Functional electrical stimulation for bladder, bowel, and sexual function

Selective Facial Muscle Activation with Acute and Chronic Multichannel Cuff Electrode Implantation in a Feline Model

OBJECTIVES

Facial paralysis is a debilitating condition with substantial functional and psychological consequences. This feline-model study evaluates whether facial muscles can be selectively activated in acute and chronic implantation of 16-channel multichannel cuff electrodes (MCE).

METHODS

Two cats underwent acute terminal MCE implantation experiments, 2 underwent chronic MCE implantation in uninjured facial nerves (FN) and tested for 6 months, and 2 underwent chronic MCE implantation experiments after FN transection injury and tested for 3 months. The MCE were wrapped around the main trunk of the skeletonized FN, and data collection consisted of EMG thresholds, amplitudes, and selectivity of muscle activation.

RESULTS

In acute experimentation, activation of specific channels (ie, channels 1-3 and 6-8) resulted in selective activation of orbicularis oculi, whereas activation of other channels (ie, channels 4, 5, or 8) led to selective activation of levator auris longus with higher EMG amplitudes. MCE implantation yielded stable and selective facial muscle activation EMG thresholds and amplitudes up to a 5-month period. Modest selective muscle activation was furthermore obtained after a complete transection-reapproximating nerve injury after a 3-month recovery period and implantation reoperation. Chronic implantation of MCE did not lead to fibrosis on histology. Field steering was achieved to activate distinct facial muscles by sending simultaneous subthreshold currents to multiple channels, thus theoretically protecting against nerve damage from chronic electrical stimulation.

CONCLUSION

Our proof-of-concept results show the ability of an MCE, supplemented with field steering, to provide a degree of selective facial muscle stimulation in a feline model, even following nerve regeneration after FN injury.

LEVEL OF EVIDENCE

N/A.

Optogenetic Neuronal Stimulation Promotes Functional Recovery After Spinal Cord Injury

Although spinal cord injury (SCI) is the main cause of disability worldwide, there is still no definite and effective treatment method for this condition. Our previous clinical trials confirmed that the increased excitability of the motor cortex was related to the functional prognosis of patients with SCI. However, it remains unclear which cell types in the motor cortex lead to the later functional recovery. Herein, we applied optogenetic technology to selectively activate glutamate neurons in the primary motor cortex and explore whether activation of glutamate neurons in the primary motor cortex can promote functional recovery after SCI in rats and the preliminary neural mechanisms involved. Our results showed that the activation of glutamate neurons in the motor cortex could significantly improve the motor function scores in rats, effectively shorten the incubation period of motor evoked potentials and increase motor potentials’ amplitude. In addition, hematoxylin-eosin staining and nerve fiber staining at the injured site showed that accurate activation of the primary motor cortex could effectively promote tissue recovery and neurofilament growth (GAP-43, NF) at the injured site of the spinal cord, while the content of some growth-related proteins (BDNF, NGF) at the injured site increased. These results suggested that selective activation of glutamate neurons in the primary motor cortex can promote functional recovery after SCI and may be of great significance for understanding the neural cell mechanism underlying functional recovery induced by motor cortex stimulation.

Clinical Efficacy of Short-Term Peripheral Nerve Stimulation in Management of Facial Pain Associated With Herpes Zoster Ophthalmicus

Objective

Peripheral nerve stimulation may be an alternative option to treat severe facial pain. We assessed the application of peripheral nerve stimulation for pain management in patients with herpes zoster ophthalmicus.

Method

A retrospective analysis was conducted in patients suffering severe facial pain caused by ophthalmic herpetic lesions. We identified the change in pain severity before and after peripheral nerve stimulation for up to 12 months.

Results

Eighteen patients were enrolled. Their mean age was 70.8 ± 9.5 years. Fifteen patients presented with subacute pain for 1–3 months, and three patients suffered postherpetic neuralgia. Dramatic relief from pain was achieved in 83% of patients (15 out of 18) upon initial removal of the stimulator, with pain reduction of > 50%. The long-term analgesic effect was reported at the 6- and 12-month follow-ups, with reductions in the visual analog scale of 4.8 ± 1.2 (n = 18) and 5.4 ± 1.4 (n = 11), respectively. The prevalence of postherpetic neuralgia was 7% (1 out of 15) in the subacute pain group. No obvious adverse effect was observed.

