Recovery from Traumatic Brain Injury Is Nociceptin/Orphanin FQ Peptide Receptor Genotype-, Sex-, and Injury Severity-Dependent

Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, and survivors often experience mental and physical health consequences that reduce quality of life. We previously reported that blockade of the nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor reduced tissue damage markers produced by blast TBI. The goal of this study was to determine the extent to which N/OFQ and NOP receptor levels change following mild (mTBI) and moderate TBI (modTBI) and whether the absence of the NOP receptor attenuates TBI-induced sequelae. Male and female NOP receptor knockout (KO) or wild-type (WT) rats received craniotomy-only (sham) or craniotomy plus mTBI, or modTBI impact to the left cerebral hemisphere. Neurologic and vestibulomotor deficits and nociceptive hyperalgesia and allodynia found in WT male and female rats following mTBI and modTBI were greatly reduced or absent in NOP receptor KO rats. NOP receptor levels increased in brain tissue from injured males but remained unchanged in females. Neurofilament light chain (NF-L) and glial fibrillary acidic protein (GFAP) expression were reduced in NOP receptor KO rats compared with WT following TBI. Levels of N/OFQ in injured brain tissue correlated with neurobehavioral outcomes and GFAP in WT males, but not with KO male or WT and KO female rats. This study reveals a significant contribution of the N/OFQ-NOP receptor system to TBI-induced deficits and suggests that the NOP receptor should be regarded as a potential therapeutic target for TBI. SIGNIFICANCE STATEMENT: This study revealed that nociceptin/orphanin FQ peptide (NOP) receptor knockout animals experienced fewer traumatic brain injury (TBI)-induced deficits than their wild-type counterparts in a sex- and injury severity-dependent manner, suggesting that NOP receptor antagonists may be a potential therapy for TBI.

Mild Traumatic Brain Injury-Induced Augmented Postsurgical Pain Is Driven by Central Serotonergic Pain-Facilitatory Signaling

BACKGROUND

Individuals recovering from mild traumatic brain injury (mTBI) have increased rates of acute and chronic pain. However, the mechanism through which mTBI triggers heightened pain responses and the link between mTBI and postsurgical pain remain elusive. Recent data suggest that dysregulated serotonergic pain-modulating circuits could be involved. We hypothesized that mTBI triggers dysfunction in descending serotonergic pain modulation, which exacerbates acute pain and delays pain-related recovery after surgery.

METHODS

Using mouse models of mTBI and hindpaw incision for postsurgical pain in C57BL/6J mice, mechanical withdrawal thresholds were assessed throughout the postsurgical period. To determine whether mTBI leads to persistent alteration of endogenous opioid tone, mu-opioid receptors (MORs) were blocked with naloxone. Finally, the role of descending serotonergic signaling on postsurgical allodynia in animals with mTBI was examined using ondansetron (5-HT 3 receptor antagonist) or a serotonin-specific neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), to ablate descending serotonergic fibers. The treatment effects on withdrawal thresholds were normalized to baseline (percentage of maximum possible effect, MPE%), and analyzed using paired t -test or 2-way repeated-measures ANOVA with post hoc multiple comparisons.

RESULTS

Post-mTBI mice demonstrated transient allodynia in hindpaws contralateral to mTBI, while no nociceptive changes were observed in sham-mTBI animals (mean difference, MD, MPE%, post-mTBI day 3: -60.9; 95% CI, -88.7 to -35.0; P < .001). After hindpaw incision, animals without mTBI exhibited transient allodynia, while mice with prior mTBI demonstrated prolonged postsurgical allodynia (MD-MPE% postsurgical day 14: -65.0; 95% CI, -125.4 to -4.5; P = .04). Blockade of MORs using naloxone transiently reinstated allodynia in mTBI animals but not in sham-mTBI mice (MD-MPE% post-naloxone: -69.9; 95% CI, -94.8 to -45.1; P < .001). Intrathecal administration of ondansetron reversed the allodynia observed post-mTBI and postincision in mTBI mice (compared to vehicle-treated mTBI mice, MD-MPE% post-mTBI day 3: 82.7; 95% CI, 58.5-106.9; P < .001; postsurgical day 17: 62.5; 95% CI, 38.3-86.7; P < .001). Both the acute allodynia after TBI and the period of prolonged allodynia after incision in mTBI mice were blocked by pretreatment with 5,7-DHT (compared to sham-mTBI mice, MD-MPE% post-mTBI day 3: 0.5; 95% CI, -18.5 to 19.5; P = .99; postsurgical day 14: -14.6; 95% CI, -16.7 to 45.9; P = .48). Similar behavioral patterns were observed in hindpaw ipsilateral to mTBI.

CONCLUSIONS

Collectively, our results show that descending serotoninergic pain-facilitating signaling is responsible for nociceptive sensitization after mTBI and that central endogenous opioid tone opposes serotonin's effects. Understanding brain injury-related changes in endogenous pain modulation may lead to improved pain control for those with TBI undergoing surgery.

CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

An Umbrella Review of Self-Management Interventions for Health Conditions With Symptom Overlap With Traumatic Brain Injury

OBJECTIVE

To synthesize evidence for the effectiveness of self-management interventions for chronic health conditions that have symptom overlap with traumatic brain injury (TBI) in order to extract recommendations for self-management intervention in persons with TBI.

DESIGN

An umbrella review of existing systematic reviews and/or meta-analyses of randomized controlled trials or nonrandomized studies targeting self-management of chronic conditions and specific outcomes relevant to persons with TBI.

METHOD

A comprehensive literature search of 5 databases was conducted using PRISMA guidelines. Two independent reviewers conducted screening and data extraction using the Covidence web-based review platform. Quality assessment was conducted using criteria adapted from the Assessing the Methodological Quality of Systematic Reviews-2 (AMSTAR-2).

RESULTS

A total of 26 reviews met the inclusion criteria, covering a range of chronic conditions and a range of outcomes. Seven reviews were of moderate or high quality and focused on self-management in persons with stroke, chronic pain, and psychiatric disorders with psychotic features. Self-management interventions were found to have positive effects on quality of life, self-efficacy, hope, reduction of disability, pain, relapse and rehospitalization rates, psychiatric symptoms, and occupational and social functioning.

CONCLUSIONS

Findings are encouraging with regard to the effectiveness of self-management interventions in patients with symptoms similar to those of TBI. However, reviews did not address adaptation of self-management interventions for those with cognitive deficits or for populations with greater vulnerabilities, such as low education and older adults. Adaptations for TBI and its intersection with these special groups may be needed.

Associations of Chronic Pain With Psychosocial Outcomes After Traumatic Brain Injury: A NIDILRR and VA TBI Model Systems Collaborative Project

OBJECTIVE

To examine the differences in participation, life satisfaction, and psychosocial outcomes among individuals with traumatic brain injury (TBI) endorsing current, past, or no chronic pain.

SETTING

Community.

PARTICIPANTS

Three thousand eight hundred four TBI Model Systems participants 1 to 30 years of age postinjury classified into 1 of 3 groups based on their pain experience: current pain, past pain, no pain completed a Pain Survey at their usual follow-up appointment which on average was approximately 8 years postinjury.

DESIGN

Multisite, cross-sectional observational cohort study.

MAIN OUTCOME MEASURES

Sociodemographic and injury characteristics and psychosocial outcomes (ie, satisfaction with life, depression, anxiety, posttraumatic stress disorder [PTSD], sleep quality, community participation).

RESULTS

Persons with current chronic pain demonstrated higher scores on measures of PTSD, anxiety, and depression, and the lower scores on measures of sleep quality, community participation and satisfaction with life. Those with resolved past pain had mean scores for these outcomes that were all between the current and no chronic pain groups, but always closest to the no pain group. After adjusting for sociodemographic and function in multivariate analysis, having current chronic pain was associated with more negative psychosocial outcomes. The largest effect sizes (ES; in absolute value) were observed for the PTSD, depression, anxiety, and sleep quality measures (ES = 0.52-0.81) when comparing current pain to past or no pain, smaller ES were observed for life satisfaction (ES = 0.22-0.37) and out and about participation (ES = 0.16-0.18). When comparing past and no pain groups, adjusted ES were generally small for life satisfaction, PTSD, depression, anxiety, and sleep quality (ES = 0.10-0.23) and minimal for participation outcomes (ES = 0.02-0.06).

CONCLUSIONS

Chronic pain is prevalent among individuals with TBI and is associated with poorer psychosocial outcomes, especially for PTSD, depression, anxiety, and sleep disturbance. The results from this study highlight the presence of modifiable comorbidities among those with chronic pain and TBI. Persons who experience persistent pain following TBI may be at greater risk for worse psychosocial outcomes.

