman, affected by relapsing-remittent MS, described a one-year history of right shoulder pain (Visual Analogue Scale = 8) that started gradually and without trauma. The patient also presented balance and gait impairments, upper limb strength deficit, and fatigue (Expanded Disability Status Scale = 5.5). A multidisciplinary treatment was proposed, including three intra-articular corticosteroid injections and one month of manual therapy, three sessions/week, based on proprioceptive neuromuscular facilitation for the upper limb. At the end of the rehabilitative treatment, pain relief and an improvement in the range of motion of the affected shoulder, upper limb muscle strength, and hand dexterity were observed. The present paradigmatic case report with literature review demonstrated that a multidisciplinary approach seems to be effective in pain relief in a patient with central neuropathic shoulder pain and relapsing-remitting MS.

Unique features of central neuropathic pain in multiple sclerosis: Results of a cluster analysis

Background

Central neuropathic pain (CNP) is an excruciating condition, prevalent in up to a third of patients with multiple sclerosis (MS). Identifying CNP among MS patients is particularly challenging considering the ample comorbid chronic pain conditions and sensory disturbances entailed by the disease. The aim was to identify sensory features unique to CNP beyond those of chronic pain and MS.

Methods

Participants were 112 MS patients: 44 with a diagnosis of CNP, 28 with a diagnosis of chronic musculoskeletal pain (MSP), and 40 pain free. Participants underwent testing of thermal and mechanical thresholds, thermal grill illusion (TGI), pain adaptation (PA), and offset analgesia (OA), and chronic pain was characterized. A two‐step cluster analysis was performed, and the association between the cluster membership and the clinical group membership (CNP, MSP, pain free) was evaluated.

Results

The CNP and MSP groups were similar in most of the chronic pain variables (e.g., severity, location and quality) and MS‐related variables (e.g., type, severity and medication intake). The three created clusters had unique sensory features: (1) ‘Hyposensitivity’ (increased thermal and touch thresholds) characterized the CNP group; (2) ‘Poor inhibition and hyperalgesia’ (worst PA and OA and decreased TGI threshold) characterized the MSP group; and (3) ‘Efficient inhibition’ (best PA and OA, smallest sensory loss) characterized the pain‐free group.

Conclusions

The unique sensory features of CNP and MSP provide insight into their pathophysiology, and evaluating them may increase the ability to provide individually based interventions. Efficient inhibition may protect MS patients from chronic pain.

Significance

Cluster analysis among patients with multiple sclerosis (MS) revealed that while central neuropathic pain is associated with thermal and mechanical hypoesthesia, musculoskeletal pain is involved with reduced pain inhibition and hyperalgesia; sensory profiles that provide insights into the mechanisms of these conditions and may promote an individually based pain management.

Prevalence of trigeminal neuralgia in multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

The prevalence of Trigeminal Neuralgia (TN) in patients diagnosed with multiple sclerosis (MS) is insufficiently understood and controversially reported. This study focused on providing a better understanding of the prevalence of TN in MS patients.

METHOD

We systematically searched PubMed, Scopus, EMBASE, Web of Science, and Google Scholar to identify studies published from January 1, 1990, to December 30, 2020. We included studies reporting the TN prevalence among MS patients and exclude case reports/series and editorial studies, review studies, and non-English written articles. We used pooled prevalence estimates to determine the TN prevalence among MS patients.

RESULTS

Pooled overall TN prevalence among 19 studies and 30,348 MS patients was estimated as 3.4% (95% CI: 1.5%-5.9%) with a high level of heterogeneity among studies (I2=98.92%; p<0.001). The pooled prevalence of TN in male and female patients across 9 surveys was 2.4% (95% CI: 0.5%-5.4%) and 3.8% (95% CI: 0.8%-8.7%), respectively. No heterogeneity between the two groups was observed (p = 0.558). A meta-regression was performed to explore the source of the heterogeneity. None of the candidate covariates, including the year of a study publication, the sample size, the average age of patients, and the disease duration, were significant in the model.

CONCLUSION

Our results showed that TN is a common problem among patients with MS, predominantly male patients. Future studies should target the general prevalence of pain in MS patients.

Central amygdala inflammation drives pain hypersensitivity and attenuates morphine analgesia in experimental autoimmune encephalomyelitis

ABSTRACT

Chronic pain is a highly prevalent symptom associated with the autoimmune disorder multiple sclerosis (MS). The central nucleus of the amygdala plays a critical role in pain processing and modulation. Neuropathic pain alters nociceptive signaling in the central amygdala, contributing to pain chronicity and opioid tolerance. Here, we demonstrate that activated microglia within the central amygdala disrupt nociceptive sensory processing and contribute to pain hypersensitivity in experimental autoimmune encephalomyelitis (EAE), the most frequently used animal model of MS. Male and female mice with EAE exhibited differences in microglial morphology in the central amygdala, which was associated with heat hyperalgesia, impaired morphine reward, and reduced morphine antinociception in females. Animals with EAE displayed a lack of morphine-evoked activity in cells expressing somatostatin within the central amygdala, which drive antinociception. Induction of focal microglial activation in naïve mice via injection of lipopolysaccharide into the central amygdala produced a loss of morphine analgesia in females, similar to as observed in EAE animals. Our data indicate that activated microglia within the central amygdala may contribute to the sexually dimorphic effects of morphine and may drive neuronal adaptations that lead to pain hypersensitivity in EAE. Our results provide a possible mechanism underlying the decreased efficacy of opioid analgesics in the management of MS-related pain, identifying microglial activation as a potential therapeutic target for pain symptoms in this patient population.

