Obstetric brachial plexus palsy: a large animal model for traction injury and its repair. Part 1: age of the recipient

Evaluation of peripheral nerve injury according to the severity of damage using 18F-FDG PET/MRI in a rat Model of sciatic nerve injury

OBJECTIVES

We ascertained that the PET scan may be a valuable imaging modality for the noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury through the previous study. This study aimed to assess peripheral nerve damage according to severity using18F-FDG PET/MRI of the rat sciatic nerve.

METHODS

Eighteen rats were divided into three groups: 30-second (G1), 2-minute (G2), and 5-minute (G3) crushing injuries. The severity of nerve damage was measured in the third week after the crushing injury using three methods: the paw withdrawal threshold test (RevWT), standardized uptake values on PET (SUVR), and intensity analysis on immunohistochemistry (IntR).

RESULTS

There were significant differences between G1 and G3 in both SUVR and IntR (p = 0.012 and 0.029, respectively), and no significant differences in RevWT among the three groups (p = 0.438). There was a significant difference in SUVR (p = 0.012), but no significant difference in IntR between G1 and G2 (p = 0.202). There was no significant difference between G2 and G3 in SUVR and IntR (p = 0.810 and 0.544, respectively).

DISCUSSION

Although PET did not show results consistent with those of immunohistochemistry in all respects, this study demonstrated that PET uptake tended to increase with severe nerve damage. If this research is supplemented by further experiments, PET/MRI can be used as an effective diagnostic modality.

Animal models in peripheral nerve transection studies: a systematic review on study design and outcomes assessment

Aim: Peripheral nerve injury regeneration studies using animal models are crucial to different pre-clinical therapeutic approaches efficacy evaluation whatever the surgical technique explored. Materials & methods: A 944 articles systematic review on 'peripheral nerve injury in animal models' over the last 9 years was carried out. Results: It was found that 91% used rodents, and only 9% employed large animals. Different nerves are studied, with generated gaps (10,78 mm) and methods applied for regeneration evaluation uniformed. Sciatic nerve was the most used (88%), followed by median and facial nerves (2.6%), significantly different. Conclusion: There has not been a significant scale-up of the in vivo testing to large animal models (anatomically/physiologically closer to humans), allowing an improvement in translational medicine for clinical cases.

In vitro, In vivo and Ex vivo Models for Peripheral Nerve Injury and Regeneration

Peripheral Nerve Injuries (PNI) frequently occur secondary to traumatic injuries. Recovery from these injuries can be expectedly poor, especially in proximal injuries. In order to study and improve peripheral nerve regeneration, scientists rely on peripheral nerve models to identify and test therapeutic interventions. In this review, we discuss the best described and most commonly used peripheral nerve models that scientists have and continue to use to study peripheral nerve physiology and function.

Small Ruminants and Its Use in Regenerative Medicine: Recent Works and Future Perspectives

Simple Summary

Small ruminants such as sheep and goats have been increasingly used as animal models due to their dimensions, physiology and anatomy identical to those of humans. Their low costs, ease of accommodation, great longevity and easy handling make them advantageous animals to be used in a wide range of research work. Although there is already a lot of scientific literature describing these species, their use still lacks some standardization. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models for scientific research.

Abstract

Medical and translational scientific research requires the use of animal models as an initial approach to the study of new therapies and treatments, but when the objective is an exploration of translational potentialities, classical models fail to adequately mimic problems in humans. Among the larger animal models that have been explored more intensely in recent decades, small ruminants, namely sheep and goats, have emerged as excellent options. The main advantages associated to the use of these animals in research works are related to their anatomy and dimensions, larger than conventional laboratory animals, but very similar to those of humans in most physiological systems, in addition to their low maintenance and feeding costs, tendency to be docile, long life expectancies and few ethical complications raised in society. The most obvious disadvantages are the significant differences in some systems such as the gastrointestinal, and the reduced amount of data that limits the comparison between works and the validation of the characterization essays. Despite everything, recently these species have been increasingly used as animal models for diseases in different systems, and the results obtained open doors for their more frequent and advantageous use in the future. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models, with a focus on regenerative medicine, to group the most relevant works and results published recently and to highlight the potentials for the near future in medical research.

