Brief electrical stimulation and synkinesis after facial nerve crush injury: a randomized prospective animal study

Safe distance from facial nerve for bipolar coagulation in parotid surgery-Animal study

OBJECTIVE

Currently no data exist on what distance from facial nerve (FN) it is safe to perform bipolar cautery (BC) in parotid surgery, although frequently performed.

METHODS

The degree of damage was measured using continuous intraoperative neuromonitoring (cIONM, NIM™ 3, Medtronic) in 16 Wistar rats. Amplitude drop of at least 50% (A50) or a loss of signal (LOS) in the cIONM was defined as harmful; BC was performed in power range 20-60 W.

RESULTS

BC ≤30 W did not cause LOS (0/14 nerves). When applying 35 W, A50 occurred at 4 mm from FN and LOS was noted in 1 of 5 nerves. BC at a power of 40 to 60 W demonstrated LOS in all nerves (12/12) at a 5 mm distance.

CONCLUSION

BC up to 30 W can be safely applied up to 3 mm distance from FN. 40 to 60 W should be avoided and used only at a distance of over 6 mm from FN.

LEVEL OF EVIDENCE

NA/animal study. Laryngoscope, 2024.

Advancements in stimulation therapies for peripheral nerve regeneration

Soft-tissue injuries affecting muscles, nerves, vasculature, tendons, and ligaments often diminish the quality of life due to pain, loss of function, and financial burdens. Both natural healing and surgical interventions can result in scarring, which potentially may impede functional recovery and lead to persistent pain. Scar tissue, characterized by a highly disorganized fibrotic extracellular matrix, may serve as a physical barrier to regeneration and drug delivery. While approaches such as drugs, biomaterials, cells, external stimulation, and other physical forces show promise in mitigating scarring and promoting regenerative healing, their implementation remains limited and challenging. Ultrasound, laser, electrical, and magnetic forms of external stimulation have been utilized to promote soft tissue as well as neural tissue regeneration. After stimulation, neural tissues experience increased proliferation of Schwann cells, secretion of neurotropic factors, production of myelin, and growth of vasculature, all aimed at supporting axon regeneration and innervation. Yet, the outcomes of healing vary depending on the pathophysiology of the damaged nerve, the timing of stimulation following injury, and the specific parameters of stimulation employed. Increased treatment intensity and duration have been noted to hinder the healing process by inducing tissue damage. These stimulation modalities, either alone or in combination with nerve guidance conduits and scaffolds, have been demonstrated to promote healing. However, the literature currently lacks a detailed understanding of the stimulation parameters used for nerve healing applications. In this article, we aim to address this gap by summarizing existing reports and providing an overview of stimulation parameters alongside their associated healing outcomes.

[Progress of electrical stimulation to promote peripheral nerve regeneration]

This study reviews the latest progress on the research of electrical stimulation（ES） in peripheral nerve regeneration, summarizes the parameters in preclinical experiments and discusses the effect on nerve regeneration. A detailed description is given in the study of conditioning electrical stimulation and nerve conduit scaffolding technology combined with ES, which have been hotly researched in recent years.

Bioelectricity in dental medicine: a narrative review

BACKGROUND

Bioelectric signals, whether exogenous or endogenous, play crucial roles in the life processes of organisms. Recently, the significance of bioelectricity in the field of dentistry is steadily gaining greater attention.

OBJECTIVE

This narrative review aims to comprehensively outline the theory, physiological effects, and practical applications of bioelectricity in dental medicine and to offer insights into its potential future direction. It attempts to provide dental clinicians and researchers with an electrophysiological perspective to enhance their clinical practice or fundamental research endeavors.

METHODS

An online computer search for relevant literature was performed in PubMed, Web of Science and Cochrane Library, with the keywords "bioelectricity, endogenous electric signal, electric stimulation, dental medicine."

RESULTS

Eventually, 288 documents were included for review. The variance in ion concentration between the interior and exterior of the cell membrane, referred to as transmembrane potential, forms the fundamental basis of bioelectricity. Transmembrane potential has been established as an essential regulator of intercellular communication, mechanotransduction, migration, proliferation, and immune responses. Thus, exogenous electric stimulation can significantly alter cellular action by affecting transmembrane potential. In the field of dental medicine, electric stimulation has proven useful for assessing pulp condition, locating root apices, improving the properties of dental biomaterials, expediting orthodontic tooth movement, facilitating implant osteointegration, addressing maxillofacial malignancies, and managing neuromuscular dysfunction. Furthermore, the reprogramming of bioelectric signals holds promise as a means to guide organism development and intervene in disease processes. Besides, the development of high-throughput electrophysiological tools will be imperative for identifying ion channel targets and precisely modulating bioelectricity in the future.