Conclusion

Peripheral nerve stimulation may be an efficacious and safe approach for pain control in patients with herpes zoster ophthalmicus.

A therapeutic effect for males with spinal cord injury using abdominal functional electrical stimulation for sexual functioning

INTRODUCTION

Sexual functioning is a high priority for people with a spinal cord injury (SCI) yet this area has received little attention. Two SCI case reports are presented which suggests there may be greater potential for the recovery of sexual functioning than previously recognised.

CASE PRESENTATION

A 74-year-old SCI male (AIS D, C5/C6) and a 36-year-old SCI male (AIS A, T4/T5) were treated for neurogenic bowel using 6 weeks of abdominal FES (ABFES) (40 Hz, 300 µ pulse width (current typically 30-60 MA) simultaneously delivered (8 s contraction with 2 s ramps and 3 s off period) from both channels). The 74-year-old AIS D, C5/C6 participant reported improved strength and duration of erectile function after using ABFES for 3 weeks. The 36-year-old AIS A, T4/T5 participant reported improvements in ejaculatory function and urine flow. Both reported a reduction in time required for bowel management.

DISCUSSION

The findings could be attributed to an improved vascularisation of the abdominal area, an improved body image and self-esteem, direct innervation of nerves involved in parasympathetic pathways or innervation of the T11/T1 area implicated in the alternative psychogenic pathway. Both participants reported they had not used ABFES during sexual activity suggesting a therapeutic effect from the treatment.

Long-term feasibility and biocompatibility of directly microsurgically implanted intrafascicular electrodes in free roaming rabbits

Novel neural interfaces capable of reliably capturing electrical signals are crucial for the development of prostheses. Longitudinal intrafascicular electrodes (LIFEs) have been proposed as a promising technology, and their feasibility and biocompatibility need to be investigated for long-term implantation. In this study, custom-designed 95%Pt-5%Ir intrafascicular electrodes were implanted into the sciatic nerves of 14 rabbits using our novel direct microsurgical technique. The biocompatibility and their ability to record electrophysiological signals were serially investigated up to 9 months after implantation. Nerve tissues were examined using light and transmitted electron microscopy, and axon diameters were quantified, evaluated over time, and compared with sham-control (N = 4). Selective stimulation and stable recording properties of electrical signals were achieved by intrafascicular electrodes along the experimental period. While electrophysiological signal amplitude decreased by as early as 1 month after implantation (p < 0.05), the signal strength recovered to baseline levels by 3-5 months (p > 0.05). Axon diameter results showed a similar trend of initial decline (10.8% reduction, p < 0.01) followed by gradual recovery by 6 months (p > 0.05). Microstructural and ultrastructural analysis revealed modest tissue damage at the implantation site after implantation with gradual normalization over time. Intrafascicular electrodes implanted with direct microsurgical techniques demonstrated good biocompatibility and have great potential for long-term implantation and electrophysiological recordings. Though subtle tissue damage impaired ability to capture electrophysiological signals in the first 2 months, this damage gradually normalized after 3 months, and was fully normalized by 6 months. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 435-444, 2019.

Interfacing with the nervous system: a review of current bioelectric technologies

The aim of this study is to discuss the state of the art with regard to established or promising bioelectric therapies meant to alter or control neurologic function. We present recent reports on bioelectric technologies that interface with the nervous system at three potential sites-(1) the end organ, (2) the peripheral nervous system, and (3) the central nervous system-while exploring practical and clinical considerations. A literature search was executed on PubMed, IEEE, and Web of Science databases. A review of the current literature was conducted to examine functional and histomorphological effects of neuroprosthetic interfaces with a focus on end-organ, peripheral, and central nervous system interfaces. Innovations in bioelectric technologies are providing increasing selectivity in stimulating distinct nerve fiber populations in order to activate discrete muscles. Significant advances in electrode array design focus on increasing selectivity, stability, and functionality of implantable neuroprosthetics. The application of neuroprosthetics to paretic nerves or even directly stimulating or recording from the central nervous system holds great potential in advancing the field of nerve and tissue bioelectric engineering and contributing to clinical care. Although current physiotherapeutic and surgical treatments seek to restore function, structure, or comfort, they bear significant limitations in enabling cosmetic or functional recovery. Instead, the introduction of bioelectric technology may play a role in the restoration of function in patients with neurologic deficits.