Branquinho M, Sousa AC, Zen F, Maurina M, Raimondo S, Mendonça C, Atayde L, Geuna S, Varejão AS, Maurício AC. Establishment of a Sheep Model for Hind Limb Peripheral Nerve Injury: Common Peroneal Nerve

Thousands of people worldwide suffer from peripheral nerve injuries and must deal daily with the resulting physiological and functional deficits. Recent advances in this field are still insufficient to guarantee adequate outcomes, and the development of new and compelling therapeutic options require the use of valid preclinical models that effectively replicate the characteristics and challenges associated with these injuries in humans. In this study, we established a sheep model for common peroneal nerve injuries that can be applied in preclinical research with the advantages associated with the use of large animal models. The anatomy of the common peroneal nerve and topographically related nerves, the functional consequences of its injury and a neurological examination directed at this nerve have been described. Furthermore, the surgical protocol for accessing the common peroneal nerve, the induction of different types of nerve damage and the application of possible therapeutic options were described. Finally, a preliminary morphological and stereological study was carried out to establish control values for the healthy common peroneal nerves regarding this animal model and to identify preliminary differences between therapeutic methods. This study allowed to define the described lateral incision as the best to access the common peroneal nerve, besides establishing 12 and 24 weeks as the minimum periods to study lesions of axonotmesis and neurotmesis, respectively, in this specie. The post-mortem evaluation of the harvested nerves allowed to register stereological values for healthy common peroneal nerves to be used as controls in future studies, and to establish preliminary values associated with the therapeutic performance of the different applied options, although limited by a small sample size, thus requiring further validation studies. Finally, this study demonstrated that the sheep is a valid model of peripheral nerve injury to be used in pre-clinical and translational works and to evaluate the efficacy and safety of nerve injury therapeutic options before its clinical application in humans and veterinary patients.

The advances in nerve tissue engineering: From fabrication of nerve conduit to in vivo nerve regeneration assays

Peripheral nerve damage is a common clinical complication of traumatic injury occurring after accident, tumorous outgrowth, or surgical side effects. Although the new methods and biomaterials have been improved recently, regeneration of peripheral nerve gaps is still a challenge. These injuries affect the quality of life of the patients negatively. In the recent years, many efforts have been made to develop innovative nerve tissue engineering approaches aiming to improve peripheral nerve treatment following nerve injuries. Herein, we will not only outline what we know about the peripheral nerve regeneration but also offer our insight regarding the types of nerve conduits, their fabrication process, and factors associated with conduits as well as types of animal and nerve models for evaluating conduit function. Finally, nerve regeneration in a rat sciatic nerve injury model by nerve conduits has been considered, and the main aspects that may affect the preclinical outcome have been discussed.

Irreversible Electroporation to Treat Malignant Tumor Recurrences Within the Pelvic Cavity: A Case Series

OBJECTIVE

To describe the initial experience with irreversible electroporation (IRE) to treat pelvic tumor recurrences.

METHODS

A retrospective single-center analysis was performed. Adverse events were recorded using Common Terminology Criteria of Adverse Events (CTCAE) 4.0. Clinical outcome was determined using pain- and general- symptom assessment, including Seddon's peripheral nerve injury (PNI) types. Radiological outcome was evaluated by comparing baseline with three-month 18F-FDG PET-CT follow-up.