Recommendations for traveling to altitude with neurological disorders

BACKGROUND

Several neurological conditions might worsen with the exposure to high altitude (HA). The aim of this review was to summarize the available knowledge on the neurological HA illnesses and the risk for people with neurological disorders to attend HA locations.

METHODS

A search of literature was conducted for several neurological disorders in PubMed and other databases since 1970. The neurological conditions searched were migraine, different cerebrovascular disease, intracranial space occupying mass, multiple sclerosis, peripheral neuropathies, neuromuscular disorders, epileptic seizures, delirium, dementia, and Parkinson's disease (PD).

RESULTS

Attempts were made to classify the risk posed by each condition and to provide recommendations regarding medical evaluation and advice for or against traveling to altitude. Individual cases should be advised after careful examination and risk evaluation performed either in an outpatient mountain medicine service or by a physician with knowledge of HA risks. Preliminary diagnostic methods and anticipation of neurological complications are needed.

CONCLUSIONS

Our recommendations suggest absolute contraindications to HA exposure for the following neurological conditions: (1) Unstable conditions-such as recent strokes, (2) Diabetic neuropathy, (3) Transient ischemic attack in the last month, (4) Brain tumors, and 5. Neuromuscular disorders with a decrease of forced vital capacity >60%. We consider the following relative contraindications where decision has to be made case by case: (1) Epilepsy based on recurrence of seizure and stabilization with the therapy, (2) PD (± obstructive sleep apnea syndrome-OSAS), (3) Mild Cognitive Impairment (± OSAS), and (4) Patent foramen ovale and migraine have to be considered risk factors for acute mountain sickness.

Multiple Sclerosis and the Endogenous Opioid System

Multiple sclerosis (MS) is an autoimmune disease characterized by chronic inflammation, neuronal degeneration and demyelinating lesions within the central nervous system. The mechanisms that underlie the pathogenesis and progression of MS are not fully known and current therapies have limited efficacy. Preclinical investigations using the murine experimental autoimmune encephalomyelitis (EAE) model of MS, as well as clinical observations in patients with MS, provide converging lines of evidence implicating the endogenous opioid system in the pathogenesis of this disease. In recent years, it has become increasingly clear that endogenous opioid peptides, binding μ- (MOR), κ- (KOR) and δ-opioid receptors (DOR), function as immunomodulatory molecules within both the immune and nervous systems. The endogenous opioid system is also well known to play a role in the development of chronic pain and negative affect, both of which are common comorbidities in MS. As such, dysregulation of the opioid system may be a mechanism that contributes to the pathogenesis of MS and associated symptoms. Here, we review the evidence for a connection between the endogenous opioid system and MS. We further explore the mechanisms by which opioidergic signaling might contribute to the pathophysiology and symptomatology of MS.

[Neuropathic pain syndromes in patients with multiple sclerosis]

Among the numerous pain syndromes (PS) of various localizations and types, observed in patients with multiple sclerosis (MS), the greatest attention of researchers is attracted by neuropathic PS. Neuropathic PS are often present already in the early stage of MS, significantly reduce the quality of life, hinder the social adaptation of patients, poorly respond to therapy. Central neuropathic PS, which pathogenesis is closely related with plaques in the central nervous system, are most common in patients with MS. Diagnostics of neuropathic PS in MS is based mainly on typical clinical symptoms; MRI and neurophysiological methods data are of secondary importance. This review focuses on modern concepts of three main neuropathic PS in MS: ongoing extremity pain, trigeminal neuralgia and Lhermitte's sign. Clinical symptoms of neuropathic PS, current ideas about their pathogenetic mechanisms, MRI and neurophysiological techniques data and the existing approaches to conservative therapy and surgical treatment based on randomized trials data are presented.

The changing face of trigeminal neuralgia-A narrative review

OBJECTIVE

This narrative review aims to update the reader on the new classification of trigeminal neuralgia (TN), clinical signs, pathophysiologic evidence, and their implications on management. This review is based on the authors' collective experience and knowledge of the literature in addition to a literature search.

BACKGROUND

In recent years, the phenotype of TN has been intensively studied leading to discrete groups of patients. These include patients with TN with additional continuous pain, and patients with and without neurovascular compression of the trigeminal dorsal root entry zone. A number of associated clinical signs such as tearing and sensory changes need further research.

METHODS

The literature on TN was searched in PubMed with the aims of providing evidence for the recently published third edition of the International Classification of Headache Disorders (ICHD) and update the clinical phenotype and management of the TN subcategories.

RESULTS

The ICHD's new classification for TN is based on reliable clinical data, imaging, and neurophysiologic studies. The TN classification reflects current knowledge and has improved the possibility for clinicians to choose adequate management options. However, there is a lack of effective, safe drugs for the management of TN and sparse, robust data on neurosurgical options.

CONCLUSION

Research into all aspects of TN-diagnosis, pharmacotherapy, surgery, long-term management prognosis, and natural history-is needed. Research should adhere to the ICHD's schema for TN. Improved drugs are needed along with rigorous research into surgical options and their efficacy for different subtypes of TN.