PROJECT HEAVEN: Preoperative Training in Virtual Reality

A cephalosomatic anastomosis (CSA; also called HEAVEN: head anastomosis venture) has been proposed as an option for patients with neurological impairments, such as spinal cord injury (SCI), and terminal medical illnesses, for which medicine is currently powerless. Protocols to prepare a patient for life after CSA do not currently exist. However, methods used in conventional neurorehabilitation can be used as a reference for developing preparatory training. Studies on virtual reality (VR) technologies have documented VR's ability to enhance rehabilitation and improve the quality of recovery in patients with neurological disabilities. VR-augmented rehabilitation resulted in increased motivation towards performing functional training and improved the biopsychosocial state of patients. In addition, VR experiences coupled with haptic feedback promote neuroplasticity, resulting in the recovery of motor functions in neurologically-impaired individuals. To prepare the recipient psychologically for life after CSA, the development of VR experiences paired with haptic feedback is proposed. This proposal aims to innovate techniques in conventional neurorehabilitation to implement preoperative psychological training for the recipient of HEAVEN. Recipient's familiarity to body movements will prevent unexpected psychological reactions from occurring after the HEAVEN procedure.

Functional and Histological Effects of Chronic Neural Electrode Implantation

Objectives

Permanent injury to the cranial nerves can often result in a substantial reduction in quality of life. Novel and innovative interventions can help restore form and function in nerve paralysis, with bioelectric interfaces among the more promising of these approaches. The foreign body response is an important consideration for any bioelectric device as it influences the function and effectiveness of the implant. The purpose of this review is to describe tissue and functional effects of chronic neural implantation among the different categories of neural implants and highlight advances in peripheral and cranial nerve stimulation.

Data Sources: PubMed, IEEE, and Web of Science literature search.

Review Methods: A review of the current literature was conducted to examine functional and histologic effects of bioelectric interfaces for neural implants.

Results

Bioelectric devices can be characterized as intraneural, epineural, perineural, intranuclear, or cortical depending on their placement relative to nerves and neuronal cell bodies. Such devices include nerve‐specific stimulators, neuroprosthetics, brainstem implants, and deep brain stimulators. Regardless of electrode location and interface type, acute and chronic histological, macroscopic and functional changes can occur as a result of both passive and active tissue responses to the bioelectric implant.

Conclusion

A variety of chronically implantable electrodes have been developed to treat disorders of the peripheral and cranial nerves, to varying degrees of efficacy. Consideration and mitigation of detrimental effects at the neural interface with further optimization of functional nerve stimulation will facilitate the development of these technologies and translation to the clinic.

Level of Evidence

3.

Epidural Spinal Stimulation to Improve Bladder, Bowel, and Sexual Function in Individuals With Spinal Cord Injuries: A Framework for Clinical Research

While some recent studies that apply epidural spinal cord stimulation (SCS) have demonstrated a breakthrough in improvement of the health and quality of the life of persons with spinal cord injury (SCI), the numbers of people who have received SCS are small. This is in sharp contrast to the thousands of persons worldwide living with SCI who have no practical recourse or hope of recovery of lost functions. Thus, the vision is to understand the full potential of this new intervention and to determine if it is safe and effective in a larger cohort, and if it is scalable so that it can be made available to all those who might benefit. To achieve this vision, the National Institute of Biomedical Imaging and Bioengineering called for and organized a consortium of multiple stakeholder groups: foundations addressing paralysis, federal and public agencies, industrial partners, academicians, and researchers, all interested in the same goal. Based on input from consortium participants, we have reasoned that a first step is to define a scalable SCS approach that is effective in restoring lost autonomic physiology, specifically bladder, bowel, and sexual function. These functions are most critical for improving the quality of life of persons living with SCI. This report outlines a framework for conducting the research needed to define such an effective SCS procedure that might seek Food and Drug Administration approval and be implemented at the population level.

