Restoration of paralyzed orbicularis oculi muscle function by controlled electrical current.

A canine model of facial nerve paralysis was studied to apply controlled electrical current to the peripherally denervated orbicularis oculi muscle, in the attempt to effectively restore the absent function of this denervated muscle. After unilateral facial nerve neurotmesis was performed in eight dogs, the denervated orbicularis oculi muscles of four dogs were electrically stimulated for 75 postoperative days (40 min/day). Denervated and normal orbicularis oculi muscles were electrophysiologically studied and compared with the Student t test. During the study period, minimum closure of denervated treated orbicularis oculi muscles was evoked with average stimulus strength (80-ms duration) of 1.61 +/- 0.22 log mA x ms, not significantly different from that of denervated nontreated or normal orbicularis oculi muscles. From days 10 through 30 only, maximum closure of denervated treated orbicularis oculi muscles was achieved with mean pulse strength (80-ms duration) of 2.37 +/- 0.09 log mA x ms, significantly lower (P less than .01) than that evoking the same type of contraction from denervated nontreated muscles (80-ms duration, mean 2.83 +/- 0.10 log mA x ms). In addition, denervated treated muscle pulse strength eliciting maximum contraction was not significantly different from that of normal orbicularis oculi muscles during the same period. This finding was not observed, however, from day 40 through the end of the study. This investigation demonstrates (1) the transient reversal of denervation changes of paralyzed orbicularis oculi muscle by daily electrical stimulation, and (2) the feasibility of restoring orbicularis oculi muscle function by controlled electrical current.     

Restoration of Paralyzed Orbicularis Oculi Muscle Function by Controlled Electrical Current

A canine model of facial nerve paralysis was studied to apply controlled electrical current to the peripherally denervated orbicularis oculi muscle, in the attempt to effectively restore the absent function of this denervated muscle. After unilateral facial nerve neurotmesis was performed in eight dogs, the denervated orbicularis oculi muscles of four dogs were electrically stimulated for 75 postoperative days (40 min/day). Denervated and normal orbicularis oculi muscles were electrophysiologically studied and compared with the Student t test. During the study period, minimum closure of denervated treated orbicularis oculi muscles was evoked with average stimulus strength (80-ms duration) of 1.61 ± 0.22 log mA × ms. not significantly different from that of denervated nontreated or normal orbicularis oculi muscles. From days 10 through 30 only, maximum closure of denervated treated orbicularis oculi muscles was achieved with mean pulse strength (80-ms duration) of 2.37 ± 0.09 log mA × ms, significantly lower (P <. 01) than that evoking the same type of contraction from denervated nontreated muscles (80-ms duration, mean 2.83 ± 0.10 log mA × ms). In addition, denervated treated muscle pulse strength eliciting maximum contraction was not significantly different from that of normal orbicularis oculi muscles during the same period. This finding was not observed, however, from day 40 through the end of the study. This investigation demonstrates (1) the transient reversal of denervation changes of paralyzed orbicularis oculi muscle by daily electrical stimulation, and (2) the feasibility of restoring orbicularis oculi muscle function by controlled electrical current.     

Conservative management of peripheral nerve injuries utilizing selective electrical stimulation of denervated muscle with exponentially progressive - - current forms

One objective of the conservative management of peripheral nerve injuries is to delay and minimize denervation atrophy of the muscle parenchyma. A properly administered program of selective electrical stimulation of denervated muscle may appreciably delay denervation atrophy. Current forms having slowly increasing intensities (exponentially progressive currents) are capable of selective stimulation of denervated muscle while awarding the stimulation of both the innervated muscles and the intact sensory nerves. The present paper discusses the rationale for the utilization of selective electrical stimulation of denervated muscle following peripheral nerve injuries.J Orthop Sports Phys Ther 1985;7(1):11-15.     

Communication between functional and denervated muscles using radiofrequency.

OBJECTIVE: This article focuses on establishing communication between a functional muscle and a denervated muscle using a radiofrequency communications link. The ultimate objective of the project is to restore the eye blink in patients with facial nerve paralysis. STUDY DESIGN AND SETTING: Two sets of experiments were conducted using the gastrocnemius leg muscles of Sprague-Dawley rats. In the initial tests, varying magnitudes of voltages ranging from 0.85 to 2.5 V were applied directly to a denervated muscle to determine the voltage required to produce visible contraction. The second set of experiments was then conducted to determine the voltage output from an in vivo muscle contraction that could be sensed and used to coordinate a signal for actuation of a muscle in a separate limb. After designing the appropriate external communication circuitry, a third experiment was performed to verify that a signal between a functional and a denervated muscle can be generated and used as a stimulus. RESULTS: Voltages below 2 V at a 10-millisecond pulse width elicited a gentle, controlled contraction of the denervated muscle in vivo. It was also observed that with longer pulse widths, higher stimulation voltages were required to produce sufficient contractions. CONCLUSION: It is possible to detect contraction of a muscle, use this to generate a signal to an external base station, and subsequently cause a separate, denervated muscle to contract in response to the signal. SIGNIFICANCE: This demonstration in vivo of a signaling system for pacing of electrical stimulation of 1 muscle to spontaneous contraction of another, separate muscle, using radiofrequency communication without direct connection, may be used in numerous ways to overcome nerve damage.     