Characterizing chronic pain phenotypes in multiple sclerosis: a nationwide survey study

ABSTRACT

Chronic pain is highly prevalent in multiple sclerosis (MS). Pain heterogeneity may contribute to poor treatment outcomes. The aim of this study was to characterize pain phenotypes distributions in persons with MS and compare pain phenotypes in terms of pain intensity, frequency of chronic overlapping pain conditions, and use and analgesic effects of different classes of pain medications. Data were collected through a national web-based survey with measures of neuropathic (painDETECT) and nociplastic pain (Fibromyalgia Survey Criteria), chronic overlapping pain conditions, and pain medication use and pain relief. In a sample of N = 842 adults with chronic pain and MS, the largest proportion (41%) showed evidence of nociceptive pain, 27% had mixed neuropathic/nociplastic pain, 23% had nociplastic pain, and 9% had neuropathic pain. Nociplastic pain was associated with significantly higher pain intensity and frequency of chronic overlapping pain conditions. Across all pain types, high frequency of pain medication use along with poor-modest pain relief was reported. Cannabis use for pain was more common, and pain relief ratings were higher among those with nociplastic pain, relative to nociceptive pain. Although NSAID use was highest among those with nociplastic pain (80%), pain relief ratings for NSAIDs were highest among those with nociceptive pain. These findings underscore the need for multidimensional assessment of pain in MS with greater emphasis on the identification of pain phenotype. An improved characterization of pain as a multifaceted condition in MS could inform therapeutic approaches.

Central neuropathic pain in multiple sclerosis is associated with impaired innocuous thermal pathways and neuronal hyperexcitability

OBJECTIVE

About a third of patients with multiple sclerosis (MS) suffer from chronic and excruciating central neuropathic pain (CNP). The mechanism underlying CNP in MS is not clear, since previous studies are scarce and their results are inconsistent. Our aim was to determine whether CNP in MS is associated with impairment of the spinothalamic-thalamocortical pathways (STTCs) and/or increased excitability of the pain system.

DESIGN

Cross sectional study.

SETTING

General hospital.

SUBJECTS

47 MS patients with CNP, 42 MS patients without CNP, and 32 healthy controls.

METHODS

Sensory testing included the measurement of temperature, pain, and touch thresholds and the thermal grill illusion (TGI) for evaluating STTCs function, and hyperpathia and allodynia as indicators of hyperexcitability. CNP was characterized using interviews and questionnaires.

RESULTS

The CNP group had higher cold and warm thresholds (p < 0.01), as well as higher TGI perception thresholds (p < 0.05), especially in painful body regions compared to controls, whereas touch and pain thresholds values were normal. The CNP group also had a significantly greater prevalence of hyperpathia and allodynia. Regression analysis revealed that whereas presence of CNP was associated with a higher cold threshold, CNP intensity, and the number of painful body regions were associated with allodynia and hyperpathia, respectively.

CONCLUSIONS

CNP in MS is characterized by a specific impairment of STTC function; the innocuous thermal pathways, and by pain hyperexcitability. Whereas CNP presence is associated with STTC impairment, its severity and extent are associated with pain hyperexcitability. Interventions that reduce excitability level may therefore mitigate CNP severity.

Behavior Change Techniques in Physical Activity Interventions for Multiple Sclerosis

OBJECTIVE

To identify and summarize the behavior change techniques (BCTs) included in behavior change interventions for promoting physical activity in persons with multiple sclerosis (MS).

DATA SOURCES

PubMed, PsycINFO, Cumulative Index to Nursing and Allied Health Complete, Scopus, and Embase were initially searched in November 2019, and data extraction began in June 2020.

STUDY SELECTION

The inclusion criteria for studies were: adults older than 18 years with diagnosed MS, English language, clinical trial designs (ie, pre-post or randomized controlled trials), group or individual interventions, and home or community-based settings wherein physical activity was defined as a primary or secondary outcome. Exclusion criteria for studies included protocol manuscripts pending results, case studies, studies focused on populations with multiple chronic diseases, and interventions targeting multiple behaviors. Two researchers completed screening for study selection, and a third researcher served as a referee. Of the initially identified 8681 studies, 54 studies met selection criteria.

DATA EXTRACTION

Data extraction was completed by 3 researchers. Each article was coded by 2 of the 3 researchers, and a fourth researcher resolved discrepancies. Data extracted from each paper included study title, authors, country, year, sample size, study design, intervention details, physical activity outcomes, and BCTs.

DATA SYNTHESIS

Thirty-eight unique behavior change interventions were identified, and 53 of the 93 possible BCTs were included across the studies. The mean number of BCTs per study was 15, and studies and effect sizes across studies ranged from 0.04-1.49.

CONCLUSIONS

This review provides a comprehensive overview of BCTs as the active ingredients in behavior change interventions targeting physical activity in MS. Results from this study provide a compendium for future intervention development for increasing physical activity and improving overall health in MS.