Emergence of taurine as a therapeutic agent for neurological disorders

Taurine is a sulfur-containing, semi-essential amino acid that occurs naturally in the body. It alternates between inflammation and oxidative stress-mediated injury in various disease models. As part of its limiting functions, taurine also modulates endoplasmic reticulum stress, Ca2+ homeostasis, and neuronal activity at the molecular level. Taurine effectively protects against a number of neurological disorders, including stroke, epilepsy, cerebral ischemia, memory dysfunction, and spinal cord injury. Although various therapies are available, effective management of these disorders remains a global challenge. Approximately 30 million people are affected worldwide. The design of taurine formation could lead to potential drugs/supplements for the health maintenance and treatment of central nervous system disorders. The general neuroprotective effects of taurine and the various possible underlying mechanisms are discussed in this review. This article is a good resource for understanding the general effects of taurine on various diseases. Given the strong evidence for the neuropharmacological efficacy of taurine in various experimental paradigms, it is concluded that this molecule should be considered and further investigated as a potential candidate for neurotherapeutics, with emphasis on mechanism and clinical studies to determine efficacy.

Characterization and Treatment of Chronic Pain After Traumatic Brain Injury-Comparison of Characteristics Between Individuals With Current Pain, Past Pain, and No Pain: A NIDILRR and VA TBI Model Systems Collaborative Project

OBJECTIVE

To estimate the prevalence of chronic pain after traumatic brain injury (TBI) and identify characteristics that differ from those without chronic pain.

SETTING

Community.

PARTICIPANTS

A total of 3804 TBI Model Systems (TBIMS) participants who completed the Pain Survey at TBIMS follow-up.

DESIGN

A multisite, cross-sectional observational cohort study.

MAIN OUTCOME MEASURES

Functional outcomes, pain experience, and treatment.

RESULTS

46% reported current chronic pain, 14% reported past (post-injury) chronic pain, and 40% reported no chronic pain. Bivariate differences in sociodemographic and injury characteristics between the 3 pain groups were generally small in effect size, reflecting little clinical difference. However, medium effect sizes were seen for all functional outcomes, such that individuals with current chronic pain had worse functional outcomes compared with individuals in the past pain or no pain groups. Treatment utilization rates were higher for individuals with current chronic pain compared with past pain, with medical treatments being most frequently utilized. Individuals with past pain perceived more improvement with treatment than did those with current chronic pain as represented by a large effect size.

CONCLUSIONS

Chronic pain affects approximately 60% of those living with TBI. The implications of chronic pain for functional outcomes support inclusion of pain metrics in prognostic models and observational studies in this population. Future research is needed to proactively identify those at risk for the development of chronic pain and determine the efficacy and access to pain treatment.

Association between the Number of Days/Week of Different Levels of Physical Activity and Chronic Pain in People of Different Races: A Mendelian Randomization Study

OBJECTIVE

Regular physical activity is beneficial for health, but the effect of the number of days/week of physical activity on chronic pain (CP) remains unclear, so we used a two-sample Mendelian randomization (MR) analysis to explore the relationship between the number of days/weeks of different levels of physical activity and chronic pain in people of different races.

METHODS

We obtained summary data from genome-wide association studies (GWASs) on the number of days/week of physical activity and multisite chronic pain in European, South Asian, East Asian, Middle Eastern, and African American populations. The single-nucleotide polymorphisms (SNPs) of the exposed data were visualized with a Manhattan plot via the R program. MR analysis was performed by the MR-Base platform.

RESULTS

The results indicated that a higher number of days/week with ≥10 min of walking protects against CP in African American and Afro-Caribbean populations (inverse-variance weighting, IVW p < 0.05) but has little effect on people of different races (IVW p > 0.05). A higher number of days/week with ≥10 min of moderate physical activity increased the risk of CP in European and South Asia (IVW p < 0.05) but had little effect on people of different races (IVW p > 0.05). The number of days/week of ≥10 min of vigorous physical activity increased the risk of CP in Europeans (IVW p < 0.05) and protected against CP in African Americans and Afro-Caribbeans (IVW p < 0.05).

CONCLUSIONS

A higher number of days/week of moderate and vigorous physical activity increased the risk of CP in Europeans; however, a higher number of days/week of walking and vigorous physical activity may protect against CP in African American and Afro-Caribbean individuals.

Mechanisms and treatments of chronic pain after traumatic brain injury

While pain after trauma generally resolves, some trauma patients experience pain for months to years after injury. An example, relevant to both combat and civilian settings, is chronic pain after traumatic brain injury (TBI). Headache as well as pain in the back and extremities are common locations for TBI-related chronic pain to be experienced. TBI-related pain can exist alone or can exacerbate pain from other injuries long after healing has occurred. Consequences of chronic pain in these settings include increased suffering, higher levels of disability, serious emotional problems, and worsened cognitive deficits. The current review will examine recent evidence regarding dysfunction of endogenous pain modulatory mechanisms, neuroplastic changes in the trigeminal circuitry and alterations in spinal nociceptive processing as contributors to TBI-related chronic pain. Key pain modulatory centers including the locus coeruleus, periaqueductal grey matter, and rostroventromedial medulla are vulnerable to TBI. Both the rationales and existing evidence for the use of monoamine reuptake inhibitors, CGRP antagonists, CXCR2 chemokine receptor antagonists, and interventional therapies will be presented. While consensus guidelines for the management of chronic post-traumatic TBI-related pain are lacking, several approaches to this clinically challenging situation deserve focused evaluation and may prove to be viable therapeutic options.

The prevalence of persistent post-traumatic headache in adult civilian traumatic brain injury: a systematic review and meta-analysis on the past 14 years

ABSTRACT

The most recent prevalence estimate of post-traumatic headache (PTH) after traumatic brain injury (TBI) in veterans and civilians dates back to 2008. The prevalence was found to be 57.8%, with surprising higher rates (75.3%) in mild TBI when compared with those with moderate/severe TBI (32.1%). However, the revision of mild TBI diagnostic criteria and an historic peak of TBI in the elderly individuals attributed to the ageing population may lead to different results. Thus, we conducted a systematic review and meta-analysis to assess the updated prevalence of PTH during the past 14 years only in civilians. A literature search was conducted following PRISMA guidelines guided by a librarian. Screening, full-text assessment, data extraction, and risk of bias assessment were performed blindly by 2 raters. Meta-analysis of proportions using the Freeman and Tukey double arcsine method of transformation was conducted. Heterogeneity, sensitivity analysis, and meta-regressions were performed with the predictors: year of publication, mean age, sex, TBI severity, and study design. Sixteen studies were selected for the qualitative analysis and 10 for the meta-analysis. The overall prevalence estimate of PTH was 47.1%, (confidence interval = 34.6, 59.8, prediction intervals = 10.8, 85.4), being similar at different time points (3, 6, 12, and 36+ months). Heterogeneity was high, and none of the meta-regressions were significant. The overall prevalence of PTH after TBI over the past 14 years remains high even if assessed only in civilians. However, the prevalence rates attributed to mild and moderate/severe TBI were similar, differing significantly from previous reports. Efforts are needed to improve TBI outcomes.

Neuropsychological Function in Traumatic Brain Injury and the Influence of Chronic Pain

Cognitive dysfunction, pain, and psychological morbidity all present unique challenges to those living with traumatic brain injury (TBI). In this study we examined (a) the impact of pain across domains of attention, memory, and executive function, and (b) the relationships between pain and depression, anxiety, and post-traumatic stress disorder (PTSD) in persons with chronic TBI. Our sample included 86 participants with a TBI and chronic pain (n = 26), patients with TBI and no chronic pain (n = 23), and a pain-free control group without TBI (n = 37). Participants visited the laboratory and completed a comprehensive battery of neuropsychological tests as part of a structured interview. Multivariate analysis of covariance using education as a covariate, failed to detect a significant group difference for neuropsychological composite scores of attention, memory, and executive function (p = .165). A follow-up analysis using multiple one-way analysis of variance (ANOVA) was conducted for individual measures of executive function. Post-hoc testing indicated that those in both TBI groups preformed significantly worse on measures of semantic fluency when compared to controls (p < 0.001, ηρ2 = .16). Additionally, multiple ANOVAs indicated that those with TBI and pain scored significantly worse across all psychological assessments (p < .001). We also found significant associations between measures of pain and most psychological symptoms. A follow-up stepwise linear regression among those in the TBI pain group indicated that post concussive complaints, pain severity, and neuropathic pain symptoms differentially contributed to symptoms of depression, anxiety, and PTSD. These findings suggest deficits in verbal fluency among those living with chronic TBI, with results also reinforcing the multidimensional nature of pain and its psychological significance in this population.

I Feel! Therefore, I Am from Pain to Consciousness in DOC Patients

Pain assessment and management in patients with disorders of consciousness (DOC) is a challenging and important aspect of care, with implications for detecting consciousness and promoting recovery. This narrative review explores the role of pain in consciousness, the challenges of pain assessment, pharmacological treatment in DOC, and the implications of pain assessment when detecting changes in consciousness. The review discusses the Nociception Coma Scale and its revised version, which are behavioral scales used to assess pain in DOC patients, and the challenges and controversies surrounding the appropriate pharmacological treatment of pain in these patients. Moreover, we highlight recent evidence suggesting that an accurate pain assessment may predict changes in the level of consciousness in unresponsive wakefulness syndrome/vegetative state patients, underscoring the importance of ongoing pain management in these patients.