Electrical stimulation treatment of dog's denervated orbicularis oculi muscle

In this investigation, the electrophysiology and pathology of denervated orbicularis oculi muscles have been studied in dogs during chronic electrical stimulation. The orbicularis oculi muscles were unilaterally denervated in 8 dogs, and 4 of these muscles were directly stimulated on a daily basis for 75 days. No difference in minimum stimulus intensities evoking orbicularis oculi muscle twitch contraction appeared between denervated treated and nontreated muscles. A significant reduction of minimum stimulus intensities evoking upper eyelid complete closure (blink), however, was found in the denervated treated muscles between 10 and 30 days (p less than 0.01). At 28 and 75 days, orbicularis oculi muscle biopsies showed no difference in muscle fiber diameter between denervated treated and nontreated muscles. At 75 days, type II muscle fiber distribution, however, was significantly increased in denervated treated muscles compared with denervated nontreated muscles (p less than 0.01). These findings of orbicularis oculi muscle electrophysiology were consistent with a transient reversal of denervation changes by electrical stimulation, partially supported by muscle biopsies.     

Multi-channel orbicularis oculi stimulation to restore eye-blink function in facial paralysis.

Facial paralysis due to facial nerve injury results in the loss of function of the muscles of the hemiface. The most serious complication in extreme cases is the loss of vision. In this study, we compared the effectiveness of single- and multiple-channel electrical stimulation to restore a complete and cosmetically acceptable eye blink. We established bilateral orbicularis oculi muscle (OOM) paralysis in eight dogs; the OOM of one side was directly stimulated using single-channel electrical stimulation and the opposite side was stimulated using multi-channel electrical stimulation. The changes in the palpebral fissure and complete palpebral closure were measured. The difference in current intensities between the multi-channel and single-channel simulation groups was significant, while only multi-channel stimulation produced complete eyelid closure. The latest electronic stimulation circuitry with high-quality implantable electrodes will make it possible to regulate precisely OOM contractions and thus generate complete and cosmetically acceptable eye-blink motion in patients with facial paralysis.     

Dynamic rehabilitation of the paralyzed face: I. Electronic control of reinnervated muscles from intact facial musculature in the rabbit

An entirely satisfactory solution to dynamic rehabilitation of the paralyzed facial musculature has not yet been found. Recent interest in selective reinnervation of the laryngeal musculature, synchronous with appropriate afferent information, has led us to propose that miniature strain gauges be placed on one or more muscles of facial expression on the intact side to channel electrical signals to the opposite corresponding facial musculature reinnervated via nerve-muscle pedicles. In order to avoid introducing extraneous factors related to facial motion, this principle was first studied on crossover ansa hypoglossi nerve-muscle pedicles in New Zealand white rabbits. Surgery was performed on a total of five animals that were under general anesthesia with xylazine and ketamine, through a midline neck incision. The animals were reexplored after 12 weeks, and after verification that reinnervation had taken place, a vertical incision was made under the external canthus, in order to expose the facial nerve. A miniature strain gauge was then sutured on the facial musculature and connected to a central modulating unit that was, in turn, linked to the nerve-muscle pedicle via a monopolar electrode. Facial wiggle that resulted from direct electrical facial nerve stimulation caused synchronous contraction of all reinnervated strap muscles under study; this was documented on film and through facial and strap muscle activity tracings. Our next step will be to extend this principle to paralyzed facial muscles. If successful, this system could be miniaturized for long-term implantation in human beings.     

Experimental study of denervated rat muscle. Part II: The effects of electrical stimulation on the denervated rat muscles

Electrical stimulation has been widely employed for the treatment of peripheral nerve lesion, however, its effects are not well known. Effects of electrical stimulation on denervated muscles were studied by measuring the weight of anterior crural muscles and the diameter of muscle fibers of the extensor digitorum longus muscle of the rat. The muscle fibers were classified by myofibrillar ATPase reaction. The denervated muscle showed loss of weight, a marked decrease in diameter of type 1 fibers and a small increase in diameter of type 2 fibers. Electrical stimulation suppressed weight loss of the denervated muscles. Electrical stimulation with high frequency cycle, like phasic motoneuron discharges, significantly suppressed the increase in diameter of type 2 muscle fibers. Electrical stimulation with low frequency cycle, like tonic motoneuron discharge, significantly suppressed the decrease in diameter of type 1 muscle fibers.     

