Peripheral Neuropathy and Nerve Compression Syndromes in Burns

Surgical Management of Chronic Neuropathic Burn Pain

Burn-related chronic neuropathic pain can contribute to a decreased quality of life. When medical and pharmacologic therapies prove ineffective, patients should undergo evaluation for surgical intervention, consisting of a detailed physical examination and elective diagnostic nerve block, to identify an anatomic cause of pain. Based on symptoms and physical examination findings, particularly Tinel's sign, treatments can vary, including a trial of laser therapies, fat grafting, or nerve surgeries (nerve decompression, neuroma excision, targeted muscle reinnervation, regenerative peripheral nerve interfaces, and vascularized denervated muscle targets). It is essential to counsel patients to establish appropriate expectations prior to treatment with a multidisciplinary team.

Neuropathic pain in burn patients - A common problem with little literature: A systematic review

BACKGROUND

The prevalence of neuropathic pain (NP) in burn patients is reported in the literature to be as high as 80%1. Given the complexity of NP in burn patients and the wide range of treatments available, a systematic review of the literature is warranted to summarize our current understanding of management and treatment of NP in this population.

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The following databases were queried to identify relevant articles: PubMed, Cochrane, Embase, Scopus, Ovid, and Web of Science. The main outcome measures were incidence and management of NP. Secondary outcomes included risk factors for NP.

RESULTS

Included articles presented findings from 11 different countries, capturing outcomes for 4366 patients. Risk factors for neuropathic pain in burn patients were identified, including older age, alcohol and substance abuse, current daily smoking, greater % total body surface area burns (TBSA), and longer hospitalizations. Pharmacologic treatments included gabapentin/pregabalin (n = 7), ascorbic acid (n = 1), and lidocaine (n = 1). Overall, the studies showed varied results regarding the efficacy of pharmacological treatments. While certain studies demonstrated gabapentanoids to be effective in reducing neuropathic symptoms, others found conflicting results. With regards to non-pharmacologic treatments, electroconvulsive therapy (n = 1), electropuncture (n = 1), nerve release/reconstruction (n = 2), and somatosensory feedback rehabilitation (n = 1) were used and demonstrated promise in reducing pain intensity and improving functionality.

CONCLUSIONS

Despite NP afflicting the majority of burn patients long after their injury, this systematic review demonstrates insufficient evidence on the pathophysiology, outcomes, and risk factors in NP, as well as the efficacy of various therapies. Future prospective and randomized studies evaluating the etiology of these factors can substantially improve our treatment strategies. This can allow for the development of well-delineated and evidence-based protocols in NP management in hopes of improving quality of life and both psychological and physical function in burn patients.

Peripheral nerve injuries in children-prevalence, mechanisms and concomitant injuries: a major trauma center's experience

BACKGROUND

Peripheral nerve injuries are severe conditions with potential lifelong impairment, which is especially meaningful for the pediatric population. Knowledge on prevalence, injury mechanisms and concomitant injuries is, therefore, of utmost importance to increase clinician awareness and enable early diagnosis and treatment. As current literature on pediatric nerve lesions and concomitant injuries is scarce, we aimed to analyze all details of our patient population.

METHODS

A total of 110 667 patients treated at our level 1 trauma center from 2012 to 2021 were evaluated for pediatric peripheral nerve injuries, causes, concomitant injuries and assessed for lesion classification (in continuity, partial lesion, dissection) and further relevant intraoperative findings.

RESULTS

We found 5026 patients of all ages with peripheral nerve lesions, whereof 288 were pediatric, resulting in a prevalence of 5.7% of pediatric patients with nerve injuries. Mean age was 12.4 ± 4.6 years. Most common lesions were digital nerves (48.2%), followed by median (14.9%), ulnar (14.6%), radial (8.8%), peroneal nerve (5.2%) and brachial plexus injuries (2.1%). Of all pediatric nerve injuries, 3.8% were iatrogenic, only 30.2% had preserved continuity and 47.3% a concomitant vessel injury. Fractures were accompanied in 22.6%.

