Nerve stretching: a history of tension

Exploring the molecular pathways and therapeutic implications of angiogenesis in neuropathic pain

Recently, much attention has been paid to chronic neuro-inflammatory condition underlying neuropathic pain. It is generally linked with thermal hyperalgesia and tactile allodynia. It results due to injury or infection in the nervous system. The neuropathic pain spectrum covers a variety of pathophysiological states, mostly involved are ischemic injury viral infections associated neuropathies, chemotherapy-induced peripheral neuropathies, autoimmune disorders, traumatic origin, hereditary neuropathies, inflammatory disorders, and channelopathies. In CNS, angiogenesis is evident in inflammation of neurons and pain in bone cancer. The role of chemokines and cytokines is dualistic; their aggressive secretion produces detrimental effects, leading to neuropathic pain. However, whether the angiogenesis contributes and exists in neuropathic pain remains doubtful. In the present review, we elucidated summary of diverse mechanisms of neuropathic pain associated with angiogenesis. Moreover, an overview of multiple targets that have provided insights on the VEGF signaling, signaling through Tie-1 and Tie-2 receptor, erythropoietin pathway promoting axonal growth are also discussed. Because angiogenesis as a result of these signaling, results in inflammation, we focused on the mechanisms of neuropathic pain. These factors are mainly responsible for the activation of post-traumatic regeneration of the PNS and CNS. Furthermore, we also reviewed synthetic and herbal treatments targeting angiogenesis in neuropathic pain.

The Grasping Test Revisited: A Systematic Review of Functional Recovery in Rat Models of Median Nerve Injury

The rat median nerve model is a well-established and frequently used model for peripheral nerve injury and repair. The grasping test is the gold-standard to evaluate functional recovery in this model. However, no comprehensive review exists to summarize the course of functional recovery in regard to the lesion type. According to PRISMA-guidelines, research was performed, including the databases PubMed and Web of Science. Groups were: (1) crush injury, (2) transection with end-to-end or with (3) end-to-side coaptation and (4) isogenic or acellular allogenic grafting. Total and respective number, as well as rat strain, type of nerve defect, length of isogenic or acellular allogenic allografts, time at first signs of motor recovery (FSR) and maximal recovery grasping strength (MRGS), were evaluated. In total, 47 articles met the inclusion criteria. Group I showed earliest signs of motor recovery. Slow recovery was observable in group III and in graft length above 25 mm. Isografts recovered faster compared to other grafts. The onset and course of recovery is heavily dependent from the type of nerve injury. The grasping test should be used complementary in addition to other volitional and non-volitional tests. Repetitive examinations should be planned carefully to optimize assessment of valid and reliable data.

Use of ultrasound and targeted physiotherapy to manage nerve sutures placed under joint flexion: a case series

Background

Joint flexion to diminish the gap and avoid nerve grafts fell into disuse for decades, but recently attention for using this technique was regained. We report a case series of nerve suture under joint flexion, ultrasound monitoring, and physiotherapy. Our main objective was to determine how effective this multimodality treatment is.

Methods

A retrospective review of 8 patients treated with direct repair with joint flexion was done. Depending on the affected nerve, either the knee or the elbow was flexed intraoperatively to determine if direct suturing was possible. After surgery, the limb was held immobilized. Through serial ultrasounds and a physiotherapy program, the limb was fully extended. If a nerve repair rupture was observed, the patient was re-operated and grafts were used.

Results

Of the eight nerve sutures analyzed, four sustained a nerve rupture revealed by US at an early stage, while four did not show any sign of dehiscence. In the patients in whom the nerve suture was preserved, an early and very good response was observed. Ultrasound was 100% accurate at identifying nerve suture preservation. Early detection of nerve failure permitted early re-do surgery using grafts without flexion, ultimately determining good final results.