Selective stimulation of facial muscles with a penetrating electrode array in the feline model

OBJECTIVES/HYPOTHESIS

Permanent facial nerve injury is a difficult challenge for both patients and physicians given its potential for debilitating functional, cosmetic, and psychological sequelae. Although current surgical interventions have provided considerable advancements in facial nerve rehabilitation, they often fail to fully address all impairments. We aim to introduce an alternative approach to facial nerve rehabilitation.

STUDY DESIGN

Acute experiments in animals with normal facial function.

METHODS

The study included three anesthetized cats. Four facial muscles (levator auris longus, orbicularis oculi, nasalis, and orbicularis oris) were monitored with a standard electromyographic (EMG) facial nerve monitoring system with needle electrodes. The main trunk of the facial nerve was exposed, and a 16-channel penetrating electrode array was placed into the nerve. Electrical current pulses were delivered to each stimulating electrode individually. Elicited EMG voltage outputs were recorded for each muscle.

RESULTS

Stimulation through individual channels selectively activated restricted nerve populations, resulting in selective contraction of individual muscles. Increasing stimulation current levels resulted in increasing EMG voltage responses. Typically, selective activation of two or more distinct muscles was successfully achieved via a single placement of the multi-channel electrode array by selection of appropriate stimulation channels.

CONCLUSION

We have established in the animal model the ability of a penetrating electrode array to selectively stimulate restricted fiber populations within the facial nerve and to selectively elicit contractions in specific muscles and regions of the face. These results show promise for the development of a facial nerve implant system.

LEVEL OF EVIDENCE

N/A.Laryngoscope, 2016 127:460-465, 2017.

New pharmacological approaches against chronic bowel and bladder problems in paralytics

Spinal cord injury (SCI) leads generally to an irreversible loss of sensory functions and voluntary motor control below injury level. Cures that could repair SCI and/or restore voluntary walking have not been yet developed nor commercialized. Beyond the well-known loss of walking capabilities, most SCI patients experience also a plethora of motor problems and health concerns including specific bladder and bowel dysfunctions. Indeed, chronic constipation and urinary retention, two significant life-threatening complications, are typically found in patients suffering of traumatic (e.g., falls or car accidents) or non-traumatic SCI (e.g., multiple sclerosis, spinal tumors). Secondary health concerns associated with these dysfunctions include hemorrhoids, abdominal distention, altered visceral sensitivity, hydronephrosis, kidney failure, urinary tract infections, sepsis and, in some cases, cardiac arrest. Consequently, individuals with chronic SCI are forced to regularly seek emergency and critical care treatments when some of these conditions occur or become intolerable. Increasing evidence supports the existence of a novel experimental approach that may be capable of preventing the occurrence or severity of bladder and bowel problems. Indeed, recent findings in animal models of SCI have revealed that, despite paraplegia or tetraplegia, it remains possible to elicit episodes of micturition and defecation by acting pharmacologically or electrically upon specialized lumbosacral neuronal networks, namely the spinal or sacral micturition center (SMC) and lumbosacral defecation center (LDC). Daily activation of SMC and LDC neurons could potentially become, new classes of minimally invasive treatments (i.e., if orally active) against these dysfunctions and their many life-threatening complications.

Electrical Stimulation and Motor Recovery

In recent years, several investigators have successfully regenerated axons in animal spinal cords without locomotor recovery. One explanation is that the animals were not trained to use the regenerated connections. Intensive locomotor training improves walking recovery after spinal cord injury (SCI) in people, and >90% of people with incomplete SCI recover walking with training. Although the optimal timing, duration, intensity, and type of locomotor training are still controversial, many investigators have reported beneficial effects of training on locomotor function. The mechanisms by which training improves recovery are not clear, but an attractive theory is available. In 1949, Donald Hebb proposed a famous rule that has been paraphrased as “neurons that fire together, wire together.” This rule provided a theoretical basis for a widely accepted theory that homosynaptic and heterosynaptic activity facilitate synaptic formation and consolidation. In addition, the lumbar spinal cord has a locomotor center, called the central pattern generator (CPG), which can be activated nonspecifically with electrical stimulation or neurotransmitters to produce walking. The CPG is an obvious target to reconnect after SCI. Stimulating motor cortex, spinal cord, or peripheral nerves can modulate lumbar spinal cord excitability. Motor cortex stimulation causes long-term changes in spinal reflexes and synapses, increases sprouting of the corticospinal tract, and restores skilled forelimb function in rats. Long used to treat chronic pain, motor cortex stimuli modify lumbar spinal network excitability and improve lower extremity motor scores in humans. Similarly, epidural spinal cord stimulation has long been used to treat pain and spasticity. Subthreshold epidural stimulation reduces the threshold for locomotor activity. In 2011, Harkema et al. reported lumbosacral epidural stimulation restores motor control in chronic motor complete patients. Peripheral nerve or functional electrical stimulation (FES) has long been used to activate sacral nerves to treat bladder and pelvic dysfunction and to augment motor function. In theory, FES should facilitate synaptic formation and motor recovery after regenerative therapies. Upcoming clinical trials provide unique opportunities to test the theory.