Moving from the clinic to telehealth during the COVID-19 pandemic - a pilot clinical trial comparing in-clinic rehabilitation versus telerehabilitation for persisting symptoms following a mild Traumatic brain injury

PURPOSE

The objective of this study was to compare the effects of an in-clinic cervicovestibular rehabilitation program (education, home exercises, manual techniques, sub-symptom threshold aerobic exercise [STAE] program) to a similar program (education, home-exercises, STAE program), but without manual techniques, provided in a telerehabilitation format in adults with persisting post-concussion symptoms (PCS).

MATERIALS AND METHODS DESIGN

In this parallel-group non-randomized clinical trial, 41 adults with persisting PCS were allocated to the in-clinic (n = 30) or telerehabilitation (n = 11) program. The outcome measures, which included the Post-Concussion Symptom Scale (PCSS; primary outcome), Numerical Pain Rating Scale (NPRS) for neck pain and headache and three disability questionnaires, were collected at baseline, weeks 6, 12, and 26. Non-parametric analysis for longitudinal data (NparLD) was used.

RESULTS

For the PCSS, there was a group-by-time interaction (p = 0.05) with significant between-group differences at week 6, 12, and 26 (p < 0.05) for the in-clinic group. There were also group-by-time interactions for NPRS neck pain and headache (p < 0.05) for the in-clinic group.

CONCLUSION

The study suggests that a telehealth format failed to reach the efficiency of an in-clinic rehabilitation program in terms of symptoms reduction and functional improvement. These results must be interpreted with caution given the limited number of participants. ClinicalTrials.gov Identifier: NCT03677661.IMPLICATION FOR REHABILITATIONThe telerehabilitation format for adults with persisting post-concussion symptoms was widely implemented in the COVID-19 pandemic without any evidence of efficacy over the more traditional in-clinic rehabilitation format.The study suggests that a telerehabilitation format failed to reach the efficiency of an in-clinic rehabilitation program in terms of symptoms reduction and functional improvement.Clinicians should try to incorporate some in-clinic appointments when a telerehabilitation format is required such as for patients in underserved area.

The Role of Hydrogen Sulfide in Regulation of Cell Death following Neurotrauma and Related Neurodegenerative and Psychiatric Diseases

Injuries of the central (CNS) and peripheral nervous system (PNS) are a serious problem of the modern healthcare system. The situation is complicated by the lack of clinically effective neuroprotective drugs that can protect damaged neurons and glial cells from death. In addition, people who have undergone neurotrauma often develop mental disorders and neurodegenerative diseases that worsen the quality of life up to severe disability and death. Hydrogen sulfide (H₂S) is a gaseous signaling molecule that performs various cellular functions in normal and pathological conditions. However, the role of H₂S in neurotrauma and mental disorders remains unexplored and sometimes controversial. In this large-scale review study, we examined the various biological effects of H₂S associated with survival and cell death in trauma to the brain, spinal cord, and PNS, and the signaling mechanisms underlying the pathogenesis of mental illnesses, such as cognitive impairment, encephalopathy, depression and anxiety disorders, epilepsy and chronic pain. We also studied the role of H₂S in the pathogenesis of neurodegenerative diseases: Alzheimer's disease (AD) and Parkinson's disease (PD). In addition, we reviewed the current state of the art study of H₂S donors as neuroprotectors and the possibility of their therapeutic uses in medicine. Our study showed that H₂S has great neuroprotective potential. H₂S reduces oxidative stress, lipid peroxidation, and neuroinflammation; inhibits processes associated with apoptosis, autophagy, ferroptosis and pyroptosis; prevents the destruction of the blood-brain barrier; increases the expression of neurotrophic factors; and models the activity of Ca²⁺ channels in neurotrauma. In addition, H₂S activates neuroprotective signaling pathways in psychiatric and neurodegenerative diseases. However, high levels of H₂S can cause cytotoxic effects. Thus, the development of H₂S-associated neuroprotectors seems to be especially relevant. However, so far, all H₂S modulators are at the stage of preclinical trials. Nevertheless, many of them show a high neuroprotective effect in various animal models of neurotrauma and related disorders. Despite the fact that our review is very extensive and detailed, it is well structured right down to the conclusions, which will allow researchers to quickly find the proper information they are interested in.

The effect of thioredoxin-1 in a rat model of traumatic brain injury depending on diurnal variation

INTRODUCTION

Traumatic brain injury (TBI) is a public health concern with limited treatment options because it causes a cascade of side effects that are the leading cause of hospital death. Thioredoxin is an enzyme with neuroprotective properties such as antioxidant, antiapoptotic, immune response modulator, and neurogenic, among others; it has been considered a therapeutic target for treating many disorders.

METHODS

The controlled cortical impact (CCI) model was used to assess the effect of recombinant human thioredoxin 1 (rhTrx1) (1 μg/2 μL, intracortical) on rats subjected to TBI at two different times of the light-dark cycle (01:00 and 13:00 h). We analyzed the food intake, body weight loss, motor coordination, pain perception, and histology in specific hippocampus (CA1, CA2, CA3, and Dental Gyrus) and striatum (caudate-putamen) areas.

RESULTS

Body weight loss, reduced food intake, spontaneous pain, motor impairment, and neuronal damage in specific hippocampus and striatum regions are more evident in rats subjected to TBI in the light phase than in the dark phase of the cycle and in groups that did not receive rhTrx1 or minocycline (as positive control). Three days after TBI, there is a recovery in body weight, food intake, motor impairment, and pain, which is more pronounced in the rats subjected to TBI at the dark phase of the cycle and those that received rhTrx1 or minocycline.

CONCLUSIONS

Knowing the time of day a TBI occurs in connection to the neuroprotective mechanisms of the immune response in diurnal variation and the usage of the Trx1 protein might have a beneficial therapeutic impact in promoting quick recovery after a TBI.

The Effect of Craniofacial Manual Lymphatic Drainage after Moderate Traumatic Brain Injury

Previous studies suggest that craniofacial manual lymphatic drainage (MLD) facilitates brain fluids clearance, reducing intracranial pressure and reabsorbing chronic subdural hematoma. This study aimed to explore the effect of craniofacial MLD in combination with pharmacological treatment for improving cranial pain intensity, vital signs, and cerebral edema (Hounsfield units, HUs) in moderate traumatic brain injury (mTBI). Patient 1 received pharmacological therapy, while patient 2 received both pharmacological and craniocervical MLD treatment. Patient 2 showed decreased cranial pain intensity and systolic blood pressure (66%-11.11%, respectively) after two 30 min daily sessions of treatment for three days. HUs in the caudate nucleus of both hemispheres (left 24.64%-right 28.72%) and in the left temporal cortical gray matter increased (17.8%). An increase in HU suggests a reduction in cerebral edema and vice versa. For patient 1, there were no changes in cranial pain intensity, but a slight increase in the systolic blood pressure was observed (0%-3.27%, respectively). HUs decreased in the temporal cortical (14.98%) and caudate nucleus gray matter (9.77%) of the left and right cerebral hemispheres (11.96%-16.74%, respectively). This case study suggests that craniofacial MLD combined with pharmacological treatment could reduce cerebral edema, decrease head pain intensity, and maintain vital signs in normal physiologic values in patients with mTBI.

Acupuncture use for pain after traumatic brain injury: a NIDILRR Traumatic Brain Injury Model Systems cohort study

BACKGROUND

Pain after traumatic brain injury (TBI) is common and can become chronic. Acupuncture is an increasingly popular non-pharmacologic option in the United States and is commonly used for pain.

OBJECTIVE

We explored demographics, injury characteristics, and pain characteristics of individuals who reported using acupuncture for chronic pain after TBI.

METHODS

We analyzed a subset of data collected as part of the Pain After Traumatic Brain Injury collaborative study and identified individuals reporting a history of acupuncture as part of management for chronic pain after TBI. We characterized and compared basic demographic data, pain treatment engagements, pain severity, pain interference, functional independence, and pain locations using descriptive and inferential statistics.

RESULTS

Our sample included 1,064 individuals. Acupuncture use (n = 208) was lower proportionally among females, Blacks/African Americans, Asians, less educated, and nonmilitary service members. Insurance type varied between acupuncture and non-acupuncture users. Functional and pain outcomes were similar, but acupuncture users reported a higher number of pain sites.

DISCUSSION

Acupuncture is one treatment utilized by individuals with TBI and chronic pain. Further investigation would be helpful to understand the barriers and facilitators of acupuncture use to inform clinical trials to examine the potential benefit of acupuncture on pain outcomes after TBI.

Deployment-related concussion and long-term health-related quality of life among US military personnel

PURPOSE

To examine the relationship between deployment-related concussion and long-term health-related quality of life (HRQoL) among injured US military personnel.

METHODS

The study sample included 810 service members with deployment-related injuries between 2008 and 2012 who responded to a web-based longitudinal health survey. Participants were categorized into three injury groups: concussion with loss of consciousness (LOC; n = 247), concussion without LOC (n = 317), or no concussion (n = 246). HRQoL was measured using the 36-Item Short Form Health Survey physical and mental component summary (PCS and MCS) scores. Current post-traumatic stress disorder (PTSD) and depression symptoms were examined. Multivariable linear regression models assessed the effects of concussion on PCS and MCS scores, while controlling for covariates.