DISCUSSION

We observed that a large proportion of injures had complete transections, often accompanied by concomitant vessel injuries especially in distally located injuries, highlighting the importance of early surgical exploration. Radial, ulnar and lower extremity nerve injuries were often associated with fractures. Early surgical nerve repair is key to improve motor and sensory outcomes. Knowledge on mechanisms and concomitant injuries facilitates timely diagnosis and treatment, thereby potentially preventing lifelong impairment.

Molecular mechanisms of post-burn muscle wasting and the therapeutic potential of physical exercise

After a severe burn injury, a systemic stress response activates metabolic and inflammatory derangements that, among other, leads to muscle mass loss (muscle wasting). These negative effects on skeletal muscle continue for several months or years and are aggravated by short-term and long-term disuse. The dynamic balance between muscle protein synthesis and muscle protein breakdown (proteolysis) is regulated by complex signalling pathways that leads to an overall negative protein balance in skeletal muscle after a burn injury. Research concerning these molecular mechanisms is still scarce and inconclusive, understanding of which, if any, molecular mechanisms contribute to muscle wasting is of fundamental importance in designing of therapeutic interventions for burn patients as well. This review not only summarizes our present knowledge of the molecular mechanisms that underpin muscle protein balance but also summarizes the effects of exercise on muscle wasting post-burn as promising strategy to counteract the detrimental effects on skeletal muscle. Future research focusing on the pathways causing post-burn muscle wasting and the different effects of exercise on them is needed to confirm this hypothesis and to lay the foundation of therapeutic strategies.

Spinal Irisin Gene Delivery Attenuates Burn Injury-Induced Muscle Atrophy by Promoting Axonal Myelination and Innervation of Neuromuscular Junctions

Muscle loss and weakness after a burn injury are typically the consequences of neuronal dysregulation and metabolic change. Hypermetabolism has been noted to cause muscle atrophy. However, the mechanism underlying the development of burn-induced motor neuropathy and its contribution to muscle atrophy warrant elucidation. Current therapeutic interventions for burn-induced motor neuropathy demonstrate moderate efficacy and have side effects, which limit their usage. We previously used a third-degree burn injury rodent model and found that irisin-an exercise-induced myokine-exerts a protective effect against burn injury-induced sensory and motor neuropathy by attenuating neuronal damage in the spinal cord. In the current study, spinal irisin gene delivery was noted to attenuate burn injury-induced sciatic nerve demyelination and reduction of neuromuscular junction innervation. Spinal overexpression of irisin leads to myelination rehabilitation and muscular innervation through the modulation of brain-derived neurotrophic factor and glial-cell-line-derived neurotrophic factor expression along the sciatic nerve to the muscle tissues and thereby modulates the Akt/mTOR pathway and metabolic derangement and prevents muscle atrophy.

Role of Intravenous Lidocaine Infusion in the Treatment of Peripheral Neuropathy

Purpose of Review

This is a comprehensive review of the literature regarding intravenous lidocaine infusion to treat peripheral neuropathy. The clinical symptoms of peripheral neuropathy occur on a broad spectrum and stem from many etiologies resulting in complex treatment approaches. This review presents the background, evidence, and indications for the use of intravenous lidocaine infusions as a treatment option for this condition.

Recent Findings

The clinical range of peripheral neuropathy symptoms includes pain, numbness, muscle weakness, paresthesia, balance difficulty, and autonomic dysfunction. However, severe neuropathic pain remains one of the most debilitating symptoms that significantly affects the quality of life. Current treatment options include antidepressants, anticonvulsants, and, in some cases, opiates, but these are often ineffective, creating the need for other therapeutic approaches.The pathophysiology of neuropathic pain involves sodium channels which create abnormal pain responses. Intravenous lidocaine primarily functions by inhibiting membrane sodium channels which desensitize peripheral nociceptors, thus creating an analgesic effect. The research in using intravenous lidocaine for neuropathic pain is not fully complete and requires further evaluation.