Optical stimulation for restoration of motor function after spinal cord injury

Spinal cord injury can be defined as a loss of communication between the brain and the body due to disrupted pathways within the spinal cord. Although many promising molecular strategies have emerged to reduce secondary injury and promote axonal regrowth, there is still no effective cure, and recovery of function remains limited. Functional electrical stimulation (FES) represents a strategy developed to restore motor function without the need for regenerating severed spinal pathways. Despite its technological success, however, FES has not been widely integrated into the lives of spinal cord injury survivors. In this review, we briefly discuss the limitations of existing FES technologies. Additionally, we discuss how optogenetics, a rapidly evolving technique used primarily to investigate select neuronal populations within the brain, may eventually be used to replace FES as a form of therapy for functional restoration after spinal cord injury.

Restoration of motor function following spinal cord injury via optimal control of intraspinal microstimulation: toward a next generation closed-loop neural prosthesis

Movement is planned and coordinated by the brain and carried out by contracting muscles acting on specific joints. Motor commands initiated in the brain travel through descending pathways in the spinal cord to effector motor neurons before reaching target muscles. Damage to these pathways by spinal cord injury (SCI) can result in paralysis below the injury level. However, the planning and coordination centers of the brain, as well as peripheral nerves and the muscles that they act upon, remain functional. Neuroprosthetic devices can restore motor function following SCI by direct electrical stimulation of the neuromuscular system. Unfortunately, conventional neuroprosthetic techniques are limited by a myriad of factors that include, but are not limited to, a lack of characterization of non-linear input/output system dynamics, mechanical coupling, limited number of degrees of freedom, high power consumption, large device size, and rapid onset of muscle fatigue. Wireless multi-channel closed-loop neuroprostheses that integrate command signals from the brain with sensor-based feedback from the environment and the system's state offer the possibility of increasing device performance, ultimately improving quality of life for people with SCI. In this manuscript, we review neuroprosthetic technology for improving functional restoration following SCI and describe brain-machine interfaces suitable for control of neuroprosthetic systems with multiple degrees of freedom. Additionally, we discuss novel stimulation paradigms that can improve synergy with higher planning centers and improve fatigue-resistant activation of paralyzed muscles. In the near future, integration of these technologies will provide SCI survivors with versatile closed-loop neuroprosthetic systems for restoring function to paralyzed muscles.

Interfaces with the peripheral nerve for the control of neuroprostheses

Nervous system injuries lead to loss of control of sensory, motor, and autonomic functions of the affected areas of the body. Provided the high amount of people worldwide suffering from these injuries and the impact on their everyday life, numerous and different neuroprostheses and hybrid bionic systems have been developed to restore or partially mimic the lost functions. A key point for usable neuroprostheses is the electrode that interfaces the nervous system and translates not only motor orders into electrical outputs that activate the prosthesis but is also able to transform sensory information detected by the machine into signals that are transmitted to the central nervous system. Nerve electrodes have been classified with regard to their invasiveness in extraneural, intraneural, and regenerative. The more invasive is the implant the more selectivity of interfacing can be reached. However, boosting invasiveness and selectivity may also heighten nerve damage. This chapter provides a general overview of nerve electrodes as well as the state-of-the-art of their biomedical applications in neuroprosthetic systems.