RESULTS

A lower PCS score was observed in participants with concussion with LOC (B =  - 2.65, p = 0.003) compared with those with no history of concussion. Symptoms of PTSD (PCS: B =  - 4.84, p < 0.001; MCS: B =  - 10.53, p < 0.001) and depression (PCS: B =  - 2.85, p < 0.001; MCS: B =  - 10.24, p < 0.001) were the strongest statistically significant predictors of lower HRQoL.

CONCLUSION

Concussion with LOC was significantly associated with lower HRQoL in the physical domain. These findings affirm that concussion management should integrate physical and psychological care to improve long-term HRQoL and warrant a more detailed examination of causal and mediating mechanisms. Future research should continue to incorporate patient-reported outcomes and long-term follow-up of military service members to further define the lifelong impact of deployment-related concussion.

The Putative Role of Neuroinflammation in the Interaction between Traumatic Brain Injuries, Sleep, Pain and Other Neuropsychiatric Outcomes: A State-of-the-Art Review

Sleep disturbances are widely prevalent following a traumatic brain injury (TBI) and have the potential to contribute to numerous post-traumatic physiological, psychological, and cognitive difficulties developing chronically, including chronic pain. An important pathophysiological mechanism involved in the recovery of TBI is neuroinflammation, which leads to many downstream consequences. While neuroinflammation is a process that can be both beneficial and detrimental to individuals' recovery after sustaining a TBI, recent evidence suggests that neuroinflammation may worsen outcomes in traumatically injured patients, as well as exacerbate the deleterious consequences of sleep disturbances. Additionally, a bidirectional relationship between neuroinflammation and sleep has been described, where neuroinflammation plays a role in sleep regulation and, in turn, poor sleep promotes neuroinflammation. Given the complexity of this interplay, this review aims to clarify the role of neuroinflammation in the relationship between sleep and TBI, with an emphasis on long-term outcomes such as pain, mood disorders, cognitive dysfunctions, and elevated risk of Alzheimer's disease and dementia. In addition, some management strategies and novel treatment targeting sleep and neuroinflammation will be discussed in order to establish an effective approach to mitigate long-term outcomes after TBI.

The Pain Disability Index: Effects of performance and symptom validity in mild traumatic brain injury litigants with persistent Post-Concussion pain complaints

OBJECTIVE

Objectives of the current study were to cross validate the Pain Disability Index (PDI) as a measure of symptom validity in a large sample of mild traumatic brain injury (MTBI) litigants with persistent post-concussive pain complaints, and investigate the effects of performance and symptom validity testing on PDI scores.

METHODS

Participants included 91 adults who underwent a comprehensive neuropsychological examination. Criterion groups were formed based upon their performance on stand-alone measures of cognitive performance validity (PVT), and the MMPI-2-RF Symptom Validity Scale (FBS-r) as a measure of symptom validity (SVT).

RESULTS

Participants who failed PVT and SVT scored significantly higher on the PDI compared to participants who passed both. Failing both was associated with a large effect size. Failing PVT, but passing SVT, was associated with a medium effect on PDI scores, while passing PVT, but failing SVT demonstrated a small effect. A PDI cutscore of 49 was associated with .90 specificity and .47 sensitivity.

CONCLUSION

The PDI demonstrates external validity as a self-report measure of symptom validity in MTBI litigants with persistent post-concussive pain complaints. A dose response relationship exists between PVT, SVT and PDI scores. Forensic examiners should include both PVT and SVT to optimize clinical decision making when evaluating MTBI litigants with complaints of pain-related disability years post-incident.

Intrathecal dexmedetomidine attenuates mechanical allodynia through the downregulation of brain-derived neurotrophic factor in a mild traumatic brain injury rat model

BACKGROUND

This study evaluated the effects of dexmedetomidine and propofol on brain-derived neurotrophic factor level in the cerebrospinal fluid (c-BDNF) and mechanical allodynia in a mild traumatic brain injury (TBI) rat model.

METHODS

After fixing the rat's skull on a stereotactic frame under general anesthesia, craniotomy was performed. After impact, 10 µl of drug was injected into the cisterna magna (group S: sham, group D: dexmedetomidine 5 μg/kg, group P: propofol 500 μg/kg, and group T: untreated TBI). The 50% mechanical withdrawal threshold (50% MWT) and c-BDNF level were measured on postoperative days (PODs) 1, 7, and 14.

RESULTS

The 50% MWT measured on PODs 1, 7, and 14 was lower and the c-BDNF level on POD 1 was higher in group T than in group S. In group D, the c-BDNF level on POD 1 was lower than that in group T and was comparable with that in group S during the whole study period. The 50% MWT of group D was higher than that of group T throughout the postoperative period. In group P, there were no significant differences in the 50% MWT during the entire postoperative period compared with group T; the c-BDNF level was higher than that in group T on POD 1.

CONCLUSIONS

Intrathecal administration of dexmedetomidine may attenuate TBI-induced mechanical allodynia for up to two weeks post-injury through immediate suppression of c-BDNF in mild TBI rats. The inhibition of c-BDNF expression in the acute phase reduced the occurrence of TBI-induced chronic neuropathic pain.

Community Integration and Associated Factors 10 Years after Moderate-to-Severe Traumatic Brain Injury

This study evaluated the impact of baseline injury characteristics and one-year functional level on the 10-year community integration outcomes for working-age patients with moderate-to-severe traumatic brain injury (TBI). Patients aged 16-55 and diagnosed with moderate-to-severe TBI within 24 h of injury were eligible for the study. Multivariable hierarchical linear regression was utilized to assess the impact of baseline characteristics and one-year functional measures on the mean Community Integration Questionnaire (CIQ) scores 10 years after injury. Of 133 original study participants, 97 survived 10 years, and 75 were available for this study. The mean total CIQ score changed positively from one to 10 years post-injury, from 18.7 (±5.5) to 19.8 (±4.8) (p = 0.04). The results suggested that age (β = -0.260, p = 0.013), FIM-Cognitive subscale (β = 0.608, p = 0.002), and the bodily pain subscale (BP) (β = 0.277, p = 0.017) of the SF-36 were significantly associated with the mean CIQ scores. In conclusion, this study demonstrated improved community integration from one to 10 years in a sample of working-age patients with moderate-to-severe TBI. The findings also showed that age, cognitive function, and bodily pain were significant predictors of long-term community integration, suggesting post-acute rehabilitation should focus on factors related to long-term risk and protective factors to improve long-term outcomes.

Hyperbaric oxygen therapy compared to pharmacological intervention in fibromyalgia patients following traumatic brain injury: A randomized, controlled trial

Fibromyalgia is a chronic pain syndrome with unsatisfactory response to current treatments. Physical trauma, including traumatic brain Injury (TBI) is among the etiological triggers. Hyperbaric Oxygen therapy (HBOT) is an intervention that combines 100% oxygen with elevated atmospheric pressure. HBOT has been applied as a neuro-modulatory treatment in central nervous system-related conditions. The current study investigated the utility of HBOT for TBI-related fibromyalgia. Fibromyalgia patients with a history of TBI were randomized to either HBOT or pharmacological intervention. HBOT protocol comprised 60 daily sessions, breathing 100% oxygen by mask at 2 absolute atmospheres (ATA) for 90 minutes. Pharmacological treatment included Pregabalin or Duloxetine. The primary outcome was subjective pain intensity on visual analogue scale (VAS); Secondary endpoints included questionnaires assessing fibromyalgia symptoms as well as Tc-99m-ECD SPECT brain imaging. Pain threshold and conditioned pain modulation (CPM) were also assessed. Results demonstrated a significant group-by-time interaction in pain intensity post-HBOT compared to the medication group (p = 0.001), with a large net effect size (d = -0.95) in pain intensity reduction following HBOT compared to medications. Fibromyalgia related symptoms and pain questionnaires demonstrated significant improvements induced by HBOT as well as improvements in quality of life and increase in pain thresholds and CPM. SPECT demonstrated significant group-by-time interactions between HBOT and medication groups in the left frontal and the right temporal cortex. In conclusion, HBOT can improve pain symptoms, quality of life, emotional and social function of patients suffering from FMS triggered by TBI. The beneficial clinical effect is correlated with increased brain activity in frontal and parietal regions, associated with executive function and emotional processing.