Summary

Peripheral neuropathy is a manifestation commonly resulting from diabetes, alcohol abuse, vitamin deficiencies, and chemotherapy, among other causes. One of the most significant complications is neuropathic pain which is often resistant to multi-modal therapeutic regimens. Intravenous lidocaine infusions are a newer treatment option for neuropathic pain, which have additional anti-inflammatory effects with a minimal side effect profile. Studies have concluded it effectively treats neuropathic pain for weeks after administration, but results are variable depending on specific procedures. Further research, including additional direct comparison studies, should be conducted to fully evaluate this drug's usefulness.

Burn-induced heterotopic ossification from incidence to therapy: key signaling pathways underlying ectopic bone formation

Burn injury is one of the potential causes of heterotopic ossification (HO), which is a rare but debilitating condition. The incidence ranges from 3.5 to 5.6 depending on body area. Burns that cover a larger percentage of the total body surface area (TBSA), require skin graft surgeries, or necessitate pulmonary intensive care are well-researched risk factors for HO. Since burns initiate such complex pathophysiological processes with a variety of molecular signal changes, it is essential to focus on HO in the specific context of burn injury to define best practices for its treatment. There are numerous key players in the pathways of burn-induced HO, including neutrophils, monocytes, transforming growth factor-β1-expressing macrophages and the adaptive immune system. The increased inflammation associated with burn injuries is also associated with pathway activation. Neurological and calcium-related contributions are also known. Endothelial-to-mesenchymal transition (EMT) and vascularization are known to play key roles in burn-induced HO, with hypoxia-inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) as potential initiators. Currently, non-steroidal anti-inflammatory drugs (NSAIDs) and radiotherapy are effective prophylaxes for HO. Limited joint motion, ankylosis and intolerable pain caused by burn-induced HO can be effectively tackled via surgery. Effective biomarkers for monitoring burn-induced HO occurrence and bio-prophylactic and bio-therapeutic strategies should be actively developed in the future.

Risk Factors Associated With the Progression From Acute to Chronic Neuropathic Pain After Burn-Related Injuries

BACKGROUND

Pain, unrelated to the initial thermal trauma itself, can result after burn injury and prolong the recovery/rehabilitation phase of the patient's care. This pain, after discharge from the burn unit, may be acute and self-limiting or chronic and contribute to long-term patient morbidity. The purposes of this study were to compare burn patients who had, after discharge from the burn unit, only acute pain with burn patients who developed chronic, neuropathic pain (CNP) and to determine risks factors for progression from acute to chronic pain in the setting of a burn center.

METHODS

A single-center, retrospective chart review of patients admitted to the adult burn center was performed from January 1, 2014, to January 1, 2019. Patients included were older than 15 years, sustained a burn injury, and admitted to the burn unit. Chronic pain was defined as pain lasting greater than 6 months after discharge from the burn unit. Pain descriptors included shooting, stabbing, sharp, burning, tingling, numbness, throbbing, pruritus, intermittent, and/or continuous dysesthetic sensations after the burn. Patients were excluded if they had preexisting neuropathic pain due to an underlying medical illness or previous surgery.

RESULTS

During a 5-year period, of the 1880 admissions to the burn unit, 143 burn patients developed post-initial-onset pain as a direct result of their burn. Of the 143 patients with acute pain, pain resolved in 30 patients, whereas pain progressed to CNP in 113 patients (79%). Patient follow-up was a median (interquartile range [IQR]) of 26.5 (10-45) months. Patients whose pain progressed to CNP had significantly greater percent total body surface area burns (median [IQR], 6 [3-25] vs 3 [1-10]; P = 0.032), had more full-thickness burns (66/113 [58%] vs 8/30 [27%] patients, P = 0.004), had surgery (85/113 [75%] vs 16/30 [53%] patients, P = 0.042), had more surgical procedures (median [IQR], 2 [1-6] vs 1 [0-3], P = 0.002), and developed more complications (32/113 [28%] vs 2/30 [7%] patients, P = 0.014) compared with those with acute neuropathic pain, respectively.

CONCLUSIONS

Burn patients who progressed from having acute to CNP had significantly greater percent total body surface area burns, had more full-thickness burns, had surgery, had more surgical procedures, and developed more complications compared with burn patients with only acute pain.