面神经颊支和下颌缘支的解剖学研究及应用

目的 观察面神经颊支与下颌缘支肌外、肌内走行分布情况，为面瘫整复术中受区神经的选择和预防神经支损伤提供依据。方法 在24侧头部标本中，分别观测颊支和下颌缘支的分支数目、吻合情况、走行中的层次、颊支与腮腺导管以及下颌缘支与下颌骨下缘、面血管的关系，结合Sihler’s肌内神经染色，明确其支配肌肉和在肌内的分布规律；并在40例面瘫手术患者受区面神经分支的寻找和选择中进行验证。结果 腮腺导管体表投影较恒定，面神经颊支以2～3支为主，占87．5％，多数分布在导管上方10．7mm和下方9．3mm的范围内，支配中面部表情肌。下颌缘支以1～2支为主，占95．9％，多数分布在下颌骨下缘上方13．4mm和下方4．8mm的范围内，跨面动脉浅面，支配下唇诸肌。结论 面神经颊支与腮腺导管、下颌缘支与面动脉及下颌骨下缘有着紧密的关系。应用改良Sihler法，可以更为清晰的显示人面部表情肌的肌内神经分布情况。     

Electrical stimulation of denervated muscles: first results of a clinical study

To evaluate the effects of electrical stimulation on denervated muscles in spinal cord injured humans, the EU Project RISE was started in 2001. The aims of this project are: to design and build sufficient stimulators; to develop stimulation protocols by means of mathematical models, animal experiments, and practice in humans with denervated lower limbs; to develop examination methods and devices for evaluation of electrical stimulation training effects; and to acquire basic scientific knowledge on denervated and stimulated denervated muscle. In the clinical study 27 spinal cord injured individuals were included, furthermore 13 pilot patients participated. After a series of initial examinations they underwent an electrical stimulation program for their denervated lower limb muscles. Some of the patients have already follow up examinations. A marked increase of muscle mass and quality was observed, the trophic situation of the denervated lower limbs had improved obviously.     

Reanimation of paralyzed laryngeal muscles by electrical stimulation synchronized with inspiration.

OBJECTIVE: To determine the effects of electrical stimulation on denervated cat posterior cricoarytenoid (PCA) muscle. STUDY DESIGN AND SETTING: This study was conducted on six cats with PCA muscle denervation. All animals were sacrificed 12 weeks after surgery and the glottal area in the live animals and the fiber diameters of PCA muscle were obtained. RESULTS: Signals synchronized with inspiration were recorded and transmitted to stimulate PCA muscle. The abduction of the paralyzed vocal cord during inspiration was observed; this allows enough flow of air through the larynx to maintain the respiration. The stimulated fiber diameters of PCA muscle were different from that of nonstimulated (P < 0.01). Although all denervated muscles were degenerated, electrical stimulation was used to prevent muscular atrophy. CONCLUSIONS: This study indicates that electrical stimulation of the PCA muscle synchronized with inspiration could restore the abduction of a paralyzed vocal cord and prevent the denervated muscles from atrophying. SIGNIFICANCE: Electrical stimulation synchronized with inspiration may lead to reanimation of paralyzed laryngeal muscles.     

Surgical rehabilitation of reversible facial palsy: facial--hypoglossal network system based on neural signal augmentation/neural supercharge concept.

To obtain symmetric appearance in facial palsy patients, it is important to retain any remaining potential of the compromised facial mimetic muscles. The purpose of the present study was to introduce surgical rehabilitation based on neural signal augmentation/neural supercharge concept for the treatment of reversible facial palsy patients. With construction of facial-hypoglossal network system using end-to-side neurorrhaphy technique, both facial and hypoglossal motor signals are provided to the compromised facial mimetic muscles. It is hypothesised that the remaining potential of incompletely or completely paralysed muscles without atrophy is activated by a neural 'supercharge' effect. To date, nine patients presented with reversible facial palsy have been treated by surgical rehabilitation with facial-hypoglossal network system in our institutes. Facial mimetic muscle function evaluated by the House-Brackmann grading system was improved from grade IV-VI to II-III in this series. The postoperative ENMG findings showed double innervation of the mimetic muscles supplied by the facial and hypoglossal donor motor sources. Hemiglossal dysfunction and mimetic muscle synkinesis associated with tongue motion were never seen with an average follow-up period of 21 months after surgery. This reconstructive concept offers a significant advantage for the treatment of the facial palsy patients with persistent incomplete type and reversible complete type without distinct mimetic muscle atrophy.     