Neurometabolite alterations in traumatic brain injury and associations with chronic pain

Traumatic brain injury (TBI) can lead to a variety of comorbidities, including chronic pain. Although brain tissue metabolite alterations have been extensively examined in several chronic pain populations, it has received less attention in people with TBI. Thus, the primary aim of this study was to compare brain tissue metabolite levels in people with TBI and chronic pain (n = 16), TBI without chronic pain (n = 17), and pain-free healthy controls (n = 31). The metabolite data were obtained from participants using whole-brain proton magnetic resonance spectroscopic imaging (¹H-MRSI) at 3 Tesla. The metabolite data included N-acetylaspartate, myo-inositol, total choline, glutamate plus glutamine, and total creatine. Associations between N-acetylaspartate levels and pain severity, neuropathic pain symptom severity, and psychological variables, including anxiety, depression, post-traumatic stress disorder (PTSD), and post-concussive symptoms, were also explored. Our results demonstrate N-acetylaspartate, myo-inositol, total choline, and total creatine alterations in pain-related brain regions such as the frontal region, cingulum, postcentral gyrus, and thalamus in individuals with TBI with and without chronic pain. Additionally, NAA levels in the left and right frontal lobe regions were positively correlated with post-concussive symptoms; and NAA levels within the left frontal region were also positively correlated with neuropathic pain symptom severity, depression, and PTSD symptoms in the TBI with chronic pain group. These results suggest that neuronal integrity or density in the prefrontal cortex, a critical region for nociception and pain modulation, is associated with the severity of neuropathic pain symptoms and psychological comorbidities following TBI. Our data suggest that a combination of neuronal loss or dysfunction and maladaptive neuroplasticity may contribute to the development of persistent pain following TBI, although no causal relationship can be determined based on these data.

Performance on the CVLT-2 during induced pain

Objective: Chronic pain patients frequently report cognitive problems including learning and memory. However, recent research involving induced pain has demonstrated an absence of reliably detectable decrements on several standard cognitive measures, suggesting that factors other than pain likely explain perceived cognitive deficits in chronic pain patients. This study examined potential effects of induced pain on verbal learning and memory as measured by the California Verbal Learning Test (CVLT-2). Potential effects of self-reported pain intensity were also evaluated. Method: Participants (111 non-clinical undergraduate students in the Southwestern United States) completed one version (Standard or Alternate) of the CVLT-2 under normal conditions, and then were administered the other version (Alternate or Standard) either while experiencing cold pressor-induced pain (Pain condition) or non-painful warm water immersion (Control condition). Results: For the Pain condition decrements in performance across most CVLT-2 variables were observed, including a mean T-score decrease of 10.98 (SD = 10.99) for Trials 1-5, whereas the comparable decrease in the Control condition was an average of 1.5 words (SD = 8.27). Self-reported pain intensity was significantly correlated with the degree of Time 1 to Time 2 performance decrement for Short-Delay Free Recall (r = -.51, p < .050), but not for Trials 1-5 (r = -.37, p = .160). Conclusion: Induced pain produces detectable decrements in performance on a standard clinical measure of verbal learning and memory performance, suggesting that pain in clinical populations may contribute to learning and memory deficits apart from potential neurological conditions.

Monoamine control of descending pain modulation after mild traumatic brain injury

Traumatic brain injury (TBI) is a significant public health concern, with the majority of injuries being mild. Many TBI victims experience chronic pain. Unfortunately, the mechanisms underlying pain after TBI are poorly understood. Here we examined the contribution of spinal monoamine signaling to dysfunctional descending pain modulation after TBI. For these studies we used a well-characterized concussive model of mild TBI. Measurements included mechanical allodynia, the efficacy of diffuse noxious inhibitory control (DNIC) endogenous pain control pathways and lumber norepinephrine and serotonin levels. We observed that DNIC is strongly reduced in both male and female mice after mild TBI for at least 12 weeks. In naïve mice, DNIC was mediated through α2 adrenoceptors, but sensitivity to α2 adrenoceptor agonists was reduced after TBI, and reboxetine failed to restore DNIC in these mice. The intrathecal injection of ondansetron showed that loss of DNIC was not due to excess serotonergic signaling through 5-HT₃ receptors. On the other hand, the serotonin-norepinephrine reuptake inhibitor, duloxetine and the serotonin selective reuptake inhibitor escitalopram both effectively restored DNIC after TBI in both male and female mice. Therefore, enhancing serotonergic signaling as opposed to noradrenergic signaling alone may be an effective pain treatment strategy after TBI.

Moderate traumatic brain injury triggers long-term risks for the development of peripheral pain sensitivity and depressive-like behavior in mice

As traumatic brain injury (TBI) is one of the major causes of permanent disability, there is increasing interest in the long-term outcome of TBI. While motor deficits, cognitive impairment and longer-term risks of neurodegenerative disease are well-established consequences in animal models of TBI, pain is discussed less often despite its high prevalence. The current study addresses the need to characterize the extent of chronic pain and long-term behavioral impairments induced by moderate lateral fluid percussion injury (latFPI) in mice up to 12 months post-TBI and evaluates the validity of the model. Adult male BALB/c mice were subjected to latFPI, and the results were compared with outcomes in sham-operated mice. Mouse behavior was assessed at 1 and 7 days and 1, 3, 6, 9, and 12 months post-injury using sensory-motor (neurological severity score, NSS), cold (acetone) and mechanical sensitivity (von Frey), depressive-like behavior (tail suspension), locomotor (open field), motor coordination (rotarod) and cognitive (Morris water maze, y-maze, passive avoidance) tests. Animals with TBI demonstrated significantly higher NSS than the sham-operated group for up to 9 months after the injury. Cold sensitization was significantly increased in the contralateral hind paw in the TBI group compared to that of the sham group at 3, 6, and 9 months after TBI. In the von Frey test, the withdrawal threshold of the contralateral and ipsilateral hind paws was reduced at 6 months after TBI and lasted for up to 12 months post-injury. latFPI induced progressive depressive-like behavior starting at 6 months post-injury. No significant deficits were observed in memory, motor coordination or locomotion over the 12-month assessment period. The present study demonstrates that moderate TBI in mice elicits long-lasting impairment of sensory-motor function, results in progressive depression and potentiates peripheral pain. Hence, the latFPI model provides a relevant preclinical setting for the study of the link between brain injury and chronic sequelae such as depression and peripheral pain.

Photosensitivity Is Associated with Chronic Pain following Traumatic Brain Injury

Individuals with a history of traumatic brain injury (TBI) report increased rates of chronic pain. Photosensitivity is also a common chronic symptom following TBI and is prevalent among other types of chronic pain. The aim of this study was to better understand the relationship between chronic pain, pain-related disability, and photosensitivity in a TBI population. We quantified participants' visual photosensitivity thresholds (VPT) using an Ocular Photosensitivity Analyzer and measured pressure-pain sensitivity using pressure algometry. Participants also completed a battery of self-report measures related to chronic pain, TBI history, and mental health. A total of 395 participants completed testing, with 233 reporting a history of TBI. The TBI group was divided into 120 symptomatic TBI participants (s-TBI), and 113 asymptomatic TBI participants (a-TBI) based on their Neurobehavioral Symptom Inventory (NSI) scores. Participants in the s-TBI group scored significantly higher on self-reported chronic pain measures compared with a-TBI and no-TBI participants, including the Symptom Impact Questionnaire Revised (SIQR; p < 0.001) and the Michigan Body Map (MBM; p < 0.001). Despite differences in chronic pain complaints, groups displayed similar pressure-pain thresholds (p = 0.270). Additionally, s-TBI participants were more sensitive to light (lower VPT, p < 0.001), and VPT was correlated with SIQR scores across all participants (R = -0.452, p < 0.001). These data demonstrate that photosensitivity is associated with self-reported chronic pain and disability in individuals with chronic TBI symptomatology. Photosensitivity could therefore serve as a simple, more highly quantitative marker of high-impact chronic pain after TBI.

Multidimensional pain phenotypes after Traumatic Brain Injury

More than 50% of individuals develop chronic pain following traumatic brain injury (TBI). Research suggests that a significant portion of post-TBI chronic pain conditions is neuropathic in nature, yet the relationship between neuropathic pain, psychological distress, and somatosensory function following TBI is not fully understood. This study evaluated neuropathic pain symptoms, psychological and somatosensory function, and psychosocial factors in individuals with TBI (TBI, N = 38). A two-step cluster analysis was used to identify phenotypes based on the Neuropathic Pain Symptom Inventory and Beck's Anxiety Inventory scores. Phenotypes were then compared on pain characteristics, psychological and somatosensory function, and psychosocial factors. Our analyses resulted in two different neuropathic pain phenotypes: (1) Moderate neuropathic pain severity and anxiety scores (MNP-AS, N = 11); and (2) mild or no neuropathic pain symptoms and anxiety scores (LNP-AS, N = 27). Furthermore, the MNP-AS group exhibited greater depression, PTSD, pain severity, and affective distress scores than the LNP-AS group. In addition, thermal somatosensory function (difference between thermal pain and perception thresholds) was significantly lower in the MNP-AS compared to the LNP-AS group. Our findings suggest that neuropathic pain symptoms are relatively common after TBI and are not only associated with greater psychosocial distress but also with abnormal function of central pain processing pathways.

Pain Behaviors Analyzed by Videorecording in Brain-Injured Patients Admitted to the Intensive Care Unit

AIM

To describe and classify pain behaviors (facial and body) in brain-injured patients with a low level of consciousness before, during, and after the performance of painful and non-painful care procedures.