CONCLUSIONS

Bioelectricity has found application in various concepts of dental medicine but large-scale, standardized, randomized controlled clinical trials are still necessary in the future. In addition, the precise, repeatable and predictable measurement and modulation methods of bioelectric signal patterns are essential research direction.

Effects of Electrical Stimulation on Facial Paralysis Recovery after Facial Nerve Injury: A Review on Preclinical and Clinical Studies

Various methods have been used to improve function and manage facial nerve injury. Although electrical stimulation therapy is frequently used to treat facial paralysis, its effects have been found to vary and no clear standards have been developed. The current review describes the results of preclinical and clinical studies evaluating the effectiveness of electrical stimulation therapy in promoting the recovery of a peripheral facial nerve injury. Evidence is presented showing the efficacy of electrical stimulation in promoting nerve regeneration after peripheral nerve injuries in both animal models and human patients. The ability of electrical stimulation to promote the recovery of facial paralysis was found to depend on the type of injury (compression or transection), the species of animal tested, the type of disease, the frequency and method of electrical stimulation, and the duration of the follow-up. Electrical stimulation, however, can also have potential negative outcomes, such as reinforcing synkinesis, including mistargeted axonal regrowth via inappropriate routes; excessive collateral axonal branching at the lesion site; and multiple innervations at neuromuscular junctions. Because of the inconsistencies among studies and the low quality of evidence, electrical stimulation therapy is not currently regarded as a primary treatment of facial paralysis in patients. However, understanding the effects of electrical stimulation, as determined in preclinical and clinical studies, is important for the potential validity of future research on electrical stimulation.

Advances in physical diagnosis and treatment of male erectile dysfunction

Erectile dysfunction (ED) is the most common male sexual dysfunction by far and the prevalence is increasing year after year. As technology advances, a wide range of physical diagnosis tools and therapeutic approaches have been developed for ED. At present, typical diagnostic devices include erection basic parameter measuring instrument, erection hardness quantitative analysis system, hemodynamic testing equipment, nocturnal erection measuring instrument, nerve conduction testing equipment, etc. At present, the most commonly used treatment for ED is pharmacological therapy represented by phosphodiesterase five inhibitors (PDE5i). As a first-line drug in clinical, PDE5i has outstanding clinical effects, but there are still some problems that deserve the attention of researchers, such as cost issues and some side effects, like visual disturbances, indigestion, myalgia, and back pain, as well as some non-response rates. Some patients have to consider alternative treatments. Moreover, the efficacy in some angiogenic EDs (diabetes and cardiovascular disease) has not met expectations, so there is still a need to continuously develop new methods that can improve hemodynamics. While drug have now been shown to be effective in treating ED, they only control symptoms and do not restore function in most cases. The increasing prevalence of ED also makes us more motivated to find safer, more effective, and simpler treatments. The exploration of relevant mechanisms can also serve as a springboard for the development of more clinically meaningful physiotherapy approaches. Therefore, people are currently devoted to studying the effects of physical therapy and physical therapy combined with drug therapy on ED. We reviewed the diagnosis of ED and related physical therapy methods, and explored the pathogenesis of ED. In our opinion, these treatment methods could help many ED patients recover fully or partially from ED within the next few decades.

Basic mechanisms of peripheral nerve injury and treatment via electrical stimulation

