The Effects of Intraoperative Electrical Stimulation on Regeneration and Recovery After Nerve Isograft Repair in a Rat Model

Types of Short-Duration Electrical Stimulation-Induced Efficiency in the Axonal Regeneration and Recovery: Comparative in Vivo Study in Rat Model of Repaired Sciatic Nerve and its Tibial Branch after Transection Injury

The restoration of adequate function and sensation in nerves following an injury is often insufficient. Electrical stimulation (ES) applied during nerve repair can promote axon regeneration, which may enhance the likelihood of successful functional recovery. However, increasing operation time and complexity are associated with limited clinical use of ES. This study aims to better assess whether short-duration ES types (voltage mode vs. current mode) are able to produce enhanced regenerative activity following peripheral nerve repair in rat models. Wistar rats were randomly divided into 3 groups: no ES (control), 30-minute ES with a current pulse, and 30-minute ES with a voltage pulse. All groups underwent sciatic nerve transection and repair using a silicone tube to bridge the 6-mm gap between the stumps. In the 2 groups other than the control, ES was applied after the surgical repair. Outcomes were evaluated using electrophysiology, histology, and serial walking track analysis. Biweekly walking tracks test over 12 weeks revealed that subjects that underwent ES experienced more rapid functional improvement than subjects that underwent repair alone. Electrophysiological analysis of the newly intratubular sciatic nerve at week 12 revealed strong motor function recovery in rats that underwent 30-minute ES. Histologic analysis of the sciatic nerve and its tibial branch at 12 weeks demonstrated robust axon regrowth in all groups. Both types of short-duration ES applied during nerve repair can promote axon regrowth and enhance the chances of successful functional recovery.

Electrical Stimulation: How It Works and How to Apply It

Electrical stimulation is emerging as a perioperative strategy to improve peripheral nerve regeneration and enhance functional recovery. Despite decades of research, new insights into the complex multifaceted mechanisms of electrical stimulation continue to emerge, providing greater understanding of the neurophysiology of nerve regeneration. In this study, we summarize what is known about how electrical stimulation modulates the molecular cascades and cellular responses innate to nerve injury and repair, and the consequential effects on axonal growth and plasticity. Further, we discuss how electrical stimulation is delivered in preclinical and clinical studies and identify knowledge gaps that may provide opportunities for optimization.

Therapeutic Electrical Stimulation for Surgeons: How it Works and How to Apply it

Electrical stimulation (ES) enhances peripheral nerve inherent regeneration capacity by promoting accelerated axonal outgrowth and selectivity toward appropriate motor and sensory targets. These effects lead to significantly improved functional outcomes and shorter recovery time. Electrical stimulation can be applied intra-operatively or immediately post-operatively. Active clinical trials are looking into additional areas of application, length of stimulation, and functional outcomes.

Physiology of Nerve Regeneration: Key Factors Affecting Clinical Outcomes

Functional recovery after peripheral nerve injuries is disappointing despite surgical advances in nerve repair. This review summarizes the relatively short window of opportunity for successful nerve regeneration due to the decline in the expression of growth-associated genes and in turn, the decline in regenerative capacity of the injured neurons and the support provided by the denervated Schwann cells, and the atrophy of denervated muscles. Brief, low-frequency electrical stimulation and post-injury exercise regimes ameliorate these deficits in animal models and patients, but the misdirection of regenerating nerve fibers compromises functional recovery and remains an important area of future research.

Enhanced nerve function recovery in radial nerve palsy patients with humerus shaft fracture: a randomized study of low-frequency pulse electrical stimulation combined with exercise therapy

Objective

To evaluate the effect of low-frequency pulse electrical stimulation plus exercise therapy on nerve function recovery in patients with radial nerve palsy after humerus shaft fracture.

Methods

A total of 110 patients with humerus shaft fracture and radial nerve injury admitted to our hospital from January 2017 to December 2021 were recruited. They were randomized to receive either conventional exercise therapy (control group) or conventional exercise therapy plus low-frequency pulse electrical stimulation (study group) according to the random number table method, with 55 cases in each. Clinical efficacy, muscle strength recovery, nerve conduction velocity (MCV), amplitude, wrist joint, and elbow joint activities of patients were analyzed and compared.