Chronic Neuropathic Pain Following Hand Burns: Etiology, Treatment, and Long-Term Outcomes

PURPOSE

Chronic neuropathic pain (CNP) after burn injury to the hand/upper extremity is relatively common, but not well described in the literature. This study characterizes patients with CNP after hand/upper extremity burns to help guide risk stratification and treatment strategies. We hypothesize that multiple risk factors contribute to the development of CNP and refractory responses to treatment.

METHODS

Patients older than 15 years admitted to the burn center after hand/upper extremity burns, from January 1, 2014, through January 1, 2019, were included. Chronic neuropathic pain was defined as self-described pain for longer than 6 months after burn injury, not including pain due to preexisting illness/medications. Two analyses were undertaken: (1) determining risk factors for developing CNP among patients with hand/upper extremity burns, and (2) determining risk factors for developing refractory pain (ie, nonresponsive to treatment) among hand/upper extremity burn patients with CNP.

RESULTS

Of the 914 patients who met the inclusion criteria, 55 (6%) developed CNP after hand/upper extremity burns. Twenty-nine of these patients (53%) had refractory CNP. Significant risk factors for developing CNP after hand/upper extremity burns included history of substance abuse and tobacco use. Among CNP patients, significant risk factors for developing refractory pain included symptoms of burning sensations. In all CNP patients, gabapentin and ascorbic acid were associated with significant decreases in pain scores on follow-up.

CONCLUSIONS

Substance abuse and tobacco use may contribute to the development of CNP after hand/upper extremity burns. Those who developed refractory CNP were more likely to use the pain descriptor, burning sensations. Pharmacological pain management with gabapentin or pregabalin and ascorbic acid may provide the most relief of CNP symptoms.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Autologous fat grafting for nerve regeneration and neuropathic pain: current state from bench-to-bedside

Despite recent advances in microsurgical techniques, functional recovery following peripheral nerve injury remains slow and inadequate. Poor peripheral nerve regeneration not only leaves patients with significant impairments, but also commonly leads to the development of debilitating neuropathic pain. Recent research has demonstrated the potential therapeutic benefits of adipose-derived stem cells, to enhance nerve regeneration. However, clinical translation remains limited due to the current regulatory burdens of the US FDA. A reliable and immediately translatable alternative is autologous fat grafting, where native adipose-derived stem cells present in the transferred tissue can potentially act upon regenerating axons. This review presents the scope of adipose tissue-based therapies to enhance outcomes following peripheral nerve injury, specifically focusing on their role in regeneration and ameliorating neuropathic pain.

Irisin Gene Delivery Ameliorates Burn-Induced Sensory and Motor Neuropathy

Burn-related neuropathy is common and often involves pain, paresthesia, or muscle weakness. Irisin, an exercise-induced myokine after cleavage from its membrane precursor fibronectin type III domain-containing 5 (FNDC5), exhibits neuroprotective and anti-inflammatory activities. A rat model of third-degree burn on the right hind paw was used to investigate the therapeutic role of irisin/FNDC5. Rats received burn injury and were treated with intrathecal recombinant adenovirus containing the irisin sequence (Ad-irisin) at 3 weeks postburn. One week later, mechanical allodynia was examined. The expression of irisin in cerebrospinal fluid (CSF) was detected. Ipsilateral gastrocnemius muscle and lumbar spinal cord were also obtained for further investigation. Furthermore, the anti-apoptotic effect of recombinant irisin in SH-SY5Y cells was evaluated through tumor necrosis factor alpha (TNFα) stimulus to mimic burn injury. We noted intrathecal Ad-irisin attenuated pain sensitization and gastrocnemius muscle atrophy by modulating the level of irisin in CSF, and the expression of neuronal FNDC5/irisin and TNFα in the spinal cord. Ad-irisin also ameliorated neuronal apoptosis in both dorsal and ventral horns. Furthermore, recombinant irisin attenuated TNFα-induced SH-SY5Y cell apoptosis. In summary, irisin attenuated allodynia and muscle wasting by ameliorating neuroinflammation-induced neuronal apoptosis.