Previous studies on the mechanisms of peripheral nerve injury (PNI) have mainly focused on the pathophysiological changes within a single injury site. However, recent studies have indicated that within the central nervous system, PNI can lead to changes in both injury sites and target organs at the cellular and molecular levels. Therefore, the basic mechanisms of PNI have not been comprehensively understood. Although electrical stimulation was found to promote axonal regeneration and functional rehabilitation after PNI, as well as to alleviate neuropathic pain, the specific mechanisms of successful PNI treatment are unclear. We summarize and discuss the basic mechanisms of PNI and of treatment via electrical stimulation. After PNI, activity in the central nervous system (spinal cord) is altered, which can limit regeneration of the damaged nerve. For example, cell apoptosis and synaptic stripping in the anterior horn of the spinal cord can reduce the speed of nerve regeneration. The pathological changes in the posterior horn of the spinal cord can modulate sensory abnormalities after PNI. This can be observed in cases of ectopic discharge of the dorsal root ganglion leading to increased pain signal transmission. The injured site of the peripheral nerve is also an important factor affecting post-PNI repair. After PNI, the proximal end of the injured site sends out axial buds to innervate both the skin and muscle at the injury site. A slow speed of axon regeneration leads to low nerve regeneration. Therefore, it can take a long time for the proximal nerve to reinnervate the skin and muscle at the injured site. From the perspective of target organs, long-term denervation can cause atrophy of the corresponding skeletal muscle, which leads to abnormal sensory perception and hyperalgesia, and finally, the loss of target organ function. The mechanisms underlying the use of electrical stimulation to treat PNI include the inhibition of synaptic stripping, addressing the excessive excitability of the dorsal root ganglion, alleviating neuropathic pain, improving neurological function, and accelerating nerve regeneration. Electrical stimulation of target organs can reduce the atrophy of denervated skeletal muscle and promote the recovery of sensory function. Findings from the included studies confirm that after PNI, a series of physiological and pathological changes occur in the spinal cord, injury site, and target organs, leading to dysfunction. Electrical stimulation may address the pathophysiological changes mentioned above, thus promoting nerve regeneration and ameliorating dysfunction.

Effect of Ultrasound Therapy on Expression of Vascular Endothelial Growth Factor, Vascular Endothelial Growth Factor Receptors, CD31 and Functional Recovery After Facial Nerve Injury

Functional recovery is provided by some neurotrophic factors released from the near vicinity of the injury site. Ultrasound treatment is known to increase neurotrophic factor expression. This study was aimed at determining the effect of ultrasound treatment on the expression of vascular endothelial growth factor (VEGF), its receptors and new vessel formation after facial nerve injury. Sixty-four Wistar rats were divided into four groups: control (group 1), sham (group 2), facial-facial coaptation (group 3), and facial-facial coaptation and ultrasound treatment (group 4). Animals in each group were evaluated on the 14th and 28th days. Immunohistochemical staining and electrophysiological and gene-level evaluations were performed for the expression of VEGF and its receptors. When the results were evaluated, it was determined that VEGF, VEGFR1 (VEGF receptor 1), VEGFR2 (VEGF receptor 2) and CD31 levels were significantly higher in groups 3 and 4 compared with the control and sham groups. The increase in these values was more prominent after 28 d of ultrasound treatment than all groups. Electrophysiological results revealed similar evident functional improvement in group 4 with decreased latency and increased amplitudes compared with group 3. Our findings suggest that ultrasound treatment might promote injured facial nerve regeneration by stimulating release of VEGF and its receptors and may result in functional improvement.

Efficacy of LED Photobiomodulation for Functional and Axonal Regeneration After Facial Nerve Section-Suture

Facial nerve damage can lead to partial or total facial nerve palsy. Photobiomodulation has been reported to improve and accelerate functional recovery following peripheral nerve lesion, depending on the type of lesion and the light exposure parameters used. The aim of this study was to investigate the effects of infrared exposure on functional and axonal regeneration after section-suture of the distal branches of the facial nerve: the buccal and marginal mandibular branches and the distal pes. The animals underwent surgery and were irradiated with infrared light at 850 nm twice daily from day 1 to day 16. The recovery of facial function was then studied at both the behavioral and morphological levels. Behavioral analyses were performed by videoscoring with a high-speed camera and using various devices to assess the recovery of whisker movement on the lesioned side from day 1 to day 30. We also assessed nasal deviation toward the intact side and the ability to close the ipsilateral eyelid completely from day 1 to day 38 and from day 1 to day 50, respectively. For morphological analyses, we assessed the re-establishment of facial motoneuron labeling with Fluorogold®, an immunofluorescent retrograde marker of axonal transport injected into the vibrissae, on D10, D14 and D30. We found that whisker movements recovery was significantly faster in treated than in control mice. A complete disappearance of nasal deviation was observed at 2 weeks in infrared-treated lesioned mice and at 5 weeks in controls. Complete eyelid closure was observed 3 weeks after surgery in treated animals and 6 weeks after surgery in controls. Finally, normal fluorogold labeling of the facial nuclei complex was restored 30 days after surgery in the treated animals, but no such restoration was ever observed in control animals. In conclusion, our data show that IR treatment at a distal site has a significant positive effect on facial nerve recovery. These findings pave the way for the clinical use of infrared photobiomodulation in patients with nerve lesions.

