Alternative Nerve Coaptations: End-To-Side and Beyond

Modern end-to-side (ETS) nerve transfers have undergone several permutations since the early 1990's. Preclinical data have revealed important mechanisms and patterns of donor axon outgrowth into the recipient nerves and target reinnervation. The versatility of ETS nerve transfers can also potentially address several processes that limit functional recovery after nerve injury by babysitting motor end-plates and/or supporting the regenerative environment within the denervated nerve. Further clinical and basic science work is required to clarify the ideal clinical indications, contraindications, and mechanisms of action for these techniques in order to maximize their potential as reconstructive options.

Sensorimotor Outcomes of Upper Extremity End-to-Side Nerve Transfers: A Meta-analysis

BACKGROUND

End-to-side nerve transfer (ETSNT) for treatment of peripheral nerve injuries is controversial given the myriad anatomic locations, injury types, and indications. Efficacy of ETSNT remains debated. We hypothesized differences in age, sex, transfer location, and time to surgery influence outcomes.

METHODS

We performed a search of the PubMed database for ETSNT in the upper extremity from 1988 to 2018. Age, sex, transfer location, time to surgery, donor and recipient axons, and strength and sensation outcomes as measured by Medical Research Council scale were extracted from articles. Meaningful recovery was classified as Medical Research Council Grade 3 or greater. Association between meaningful recovery and younger (<25) and older (≥25) patients, injury mechanism, sex, transfer location, donor axons, and recipient axons were calculated using a χ 2 or Fisher exact test. A logistic mixed effect model was used with time to surgery, age (categorical), transfer location, and injury type as a fixed effect, and a random paper effect was included to account for correlation among patients from the same paper.

RESULTS

One hundred fifteen patients from 11 studies were included. Neither age (continuous variable, P = 0.68) nor time to surgery ( P = 0.28) affected meaningful recovery. Injury mechanism, sex, and younger age (<25 vs ≥25 years) were not associated with meaningful recovery. Within the brachial plexus ETSNT demonstrated median M4 ± 1 postoperative strength, with trunks/cords as the primary axon donor ( P = 0.03). The musculocutaneous nerve demonstrated promising but variable results in 31 patients with median strength M3 ± 4. Digital nerves consistently demonstrated meaningful sensory recovery as both donor and recipient axons (15 of 15, 100%). Logistic regression analysis demonstrated that odds of meaningful recovery after ETSNT are significantly greater for transfers within the brachial plexus compared with the distal arm (odds ratio, 41.9; 95% CI, 1.1-1586.7, P = 0.04), but location does not significantly affect meaningful recovery ( P = 0.22).

CONCLUSIONS

Patients undergoing ETSNT for digital nerve injury demonstrated meaningful recovery. End-to-side nerve transfer seems to be more efficacious when performed within the brachial plexus. This study did not find sex, injury mechanism, or time to surgery to significantly affect meaningful recovery. Additional study is needed to better evaluate the effectiveness of ETSNT in the upper extremity.

Physiologic signaling and viability of the muscle cuff regenerative peripheral nerve interface (MC-RPNI) for intact peripheral nerves