METHODS

Facial behaviors and body movements in brain-injured patients were videotaped at rest, during the application of three care procedures (two painful and one non-painful), and 15 minutes after completion of these procedures. Each video recording was evaluated by expert evaluators blinded to each other. For each of the behaviors observed, all possible combinations between the three procedures and/or time were compared using the McNemar test. Effect size was measured by the difference in proportions using the Wilson score 95% confidence intervals.

RESULTS

Twenty-seven patients were included. The mean (standard deviation) Glasgow Coma Score was 5.4 (1.9). A total of 33 behaviors (29 active, four neutral) were registered. Expression of behaviors was more common during the painful procedures compared with the other time points (non-painful procedures, baseline, and final evaluation). Inter-evaluator agreement was substantial (Kappa index >0.7) in more than 50% of the observed behaviors.

CONCLUSIONS

In this study involving brain-injured patients with a low level of consciousness, facial, body, and ventilation-related behaviors were more common during painful procedures. Agreement between evaluators to detect the presence or absence of these behaviors was substantial. These findings underscore the need to develop pain assessment measures specific to this patient population.

Cellular and Molecular Machinery of Neuropathic Pain: an Emerging Insight

Purpose of Review

Neuropathic pain (NP) has been ubiquitously characterized by lesion and its linked somatosensory system either the central nervous system (CNS) or peripheral nervous system (PNS) This PNS episode is the most prevalent site of NP origin and is found to be associated with afferent nerve fibers carrying pain signals from injured/trauma site to the CNS including the brain. Several kinds of pharmacotherapeutic drugs shuch as analgesics, anti-convulsants, and anti-depressants are being employed for the its possible interventions. The NP has been a great interest to follow different pathophysiological mechanisms which are often considered to correlate with the metabolic pathways and its mediated disease. There is paucity of knowledge to make such mechanism via NP.

Recent Finding

Most notably, recent pandemic outbreak of COVID-19 has also been reported in chronic pain mediated diabetes, inflammatory disorders, and cancers. There is an increasing incidence of NP and its complex mechanism has now led to identify the possible investigations of responsible genes and proteins via bioinformatics tools. The analysis might be more instrumental as collecting the genes from pain genetic database, analyzing the variants through differential gene expression (DEG) and constructing the protein–protein interaction (PPI) networks and thereby determining their upregulating and downregulating pathways.

Summary

This review sheds a bright light towards several mechanisms at both cellular and molecular level, correlation of NP-mediated disease mechanism and possible cell surface biomarkers (receptors), and identified genes could be more promising for their pharmacological targets.

Activation of the Locus Coeruleus Mediated by Designer Receptor Exclusively Activated by Designer Drug Restores Descending Nociceptive Inhibition after Traumatic Brain Injury in Rats

Disruption of endogenous pain control mechanisms including descending pain inhibition has been linked to several forms of pain including chronic pain after traumatic brain injury (TBI). The locus coeruleus (LC) is the principal noradrenergic (NA) nucleus participating in descending pain inhibition. We therefore hypothesized that selectively stimulating LC neurons would reduce nociception after TBI. All experiments used a well-characterized rat lateral fluid percussion model of TBI. NA neurons were stimulated by administering clozapine N-oxide (CNO) to rats selectively expressing a designer receptor exclusively activated by designer drug (DREADD) viral construct in their LC's. Mechanical nociceptive thresholds were measured using von Frey fibers. The efficacy of diffuse noxious inhibitory control (DNIC), a critical endogenous pain control mechanism, was assessed using the hindpaw administration of capsaicin. Immunohistochemical analyses demonstrated the selective expression of the DREADD construct in LC neurons after stereotactic injection. During the 1st week after TBI, when rats demonstrated hindlimb (HL) nociceptive sensitization, CNO administration provided transient anti-allodynia in DREADD-expressing rats but not in rats injected with control virus. Seven weeks after TBI we observed a complete loss of DNIC in response to capsaicin. However, CNO administration largely restored DNIC in TBI DREADD-expressing rats but not those injected with control virus. Unexpectedly, the effects of LC activation in the DREADD-expressing rats were blocked by the α-1 adrenergic receptor antagonist prazosin, but not the α-2 adrenergic receptor antagonist atipamezole. These results suggest that directly stimulating the LC after TBI can reduce both early and late manifestations of dysfunctional endogenous pain regulation. Clinical approaches to activating descending pain circuits may reduce suffering in those with pain after TBI.

Pain in Persons with Disorders of Consciousness

Pain and suffering in persons with disorders of consciousness (DoC) remain poorly understood, frequently unaddressed or inadequately addressed, and controversial on numerous levels. This narrative literature review will address a number of critical issues germane to pain and suffering in this challenging group of patients, providing an introductory overview of the topic, perspectives on current knowledge regarding pain pathoanatomy and pathophysiology, and a review of common pain generators and factors that can lead to the chronifcation of pain. Caveats on bedside pain assessment challenges, as well as electrophysiologic and neuroimaging findings in these patients, will also be explored. Pain management techniques, including non-pharmacological and pharmacological, will be reviewed. Ethical considerations in the context of pain and suffering in persons with disorders of consciousness will round out the review prior to our concluding comments.

Cervicovestibular Rehabilitation in Adults with Mild Traumatic Brain Injury: A Randomised Clinical Trial

The objective of this study was to compare the effects of a cervicovestibular rehabilitation program combined with symptom-limited aerobic exercise (SLAE) program to a SLAE program alone in adults with persistent symptoms following mild traumatic brain injury (mTBI) on severity of symptoms and other indicators of clinical recovery. In this single-blind, parallel-group randomised clinical trial, 60 adults with persistent symptoms following mTBI were randomly assigned to: 1) a 6-week SLAE program or 2) a 6-week cervicovestibular rehabilitation program combined with SLAE program. All participants took part in 4 evaluation sessions (baseline, week 6, 12 and 26) performed by a blinded evaluator. The primary outcome was the Post-Concussion Symptoms Scale (PCSS). The secondary outcomes were Numerical Pain Rating Scale (NPRS), Neck Disability Index (NDI), Headache Disability Inventory (HDI), Dizziness Handicap Inventory (DHI), time to return to function, and physical cervical and vestibular measures. Nonparametric analysis for longitudinal data was used to evaluate the effect of interventions on outcomes. For PCSS, NPRS, NDI, HDI, DHI and return to function, there were no group-by-time interactions at any time-points follow-up (p>0.05); clinically significant time effects were however observed (p0.05). There were group-by-time interactions at weeks 6 and 12 for vestibulo-ocular reflex (p0.003) and the cranio-vertebral mobility (p0.001) measures in favor of the cervicovestibular rehabilitation group. The study indicates that a cervicovestibular rehabilitation program combined with SLAE was not superior to a SLAE program alone in term of symptoms and functional level improvement but resulted in improved physical cervical and vestibular function. Keywords: mild traumatic brain injury, rehabilitation, neck pain, dizziness, headache.

Quantitative Proteomics Reveals the Dynamic Pathophysiology Across Different Stages in a Rat Model of Severe Traumatic Brain Injury

Background

Severe traumatic brain injury (TBI) has become a global health problem and causes a vast worldwide societal burden. However, distinct mechanisms between acute and subacute stages have not been systemically revealed. The present study aimed to identify differentially expressed proteins in severe TBI from the acute to subacute phase.

Methods

Sixty Sprague Dawley (SD) rats were randomly divided into sham surgery and model groups. The severe TBI models were induced by the controlled cortical impact (CCI) method. We evaluated the neurological deficits through the modified neurological severity score (NSS). Meanwhile, H&E staining and immunofluorescence were performed to assess the injured brain tissues. The protein expressions of the hippocampus on the wounded side of CCI groups and the same side of Sham groups were analyzed by the tandem mass tag-based (TMT) quantitative proteomics on the third and fourteenth days. Then, using the gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG), and protein–protein interaction (PPI), the shared and stage-specific differentially expressed proteins (DEPs) were screened, analyzed, and visualized. Eventually, target proteins were further verified by Western blotting (WB).

Results

In the severe TBI, the neurological deficits always exist from the acute stage to the subacute stage, and brain parenchyma was dramatically impaired in either period. Of the significant DEPs identified, 312 were unique to the acute phase, 76 were specific to the subacute phase, and 63 were shared in both. Of the 375 DEPs between Sham-a and CCI-a, 240 and 135 proteins were up-regulated and down-regulated, respectively. Of 139 DEPs, 84 proteins were upregulated, and 55 were downregulated in the Sham-s and CCI-s. Bioinformatics analysis revealed that the differential pathophysiology across both stages. One of the most critical shared pathways is the complement and coagulation cascades. Notably, three pathways associated with gastric acid secretion, insulin secretion, and thyroid hormone synthesis were only enriched in the acute phase. Amyotrophic lateral sclerosis (ALS) was significantly enriched in the subacute stage. WB experiments confirmed the reliability of the TMT quantitative proteomics results.

Conclusion

Our findings highlight the same and different pathological processes in the acute and subacute phases of severe TBI at the proteomic level. The results of potential protein biomarkers might facilitate the design of novel strategies to treat TBI.