Differences in physical, mental, and social functions between males and females in multiple sclerosis: A multicenter cross-sectional study in China

Background Sex-specific differences in multiple sclerosis (MS) have been recognized, but few were known about how sex influences the characteristics of MS in Asian and the social burden of MS. This study aimed to investigate the symptoms, mental health, and social functions of Chinese MS patients and find differences between sexes. Methods MS patients were enrolled from January 2004 to September 2018. A questionnaire was distributed by 47 medical centers. Patients' physical symptoms, negative emotions, interpersonal communication, social intercourse, employment condition, and suicidal thoughts and behavior were collected. Patients were asked to fill in the questionnaire independently and undergo Expanded Disability Status Scale (EDSS) measurement. Unpaired t-tests between sexes were conducted for normally distributed continuous variables. Mann-Whitney u-tests were conducted for non-normally distributed data. Chi-square tests, Fisher exact tests and rank sum tests were performed for categorical variables. Results 931 patients were enrolled and 631 were female. Frequency of fatigue and pain were higher in female MS patients (P<0.05), while male patients complained more weakness, diplopia, sexual dysfunction, and micturition and defecation dysfunction (P<0.05). Females were more likely to experience sadness and helplessness than males (P<0.05) while males were more likely to experience nonacceptance than females (P<0.05). MS had a worse influence on male patients in relationships with family and friends (P<0.05). The employment rate of MS patients was 39.31%. The frequency of suicidal attempt was 2.36%, which was higher than general population. Conclusions The study provided evidence that characteristics of MS were different between males and females, and influence in mental and social function was a common problem among MS patients. More attention should be paid to the mental health and social function of MS patients.

Pathogenic mechanisms of lipid mediator lysophosphatidic acid in chronic pain

A number of membrane lipid-derived mediators play pivotal roles in the initiation, maintenance, and regulation of various types of acute and chronic pain. Acute pain, comprising nociceptive and inflammatory pain warns us about the presence of damage or harmful stimuli. However, it can be efficiently reversed by opioid analgesics and anti-inflammatory drugs. Prostaglandin E₂ and I₂, the representative lipid mediators, are well-known causes of acute pain. However, some lipid mediators such as lipoxins, resolvins or endocannabinoids suppress acute pain. Various types of peripheral and central neuropathic pain (NeuP) as well as fibromyalgia (FM) are representatives of chronic pain and refractory owing to abnormal pain processing distinct from acute pain. Accumulating evidence demonstrated that lipid mediators represented by lysophosphatidic acid (LPA) are involved in the initiation and maintenance of both NeuP and FM in experimental animal models. The LPAR₁-mediated peripheral mechanisms including dorsal root demyelination, Ca_vα2δ1 expression in dorsal root ganglion, and LPAR₃-mediated amplification of central LPA production via glial cells are involved in the series of molecular mechanisms underlying NeuP. This review also discusses the involvement of lipid mediators in emerging research directives, including itch-sensing, sexual dimorphism, and the peripheral immune system.

Sensory and pain modulation profiles of ongoing central neuropathic extremity pain in multiple sclerosis

BACKGROUND

Central neuropathic extremity pain (CNEP) is the most frequent type of pain in multiple sclerosis (MS). The aim of the present study was to evaluate sensory and pain modulation profiles in MS patients with CNEP.

METHODS

In a single-centre observational study, a group of 56 CNEP MS patients was compared with 63 pain-free MS patients and with a sex- and age-adjusted control group. Standardized quantitative sensory testing (QST) and dynamic QST (dQST) protocols comprising temporal summation and conditioned pain modulation tests were used to compare sensory profiles.

RESULTS

Loss-type QST abnormalities in both thermal and mechanical QST modalities prevailed in both MS subgroups and correlated significantly with higher degree of disability expressed as Expanded Disability Status Scale (EDSS). Comparison of sensory phenotypes disclosed a higher frequency of the 'sensory loss' prototypic sensory phenotype in the CNEP subgroup (30%) compared with pain-free MS patients (6%; p = .003).

CONCLUSION

The role of aging process and higher lesion load in the spinothalamocortical pathway might be possible explanation for pain development in this particular 'deafferentation' subtype of central neuropathic pain in MS. We were unable to support the role of central sensitization or endogenous facilitatory and inhibitory mechanisms in the development of CNEP in MS.

SIGNIFICANCE

This article presents higher prevalence of the 'sensory loss' prototypic sensory phenotype in multiple sclerosis patients with central extremity neuropathic pain compared to pain-free patients. Higher degree of disability underlines the possible role of higher lesion load in the somatosensory pathways in this particular 'deafferentation' type of central neuropathic pain.

Repetitive percutaneous radiofrequency thermocoagulation for persistent idiopathic facial pain and central neuropathic pain attributed to multiple sclerosis-a retrospective monocentric analysis

BACKGROUND

Persistent idiopathic facial pain (PIFP) is a debilitating chronic pain condition with pain radiating to trigeminal dermatomes. Typically, there are no pathological findings that can be identified during workup and therapy is symptomatic. Facial pain is common in patients with multiple sclerosis (central neuropathic pain attributed to MS). Our aim was to evaluate the effectiveness of percutaneous radiofrequency thermocoagulation (PRTC) of the gasserian ganglion and the duration of pain relief, as well as the identification of factors associated with its outcome.

METHODS

Data on all the above-mentioned patients that have been treated with PRTC between 2009 and 2019 were included into the study. The outcome was assessed with a six-tiered score from 1 (complete remission) to 6 (no benefit). Univariate and multivariate analyses were performed in order to obtain factors associated with the outcome.

RESULTS

A total of 52 patients were included. The total number of procedures performed was 114. 61.5% of patients who experienced temporary pain relief that lasted for a median of 60 days (range 3-1490 days). In patients with recurrence, the fraction of successful interventions was higher, and also transient, with successful pain amelioration in over 80% of patients. Successful responses to PRTC were observed in 27.9% after 1 year, 19.4% after 2 years, and 8.3% after 3 years. The only independent variable predicting pain relief was a repeat intervention with a history of ≥ 2 interventions (OR: 4.36, 95%-CI: 1.34-14.34, p = 0.015). No severe complications occurred.