Background. Robotic exoskeleton devices have become a promising modality for restoration of extremity function in individuals with limb loss or functional weakness. However, there exists no consistent or reliable way to record efferent motor action potentials from intact peripheral nerves to control device movement. Peripheral nerve motor action potentials are similar in amplitude to that of background noise, producing an unfavorable signal-to-noise ratio (SNR) that makes these signals difficult to detect and interpret. To address this issue, we have developed the muscle cuff regenerative peripheral nerve interface (MC-RPNI), a construct consisting of a free skeletal muscle graft wrapped circumferentially around an intact peripheral nerve. Over time, the muscle graft regenerates, and the intact nerve undergoes collateral axonal sprouting to reinnervate the muscle. The MC-RPNI amplifies efferent motor action potentials by several magnitudes, thereby increasing the SNR, allowing for higher fidelity signaling and detection of motor intention. The goal of this study was to characterize the signaling capabilities and viability of the MC-RPNI over time.Methods. Thirty-seven rats were randomly assigned to one of five experimental groups (Groups A-E). For MC-RPNI animals, their contralateral extensor digitorum longus (EDL) muscle was harvested and trimmed to either 8 mm (Group A) or 13 mm (Group B) in length, wrapped circumferentially around the intact ipsilateral common peroneal (CP) nerve, secured, and allowed to heal for 3 months. Additionally, one 8 mm (Group C) and one 13 mm (Group D) length group had an epineurial window created in the CP nerve immediately preceding MC-RPNI creation. Group E consisted of sham surgery animals. At 3 months, electrophysiologic analyses were conducted to determine the signaling capabilities of the MC-RPNI. Additionally, electromyography and isometric force analyses were performed on the CP-innervated EDL to determine the effects of the MC-RPNI on end organ function. Following evaluation, the CP nerve, MC-RPNI, and ipsilateral EDL muscle were harvested for histomorphometric analysis.Results. Study endpoint analysis was performed at 3 months post-surgery. All rats displayed visible muscle contractions in both the MC-RPNI and EDL following proximal CP nerve stimulation. Compound muscle action potentials were recorded from the MC-RPNI following proximal CP nerve stimulation and ranged from 3.67 ± 0.58 mV to 6.04 ± 1.01 mV, providing efferent motor action potential amplification of 10-20 times that of a normal physiologic nerve action potential. Maximum tetanic isometric force (F_o) testing of the distally-innervated EDL muscle in MC-RPNI groups producedF_o(2341 ± 114 mN-2832 ± 102 mN) similar to controls (2497 ± 122 mN), thus demonstrating that creation of MC-RPNIs did not adversely impact the function of the distally-innervated EDL muscle. Overall, comparison between all MC-RPNI sub-groups did not reveal any statistically significant differences in signaling capabilities or negative effects on distal-innervated muscle function as compared to the control group.Conclusions. MC-RPNIs have the capability to provide efferent motor action potential amplification from intact nerves without adversely impacting distal muscle function. Neither the size of the muscle graft nor the presence of an epineurial window in the nerve had any significant impact on the ability of the MC-RPNI to amplify efferent motor action potentials from intact nerves. These results support the potential for the MC-RPNI to serve as a biologic nerve interface to control advanced exoskeleton devices.

Reverse End-to-Side Anterior Interosseous Nerve-to-Ulnar Motor Transfer for Severe Ulnar Neuropathy

BACKGROUND

Reverse end-to-side anterior interosseous nerve transfer has been reported to enhance treatment of severe, proximal ulnar neuropathy. The authors report on patients with severe neuropathy treated with ulnar nerve transposition and distal reverse end-to-side anterior interosseous nerve transfer.

METHODS

Thirty patients with severe ulnar neuropathy at the elbow were reviewed. Clinical parameters included preoperative and postoperative Medical Research Council muscle strength, clawing, and degree of wasting. Electrodiagnostic data included compound motor action potential and sensory nerve action potential amplitudes. Summary statistics were used for demographic and clinical data. The t test and Wilcoxon signed rank test were used where appropriate.

RESULTS

Average follow-up was 18.6 months. Preoperatively, 20 patients had Medical Research Council less than or equal to grade 1 in hand intrinsics, small finger sensory nerve action potentials were absent in all patients except for three, and average compound motor action potentials were severely reduced (absent in nearly 40 percent) confirming severity. All groups had a statistically significant increase in strength. More than three-quarters of patients noted partial or complete resolution of clawing and intrinsic muscle wasting. Seventy-three percent of patients regained Medical Research Council greater than or equal to grade 3 and 47 percent achieved Medical Research Council greater than or equal to grade 4. Mean time to observation of nascent units was 8.5 months, and 77 percent of patients demonstrated an augmentation of motor unit numbers with forearm pronation on needle electromyography CONCLUSION:: Proximal subcutaneous ulnar nerve transposition when combined with reverse end-to-side anterior interosseous nerve-to-ulnar nerve transfer demonstrates significant clinical and electrodiagnostic improvement of intrinsic muscle function.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Electromyography as an intraoperative test to assess the quality of nerve anastomosis - experimental study on rats

Background

Many factors contribute to successful nerve reconstruction. The correct technique of anastomosis is one of the key elements that determine the final result of a surgery. The aim of this study is to examine how useful an electromyography (EMG) can be as an objective intraoperative anastomosis assessment method.

Methods

The study material included 12 rats. Before the surgery, the function of the sciatic nerve was tested using hind paw prints. Then, both nerves were cut. The left nerve was sutured side-to-side, and the right nerve was sutured end-to-end. Intraoperative electromyography was performed. After 4 weeks, the rats were reassessed using the hind paw print analysis and electromyography.