Endogenous Opioid Dynorphin Is a Potential Link between Traumatic Brain Injury, Chronic Pain, and Substance Use Disorder

Traumatic brain injury (TBI) is a serious public health problem associated with numerous physical and neuropsychiatric comorbidities. Chronic pain is prevalent and interferes with post-injury functioning and quality of life, whereas substance use disorder (SUD) is the third most common neuropsychiatric diagnosis after TBI. Neither of these conditions has a clear mechanistic explanation based on the known pathophysiology of TBI. Dynorphin is an endogenous opioid neuropeptide that is significantly dysregulated after TBI. Both dynorphin and its primary receptor, the ĸ-opioid receptor (KOR), are implicated in the neuropathology of chronic pain and SUD. Here, we review the known roles of dynorphin and KORs in chronic pain and SUDs. We synthesize this information with our current understanding of TBI and highlight potential mechanistic parallels between and across conditions that suggest a role for dynorphin in long-term sequelae after TBI. In pain studies, dynorphin/KOR activation has either antinociceptive or pro-nociceptive effects, and there are similarities between the signaling pathways influenced by dynorphin and those underlying development of chronic pain. Moreover, the dynorphin/KOR system is considered a key regulator of the negative affective state that characterizes drug withdrawal and protracted abstinence in SUD, and molecular and neurochemical changes observed during the development of SUD are mirrored by the pathophysiology of TBI. We conclude by proposing hypotheses and directions for future research aimed at elucidating the potential role of dynorphin/KOR in chronic pain and/or SUD after TBI.

Neurological Symptoms and Their Associations With Inflammatory Biomarkers in the Chronic Phase Following Traumatic Brain Injuries

BACKGROUND

The underlying biological mechanisms for neurological symptoms following a traumatic brain injury (TBI) remain poorly understood. This study investigated the associations between serum inflammatory biomarkers and neurological symptoms in the chronic phase following moderate to severe TBI.

METHODS

The serum interleukin [IL]-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, and the tumor necrosis factor [TNF]-α in 72 TBI patients 6 months to 2 years post injury were measured. Neurological symptoms including depression, chronic headache, sleep disturbance, irritability, anxiety, and global neurological disability was assessed. The associations between the biomarkers and the neurological symptoms were assessed using correlation and regression analysis.

RESULTS

It was found that the most common post-injury symptom was sleep disturbance (84.7%), followed by chronic headaches (59.7%), irritability (55.6%), and depression (54.2%). TNF-α was a protective factor for chronic headache (OR = 0.473, 95% CI = 0.235-0.952). IL-6 was positively associated with sleep disturbance (r = 0.274, p = 0.021), while IL-5 and IL-12p70 were negatively associated with the degree of global neurological disability (r = -0.325, p = 0.006; r = -0.319, p = 0.007).

CONCLUSION

This study provides preliminary evidence for the association between chronic inflammation with neurological symptoms following a TBI, which suggests that anti-inflammatory could be a potential target for post-TBI neurological rehabilitation. Further research with larger sample sizes and more related biomarkers are still needed, however, to elucidate the inflammatory mechanisms for this association.

Increased Brain-Derived Neurotrophic Factor Levels in Cerebrospinal Fluid During the Acute Phase in TBI-Induced Mechanical Allodynia in the Rat Model

Background

The present study aimed to develop a rat model for mechanical allodynia after traumatic brain injury (TBI) and to investigate the expression of brain-derived neurotrophic factor (BDNF) in the cerebrospinal fluid (CSF) using this model.

Methods

A total of 180 rats were randomly allocated into three groups: a control group (group C), a sham-operated group (group S), and a controlled cortical impact induced TBI group (group T), 60 in each group. Von Frey test was performed to evaluate mechanical withdrawal thresholds. An enzyme-linked immunosorbent assay was performed to quantify BDNF level in CSF.

Results

The 50% withdrawal thresholds of group T were lower than those of group C and group S at all measuring points except for the preoperative period (P = 0.026, <0.001, and <0.001 for POD1, POD7, and POD14, respectively). The BDNF level of group T was higher than those of group C and group S at POD1 (P = 0.005).

Conclusion

Upregulation of the BDNF expression in CSF was observed in rats who developed mechanical allodynia on the day after TBI. Based on our findings, to elucidate the relationship between TBI-induced neuropathic pain and BDNF expression in CSF, further research should be carried out through a multifaceted approach to a broad spectrum of pain behavior models.

The educational needs of Canadian homeless shelter workers related to traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) has a higher prevalence in the homeless population. Caregivers to individuals who have TBIs may require better education surrounding screening, diagnosis and management of this disease to tailor interventions to their clients' needs.

OBJECTIVE

To assess the insight and educational needs of homeless care providers in recognizing and dealing with clients who had experienced a TBI.

METHODS

A survey assessing the point of views of homeless care providers across Canada regarding their level of confidence in identifying and managing symptoms of TBI.

RESULTS

Eight-eight completed surveys were included. Overall, frontline workers expressed a moderate level of confidence in identifying and managing TBI, stating that educational initiatives in this context would be of high value to themselves and their clients.

CONCLUSIONS

Frontline workers to homeless clients rate their educational needs on the identification and management of TBI to be high such that educational initiatives for shelter workers across Canada may be beneficial to increase their knowledge in identifying and managing the TBI-related symptoms. Improved education would not only benefit frontline workers but may also have a positive effect on health outcomes for their clients.

Sevoflurane Inhibits Traumatic Brain Injury-Induced Neuron Apoptosis via EZH2-Downregulated KLF4/p38 Axis

Traumatic brain injury (TBI) is characterized by physical damage to the brain tissues, ensuing transitory or permanent neurological dysfunction featured with neuronal loss and subsequent brain damage. Sevoflurane, a widely used halogenated anesthetic in clinical settings, has been reported to alleviate neuron apoptosis in TBI. Nevertheless, the underlying mechanism behind this alleviation remains unknown, and thus was the focus of the current study. First, Feeney models were established to induce TBI in rats. Subsequently, evaluation of the modified neurological severity scores, measurement of brain water content, Nissl staining, and TUNEL assay were employed to investigate the neuroprotective effects of sevoflurane. Immunofluorescence and Western blot analysis were further applied to detect the expression patterns of apoptosis-related proteins as well as the activation of the p38-mitogen-activated protein kinase (MAPK) signaling pathway within the lesioned cortex. Additionally, a stretch injury model comprising cultured neurons was established, followed by neuron-specific enolase staining and Sholl analysis. Mechanistic analyses were performed using dual-luciferase reporter gene and chromatin immunoprecipitation assays. The results demonstrated sevoflurane treatment brought about a decrease blood-brain barrier (BBB) permeability, brain water content, brain injury and neuron apoptosis, to improve neurological function. The neuroprotective action of sevoflurane could be attenuated by inactivation of the p38-MAPK signaling pathway. Mechanistically, sevoflurane exerted an inhibitory effect on neuron apoptosis by up-regulating enhancer of zeste homolog 2 (EZH2), which targeted Krüppel-like factor 4 (KLF4) and inhibited KLF4 transcription. Collectively, our findings indicate that sevoflurane suppresses neuron apoptosis induced by TBI through activation of the p38-MAPK signaling pathway via the EZH2/KLF4 axis, providing a novel mechanistic explanation for neuroprotection of sevoflurane in TBI.

CGRP monoclonal antibody prevents the loss of diffuse noxious inhibitory controls (DNIC) in a mouse model of post-traumatic headache

AIM

Determine the role of calcitonin-gene related peptide in promoting post-traumatic headache and dysregulation of central pain modulation induced by mild traumatic brain injury in mice.

METHODS

Mild traumatic brain injury was induced in lightly anesthetized male C57BL/6J mice by a weight drop onto a closed and unfixed skull, which allowed free head rotation after the impact. We first determined possible alterations in the diffuse noxious inhibitory controls, a measure of net descending pain inhibition called conditioned pain modulation in humans at day 2 following mild traumatic brain injury. Diffuse noxious inhibitory control was assessed as the latency to a thermally induced tail-flick that served as the test stimulus in the presence of right forepaw capsaicin injection that provided the conditioning stimulus. Post-traumatic headache-like behaviors were assessed by the development of cutaneous allodynia in the periorbital and hindpaw regions after mild traumatic brain injury. We then determined if intraperitoneal fremanezumab, an anti-calcitonin-gene related peptide monoclonal antibody or vehicle administered 2 h after sham or mild traumatic brain injury induction could alter cutaneous allodynia or diffuse noxious inhibitory control responses on day 2 post mild traumatic brain injury.

RESULTS

In naïve and sham mice, capsaicin injection into the forepaw elevated the latency to tail-flick, reflecting the antinociceptive diffuse noxious inhibitory control response. Periorbital and hindpaw cutaneous allodynia, as well as a loss of diffuse noxious inhibitory control, was observed in mice 2 days after mild traumatic brain injury. Systemic treatment with fremanezumab blocked mild traumatic brain injury-induced cutaneous allodynia and prevented the loss of diffuse noxious inhibitory controls in mice subjected to a mild traumatic brain injury.