RESULTS

Eight patients (nine tumors [recurrences of primary rectal (n = 4), anal (n = 1), sigmoid (n = 1), cervical (n = 1), and renal cell carcinoma (n = 1)]) underwent percutaneous IRE as salvage therapy. Median longest tumor diameter was 3.7 cm (range 1.2-7.0). One CTCAE grade III adverse event (hemorrhage) and eight CTCAE grade II complications occurred in 6/8 patients: vagino-tumoral fistula (n = 1), lower limb motor loss (n = 3; PNI type II) with partial recovery in one patient, hypotonic bladder (n = 2; PNI types I and II) with complete recovery in one patient, and upper limb motor loss (n = 2; PNI type II) with partial recovery in both patients. No residual tumor tissue was observed at 3-month follow-up. After a median follow-up of 12 months, local progression was observed in 5/9 lesions (4/5 were >3 cm pre-IRE); one lesion was successfully retreated. Debilitating preprocedural pain (n = 3) remained unchanged (n = 1) or improved (n = 2).

CONCLUSION

IRE may represent a suitable technique to treat pelvic tumor recurrences, although permanent neural function loss can occur. Complete ablation seems realistic for smaller lesions; for larger lesions symptom control should be the focus.

Penile erectile dysfunction after brachial plexus root avulsion injury in rats

Our previous studies have demonstrated that some male patients suffering from brachial plexus injury, particularly brachial plexus root avulsion, show erectile dysfunction to varying degrees. However, the underlying mechanism remains poorly understood. In this study, we evaluated the erectile function after establishing brachial plexus root avulsion models with or without spinal cord injury in rats. After these models were established, we administered apomorphine (via a subcutaneous injection in the neck) to observe changes in erectile function. Rats subjected to simple brachial plexus root avulsion or those subjected to brachial plexus root avulsion combined with spinal cord injury had significantly fewer erections than those subjected to the sham operation. Expression of neuronal nitric oxide synthase did not change in brachial plexus root avulsion rats. However, neuronal nitric oxide synthase expression was significantly decreased in brachial plexus root avulsion + spinal cord injury rats. These findings suggest that a decrease in neuronal nitric oxide synthase expression in the penis may play a role in erectile dysfunction caused by the combination of brachial plexus root avulsion and spinal cord injury.

Effect of locally administered ciliary neurotrophic factor on the survival of transected and repaired adult sheep facial nerve

OBJECTIVE

to determine whether the administration of Ciliary Neurotrophic Factor (CNTF) at the site of repaired facial nerve enhances regeneration in the adult sheep model.

METHODS

Ten adult sheep were divided into 2 groups: control and study group (CNTF group). In the CNTF group, the buccal branch of the facial nerve was transected and then repaired by epineural sutures. CNTF was injected over the left depressor labii maxillaris muscle in the vicinity of the transected and repaired nerve for 28 days under local anesthesia. In the CNTF group, the sheep were again anesthetized after nine months and the site of facial nerve repair was exposed. Detailed electrophysiological, tension experiments and morphometric studies were carried out and then analyzed statistically.

RESULTS

The skin CV min, refractory period, Jitter and tension parameters were marginally raised in the CNTF group than the control but the difference was statistically insignificant between the two groups. Morphometric indices also did not show any significant changes in the CNTF group.

CONCLUSION

CNTF has no profound effect on neuronal regeneration of adult sheep animal model.

KEYWORDS

CNTF; Neurtrophic factors; Sheep; Facial nerve; Regeneration.

A cross-sectional study of hand sensation in adults with conservatively treated obstetric brachial plexus lesion

AIM

Sensory function is assumed to recover almost completely in obstetric brachial plexus lesion (OBPL), and is reported to recover much better than motor function. However, there is no obvious physiological reason why this should be so. Any persistent problems with sensory innervation might contribute to disability, therefore we aimed to assess sensory dysfunction in adults resulting from OBPL.

METHOD

Adults with conservatively treated OBPL (n=17; 12 females, five males; median age 38y; lesion levels: C5-C6, n=7; C5-C7, n=7; C5-C8, n=2; C5-Th1, n=1) and 19 healthy comparison persons (10 females, nine males; median age 23y) were investigated. Sensory function was measured using Semmes-Weinstein monofilaments, two-point discrimination, object recognition, and a locognosia test.

RESULTS

Scores of the Semmes-Weinstein monofilaments and two-point discrimination, but not object recognition or locognosia, were significantly worse in those with OBPL than in those without OBPL.