Results

An analysis of left and right hind paw prints did not reveal any significant differences between the length of the steps, the spread of the digits in the paws, or the deviation of a paw. The width of the steps also did not change.Electromyography revealed that immediately after a nerve anastomosis (as well as 4 weeks after the surgery), better nerve conduction was observed through an end-to-end anastomosis. Four weeks after the surgery, better nerve conduction was seen distally to the end-to-end anastomosis.

Conclusions

The results indicate that in acute nerve injuries intraoperative electromyography may be useful to obtain unbiased information on whether the nerve anastomosis has been performed correctly - for example, in limb replantation.When assessing a nerve during a procedure, EMG should be first performed distally to the anastomosis (the part of the nerve leading to muscle fibers) and then proximally to the anastomosis (the proximal part of the nerve). Similar EMG results can be interpreted as a correct nerve anastomosis.The function of the distal part of the nerve and the muscle remains intact if the neuromuscular transmission is sustained.

Assessment of axonal sprouting and motor performance after hypoglossal-facial end-to-side nerve repair: experimental study in rats

Hypoglossal-facial nerve anastomosis (HFA) aims to reanimate denervated mimic muscles with hypoglossal axons when the transected facial nerve is not accessible. The aim of this study was to evaluate the recovery of HFA using a "Y" tube in two variants: (1) the proximal stump of the hypoglossal nerve was entubulated to the "Y" tube (classic "Y" tube HFA) and (2) the "Y" tube was sutured to an epineurial window of a slightly damaged hypoglossal nerve (end-to-side "Y" tube HFA). A total of 48 adult female rats were divided into four groups: intact controls (group 1), sham operated (group 2), classic "Y" tube HFA (group 3) and end-to-side "Y" tube HFA (group 4). The abdominal aorta with both common iliac arteries of isogeneic male rats served as the Y-tube conduit. Animals from group 4 recovered better than those from group 3: the degree of collateral axonal branching (3 ± 1%) was significantly lower than that determined in group 3 (13 ± 1%). The mean deviation of the tongue from the midline was significantly smaller in group 4 (6 ± 4°) than that measured in animals from group 3 (41 ± 6°). In the determination of vibrissal motor function in group 3 and group 4, a decrease in amplitude was found to be - 66% and - 92%, respectively. No differences in the reinnervation pattern of the target muscles were detected. As a result, these surgical models were not determined to be able to improve vibrissal movements. It was concluded that performance of end-to-side "Y" tube HFA diminishes collateral axonal branching at the lesion site, which in turn, promotes better recovery of tongue- and vibrissal-motor performance.

End-to-side neurorrhaphy repairs peripheral nerve injury: sensory nerve induces motor nerve regeneration

End-to-side neurorrhaphy is an option in the treatment of the long segment defects of a nerve. It involves suturing the distal stump of the disconnected nerve (recipient nerve) to the side of the intimate adjacent nerve (donor nerve). However, the motor-sensory specificity after end-to-side neurorrhaphy remains unclear. This study sought to evaluate whether cutaneous sensory nerve regeneration induces motor nerves after end-to-side neurorrhaphy. Thirty rats were randomized into three groups: (1) end-to-side neurorrhaphy using the ulnar nerve (mixed sensory and motor) as the donor nerve and the cutaneous antebrachii medialis nerve as the recipient nerve; (2) the sham group: ulnar nerve and cutaneous antebrachii medialis nerve were just exposed; and (3) the transected nerve group: cutaneous antebrachii medialis nerve was transected and the stumps were turned over and tied. At 5 months, acetylcholinesterase staining results showed that 34% ± 16% of the myelinated axons were stained in the end-to-side group, and none of the myelinated axons were stained in either the sham or transected nerve groups. Retrograde fluorescent tracing of spinal motor neurons and dorsal root ganglion showed the proportion of motor neurons from the cutaneous antebrachii medialis nerve of the end-to-side group was 21% ± 5%. In contrast, no motor neurons from the cutaneous antebrachii medialis nerve of the sham group and transected nerve group were found in the spinal cord segment. These results confirmed that motor neuron regeneration occurred after cutaneous nerve end-to-side neurorrhaphy.

Side-To-Side Nerve Bridges Support Donor Axon Regeneration Into Chronically Denervated Nerves and Are Associated With Characteristic Changes in Schwann Cell Phenotype

BACKGROUND

Chronic denervation resulting from long nerve regeneration times and distances contributes greatly to suboptimal outcomes following nerve injuries. Recent studies showed that multiple nerve grafts inserted between an intact donor nerve and a denervated distal recipient nerve stump (termed "side-to-side nerve bridges") enhanced regeneration after delayed nerve repair.