CONCLUSIONS

Our data showed good and immediate pain relief after PRTC in the majority of our patients. PRTC is a low-risk procedure that can be discussed as an option in case of failure of medical treatment even in critically ill patients and can be repeated with good results when necessary. Long-term pain amelioration, even with repeated procedures, was not possible and no patient was permanently cured.

Effects of alkaloids on peripheral neuropathic pain: a review

Neuropathic pain is a debilitating pathological pain condition with a great therapeutic challenge in clinical practice. Currently used analgesics produce deleterious side effects. Therefore, it is necessary to investigate alternative medicines for neuropathic pain. Chinese herbal medicines have been widely used in treating intractable pain. Compelling evidence revealed that the bioactive alkaloids of Chinese herbal medicines stand out in developing novel drugs for neuropathic pain due to multiple targets and satisfactory efficacy. In this review, we summarize the recent progress in the research of analgesic effects of 20 alkaloids components for peripheral neuropathic pain and highlight the potential underlying molecular mechanisms. We also point out the opportunities and challenges of the current studies and shed light on further in-depth pharmacological and toxicological studies of these bioactive alkaloids. In conclusion, the alkaloids hold broad prospects and have the potentials to be novel drugs for treating neuropathic pain. This review provides a theoretical basis for further applying some alkaloids in clinical trials and developing new drugs of neuropathic pain.

Central pain syndromes

The management of pain in persons with neurological injuries is challenging and complex. A holistic view and clinical approach are necessary when addressing pain in patients with neurological impairment because interpreting signs and symptoms and deciphering sources of pain is never a straightforward process. This problem is further magnified with the management of central pain syndromes. The best approach is to have a good understanding of the clinical characteristics commonly found in this patient population, in particular for patients with stroke, multiple sclerosis (MS), or spinal cord injury (SCI), as central pain manifests differently between these groups. This paper will focus on the history, clinical presentation, pathophysiology, assessment, and treatment of central pain in patients with these types of neurological conditions. In addition to being at risk for a decline in quality of life, patients with pain syndromes are also prone to adverse responses to treatments (e.g., opioid addiction). It is therefore important to methodically analyze the similarities and differences between patients with different pain syndromes.

Clinical perspective on pain in multiple sclerosis

Pain is an important and frequent symptom in multiple sclerosis (MS), which leads to a low quality of life, increased disability level, and lack of employment and mental health. Recently, studies have shown increased interest in pain in MS and there is a growing evidence of its prevalence. However, the literature suffers from lack of experimental studies focusing on pain reduction. This topical review summarizes the current knowledge about pain in MS with its definitions, assessments, treatments and rehabilitation within a holistic perspective.

Cathepsin E in neutrophils contributes to the generation of neuropathic pain in experimental autoimmune encephalomyelitis

Pain is a frequent and disabling symptom in patients with multiple sclerosis (MS); however, the underlying mechanisms of MS-related pain are not fully understood. Here, we demonstrated that cathepsin E (CatE) in neutrophils contributes to the generation of mechanical allodynia in experimental autoimmune encephalomyelitis, an animal model of MS. We showed that CatE-deficient (CatE) mice were highly resistant to myelin oligodendrocyte glycoprotein (MOG35-55)-induced mechanical allodynia. After MOG35-55 immunization, neutrophils immediately accumulated in the dorsal root ganglion (DRG). Adoptive transfer of MOG35-55-stimulated wild-type neutrophils into the dorsal root ganglion induced mechanical allodynia in the recipient C57BL/6 mice. However, the pain threshold did not change when MOG35-55-stimulated CatE neutrophils were transferred into the recipient C57BL/6 mice. MOG35-55 stimulation caused CatE-dependent secretion of elastase in neutrophils. Behavioral analyses revealed that sivelestat, a selective neutrophil elastase inhibitor, suppressed mechanical allodynia induced by adoptively transferred MOG35-55-stimulated neutrophils. MOG35-55 directly bound to toll-like receptor 4, which led to increased production of CatE in neutrophils. Our findings suggest that inhibition of CatE-dependent elastase production in neutrophil might be a potential therapeutic target for pain in patients with MS.

The Prevalence of Trigeminal Neuralgia in Turkey: A Population-Based Study

OBJECTIVE

Population-based studies on the prevalence of trigeminal neuralgia (TN) worldwide are rare and the epidemiology of TN in Turkey is unknown. The aim of this study is to determine the prevalence of TN in Turkey.

METHODS

We conducted a cross-sectional, population-based, descriptive epidemiological study in Ereğli, Turkey. Participants over the age of 18 were screened using a self-assessment form, and potential patients were identified by a 'neuroscreening team'. Suspected patients were invited for a clinical examination and evaluated by a senior neurologist. Any required imaging was carried out at a university hospital.

RESULTS

Data were collected from a total of 9605 participants, after the exclusion of 247 individuals who refused to participate. Seven suspected patients were invited to a public health center for clinical evaluation. One patient was diagnosed with SUNCT (Short-lasting, Unilateral, Neuralgiform headache attacks with Conjunctival injection and Tearing) and one patient was diagnosed with post-herpetic neuralgia. A definite diagnosis of TN was confirmed in five participants. The crude prevalence was found to be 52.1/100.000. The mean age of cases was 62.2 ± 8.3 years and the female/male ratio was 4/1. TN was classified as 'symptomatic' in one patient with multiple sclerosis. The other four cases were diagnosed with classical TN. Right side involvement was identified in three cases (60%), whereas left side involvement was seen in two cases (40%).