INTERPRETATION

There may be systematic abnormalities in sensory function in adults with conservatively treated OBPL. The existence of these impairments and their contribution to functional impairment needs to be acknowledged.

The effects of irreversible electroporation (IRE) on nerves

Background

If a critical nerve is circumferentially involved with tumor, radical surgery intended to cure the cancer must sacrifice the nerve. Loss of critical nerves may lead to serious consequences. In spite of the impressive technical advancements in nerve reconstruction, complete recovery and normalization of nerve function is difficult to achieve. Though irreversible electroporation (IRE) might be a promising choice to treat tumors near or involved critical nerve, the pathophysiology of the nerve after IRE treatment has not be clearly defined.

Methods

We applied IRE directly to a rat sciatic nerve to study the long term effects of IRE on the nerve. A sequence of 10 square pulses of 3800 V/cm, each 100 µs long was applied directly to rat sciatic nerves. In each animal of group I (IRE) the procedure was applied to produce a treated length of about 10 mm. In each animal of group II (Control) the electrodes were only applied directly on the sciatic nerve for the same time. Electrophysiological, histological, and functional studies were performed on immediately after and 3 days, 1 week, 3, 5, 7 and 10 weeks following surgery.

Findings

Electrophysiological, histological, and functional results show the nerve treated with IRE can attain full recovery after 7 weeks.

Conclusion

This finding is indicative of the preservation of nerve involving malignant tumors with respect to the application of IRE pulses to ablate tumors completely. In summary, IRE may be a promising treatment tool for any tumor involving nerves.

Electromyography, nerve action potential, and compound motor action potentials in obstetric brachial plexus lesions: validation in the absence of a "gold standard"

OBJECTIVE

Obstetric brachial plexus lesions (OBPLs) are caused by traction to the brachial plexus during labor. Typically, in these lesions, the nerves are usually not completely ruptured but form a "neuroma-in-continuity." Even in the most severe OBPL lesions, at least some axons will pass through this neuroma-in-continuity and reach the tubes distal to the lesion site. These axons may be particularly prone to abnormal branching and misrouting, which may explain the typical feature of co-contraction. An additional factor that may reduce functional regeneration is that improper central motor programming may occur. Surgery should be restricted to severe cases in which spontaneous restoration of function will not occur, i.e., in neurotmesis or root avulsions. A major problem is how to predict whether function will be best after spontaneous nerve outgrowth or after nerve reconstructive surgery. When a decision has been made to perform an early surgical exploration, what to do with the neuroma-in-continuity can be a problem. The intraoperative appraisal is difficult and depends on experience, but even in experienced hands, misjudgment can be made.

METHODS

We performed an observational study to assess whether early electromyography (at the age of 1 month) is able to predict severe lesions. Additionally, the value of intraoperative nerve action potential and compound motor action potentials was investigated.

RESULTS

Severe cases of OBPL can be identified at 1 month of age on the basis of clinical findings and needle electromyography of the biceps. This outcome needs independent validation, which is currently in progress. Nerve action potential and compound motor action potential recordings show statistically significant differences on the group level between avulsion, neurotmesis, axonotmesis, and normal. For the individual patient, a clinically useful cutoff point could not be found. Intraoperative nerve action potential and compound motor action potential recordings do not add to the decision making during surgery.

CONCLUSION

The absence of a "gold standard" for the assessment of the severity of the OBPL lesion makes prognostic studies of OBPL complex. The currently available assessment strategies used to obtain the best possible solutions are discussed.

Prevention of adhesions in surgery of the flexor tendons of the hand: what is the evidence?

INTRODUCTION

Despite advances in knowledge and refinements of technique, the management of flexor tendon injuries within the digital sheath continues to present a formidable challenge. This in turn has led to a massive expansion in search of modified surgical therapies and various adjuvant therapies, which could prevent adhesion formation without compromising digital function.