Occupational Hand-Related Injuries at a Major Tertiary Care Burn and Reconstructive Center in Pakistan

Introduction

Work-related hand injuries are usually a consequence of mechanical force on hand. This study retrospectively investigated the occurrence of work-related hand injuries in patients belonging to different age groups, gender, educational status, occupation, etc. 

Methodology

This cross-sectional study was conducted from October 2018 to December 2019 at the Department of Burn and Plastic Surgery, Holy Family Hospital, Rawalpindi, Pakistan. Demographic and clinical characteristics were gathered through a structured questionnaire based on relevant literature. Patients were assessed using the purposive sampling technique and written informed consent was taken from each participant. A p-value of <0.05 was considered statistically significant. Statistical tests were performed using the Statistical Package for the Social Sciences (SPSS).

Results

One hundred and twenty participants were interviewed, and 87.5% of patients did not have a vascular injury, and 62.5% of patients had an associated fracture. Over half of them (57.5%) had injuries of their dominant hands. Most of the injuries (67.5%) involved fingers while the rest of the injuries were found either in the palm or the dorsum of the hand. Among the causes of accidents, the majority didn't wear or wore unfitted gloves (76.6%) and the main causes of the hand injuries were related to defects in the workplace (53.3%). Lack of concentration (11.7%), wearing loose or unfitted clothes or jewelry (19.2%), lack of machine maintenance (29.2%), and a patient’s chronic disease (1.66%) were among the less frequent causes. 

Conclusion

It is important to understand the relationship between occupational and hand injuries. It provides an insight into the lack of protection and guidance of workers.

Burn-Induced Microglia Activation is Associated With Motor Neuron Degeneration and Muscle Wasting in Mice

INTRODUCTION

Burn injury (BI) leads to both systemic and neuro-inflammation and is associated with muscle wasting and weakness, which increase morbidity and mortality. Disuse atrophy is concomitantly present in BI patients. Most studies have focused on muscle with little attention to role of central nervous system (CNS) in the neuromuscular changes. We tested the hypothesis that BI-induced muscle wasting stems from CNS microglia activation and cytokines and chemokine release, which is associated with spinal ventral horn motor neuron degeneration.

METHODS

Body surface (35%) BI, immobilization alone (Immob), BI with immobilization (BI + Immob), or Sham BI were administered to mice. Spinal cord (L3-L4 segments) and skeletal muscle tissues were harvested on days 7 and 14 after perturbations to examine microglia, motor neuron, and skeletal muscle changes.

RESULTS

BI and BI + Immob significantly (P < 0.05) activated microglia, evidenced by its increased density around motor neurons, upregulated neuroinflammation-marker, translocator protein 18 kDa expression and inflammatory cytokines (interleukin-1β, tumor necrosis factor-α) and/or chemokines (CXCL2) expression at days 7 and 14. Ventral horn motor neurons apoptosis and downregulation were observed at both periods after BI and was significantly magnified by concomitant BI + Immob. BI and more prominently BI + Immob disintegrated and fragmented the pretzel-shaped synapse and was associated with significantly decreased gastrocnemius, tibialis, and soleus muscle masses.

CONCLUSION

BI induces microglia proliferation and activation (cytokine and chemokine release), degeneration of ventral horn motor neurons and muscle mass loss, all of which were accentuated by concomitant immobilization. The mechanisms connecting microglia activation and motor neuron degeneration to muscle mass loss require further delineation.

Prevalence and associated predictors for patients developing chronic neuropathic pain following burns

BACKGROUND

Chronic pain, unrelated to the burn itself, can manifest as a long-term complication in patients sustaining burn injuries. The purpose of this study was to determine the prevalence of chronic neuropathic pain (CNP) and compare burn characteristics between patients who developed CNP and patients without CNP who were treated at a burn center.

METHODS

A single-center, retrospective analysis of 1880 patients admitted to the adult burn center was performed from 1 January 2014 to 1 January 2019. Patients included were over the age of 15 years, sustained a burn injury and were admitted to the burn center. CNP was diagnosed clinically following burn injury. Patients were excluded from the definition of CNP if their pain was due to an underlying illness or medication. Comparisons between patients admitted to the burn center with no pain and patients admitted to the burn center who developed CNP were performed.