Conclusions

We observed a high rate of dehiscence in our group of patients treated with direct repair and joint flexion. We believe this was due to an incorrect use of the immobilization device, excessive movement, or a broken device. In opposition to this, we observed that applying direct nerve sutures and joint flexion offers unusually good and fast results. If this technique is employed, it is mandatory to closely monitor suture status with US, together with physiotherapy providing progressive, US-guided extension of the flexed joint. If nerve rupture occurs, the close monitoring dictated by this protocol should ensure the timely application of a successful graft repair.

Incorporating Blood Flow in Nerve Injury and Regeneration Assessment

Peripheral nerve injury is a significant public health challenge, with limited treatment options and potential lifelong impact on function. More than just an intrinsic part of nerve anatomy, the vascular network of nerves impact regeneration, including perfusion for metabolic demands, appropriate signaling and growth factors, and structural scaffolding for Schwann cell and axonal migration. However, the established nerve injury classification paradigm proposed by Sydney Sunderland in 1951 is based solely on hierarchical disruption to gross anatomical nerve structures and lacks further information regarding the state of cellular, metabolic, or inflammatory processes that are critical in determining regenerative outcomes. This review covers the anatomical structure of nerve-associated vasculature, and describes the biological processes that makes these vessels critical to successful end-organ reinnervation after severe nerve injuries. We then propose a theoretical framework that incorporates measurements of blood vessel perfusion and inflammation to unify perspectives on all mechanisms of nerve injury.

Comparative Effects of Tensioning and Sliding Neural Mobilization on Peripheral and Autonomic Nervous System Function: A Randomized Controlled Trial

Background:

Although different types of neural mobilization (NM) exercises induce different amounts of longitudinal nerve excursion and strain, the question whether the increased longitudinal stress and nerve excursion from sliding or tensioning intervention may subtly affect the neural functions has not been answered yet.

Objective:

To compare the effects of tensioning NM versus sliding NM of the median nerve on peripheral and autonomic nervous system function.

Methods:

In this randomized controlled trial, 90 participants were randomly assigned to tensioning NM, sliding NM, or sham NM. The neurophysiological outcome measures included peak-to-peak amplitude of the dermatomal somatosensory evoked potential (DSSEP) for dermatomes C6, C7, C8, and T1. Secondary outcome measures included amplitude and latency of skin sympathetic response. All outcome measures were assessed pretreatment, immediately after the two weeks of treatment and one week after the last session of the treatment.

Results:

A 2-way repeated measures ANOVA revealed significant differences between the three groups. The post hoc analysis indicated that tensioning NM significantly decreased the dermatomal amplitude for C6, C7, C8, and T1 (p<0.005). Sympathetic skin responses in the gliding NM group showed lower amplitudes and prolonged latencies post-treatment when compared to tensioning NM group (p<0.05). In contrast, no significant changes were observed in the DSSEPs and skin sympathetic responses for participants in the sham treatment group (p>0.05).

Conclusions:

A tensioning NM on the median nerve had a possible adverse effect on the neurophysiology variables of the nerves involved in the neural mobilization. Thus, tensioning NM with the current parameters that place increased stress and strain on the peripheral nervous system should be avoided.

A Brief Review of In Vitro Models for Injury and Regeneration in the Peripheral Nervous System

Nerve axonal injury and associated cellular mechanisms leading to peripheral nerve damage are important topics of research necessary for reducing disability and enhancing quality of life. Model systems that mimic the biological changes that occur during human nerve injury are crucial for the identification of cellular responses, screening of novel therapeutic molecules, and design of neural regeneration strategies. In addition to in vivo and mathematical models, in vitro axonal injury models provide a simple, robust, and reductionist platform to partially understand nerve injury pathogenesis and regeneration. In recent years, there have been several advances related to in vitro techniques that focus on the utilization of custom-fabricated cell culture chambers, microfluidic chamber systems, and injury techniques such as laser ablation and axonal stretching. These developments seem to reflect a gradual and natural progression towards understanding molecular and signaling events at an individual axon and neuronal-soma level. In this review, we attempt to categorize and discuss various in vitro models of injury relevant to the peripheral nervous system and highlight their strengths, weaknesses, and opportunities. Such models will help to recreate the post-injury microenvironment and aid in the development of therapeutic strategies that can accelerate nerve repair.