Repairing whole facial nerve defects with xenogeneic acellular nerve grafts in rhesus monkeys

Acellular nerve allografts conducted via chemical extraction have achieved satisfactory results in bridging whole facial nerve defects clinically, both in terms of branching a single trunk and in connecting multiple branches of an extratemporal segment. However, in the clinical treatment of facial nerve defects, allogeneic donors are limited. In this experiment, we exposed the left trunk and multiple branches of the extratemporal segment in six rhesus monkeys and dissected a gap of 25 mm to construct a monkey model of a whole left nerve defect. Six monkeys were randomly assigned to an autograft group or a xenogeneic acellular nerve graft group. In the autograft group, the 25-mm whole facial nerve defect was immediately bridged using an autogenous ipsilateral great auricular nerve, and in the xenogeneic acellular nerve graft group, this was done using a xenogeneic acellular nerve graft with trunk-branches. Examinations of facial symmetry, nerve-muscle electrophysiology, retrograde transport of labeled neuronal tracers, and morphology of the regenerated nerve and target muscle at 8 months postoperatively showed that the faces of the monkey appeared to be symmetrical in the static state and slightly asymmetrical during facial movement, and that they could actively close their eyelids completely. The degree of recovery from facial paralysis reached House-Brackmann grade II in both groups. Compound muscle action potentials were recorded and orbicularis oris muscles responded to electro-stimuli on the surgical side in each monkey. FluoroGold-labeled neurons could be detected in the facial nuclei on the injured side. Immunohistochemical staining showed abundant neurofilament-200-positive axons and soluble protein-100-positive Schwann cells in the regenerated nerves. A large number of mid-graft myelinated axons were observed via methylene blue staining and a transmission electron microscope. Taken together, our data indicate that xenogeneic acellular nerve grafts from minipigs are safe and effective for repairing whole facial nerve defects in rhesus monkeys, with an effect similar to that of autologous nerve transplantation. Thus, a xenogeneic acellular nerve graft may be a suitable choice for bridging a whole facial nerve defect if no other method is available. The study was approved by the Laboratory Animal Management Committee and the Ethics Review Committee of the Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, China (approval No. 2018-D-1) on March 15, 2018.

Dental Pulp Cell Sheets Enhance Facial Nerve Regeneration via Local Neurotrophic Factor Delivery

An effective strategy for sustained neurotrophic factor (NTF) delivery to sites of peripheral nerve injury (PNI) would accelerate healing and enhance functional recovery, addressing the major clinical challenges associated with the current standard of care. In this study, scaffold-free cell sheets were generated using human dental pulp stem/progenitor cells, that endogenously express high levels of NTFs, for use as bioactive NTF delivery systems. Additionally, the effect of fibroblast growth factor 2 (FGF2) on NTF expression by dental pulp cell (DPC) sheets was evaluated. In vitro analysis confirmed that DPC sheets express high levels of NTF messenger RNA (mRNA) and proteins, and the addition of FGF2 to DPC sheet culture increased total NTF production by significantly increasing the cellularity of sheets. Furthermore, the DPC sheet secretome stimulated neurite formation and extension in cultured neuronal cells, and these functional effects were further enhanced when DPC sheets were cultured with FGF2. These neuritogenic results were reversed by NTF inhibition substantiating that DPC sheets have a positive effect on neuronal cell activity through the production of NTFs. Further evaluation of DPC sheets in a rat facial nerve crush injury model in vivo established that in comparison with untreated controls, nerves treated with DPC sheets had greater axon regeneration through the injury site and superior functional recovery as quantitatively assessed by compound muscle action potential measurements. This study demonstrates the use of DPC sheets as vehicles for NTF delivery that could augment the current methods for treating PNIs to accelerate regeneration and enhance the functional outcome. Impact statement The major challenges associated with current treatments of peripheral nerve injuries (PNIs) are prolonged repair times and insufficient functional recovery. Dental pulp stem/progenitor cells (DPCs) are known to endogenously express high levels of neurotrophic factors (NTFs), growth factors that enhance axon regeneration. In this study, we demonstrate that scaffold-free DPC sheets can act as effective carrier systems to facilitate the delivery and retention of NTF-producing DPCs to sites of PNIs and improve functional nerve regeneration. DPC sheets have high translational feasibility and could augment the current standard of care to enhance the quality of life for patients dealing with PNIs.