DISCUSSION

This study establishes the prevalence of TN in Turkey for the first time. The prevalence rate is low when compared with other international studies.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Microglia-Mediated Regulation of Neuropathic Pain: Molecular and Cellular Mechanisms

Pain is a defense system that responds rapidly to harmful internal and external stimuli through the somatosensory neuronal pathway. However, damage to the nervous system through cancer, diabetes, infection, autoimmune disease, chemotherapy or trauma often leads to neuropathic pain, a debilitating chronic pain condition. Neuropathic pain is not simply a temporal continuum of acute nociceptive signals from the periphery, but rather due to pathologically altered functions in the nervous system, which shift the net neuronal excitatory balance toward excitation. Although alterations were long thought to be a result of changes in neurons, but an increasing body of evidence over the past decades indicates the necessity and sufficiency of microglia, the tissue-resident macrophages of the spinal cord and brain, for nerve injury-induced malfunction of the nervous system. In this review article, I describe our current understanding of the molecular and cellular mechanisms underlying the role of microglia in the pathogenesis of neuropathic pain and discuss the therapeutic potential of microglia from recent advances in the development of new drugs targeting microglia.

Microvascular decompression in patients with trigeminal neuralgia and multiple sclerosis: results and analysis of possible prognostic factors

We evaluated the results of microvascular decompression (MVD) in patients with trigeminal neuralgia (TN) and multiple sclerosis (MS) and we studied the role of several clinical and surgical factors as possible prognosticators of good outcome. To do this we performed, to our knowledge, the first literature review with a pooled analysis of data. A PubMed search of literature was conducted using the following terms: "microvascular decompression", "trigeminal neuralgia" and "multiple sclerosis". We screened 64 articles. Of them, 7 studies were eligible for this review. As outcome indicators we used the acute pain relief (APR) and the recurrence of pain. An APR was obtained in 71.42% and a recurrence of pain was reported in 26.00% of cases, respectively. At univariate analysis, younger age at surgery (p = 0.0419) and performing MVD as the first treatment (p = 0.0384) were associated to a higher probability of APR. The evidence of an MRI brainstem lesion related to the TN (p = 0.0482) was associated to a lower probability to obtain an APR after MVD. None of the evaluated factors affect the probability of recurrence of pain. At multivariate analysis the evidence of a brainstem MRI lesion related to the TN emerged as a negative prognosticator of APR (p = 0.0169). Our literature pooled analysis showed that MVD is effective in treating patients with MS-related TN. The evidence on MRI of a demyelinating plaque related to the TN is associated with a worse response to MVD. These data could suggest that MVD would be indicated mainly in patients without brainstem MRI lesions.

Facial Pain: A Comprehensive Review and Proposal for a Pragmatic Diagnostic Approach

BACKGROUND

Facial pain, alone or combined with other symptoms, is a frequent complaint. Moreover, it is a symptom situated at, more than any other pain condition, a crosspoint where several disciplines meet, for example, dentists; manual therapists; ophthalmologists; psychologists; and ear-nose-throat, pain, and internal medicine physicians besides neurologists and neurosurgeons. Recently, a new version of the most widely used classification system among neurologists for headache and facial pain, the International Classification of Headache Disorders, has been published.

OBJECTIVE

The aims of this study were to provide an overview of the most prevalent etiologies of facial pain and to provide a generic framework for the neurologist on how to manage patients presenting with facial pain.

METHODS

An overview of the different etiologies of facial pain is provided from the viewpoint of the respective clinical specialties that are confronted with facial pain. Key message: Caregivers should "think outside their own box" and refer to other disciplines when indicated. If not, a correct diagnosis can be delayed and unnecessary treatments might be given. The presented framework is aimed at excluding life- or organ-threatening diseases, providing several clinical clues and indications for technical investigations, and ultimately leading to the correct diagnosis and/or referral to other disciplines.

Nociception in a Progressive Multiple Sclerosis Model in Mice Is Dependent on Spinal TRPA1 Channel Activation

Central neuropathic pain is a common untreated symptom in progressive multiple sclerosis (PMS) and is associated with poor quality of life and interference with patients' daily activities. The neuroinflammation process and mitochondrial dysfunction in the PMS lesions generate reactive species. The transient potential receptor ankyrin 1 (TRPA1) has been identified as one of the major mechanisms that contribute to neuropathic pain signaling and can be activated by reactive compounds. Thus, the goal of our study was to evaluate the role of spinal TRPA1 in the central neuropathic pain observed in a PMS model in mice. We used C57BL/6 female mice (20-30 g), and the PMS model was induced by the experimental autoimmune encephalomyelitis (EAE) using mouse myelin oligodendrocyte glycoprotein (MOG_35-55) antigen and CFA (complete Freund's adjuvant). Mice developed progressive clinical score, with motor impairment observed after 15 days of induction. This model induced mechanical and cold allodynia and heat hyperalgesia which were measured up to 14 days after induction. The hypersensitivity observed was reduced by the administration of selective TRPA1 antagonists (HC-030031 and A-967079, via intrathecal and intragastric), antioxidants (α-lipoic acid and apocynin, via intrathecal and intragastric), and TRPA1 antisense oligonucleotide (via intrathecal). We also observed an increase in TRPA1 mRNA levels, NADPH oxidase activity, and 4-hydroxinonenal (a TRPA1 agonist) levels in spinal cord samples of PMS-EAE induced animals. In conclusion, these results support the hypothesis of the TRPA1 receptor involvement in nociception observed in a PMS-EAE model in mice.