OBJECTIVE

To examine the cellular aspects of axon growth across these bridges to explore the "protective" mechanism of donor axons on chronically denervated Schwann cells.

METHODS

In Sprague Dawley rats, 3 side-to-side nerve bridges were placed over a 10-mm distance between an intact donor tibial (TIB) nerve and a recipient denervated common peroneal (CP) distal nerve stump. Green fluorescent protein-expressing TIB axons grew across the bridges and were counted in cross section after 4 weeks. Immunofluorescent axons and Schwann cells were imaged over a 4-month period.

RESULTS

Denervated Schwann cells dedifferentiated to a proliferative, nonmyelinating phenotype within the bridges and the recipient denervated CP nerve stump. As donor TIB axons grew across the 3 side-to-side nerve bridges and into the denervated CP nerve, the Schwann cells redifferentiated to the myelinating phenotype. Bridge placement led to an increased mass of hind limb anterior compartment muscles after 4 months of denervation compared with muscles whose CP nerve was not "protected" by bridges.

CONCLUSION

This study describes patterns of donor axon regeneration and myelination in the denervated recipient nerve stump and supports a mechanism where these donor axons sustain a proregenerative state to prevent deterioration in the face of chronic denervation.

Pre-implanted Sensory Nerve Could Enhance the Neurotization in Tissue-Engineered Bone Graft

In our previous study, it was found that implanting the sensory nerve tract into the tissue-engineered bone to repair large bone defects can significantly result in better osteogenesis effect than tissue-engineered bone graft (TEBG) alone. To study the behavior of the preimplanted sensory nerve in the TEBG, the TEBG was constructed by seeding bone mesenchymal stem cells into β-tricalcium phosphate scaffold with (treatment group) or without (blank group) implantation of the sensory nerve. The expression of calcitonin gene-related peptide (CGRP), which helps in the healing of bone defect in the treatment group was significantly higher than the blank group at 4, 8, and 12 weeks. The expression of growth-associated protein 43 (GAP43), which might be expressed during nerve healing in the treatment group, was significantly higher than the blank group at 4 and 8 weeks. The nerve tracts of the preimplanted sensory nerve were found in the scaffold by the nerve tracing technique. The implanted sensory nerve tracts grew into the pores of scaffolds much earlier than the vascular. The implanted sensory nerve tracts traced by Dil could be observed at 4 weeks, but at the same time, no vascular was observed. In conclusion, the TEBG could be benefited from the preimplanted sensory nerve through the healing behavior of the sensory nerve. The sensory nerve fibers could grow into the pores of the TEBG rapidly, and increase the expression of CGRP, which is helpful in regulating the bone formation and the blood flow.

Outer electrospun polycaprolactone shell induces massive foreign body reaction and impairs axonal regeneration through 3D multichannel chitosan nerve guides

We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.

Comparison of muscle force after immediate and delayed reinnervation using nerve-muscle-endplate band grafting

BACKGROUND

Because of poor functional outcomes of currently used reinnervation methods, we developed novel treatment strategy for the restoration of paralyzed muscles-the nerve-muscle-endplate band grafting (NMEG) technique. The graft was obtained from the sternohyoid muscle (donor) and implanted into the ipsilateral paralyzed sternomastoid (SM) muscle (recipient).

METHODS

Rats were subjected to immediate or delayed (1 or 3 mo) reinnervation of the experimentally paralyzed SM muscles using the NMEG technique or the conventionally used nerve end-to-end anastomosis. The SM muscle at the opposite side served as a normal control.

RESULTS

NMEG produced better recovery of muscle force as compared with end-to-end anastomosis. A larger force produced by NMEG was most evident for small stimulation currents.

CONCLUSIONS

The NMEG technique holds great potential for successful muscle reinnervation. We hypothesize that even better muscle reinnervation and functional recovery could be achieved with further improvement of the environment that favors axon-end plate connections and accelerates axonal growth and sprouting.