Electrical stimulation to enhance peripheral nerve regeneration: Update in molecular investigations and clinical translation

Peripheral nerve injuries are common and frequently result in incomplete functional recovery even with optimal surgical treatment. Permanent motor and sensory deficits are associated with significant patient morbidity and socioeconomic burden. Despite substantial research efforts to enhance peripheral nerve regeneration, few effective and clinically feasible treatment options have been found. One promising strategy is the use of low frequency electrical stimulation delivered perioperatively to an injured nerve at the time of surgical repair. Possibly through its effect of increasing intraneuronal cyclic AMP, perioperative electrical stimulation accelerates axon outgrowth, remyelination of regenerating axons, and reinnervation of end organs, even with delayed surgical intervention. Building on decades of experimental evidence in animal models, several recent, prospective, randomized clinical trials have affirmed electrical stimulation as a clinically translatable technique to enhance functional recovery in patients with peripheral nerve injuries requiring surgical treatment. This paper provides an updated review of the cellular physiology of electrical stimulation and its effects on axon regeneration, Level I evidence from recent prospective randomized clinical trials of electrical stimulation, and ongoing and future directions of research into electrical stimulation as a clinically feasible adjunct to surgical intervention in the treatment of patients with peripheral nerve injuries.

Electrical stimulation for neuroregeneration in urology: a new therapeutic paradigm

PURPOSE OF REVIEW

The present review highlights regenerative electrical stimulation (RES) as potential future treatment options for patients with nerve injuries leading to urological dysfunction, such as urinary incontinence, voiding dysfunction or erectile dysfunction. Additionally, it will highlight the mechanism of nerve injury and regeneration as well as similarities and differences between RES and current electrical stimulation treatments in urology, functional electrical stimulation (FES) and neuromodulation.

RECENT FINDINGS

It has been demonstrated that RES upregulates brain-derived neurotrophic factor (BDNF) and its receptor to facilitate neuroregeneration, facilitating accurate reinnervation of muscles by motoneurons. Further, RES upregulates growth factors in glial cells. Within the past 2 years, RES of the pudendal nerve upregulated BDNF in Onuf's nucleus, the cell bodies of motoneurons that course through the pudendal nerve and accelerated functional recovery in an animal model of stress urinary incontinence. Additionally, electrical stimulation of the vaginal tissue in an animal model of stress urinary incontinence accelerated functional recovery.

SUMMARY

RES has great potential but future research is needed to expand the potential beneficial effects of RES in the field of urology.

Peripheral nerve injury and myelination: Potential therapeutic strategies

Traumatic peripheral nerve injury represents a major clinical and public health problem that often leads to significant functional impairment and permanent disability. Despite modern diagnostic procedures and advanced microsurgical techniques, functional recovery after peripheral nerve repair is often unsatisfactory. Therefore, there is an unmet need for new therapeutic or adjunctive strategies to promote the functional recovery in nerve injury patients. In contrast to the central nervous system, Schwann cells in the peripheral nervous system play a pivotal role in several aspects of nerve repair such as degeneration, remyelination, and axonal growth. Several non-surgical approaches, including pharmacological, electrical, cell-based, and laser therapies, have been employed to promote myelination and enhance functional recovery after peripheral nerve injury. This review will succinctly discuss the potential therapeutic strategies in the context of myelination following peripheral neurotrauma.

4-Aminopyridine attenuates muscle atrophy after sciatic nerve crush injury in mice

INTRODUCTION

We recently demonstrated the beneficial effects of 4-aminopyridine (4-AP), a potassium channel blocker, in enhancing remyelination and recovery of nerve conduction velocity and motor function after sciatic nerve crush injury in mice. Although muscle atrophy occurs very rapidly after nerve injury, the effect of 4-AP on muscle atrophy and intrinsic muscle contractile function is largely unknown.

METHODS

Mice were assigned to sciatic nerve crush injury and no-injury groups and were followed for 3, 7, and 14 days with/without 4-AP or saline treatment. Morphological, functional, and transcriptional properties of skeletal muscle were assessed.

RESULTS

In addition to improving in vivo function, 4-AP significantly reduced muscle atrophy with increased muscle fiber diameter and contractile force. Reduced muscle atrophy was associated with attenuated expression of atrophy-related genes and increased expression of proliferating stem cells.

DISCUSSION

These findings provide new insights into the potential therapeutic benefits of 4-AP against nerve injury-induced muscle atrophy and dysfunction. Muscle Nerve 60: 192-201, 2019.