Central Neuropathic Pain and Profiles of Quantitative Electroencephalography in Multiple Sclerosis Patients

Pain has a significant impact on the quality of life of patients with multiple sclerosis (MS). However, the neurophysiological mechanisms of central neuropathic pain in a MS course are not known. We hypothesized that changes in power spectral density (PSD) that take place in the electroencephalography (EEG) of MS patients with and without the central neuropathic pain (CNP) would differ. The study aimed to assess the features of quantitative EEG using the PSD indicator along with peak frequencies in the standard frequency bands in MS patients with and without CNP. We have analyzed the quantitative spectral content of the EEG at a resting state in 12 MS patients with CNP, 12 MS patients without CNP, and 12 gender- and age-matched healthy controls using fast Fourier transformation. Based on the ANOVA, at the group level, the theta band absolute and relative PSD showed an increase, whereas alpha band relative PSD showed a decrease in MS patients both with and without CNP. However, only in MS with CNP group, the absolute and relative PSD in the beta1 and beta2 bands increased and exceeded that in patients without pain. Only MS patients with CNP demonstrated the significantly increased absolute PSD for the theta, beta1, and beta2 frequency bands in most regions of interest. In the theta band, MS patients with CNP displayed the increase in absolute spectral power for the mid-temporal derivation of the right hemisphere and the increase in relative spectral power for the prefrontal derivation of this hemisphere. In the beta1 band, the increase in absolute spectral power was observed for the three temporal derivations of the right hemisphere, whereas in the beta2 band, for the occipital, parietal, and temporal lobes of both hemispheres. In the alpha band, only a relative spectral power decrease was revealed for the occipital lobes of both hemispheres and parietal lobe of the right hemisphere. In MS patients with CNP, the frequencies of the dominant spectral power (peak frequencies) in the high-frequency beta band were higher than in the healthy control in posterior areas of the left hemisphere. Data could represent central nervous system alterations related to central neuropathic pain in MS patients that lead to the disturbances in cortical communication.

The role of glial-neuronal metabolic cooperation in modulating progression of multiple sclerosis and neuropathic pain

While the etiology of multiple sclerosis (MS) remains unclear, research from the clinic and preclinical models identified the essential role of inflammation and demyelination in the pathogenesis of MS. Current treatments focused on anti-inflammatory processes are effective against acute episodes and relapsing-remitting MS, but patients still move on to develop secondary progressive MS. MS progression is associated with activation of microglia and astrocytes, and importantly, metabolic dysfunction leading to neuronal death. Neuronal death also contributes to chronic neuropathic pain. Metabolic support of neurons by glia may play central roles in preventing progression of MS and chronic neuropathic pain. Here, we review mechanisms of metabolic cooperation between glia and neurons and outline future perspectives exploring metabolic support of neurons by glia.

A TLR-CXCL1 pathway in DRG neurons induces neutrophil accumulation in the DRG and mechanical allodynia in EAE mice

Multiple sclerosis (MS) is a potentially disabling disease of the central nervous system. Approximately half of the patients with MS experience severe pain; however, currently available therapeutics provide only insufficient relief. The mechanisms underlying the generation of neuropathic pain in patients with MS are not fully understood. Recently, we found that neutrophil elastase from accumulated neutrophils in the dorsal root ganglion (DRG) sensitizes DRG neurons and induces mechanical allodynia in a mouse model of experimental autoimmune encephalomyelitis (EAE). However, the mechanism underlying neutrophil accumulation in the DRG after myelin oligodendrocyte glycoprotein (MOG_35–55, immunogenic peptide) immunization remains unclear. Here, we found that C-X-C motif ligand 1 (CXCL1) was upregulated in DRG neurons after MOG_35–55 immunization. Increased expression of CXCL1 protein was also observed in primary cultured DRG neurons treated with MOG_35–55, which was mediated through toll-like receptor 4 (TLR4). Gene silencing of TLR4 or CXCL1 in DRG neurons significantly attenuated neutrophil accumulation in the DRG and mechanical allodynia during the preclinical phase of EAE (around day 5 after immunization). Our results thus suggest that a TLR4–CXCL1 pathway in DRG neurons triggers neutrophil recruitment in the DRG and subsequent mechanical allodynia in response to MOG_35–55.

EEG Correlates of Self-Managed Neurofeedback Treatment of Central Neuropathic Pain in Chronic Spinal Cord Injury

BACKGROUND

Neurofeedback (NFB) is a neuromodulatory technique that enables voluntary modulation of brain activity in order to treat neurological condition, such as central neuropathic pain (CNP). A distinctive feature of this technique is that it actively involves participants in the therapy. In this feasibility study, we present results of participant self-managed NFB treatment of CNP.

METHODS

Fifteen chronic spinal cord injured (SCI) participants (13M, 2F), with chronic CNP equal or greater than 4 on the Visual Numeric Scale, took part in the study. After initial training in hospital (up to 4 sessions), they practiced NF at home, on average 2-3 times a week, over a period of several weeks (min 4, max 20). The NFB protocol consisted of upregulating the alpha (9-12 Hz) and downregulating the theta (4-8 Hz) and the higher beta band (20-30 Hz) power from electrode location C4, for 30 min. The output measures were pain before and after NFB, EEG before and during NFB and pain questionnaires. We analyzed EEG results and show NFB strategies based on the Power Spectrum Density of each single participant.