Emerging issues in peripheral nerve repair

It is today widely acknowledged that nerve repair is now more than a matter of perfect microsurgical reconstruction only and that, to further improve clinical outcome, the involvement of different scientific disciplines is required. This evolving reconstructive/regenerative approach is based on the interdisciplinary and integrated pillars of tissue engineering such as reconstructive microsurgery, transplantation and biomaterials. In this paper, some of the most promising innovations for the tissue engineering of nerves, emerging from basic science investigation, are critically overviewed with special focus on those approaches that appear today to be more suitable for clinical translation.

Retrograde tracing and toe spreading after experimental autologous nerve transplantation and crush injury of the sciatic nerve: a descriptive methodological study

Evaluation of functional and structural recovery after peripheral nerve injury is crucial to determine the therapeutic effect of a nerve repair strategy. In the present study, we examined the relationship between the structural evaluation of regeneration by means of retrograde tracing and the functional analysis of toe spreading. Two standardized rat sciatic nerve injury models were used to address this relationship. As such, animals received either a 2 cm sciatic nerve defect (neurotmesis) followed by autologous nerve transplantation (ANT animals) or a crush injury with spontaneous recovery (axonotmesis; CI animals). Functional recovery of toe spreading was observed over an observation period of 84 days. In contrast to CI animals, ANT animals did not reach pre-surgical levels of toe spreading. After the observation period, the lipophilic dye DiI was applied to label sensory and motor neurons in dorsal root ganglia (DRG; sensory neurons) and spinal cord (motor neurons), respectively. No statistical difference in motor or sensory neuron counts could be detected between ANT and CI animals.

In the present study we could indicate that there was no direct relationship between functional recovery (toe spreading) measured by SSI and the number of labelled (motor and sensory) neurons evaluated by retrograde tracing. The present findings demonstrate that a multimodal approach with a variety of independent evaluation tools is essential to understand and estimate the therapeutic benefit of a nerve repair strategy.

The role of immunophilin ligands in nerve regeneration

Tacrolimus (FK506) is a widely used immunosuppressant in organ transplantation. However, it also has neurotrophic activity that occurs independently of its immunosuppressive effects. Other neurotrophic immunophilin ligands that do not exhibit immunosuppression have subsequently been developed and studied in various models of nerve injury. This article reviews the literature on the use of tacrolimus and other immunophilin ligands in peripheral nerve, cranial nerve and spinal cord injuries. The most convincing evidence of enhanced nerve regeneration is seen with systemic administration of tacrolimus in peripheral nerve injury, although clinical use is limited due to its immunosuppressive side effects. Local tacrolimus delivery to the site of nerve repair in peripheral and cranial nerve injury is less effective but requires further investigation. Tacrolimus can enhance outcomes in nerve allograft reconstruction and accelerates reinnervation of complex functional allograft transplants. Other non-immunosuppressive immunophilins ligands such as V-10367 and FK1706 demonstrate enhanced neuroregeneration in the peripheral nervous system and CNS. Mixed results are found in the application of immunophilin ligands to treat spinal cord injury. Immunophilin ligands have great potential in the treatment of nerve injury, but further preclinical studies are necessary to permit translation into clinical trials.

C3 peptide promotes axonal regeneration and functional motor recovery after peripheral nerve injury

Peripheral nerve injuries are frequently seen in trauma patients and due to delayed nerve repair, lifelong disabilities often follow this type of injury. Innovative therapies are needed to facilitate and expedite peripheral nerve regeneration. The purpose of this study was to determine the effects of a 1-time topical application of a 26-amino-acid fragment (C3(156-181)), derived from the Clostridium botulinum C3-exoenzyme, on peripheral nerve regeneration in 2 models of nerve injury and repair in adult rats. After sciatic nerve crush, different dosages of C3(156-181) dissolved in buffer or reference solutions (nerve growth factor or C3(bot)-wild-type protein) or vehicle-only were injected through an epineurial opening into the lesion sites. After 10-mm nerve autotransplantation, either 8.0 nmol/kg C3(156-181) or vehicle were injected into the proximal and distal suture sites. For a period of 3 to 10 postoperative weeks, C3(156-181)-treated animals showed a faster motor recovery than control animals. After crush injury, axonal outgrowth and elongation were activated and consequently resulted in faster motor recovery. The nerve autotransplantation model further elucidated that C3(156-181) treatment accounts for better axonal elongation into motor targets and reduced axonal sprouting, which are followed by enhanced axonal maturation and better axonal functionality. The effects of C3(156-181) are likely caused by a nonenzymatic down-regulation of active RhoA. Our results indicate the potential of C3(156-181) as a therapeutic agent for the topical treatment of peripheral nerve repair sites.