SOURCES OF DATA

A search of PubMed, Medline, CINAHL and Embase databases was performed using the keywords 'tendon adhesion prevention', 'tendon healing', 'adhesion prevention in tendons' and 'adjuvants for adhesion prevention'. Studies detailing the use of surgical, pharmacological and non-pharmacological agents for adhesion prevention in digital flexor tendons were identified, and their bibliographies were thoroughly reviewed to identify further related articles. This search identified 41 studies, which investigated the use of various pharmacological agents in adhesion prevention in digital tendons.

AREAS OF AGREEMENT

There is a need to develop and utilize an optimal method for the prevention of adhesions in the flexor tendons of the hand, due to post-surgical complications.

AREAS OF CONTROVERSY

Even though there have been significant advances in the prevention of adhesions in flexor tendons, it remains to be proved which, if any, of the current methods are the most beneficial.

GROWING POINTS

The only thing that appears clinically justified in adhesion prevention is the need for early post-operative mobilization of digits after tendon injury or repair but the best method of mobilization remains controversial.

AREAS TIMELY FOR DEVELOPING RESEARCH

Suggested changes in surgical techniques and various proposed pharmacological and non-pharmacological modalities need to withstand the test of adequately powered human trials, before their justification for potential benefit in clinical practice is accepted.

Use of a static magnetic field to promote recovery after peripheral nerve injury

Object

While pulsed electromagnetic stimulation has been shown to enhance peripheral nerve regeneration, the effect of a static magnetic field on nerve repair is less clear. The aim of this study was to establish what effect an imposed exogenous static magnetic field has on peripheral nerve regeneration after transection and repair.

Methods

Three groups of six adult sheep were used. The first group acted as normal controls. In the second group, the median nerve was divided and immediately repaired by entubulation within a “controlled-release” biodegradable glass tube. In the third group, small magnets were applied to the sides of the biodegradable glass tubes before the median nerve was repaired using these magnetic tubes. The sheep were allowed to recover and were reexamined 10 months later. The animals underwent comprehensive morphometric (cross-sectional morphometry and measurement of internodal lengths), electrophysiological (determinations of stimulated jitter, maximum conduction velocity, refractory period, and F waves), and isometric tension (isometric twitch and tetanic tension) assessments.

Conclusions

Exogenously applied static electromagnetic fields do not enhance peripheral nerve regeneration.

The use of ciliary neurotrophic factor to promote recovery after peripheral nerve injury by delivering it at the site of the cell body

Despite a body of evidence showing that various neurotrophic factors support the survival of nerve cells and stimulate axonal outgrowth, doubt remains about their optimal site of application as well as the more compelling question of what clinical benefit, if any, they would confer. Ciliary neurotrophic factor (CNTF) supports the survival of motorneurons in vitro and in vivo. Direct delivery of CNTF to the cell bodies may help reduce the side effects and overcome the problem of rapid systemic clearance. The aim of this study was to establish whether nerve regeneration may be improved upon by the controlled addition of a specific humoral neurotrophic substance (CNTF) at the level of the cell body. Three groups of five adult sheep were used. The first group acted as normal controls. In the second and third groups, the median nerve was divided and repaired using an epineurial suture technique. In the second group, CNTF was supplied into the CSF at the level of C6 by an implanted osmotic pump. In the third group physiological saline was placed in the osmotic pump. The animals underwent comprehensive electrophysiological and isometric tension experiments at six months. All of the animals had reduced electrophysiological, morphometric and isometric tension indices after surgery compared to normal. The CNTF group had better results than the saline group in the following; (1) area and amplitude of the muscle action potential (2) the percentage of tetanus and muscle mass preserved after repair. These differences were only statistically significant for amplitude of the muscle action potential. No statistical difference was found in the morphological indices (fibre diameter, axon diameter, myelin thickness and internodal length) between the CNTF and saline groups. CNTF does not confer a functional benefit when applied at the level of the cell body.