INTERPRETATION

Sequestration of calcitonin-gene related peptide in the initial stages following mild traumatic brain injury blocked the acute allodynia that may reflect mild traumatic brain injury-related post-traumatic headache and, additionally, prevented the loss of net descending inhibition within central pain modulation pathways. As loss of conditioned pain modulation has been linked to multiple persistent pain conditions, dysregulation of descending modulatory pathways may contribute to the persistence of post-traumatic headache. Additionally, evaluation of the conditioned pain modulation/diffuse noxious inhibitory controls response may serve as a biomarker of vulnerability for chronic/persistent pain. These findings suggest that early anti-calcitonin-gene related peptide intervention has the potential to be effective both for the treatment of mild traumatic brain injury-induced post-traumatic headache, as well as inhibiting mechanisms that may promote post-traumatic headache persistence.

Addressing Pain for a Proper Rehabilitation Process in Patients With Severe Disorders of Consciousness

Consciousness constitutes a fundamental prerequisite in the individual appraisal and experience of pain. In the same way, a person needs to be able to report on pain perception. Patients who suffered a severe brain injury with disorders of consciousness (DOC) represent a spectrum of pathologies affecting patients' capacity to interact with the external world. In these patients, the most relevant aspects in response to pain are physiologic and behavioral. The treatments and management of pain are challenging issues in these patients, arising serious ethical concerns and bringing emotional load among medical staff, caregivers, and relatives. In this review, we report the importance of having a correct pain management in DOC patients, to individuate the best pharmacological treatment that can make the difference in detecting a behavioral response, indicative of a change in the level of consciousness, and in planning a more effective rehabilitative approach.

Pain and Symptoms after Mild Traumatic Brain Injury: Should Technology Play a Role in Self-Management?

BACKGROUND

Those with mild traumatic brain injury (mTBI) often experience pain and symptoms long after their initial injury. A gap in current knowledge is how persons would prefer to monitor and manage these symptoms following mTBI.

AIMS

The purpose of this study was to explore self-management strategies to inform design of an informatics tool to support self-management of pain and symptoms following mTBI.

DESIGN

A qualitative descriptive approach using semi-structured interviews of participants was used.

SETTINGS

Participants were interviewed by phone.

PARTICIPANTS

Seven female participants with recent mTBI completed interviews.

METHODS

A descriptive approach was utilized to determine what the tool should address, and which features should be included in a future tool. Themes were identified using a Qualitative Description analysis approach, which is based in naturalistic inquiry.

RESULTS

Participants described difficulty coping with symptoms, limited access to or knowledge of treatments and trial and error with compensatory strategies. These challenges often led to difficulty keeping up with work, school and other commitments. All participants indicated that they were interested in a tool that addresses pain, memory and concentration. The main features that participants wanted were pain and symptom tracking as well as suggestions based on tracking information.

CONCLUSIONS

Patients are interested in using technology to help with self-management of their pain and symptoms following mTBI. Tools that help patients with self-management should integrate into health systems and provide ways to effectively interact with providers during the most vulnerable phases of recovery.

Pain anxiety and rehabilitation outcomes after acquired brain injury

Purpose: The purpose of this study was to examine pain anxiety after acquired brain injury (ABI) and its relationship to rehabilitation outcomes.Materials and Method: Participants consisted of 89 adults with an ABI participating in outpatient rehabilitation therapy. They completed a battery of neuropsychological tests at baseline along with surveys of mood, health-related self-efficacy, and pain anxiety. Separately, occupational therapists assessed basic and instrumental activities of daily living (ADLs) as well as therapy engagement across treatment after the sixth session.Results: Individuals who reported high pain anxiety had fewer years of formal education, lower self-efficacy, and more emotional distress than those with low pain anxiety. Although Blacks were about half (56%) of the study sample, they comprised the majority (73.1%) of individuals in the high pain anxiety group. Pain anxiety was negatively related to therapy engagement. Moderation analysis using linear regression indicated that pain anxiety moderated the influence of self-efficacy on basic ADLs.Conclusions: Pain anxiety, particularly when high, is negatively associated with rehabilitation outcomes for individuals with ABI. Among those with high pain anxiety, health-related self-efficacy is an important resilience characteristic to improve functional outcomes. In rehabilitation therapy, pain anxiety provides a novel intervention target to enhance ABI recovery.

Shared correlates of prescription drug misuse and severe suicide ideation among clinical patients at risk for suicide

OBJECTIVE

Unintentional drug overdose and suicide have emerged as public health problems. Prescription drug misuse can elevate risk of overdose. Severe suicidal ideation increases risk of suicide. We identified shared correlates of both risk factors to inform cross-cutting prevention efforts.

METHODS

We conducted a cross-sectional study using the Military Suicide Research Consortium's Common Data Elements survey; 2012-2017 baseline data collected from 10 research sites were analyzed. The sample included 3962 clinical patients at risk of suicide. Factors examined in relation to the outcomes, prescription drug misuse and severe suicidal ideation, included demographic characteristics and symptoms of: hopelessness; anxiety; post-traumatic stress disorder; alcohol use; other substance use; prior head/neck injury; insomnia; and belongingness. Poisson regression models with robust estimates provided adjusted prevalence ratios (aPRs) and 97.5% confidence intervals (CIs).

RESULTS

Medium and high (vs. low) levels of insomnia were positively associated with prescription drug misuse (aPRs p < 0.025). Medium (vs. low) level of insomnia was positively associated with severe suicidal ideation (aPR: 1.09; CI: 1.01-1.18). Medium and high (vs. low) levels of perceived belongingness were inversely associated with both outcomes (aPRs p < 0.025).

CONCLUSIONS

Research should evaluate whether addressing sleep problems and improving belongingness can reduce prescription drug misuse and suicidal ideation simultaneously.

Traumatic brain injury and the misuse of alcohol, opioids, and cannabis

Traumatic brain injury (TBI), most often classified as concussion, is caused by biomechanical forces to the brain resulting in short- or long-term impairment in brain function. TBI resulting from military combat, sports, violence, falls, and vehicular accidents is a major cause of long-term physical, cognitive, and psychiatric dysfunction. Psychiatric disorders associated with TBI include depression, anxiety, and substance use disorder, all having significant implications for post-TBI recovery and rehabilitation. This chapter reviews the current preclinical and clinical literature describing the bidirectional relationship between TBI and misuse of three commonly abused drugs: alcohol, opioids, and cannabis. We highlight the influence of each of these drugs on the incidence of TBI, as well as trends in their use after TBI. Furthermore, we discuss factors that may underlie post-injury substance use. Understanding the complex relationship between TBI and substance misuse will enhance the clinical treatment of individuals suffering from these two highly comorbid conditions.

Recommendations for Prescribing Opioids for People With Traumatic Brain Injury

Our objective was to make recommendations intended to reduce the rate of opioid misuse and overdose for a particularly high-risk group of people with traumatic brain injury (TBI). A consensus process conducted with TBI researchers and expert practitioners developed practical recommendations to inform prescribing of opioids for people with TBI. After determining key general principles for prescribing opioids for people with TBI, 6 TBI-specific recommendations were developed, 1 for acute pain in the agitated patient with TBI, 3 recommendations to be considered before prescribing an opioid, and 2 for follow-up and use by mental health and substance use disorder providers. While there is much needed research to examine the relationship between opioid misuse and TBI, the present recommendations provide at least some clinical considerations that might serve to prevent further deaths among a high-risk group.

Loss of diffuse noxious inhibitory control after traumatic brain injury in rats: A chronic issue

Chronic pain is one of the most challenging and debilitating symptoms to manage after traumatic brain injury (TBI), yet the underlying mechanisms remain elusive. The disruption of normal endogenous pain control mechanisms has been linked to several forms of chronic pain and may play a role in pain after TBI. We hypothesized therefore that dysfunctional descending noradrenergic and serotonergic pain control circuits may contribute to the loss of diffuse noxious inhibitory control (DNIC), a critical endogenous pain control mechanism, weeks to months after TBI. For these studies, the rat lateral fluid percussion model of mild TBI was used along with a DNIC paradigm involving a capsaicin-conditioning stimulus. We observed sustained failure of the DNIC response up to 180-days post injury. We confirmed, that descending α₂ adrenoceptor-mediated noradrenergic signaling was critical for endogenous pain inhibition in uninjured rats. However, augmenting descending noradrenergic signaling using reboxetine, a selective noradrenaline reuptake inhibitor, failed to restore DNIC after TBI. Furthermore, blocking serotonin-mediated descending signaling using selective spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine was also unsuccessful at restoring endogenous pain modulation after TBI. Unexpectedly, increasing descending serotonergic signaling using the selective serotonin reuptake inhibitor escitalopram and the serotonin-norepinephrine reuptake inhibitor duloxetine restored the DNIC response in TBI rats at both 49- and 180- days post injury. Consistent with these observations, spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine eliminated the effects of escitalopram. Intact α₂ adrenoceptor signaling, however, was not required for the serotonin-mediated restoration of DNIC after TBI. These results suggest that TBI causes maladaptation of descending nociceptive signaling mechanisms and changes in the function of both adrenergic and serotonergic circuits. Such changes could predispose those with TBI to chronic pain.