Association between overactive bladder and pelvic organ mobility as evaluated by dynamic magnetic resonance imaging

Overactive bladder (OAB) is a prevalent condition, which negatively impacts patients’ quality of life. Pelvic organ prolapse (POP), also prevalent in women, has been recognized as an important etiology of female OAB, although the pathophysiological mechanisms remain controversial. In this study, we reviewed findings of dynamic magnetic resonance imaging (dMRI) in 118 patients with POP and investigated the association between dMRI findings, including positions and mobilities of pelvic organs as well as parameters of pelvic organ support and bladder outlet obstruction (urethral kinking), and OAB in order to elucidate the pathophysiology of OAB in patients with POP. Our results showed that compared with non-OAB patients, OAB patients had a significantly higher body mass index, more severe pelvic floor muscle impairment, and more profound supportive defects in the uterine cervix (apical compartment). On the other hand, dMRI parameters showed hardly any significant difference between patients with mild and moderate to severe OAB. These findings may imply that levator ani impairment and defective supports of the apical compartment could be associated with the presence of OAB and that the severity of OAB could be affected by factors other than those related to pelvic organ mobility and support or urethral kinking.

Nerve Ultrasound in Traumatic and Iatrogenic Peripheral Nerve Injury

Peripheral nerve injury is a potentially debilitating disorder that occurs in an estimated 2–3% of all patients with major trauma, in a similar percentage of medical procedures. The workup of these injuries has traditionally been clinical, combined with electrodiagnostic testing. However, this has limitations, especially in the acute phase of the trauma or lack of any recovery, when it is very important to determine nerve continuity and perform surgical exploration and repair in the case of the complete transection or intraneural fibrosis. Ultrasound can help in those situations. It is a versatile imaging technique with a high sensitivity of 93% for detecting focal nerve lesions. Ultrasound can assess the structural integrity of the nerve, neuroma formation and other surrounding abnormalities of bone or foreign bodies impeding the nerve. In addition, this can help to prevent iatrogenic nerve injury by marking the nerve before the procedure. This narrative review gives an overview of why and how nerve ultrasound can play a role in the detection, management and prevention of peripheral nerve injury.

Pathologic remodeling in human neuromas: insights from clinical specimens

BACKGROUND

Neuroma pathology is commonly described as lacking a clear internal structure, but we observed evidence that there are consistent architectural elements. Using human neuroma samples, we sought to identify molecular features that characterize neuroma pathophysiology.

METHODS

Thirty specimens-12 neuromas-in-continuity (NICs), 11 stump neuromas, two brachial plexus avulsions, and five controls-were immunohistochemically analyzed with antibodies against various components of normal nerve substructures.

RESULTS

There were no substantial histopathologic differences between stump neuromas and NICs, except that NICs had intact fascicle(s) in the specimen. These intact fascicles showed evidence of injury and fibrosis. On immunohistochemical analysis of the neuromas, laminin demonstrated a consistent double-lumen configuration. The outer lumen stained with GLUT1 antibodies, consistent with perineurium and microfascicle formation. Antibodies to NF200 revealed small clusters of small-diameter axons within the inner lumen, and the anti-S100 antibody showed a relatively regular pattern of non-myelinating Schwann cells. CD68+ cells were only seen in a limited temporal window after injury. T-cells were seen in neuroma specimens, with both a temporal evolution as well as persistence long after injury. Avulsion injury specimens had similar architecture to control nerves. Seven pediatric specimens were not qualitatively different from adult specimens. NICs demonstrated intact but abnormal fascicles that may account for the neurologically impoverished outcomes from untreated NICs.

CONCLUSIONS

We propose that there is consistent pathophysiologic remodeling after fascicle disruption. Particular features, such as predominance of small caliber axons and persistence of numerous T-cells long after injury, suggest a potential role in chronic pain associated with neuromas.