Mécanismes contrôlant le bourgeonnement axonal à la jonction neuromusculaire

This paper explores the specific roles of sprouting stimuli, perisynaptic Schwann cells and neuromuscular activity in axonal sprouting at the neuromuscular junction in partially denervated muscles. As for sprouting stimuli, insulin-like growth factor II which is generated from inactive muscle fibers in partially denervated and paralysed skeletal muscle is described. Likewise, perisynaptic Schwann cells can induce and guide axonal sprouting in partially denervated muscles. Finally, excessive neuromuscular activity significantly reduces bridging of the perisynaptic Schwann cell processes between denervated and innervated endplates and thereby inhibits axonal sprouting in partially denervated muscle. The lack of neuromuscular activity is also harmful in axonal sprouting, probably by impeding calcium influx into the nerve.     

Distribution of rest periods between electrically generated contractions in denervated muscles of rats

Stimulation protocols for denervated muscles distribute the generated contractions either within treatment sessions followed by hours of rest, or repeated 24 h per day with each contraction followed by a constant interval of rest. Our purpose was to directly compare the effects of the same number of identically generated contractions having different temporal daily distributions. For 5 weeks in denervated extensor digitorum longus muscles of rats, between 100 and 800 contractions were generated daily, distributed either within worksets that alternated periods of activity and rest, or separated by constant intervals of rest. Most of the tested protocols maintained muscle mass and maximum force near values of innervated controls. Although 100 contractions daily generated at constant intervals were sufficient to maintain mass and force, 100 contractions during a 4-h treatment session followed by 20 h of rest were not sufficient, and mass and force were not different from values of denervated muscles.     

Evaluation of the lower motor neuron integrity of upper extremity muscles in high level spinal cord injury.

PURPOSE: To evaluate the lower motor neuron (LMN) integrity of upper extremity muscles of persons with high tetraplegia (C1-C4) in order to determine muscles available for stimulation. METHODS: Fourteen subjects (23 arms) were evaluated for LMN integrity. Muscles that elicited a functional response (grade 3 or better) to surface electrical stimulation were considered to have intact LMN and good candidates for FES. Strength-duration (S-D) curves were generated on muscles that showed weak (less than grade 3) or no response to surface stimulation. Muscles were considered denervated if S-D curves were discontinuous or depicted steep, increasing amplitude for pulse durations greater than 1 m. RESULTS: Muscles for grasp and release had intact LMN in 19 of 23 (83%) arms. The wrist extensors and flexors and pronator were excitable in 17 (74%), 20 (87%) and 19 (83%) arms, respectively. The supinator demonstrated LMN lesion in 80% of the arms. Over 90% of the biceps muscles were unresponsive to electrical stimulation and 85% and 87% of the deltoid and supraspinatus muscles, respectively, were not electrically excitable. The latissimus dorsi and triceps muscles were typically innervated (78% and 91%, respectively) and slightly more than half (52%) of the pectoralis major muscles were excitable. CONCLUSION: These data suggest that application of FES in high tetraplegia for hand and arm function would require augmentation because of the inability to stimulate the elbow flexors, deltoid and rotator cuff muscles. These data also show that several paralyzed proximal muscles with intact LMN that have been historically transferred to address shoulder paralysis in other patient populations are available for transfer and stimulation in the population with high level spinal injuries.     

Structural Aging: The Facial Recurve Concept

Cutaneous facial aging is responsible for the increasingly wrinkled and blotchy appearance of the skin, whereas aging of the facial structures is attributed primarily to gravity. This article purports to show, however, that the primary etiology of structural facial aging relates instead to repeated contractions of certain facial mimetic muscles, the age marker fascicules, whereas gravity only secondarily abets an aging process begun by these muscle contractions. Magnetic resonance imaging (MRI) has allowed us to study the contrasts in the contour of the facial mimetic muscles and their associated deep and superficial fat pads in patients of different ages. The MRI model shows that the facial mimetic muscles in youth have a curvilinear contour presenting an anterior surface convexity. This curve reflects an underlying fat pad lying deep to these muscles, which acts as an effective mechanical sliding plane. The muscle’s anterior surface convexity constitutes the key evidence supporting the authors’ new aging theory. It is this youthful convexity that dictates a specific characteristic to the muscle contractions conveyed outwardly as youthful facial expression, a specificity of both direction and amplitude of facial mimetic movement. With age, the facial mimetic muscles (specifically, the age marker fascicules), as seen on MRI, gradually straighten and shorten. The authors relate this radiologic end point to multiple repeated muscle contractions over years that both expel underlying deep fat from beneath the muscle plane and increase the muscle resting tone. Hence, over time, structural aging becomes more evident as the facial appearance becomes more rigid.     