RESULTS

One hundred and thirteen of the 1880 burn patients developed CNP as a direct result of burn injury over 5 years with a prevalence of 6.01%. Patients who developed CNP were a significantly older median age (54 years vs. 46 years, p = 0.002), abused alcohol (29% vs. 8%, p < 0.001),abused substances (31% vs. 9%, p < 0.001), were current daily smokers (73% vs. 33%, p < 0.001), suffered more full-thickness burns (58% vs. 43%, p < 0.001), greater median percent of total body surface area (%TBSA) burns (6 vs. 3.5, p < 0.001), were more often intubated on mechanical ventilation (33% vs. 14%, p < 0.001), greater median number of surgeries (2 vs. 0, p < 0.001) and longer median hospital length of stay (LOS) (10 days vs. 3 days, p < 0.001), compared to those who did not develop CNP, respectively. Median patient follow-up was 27 months.

CONCLUSIONS

The prevalence of CNP over 5 years was 6.01% in the burn center. Older ages, alcohol abuse, substance abuse, current daily smoking, greater percent of total body surface area (%TBSA) burns, third degree burns, being intubated on mechanical ventilation, having more surgeries and longer hospital LOS were associated with developing CNP following burn injury, compared to patients who did not develop CNP following burn injury.

Spinal cord motor neuron plasticity accompanies second-degree burn injury and chronic pain

Burn injuries and associated complications present a major public health challenge. Many burn patients develop clinically intractable complications, including pain and other sensory disorders. Recent evidence has shown that dendritic spine neuropathology in spinal cord sensory and motor neurons accompanies central nervous system (CNS) or peripheral nervous system (PNS) trauma and disease. However, no research has investigated similar dendritic spine neuropathologies following a cutaneous thermal burn injury. In this retrospective investigation, we analyzed dendritic spine morphology and localization in alpha-motor neurons innervating a burn-injured area of the body (hind paw). To identify a molecular regulator of these dendritic spine changes, we further profiled motor neuron dendritic spines in adult mice treated with romidepsin, a clinically approved Pak1-inhibitor, or vehicle control at two postburn time points: Day 6 immediately after treatment, or Day 10 following drug withdrawal. In control treated mice, we observed an overall increase in dendritic spine density, including structurally mature spines with mushroom-shaped morphology. Pak1-inhibitor treatment reduced injury-induced changes to similar levels observed in animals without burn injury. The effectiveness of the Pak1-inhibitor was durable, since normalized dendritic spine profiles remained as long as 4 days despite drug withdrawal. This study is the first report of evidence demonstrating that a second-degree burn injury significantly affects motor neuron structure within the spinal cord. Furthermore, our results support the opportunity to study dendritic spine dysgenesis as a novel avenue to clarify the complexities of neurological disease following traumatic injury.

A Histologic Perspective on Electrical and Thermal Burn-Injured Human Skin

OBJECTIVE

To analyze specific spectroscopic (FT-Raman) and thermal (limiting oxygen index) aspects of skin samples exposed to electrical injury compared with thermal injury.

METHODS

An observational case-control study was conducted at the Dr Stanislaw Sakiel Center for Burns Treatment in Siemianowice, Silesia, Poland. A scanning electron microscope was used to diagnose and illustrate the topography of skin samples from electrical and thermal burns and the morphologic effects on damaged versus undamaged skin surfaces. In particular, researchers attempted to detect spectroscopic and thermal changes at the molecular level, namely, specific biomarkers of tissue degeneration and their regeneration under the influence of the applied modifiers (antioxidants and orthosilicic acid solutions).

RESULTS

Modification with L-ascorbic acid and hydrogel of orthosilicic acid caused an increase in the intensity of the amide I Raman peaks, whereas modification with sodium ascorbate and orthosilicic acid resulted in the separation of the band protein side chains (1,440-1,448 cm), which is a part of tissue regeneration. The best result was obtained when the skin was treated with 7% orthosilicic acid (limiting oxygen index, 26%).

CONCLUSIONS

Antioxidant treatment may be advantageous in minimizing injury in patients with thermal burns but not always in electrical burns.