The role of electromyography in the management of the brachial plexus palsy of the newborn

Despite being the foremost examination in the management of traumatic nerve damage electromyography (EMG) has an uncertain and ill-defined role in the investigation of brachial plexus palsy of the newborn (BPPN). This may be because EMG, which is used most commonly several months after birth, fails to answer adequately two of the most important questions posed by this condition: its aetiology and the likely prognosis. In this review, we contend that EMG has important contributions to the solution of both of these questions but only if the timing of the investigation is altered. Used early on in the first few days after birth, EMG can separate the rare palsies that occurred during the intrauterine period from those caused by events at the time of birth, and thus have an important role in directing the investigations of the aetiology more appropriately. EMG alone would still not be able to determine which of the perinatal events were responsible. If the EMG is then repeated before reinnervation complicates interpretation, it seems probable that it would identify accurately those cases, where neurotmesis and avulsion have occurred, much earlier than 3 months of age, the crucial age in the clinical assessment of BPPN for consideration for surgery. This might have very important implications for the future directions of treatment.

Assessment of the method and timing of repair of a brachial plexus traction injury in an animal model for obstetric brachial plexus palsy

A Sunderland type IV traction injury to the C6 root of adult sheep or newborn lamb brachial plexus was used as a model for obstetric traction injury to the C5 root in humans. In one experimental cohort the injury was created and repaired using interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in a group of adult sheep and in a group of newborn lambs. In a second cohort a similar injury was created and repaired either immediately or after a delay of 30 days, using either interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in four groups of six newborn lambs. In all cases both functional and morphometric indices of nerve regeneration were poorer in the injured and repaired nerves than in normal nerves. In lambs the method of repair made no difference and no significant differences were found for any of the indices of nerve function or morphology. In sheep the use of muscle grafts was associated with a poorer outcome than the use of nerve autografts. Where a delay of 30 days had elapsed between injury and repair, the results using nerve autografts were not significantly different. Where freeze-thawed muscle autografts had been used, the maturation of the regenerated nerve fibres after delay was significantly poorer than after immediate repair. The electrophysiological variables CV(max) and jitter, which may be applied clinically, were found to be good discriminators of recovery in all of the animals and in respect of all procedures.

Obstetric brachial plexus palsy: a comparison of the degree of recovery after repair of a C6 ventral root avulsion in newborn and adult sheep

The C6 motor rootlets were avulsed from the spinal cord in six newborn lambs to simulate a birth lesion of the upper root of the brachial plexus. Six 1-year-old sheep were used for comparison, and treated in a similar manner. The injury was repaired immediately in each group using an autologous coaxial freeze-thawed skeletal muscle graft. The animals were allowed to recover for 1 year after the surgery. The C6 root was then examined electrophysiologically and morphologically. The results were compared with those obtained from a group of untreated intact 1-year-old sheep. The fibre and axon diameters and myelin sheath thickness were significantly different in the group repaired as lambs when compared with the group repaired at the age of 1 year. There was also a significantly increased maximum conduction velocity and a greater range of conduction velocities within the nerve in the lambs. Central motor latency was significantly slower in the sheep than in the lambs. These findings would suggest a greater potential for recovery in the lambs after brachial plexus root avulsion injuries.

Obstetric lesions of the brachial plexus

The few studies on prognosis of obstetric lesions of the brachial plexus that are not hampered by selection bias or a short follow-up suggest that functional impairment persists in 20-25% of cases, more than commonly thought. Electromyography (EMG), potentially useful for prognosis, is often considered of little value. Denervation in the first week of life has been interpreted as evidence of an antenatal lesion, but is the logical result of the short axonal length affected. EMG performed at close to the time of possible intervention (3 months) usually shows a discrepancy: motor unit potentials are seen in clinically paralyzed muscles. This can be explained in five ways: an overly pessimistic clinical examination; overestimation of EMG recruitment due to small muscle fibers; persistent fetal innervation; developmental apraxia; or misdirection, in which axons reach inappropriate muscles. Further research into the pathophysiology of obstetric lesions of the brachial plexus is needed to improve prognostication.