Body movement induced by electrical stimulation of toe muscles during standing

Abstract:  The purpose of this study was to investigate whether artificially induced muscle contractions of toe muscles using functional electrical stimulation (FES) would cause center of pressure (COP) displacement and corresponding body acceleration. Ten able-bodied subjects were asked to stand still on force plates. The flexor digitorum brevis and the flexor hallucis brevis in both legs were simultaneously stimulated using a transcutaneous FES device. The muscles were stimulated 20 times at random intervals with four different stimulation intensities. We demonstrated that the toe muscle activity induced by electrical stimulation evoked COP displacement, which generated body acceleration. As expected, a larger stimulation induced a larger COP movement and acceleration. Therefore, we propose the use of FES-induced contractions of the toe muscles as a means to control balance during FES-assisted quiet standing. Spinal cord-injured and severe-stroke patients could benefit from this electrical stimulation technique for improving FES-assisted standing.     

Determination of the chronaxie and rheobase of denervated limb muscles in conscious rabbits

Measurements of the rheobase and chronaxie can be used to define the excitability of nerves and muscles. The aim of this study was to obtain a record over many weeks of changes in the rheobase and chronaxie of denervated rabbit tibialis anterior muscle (TA). A custom-built electronic stimulator was implanted into the peritoneal cavity of New Zealand White rabbits. Large stainless steel electrodes were placed on the denervated TA muscle. Rheobase and chronaxie were measured noninvasively at weekly intervals by means of a laptop PC, which communicated with the stimulator via a radio-frequency link. At each setting the denervated TA was palpated manually to detect the response of the muscle. During the first few days after denervation the rheobase increased transiently to 0.8 +/- 0.13 mA, approximately twice the value for normal innervated muscle, then decreased to normal for the remainder of the experimental period. Chronaxie underwent a significant 3-fold increase from 4.5 +/- 1.1 ms to 14.1 +/- 1.1 ms during the first two weeks of denervation and remained elevated throughout. The custom-built implantable electronic stimulator allowed changes in muscle excitability to be studied over a long period of denervation within individual animals, providing an accurate assessment of the time course of denervation-induced changes in muscle excitability.     

Restoration of muscle volume and shape induced by electrical stimulation of denervated degenerated muscles: qualitative and quantitative measurement of changes in rectus femoris using computer tomography and image segmentation

Abstract:  This study demonstrates in a novel way how volume and shape are restored to denervated degenerated muscles due to a special pattern of electrical stimulation. To this purpose, Spiral Computer Tomography (CT) and special image processing tools were used to develop a method to isolate the rectus femoris from other muscle bellies in the thigh and monitor growth and morphology changes very accurately. During 4 years of electrical stimulation, three-dimensional (3D) reconstructions of the rectus femoris muscles from patients with long-term flaccid paraplegia were made at different points in time. The growth of the muscle and its changes through the time period are seen in the 3D representation and are measured quantitatively. Furthermore, changes in shape are compared with respect to healthy muscles in order to estimate the degree of restoration. The results clearly show a slow but continuing muscle growth induced by electrical stimulation; the increase of volume is accompanied by the return of a quasi-normal muscle shape. This technique allows a unique way of monitoring which provides qualitative and quantitative information on the denervated degenerated muscle behavior otherwise hidden.     

Muscle preservation using an implantable electrical system after nerve injury and repair.

The value of continuous electrical stimulation of denervated muscles after nerve injury and repair has been clearly shown in a series of laboratory experiments in three animal models. This experimental background, which showed improved muscle preservation and better functional results, evolved into a clinical study that included 15 patients with peripheral nerve injuries in the upper extremities, 3 patients with brachial plexus injuries, and three patients with facial nerve paralysis. Improved functional results were obtained using this implantable system, which were similar to those achieved with the animal experiments. All patients had muscle stimulation for extended periods ranging from 127 to 346 days. Analysis of the results showed satisfactory nerve regeneration on clinical examination and with electromyographic studies. Functional muscle analysis varied somewhat from patient to patient, but every patient had a satisfactory to excellent recovery. The results from this study have clearly shown the benefits of continuous muscle stimulation using an implantable electrical system after nerve injury and repair expansion of the project to a larger patient cohort is indicated.