Results

Patients with low frequency stimulation (LFS) showed significantly higher treatment effectiveness (89.09%) than those with exercise therapy only (69.09%). The incorporation of LFS with exercise therapy provided more enhancement in the muscle strength of wrist extensor and total finger extensor in patients when compared with a mere exercise intervention, suggesting better muscle function recovery of patients produced by LFS. Moreover, a significant increase in MCV and its amplitude was observed in all included patients, among which those receiving LFS showed a greater escalation of MCV and its amplitude. Following a treatment duration of 6 months, more patients in the LFS cohort were reported to achieve a wrist extension and elbow extension with an angle over 45° than the controls. There was no notable variance in adverse responses noted between the two patient groups.

Conclusion

In patients afflicted with humerus shaft fracture and radial nerve injury, the amalgamation of exercise therapy with low-frequency pulse electrical stimulation can significantly improve clinical efficacy, promote nerve function, and muscle strength recovery, and features a high safety profile.

Relevance to clinical practice

The combination of exercise therapy and low-frequency pulsed electrical stimulation can notably improve the promotion of neurologic function and muscle strength recovery in patients with humerus shaft fractures and radial nerve injuries with a high degree of safety.Clinical trial registration:https://www.researchregistry.com, identifier researchregistry9461.

A Perspective on Electrical Stimulation and Sympathetic Regeneration in Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are common and devastating. The current standard of care relies on the slow and inefficient process of nerve regeneration after surgical intervention. Electrical stimulation (ES) has been shown to both experimentally and clinically result in improved regeneration and functional recovery after PNI for motor and sensory neurons; however, its effects on sympathetic regeneration have never been studied. Sympathetic neurons are responsible for a myriad of homeostatic processes that include, but are not limited to, blood pressure, immune response, sweating, and the structural integrity of the neuromuscular junction. Almost one quarter of the axons in the sciatic nerve are from sympathetic neurons, and their importance in bodily homeostasis and the pathogenesis of neuropathic pain should not be underestimated. Therefore, as ES continues to make its way into patient care, it is not only important to understand its impact on all neuron subtypes, but also to ensure that potential adverse effects are minimized. This piece gives an overview of the effects of ES in animals models and in humans while offering a perspective on the potential effects of ES on sympathetic axon regeneration.

Brief Electrical Stimulation Promotes Recovery after Surgical Repair of Injured Peripheral Nerves

Injured peripheral nerves regenerate their axons in contrast to those in the central nervous system. Yet, functional recovery after surgical repair is often disappointing. The basis for poor recovery is progressive deterioration with time and distance of the growth capacity of the neurons that lose their contact with targets (chronic axotomy) and the growth support of the chronically denervated Schwann cells (SC) in the distal nerve stumps. Nonetheless, chronically denervated atrophic muscle retains the capacity for reinnervation. Declining electrical activity of motoneurons accompanies the progressive fall in axotomized neuronal and denervated SC expression of regeneration-associated-genes and declining regenerative success. Reduced motoneuronal activity is due to the withdrawal of synaptic contacts from the soma. Exogenous neurotrophic factors that promote nerve regeneration can replace the endogenous factors whose expression declines with time. But the profuse axonal outgrowth they provoke and the difficulties in their delivery hinder their efficacy. Brief (1 h) low-frequency (20 Hz) electrical stimulation (ES) proximal to the injury site promotes the expression of endogenous growth factors and, in turn, dramatically accelerates axon outgrowth and target reinnervation. The latter ES effect has been demonstrated in both rats and humans. A conditioning ES of intact nerve days prior to nerve injury increases axonal outgrowth and regeneration rate. Thereby, this form of ES is amenable for nerve transfer surgeries and end-to-side neurorrhaphies. However, additional surgery for applying the required electrodes may be a hurdle. ES is applicable in all surgeries with excellent outcomes.

Stem Cell Scaffolds for the Treatment of Spinal Cord Injury-A Review

Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.

Lidocaine Nerve Block Diminishes the Effects of Therapeutic Electrical Stimulation to Enhance Nerve Regeneration in Rats

BACKGROUND

Although electrical stimulation (ES) can improve nerve regeneration, the impact of nerve block, such as lidocaine (Lido), on the therapeutic benefits of ES remains unclear. We used a rat tibial nerve transection-and-repair model to explore how either preoperative (PreOp) or postoperative (PostOp) nerve block affects ES-related improvement in regeneration.