RESULTS

Twelve participants achieved statistically significant reduction in pain and in eight participants this reduction was clinically significant (larger than 30%). The most successfully regulated frequency band during NFB was alpha. However, most participants upregulated their individual alpha band, that had an average dominant frequency at αp = 7.6 ± 0.8 Hz (median 8 Hz) that is lower than the average of the general population, which is around 10 Hz. Ten out of fifteen participants significantly upregulated their individual alpha power (αp ± 2 Hz) as compared to 4 participants who upregulated the power in the fixed alpha band (8-12 Hz). Eight out of the twelve participants who achieved a significant reduction of pain, significantly upregulated their individual alpha band power. There was a significantly larger increase in alpha power (p < 0.0001) and decrease of theta power (p < 0.04) in participant specific rather than in fixed frequency bands.

CONCLUSION

Neurofeedback is a neuromodulatory technique that gives participants control over their pain and can be self-administered at home. Regulation of individual frequency band was related to a significant reduction in pain.

Chronic Central Pain Among Community-Dwelling Survivors of Moderate-to-Severe Traumatic Brain Injury: A Quantitative Sensory Testing Study

Background:

Central pain associated with changes in sensory thresholds is one of the most enduring consequences of major trauma. Yet it remains sparsely studied among community-dwelling survivors of moderate-to-severe traumatic brain injury (TBI).

Purpose:

To describe and compare thermal and mechanical sensory thresholds in home-based patients with and without central pain after moderate-to-severe TBI with a cohort of healthy controls.

Design:

Cross-sectional.

Method:

Thresholds for cold/heat detection, thermal pain, touch, and distorted sensation were gathered using quantitative sensory testing (QST). QST was performed on the painful and contralateral pain-free body regions in TBI participants with pain (TBI-P) and on both forearms in TBI participants without pain (TBI-NP) and healthy controls (HC). Central pain was characterized using the Brief Pain Inventory–Short Form.

Results:

We tested 16 TBI-P patients, 17 TBI-NP patients, and 16 HC. Mean time since injury for TBI patients was 24 ± 15 months. TBI-P and TBI-NP patients showed significant loss in innocuous mechanical sensitivity compared to HC ( F = 18.929; Bonferroni-adjusted p ≤ .001). Right–left differences in cold pain sensations were significantly larger in TBI-P than in TBI-NP and HC participants ( F = 14.352; Bonferroni-adjusted p ≤ .001). Elevated heat sensitivity thresholds were also observed in TBI-P participants but remained within normal range.

Conclusion:

Damage to cutaneous mechanoreceptors is a necessary, but not sufficient, condition for the development of chronic central pain following TBI. Damage or incomplete recovery of cutaneous thermoreceptors may be a contributing factor to chronic pain after TBI.

Sex differences in central nervous system plasticity and pain in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a neurodegenerative autoimmune disease with many known structural and functional changes in the central nervous system. A well-recognized, but poorly understood, complication of MS is chronic pain. Little is known regarding the influence of sex on the development and maintenance of MS-related pain. This is important to consider, as MS is a predominantly female disease. Using the experimental autoimmune encephalomyelitis (EAE) mouse model of MS, we demonstrate sex differences in measures of spinal cord inflammation and plasticity that accompany tactile hypersensitivity. Although we observed substantial inflammatory activity in both sexes, only male EAE mice exhibit robust staining of axonal injury markers and increased dendritic arborisation in morphology of deep dorsal horn neurons. We propose that tactile hypersensitivity in female EAE mice may be more immune-driven, whereas pain in male mice with EAE may rely more heavily on neurodegenerative and plasticity-related mechanisms. Morphological and inflammatory differences in the spinal cord associated with pain early in EAE progression supports the idea of differentially regulated pain pathways between the sexes. Results from this study may indicate future sex-specific targets that are worth investigating for their functional role in pain circuitry.

Anti-IL-6 Receptor Antibody Inhibits Spontaneous Pain at the Pre-onset of Experimental Autoimmune Encephalomyelitis in Mice

Chronic pain is a significant symptom in patients with autoimmune encephalomyelitis, such as multiple sclerosis and neuromyelitis optica. The most commonly used animal model of these diseases is experimental autoimmune encephalomyelitis (EAE). We previously reported that evoked pain, such as mechanical allodynia, was improved by an anti-IL-6 receptor antibody in EAE mice. However, few reports have evaluated spontaneous pain in EAE mice. Here, we assessed spontaneous pain in EAE mice by utilizing the Mouse Grimace Scale (MGS, a standardized murine facial expression-based coding system) and evaluated the influence of an anti-IL-6 receptor antibody (MR16-1). EAE was induced in female C57BL/6J mice by subcutaneous immunization with myelin oligodendrocyte glycoprotein 35–55 emulsified in adjuvant and administration of pertussis toxin. Mice were placed individually in cubicles and filmed for about 10 min. Ten clear head shots per mouse from the video recording were given a score of 0, 1, or 2 for each of three facial action units: orbital tightening, nose bulge, and ear position. Clinical symptoms of EAE were also scored. Measurement of 5-HT in the spinal cord and functional imaging of the periaqueductal gray (PAG) were also performed. Compared with control mice, MGS score was significantly higher in EAE mice. MR16-1 prevented this increase, especially in pre-onset EAE mice. Promotion of spinal 5-HT turnover and reduction of PAG activity were observed in pre-onset EAE mice. These results suggest that MR16-1 prevented spontaneous pain developed before EAE onset.