Growth-Promoting Effects of Quercetin on Peripheral Nerves in Rats

Objectives

The present study evaluated in vitro and in vivo the effects of quercetin (QC), a major ingredient in various flavonoids, on peripheral nerve regeneration.

Methods

In the in vitro study, we found that QC at concentrations of 0.1, 1, and 10 μg/mL could significantly promote the survival and outgrowth of cultured Schwann cells as compared with the controls treated with culture medium only. In the in vivo study, we evaluated peripheral nerve regeneration across a 15-mm gap in the sciatic nerve of the rat, using a silicone rubber nerve chamber filled with the QC solution. In the control group, the chambers were filled with normal saline only.

Results

At the end of 8 weeks, morphometric data revealed that all 3 QC groups significantly increased the count and density of myelinated axons as compared with the controls. Electro-physiological measurements showed that the QC-treated group at 1 μg/mL had a significantly larger area of evoked muscle action potential (MAP) compared with the controls. In addition, the amplitude of the MAP in the QC-treated groups at 0.1 and 1 μg/mL was significantly larger than that in the controls.

Conclusions

All of these results indicate that QC treatment has nerve growth–promoting effects which may lead to a promising herbal medicine for the recovery of regenerating peripheral nerves.

Nerve-muscle-endplate band grafting: a new technique for muscle reinnervation

BACKGROUND

Because currently existing reinnervation methods result in poor functional recovery, there is a great need to develop new treatment strategies.

OBJECTIVE

To investigate the efficacy of our recently developed nerve-muscle-endplate band grafting (NMEG) technique for muscle reinnervation.

METHODS

Twenty-five adult rats were used. Sternohyoid (SH) and sternomastoid (SM) muscles served as donor and recipient muscle, respectively. Neural organization of the SH and SM muscles and surgical feasibility of the NMEG technique were determined. An NMEG contained a muscle block, a nerve branch with nerve terminals, and a motor endplate band with numerous neuromuscular junctions. After a 3-month recovery period, the degree of functional recovery was evaluated with a maximal tetanic force measurement. Retrograde horseradish peroxidase tracing was used to track the origin of the motor innervation of the reinnervated muscles. The reinnervated muscles were examined morphohistologically and immunohistochemically to assess the extent of axonal regeneration.

RESULTS

Nerve supply patterns and locations of the motor endplate bands in the SH and SM muscles were documented. The results demonstrated that the reinnervated SM muscles gained motor control from the SH motoneurons. The NMEG technique yielded extensive axonal regeneration and significant recovery of SM muscle force-generating capacity (67% of control). The mean wet weight of the NMEG-reinnervated muscles (87% of control) was greater than that of the denervated SM muscles (36% of control).

CONCLUSION

The NMEG technique resulted in successful muscle reinnervation and functional recovery. This technique holds promise in the treatment of muscle paralysis.

Comparison of the effects of different electrocautery applications to peripheral nerves: an experimental study

BACKGROUND

This study was designed to investigate the effects of bipolar and mononopolar electrocauterization on peripheral nerve tissue. The comparison on the deleterious effects of the different cautery modalities and the importance of probe tip placement are evaluated using electrophysiological, electron microscopic and biochemical assessment parameters.

METHODS

Ninety-eight male Wistar albino rats, each weighing 250-275 g, were randomly divided into 14 groups. Each group consisted of seven animals. Monopolar and bipolar electrocautery were performed at 15 watts. The application was performed either directly on the nerve or 1 mm lateral to the longitudinal axis of the nerve for 'near the nerve groups', respectively.

RESULTS

The electrophysiological findings showed that the mean amplitudes were at the lowest value in the first day for all the groups. At the end of the 3rd week, we recognised that the electrophysiological recovery continued. Electron microscopic evaluation showed myelin disruption in all groups. Myelin disruption of healthy neurons was at the highest level in the 1st day of application in accordance with the electrophysiological findings. Biochemical evaluation revealed statistical significance between the control and the two of the 'near the nerve groups' (GIII and GV) for NO (nitrite and nitrate) serum level.

CONCLUSION

The data of the present study might suggest that electrocautery, independent of the type and form of application, may result in significant damage in histological and electrophysological basis. Although the relative proportions cannot be ascertained, the time course of recovery suggests that both axon and myelin damage have occurred. The probable electrocautery damage may be of substantial importance for the situation that the nerves are displaced by tumor masses or atypical neural traces.