METHODS

Lewis rats were used in 1 of 2 studies. The first evaluated the effects of extraneural Lido on both healthy and injured nerves. In the second study, rats were randomized to 5 experimental groups: No ES (negative control), PreOp Lido, ES + PreOp Lido, PostOp + ES, and ES (positive control). All groups underwent tibial nerve transection and repair. In both studies, nerves were harvested for histological analysis of regeneration distal to the injury site.

RESULTS

Application of extraneural Lido did not damage healthy or injured nerve based on qualitative histological observations. In the context of nerve transection and repair, the ES group exhibited improved axon regeneration at 21 days measured by the total number of myelinated fibers compared with No ES. Fiber density and percentage of neural tissue in the ES group were greater than those in both No ES and PreOp Lido + ES groups. ES + PostOp Lido was not different from No ES or ES group.

CONCLUSIONS

Extraneural application of Lido did not damage nerves. Electrical stimulation augmented nerve regeneration, but Lido diminished the ES-related improvement in nerve regeneration. Clinical studies on the effects of ES to nerve regeneration may need to consider nerve block as a variable affecting ES outcome.

Electrical stimulation therapy for peripheral nerve injury

Peripheral nerve injury is common and frequently occurs in extremity trauma patients. The motor and sensory impairment caused by the injury will affect patients' daily life and social work. Surgical therapeutic approaches don't assure functional recovery, which may lead to neuronal atrophy and hinder accelerated regeneration. Rehabilitation is a necessary stage for patients to recover better. A meaningful role in non-pharmacological intervention is played by rehabilitation, through individualized electrical stimulation therapy. Clinical studies have shown that electrical stimulation enhances axon growth during nerve repair and accelerates sensorimotor recovery. According to different effects and parameters, electrical stimulation can be divided into neuromuscular, transcutaneous, and functional electrical stimulation. The therapeutic mechanism of electrical stimulation may be to reduce muscle atrophy and promote muscle reinnervation by increasing the expression of structural protective proteins and neurotrophic factors. Meanwhile, it can modulate sensory feedback and reduce neuralgia by inhibiting the descending pathway. However, there are not many summary clinical application parameters of electrical stimulation, and the long-term effectiveness and safety also need to be further explored. This article aims to explore application methodologies for effective electrical stimulation in the rehabilitation of peripheral nerve injury, with simultaneous consideration for fundamental principles of electrical stimulation and the latest technology. The highlight of this paper is to identify the most appropriate stimulation parameters (frequency, intensity, duration) to achieve efficacious electrical stimulation in the rehabilitation of peripheral nerve injury.

The Effect of Electrical Stimulation on Nerve Regeneration Following Peripheral Nerve Injury

Peripheral nerve injuries (PNI) are common and often result in lifelong disability. The peripheral nervous system has an inherent ability to regenerate following injury, yet complete functional recovery is rare. Despite advances in the diagnosis and repair of PNIs, many patients suffer from chronic pain, and sensory and motor dysfunction. One promising surgical adjunct is the application of intraoperative electrical stimulation (ES) to peripheral nerves. ES acts through second messenger cyclic AMP to augment the intrinsic molecular pathways of regeneration. Decades of animal studies have demonstrated that 20 Hz ES delivered post-surgically accelerates axonal outgrowth and end organ reinnervation. This work has been translated clinically in a series of randomized clinical trials, which suggest that ES can be used as an efficacious therapy to improve patient outcomes following PNIs. The aim of this review is to discuss the cellular physiology and the limitations of regeneration after peripheral nerve injuries. The proposed mechanisms of ES protocols and how they facilitate nerve regeneration depending on timing of administration are outlined. Finally, future directions of research that may provide new perspectives on the optimal delivery of ES following PNI are discussed.

Promoting Nerve Regeneration: Electrical Stimulation, Gene Therapy, and Beyond

Peripheral nerve injuries often result in life-altering functional deficits even with optimal management. Unlike the central nervous system, peripheral nerves have the ability to regenerate lost axons after injury; however, axonal regeneration does not equate to full restoration of function. To overcome this physiological shortcoming, advances in nerve regeneration and repair are paramount, including electrical stimulation, gene therapy, and surgical technique advancements.