Cortical Plasticity Following Upper Extremity Injury and Reconstruction

Surgery for mononeuropathies

Advancement in microsurgical techniques and innovative approaches including greater use of nerve and tendon transfers have resulted in better peripheral nerve injury (PNI) surgical outcomes. Clinical evaluation of the patient and their injury factors along with a shift toward earlier time frame for intervention remain key. A better understanding of the pathophysiology and biology involved in PNI and specifically mononeuropathies along with advances in ultrasound and magnetic resonance imaging allow us, nowadays, to provide our patients with a logical and sophisticated approach. While functional outcomes are constantly being refined through different surgical techniques, basic scientific concepts are being advanced and translated to clinical practice on a continuous basis. Finally, a combination of nerve transfers and technological advances in nerve/brain and machine interfaces are expanding the scope of nerve surgery to help patients with amputations, spinal cord, and brain lesions.

Traumatic peripheral nerve injuries: diagnosis and management

PURPOSE OF REVIEW

To review advances in the diagnostic evaluation and management of traumatic peripheral nerve injuries.

RECENT FINDINGS

Serial multimodal assessment of peripheral nerve injuries facilitates assessment of spontaneous axonal regeneration and selection of appropriate patients for early surgical intervention. Novel surgical and rehabilitative approaches have been developed to complement established strategies, particularly in the area of nerve grafting, targeted rehabilitation strategies and interventions to promote nerve regeneration. However, several management challenges remain, including incomplete reinnervation, traumatic neuroma development, maladaptive central remodeling and management of fatigue, which compromise functional recovery.

SUMMARY

Innovative approaches to the assessment and treatment of peripheral nerve injuries hold promise in improving the degree of functional recovery; however, this remains a complex and evolving area.

Reflections of the sensory findings in the central nervous system in patients with neuropathic pain

This study aimed to evaluate whether there was a difference in functional magnetic resonance imaging (fMRI) findings in patients who were found having hyperalgesia or hypoesthesia according to Quantitative Sensory Tests (QST). Forty participants were included in the study: 20 with neuropathic pain (NP) due to cervical disc pathology (NP group) and 20 healthy volunteers. After obtaining the socio-demographic and clinical data of the participants, the painDETECT questionnaire was administered, followed by QST analysis to show the presence of hypoesthesia and/or hyperalgesia, and fMRI examinations, which included sensory stimulation of both extremities. Sensory threshold tests were found to be higher in the NP group compared with the healthy volunteers, and the heat pain threshold was found to be lower in the tests showing pain thresholds in the intergroup analyses (p < 0.05). The changes described were found in both painful and non-painful limbs. In the hypoesthetic NP group, a lower somatosensory cortex activity was found in non-painful limbs compared with the healthy volunteers (p < 0.05). In the unilateral hyperalgesic NP group, a lower somatosensory cortex activity was found on the painful side, and if the hyperalgesia was widespread, lower blood oxygen-level-dependent activity was also found in the operculum and insular cortex (p < 0.05). The patients with different phenotypes of NP had different activities in the areas related to the processing of pain, and were more prominent in patients with widespread hyperalgesia. Studies with larger numbers of patients are required for a definite statement.

Cortical Plasticity in Rehabilitation for Upper Extremity Peripheral Nerve Injury: A Scoping Review

IMPORTANCE

Poor outcomes after upper extremity peripheral nerve injury (PNI) may arise, in part, from the challenges and complexities of cortical plasticity. Occupational therapy practitioners need to understand how the brain changes after peripheral injury and how principles of cortical plasticity can be applied to improve rehabilitation for clients with PNI.

OBJECTIVE

To identify the mechanisms of cortical plasticity after PNI and describe how cortical plasticity can contribute to rehabilitation.

DATA SOURCES

PubMed and Embase (1900-2017) were searched for articles that addressed either (1) the relationship between PNI and cortical plasticity or (2) rehabilitative interventions based on cortical plastic changes after PNI.

Study Selection and Data Collectio

: PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. Articles were selected if they addressed all of the following concepts: human PNI, cortical plasticity, and rehabilitation. Phantom limb pain and sensation were excluded.

FINDINGS

Sixty-three articles met the study criteria. The most common evidence level was Level V (46%). We identified four commonly studied mechanisms of cortical plasticity after PNI and the functional implications for each. We found seven rehabilitative interventions based on cortical plasticity: traditional sensory reeducation, activity-based sensory reeducation, selective deafferentation, cross-modal sensory substitution, mirror therapy, mental motor imagery, and action observation with simultaneous peripheral nerve stimulation.

CONCLUSION AND RELEVANCE

The seven interventions ranged from theoretically well justified (traditional and activity-based sensory reeducation) to unjustified (selective deafferentation). Overall, articles were heterogeneous and of low quality, and future research should prioritize randomized controlled trials for specific neuropathies, interventions, or cortical plasticity mechanisms.

WHAT THIS ARTICLE ADDS

This article reviews current knowledge about how the brain changes after PNI and how occupational therapy practitioners can take advantage of those changes for rehabilitation.

Peripheral nerve injuries, pain, and neuroplasticity

INTRODUCTION

Peripheral nerve injuries (PNIs) cause both structural and functional brain changes that may be associated with significant sensorimotor abnormalities and pain.

PURPOSE OF THE STUDY

The aim of this narrative review is to provide hand therapists an overview of PNI-induced neuroplasticity and to explain how the brain changes following PNI, repair, and during rehabilitation.

METHODS

Toward this goal, we review key aspects of neuroplasticity and neuroimaging and discuss sensory testing techniques used to study neuroplasticity in PNI patients.

RESULTS

We describe the specific brain changes that occur during the repair and recovery process of both traumatic (eg, transection) and nontraumatic (eg, compression) nerve injuries. We also explain how these changes contribute to common symptoms including hypoesthesia, hyperalgesia, cold sensitivity, and chronic neurogenic pain. In addition, we describe how maladaptive neuroplasticity as well as psychological and personality characteristics impacts treatment outcome.

DISCUSSION AND CONCLUSION

Greater understanding of the brain's contribution to symptoms in recovering PNI patients could help guide rehabilitation strategies and inform the development of novel techniques to counteract these maladaptive brain changes and ultimately improve outcomes.

The lived experience of motor recovery of elbow flexion following Oberlin nerve transfer: A qualitative analysis

Introduction

Nerve injuries to the upper trunk, lateral cord and musculocutaneous nerve can result in the loss of active biceps contraction. Oberlin nerve transfer surgery is often performed to re-animate the biceps muscle. Outcome studies following this surgery almost exclusively focus on muscle strength. To date, no research has focused on the lived experience of motor recovery following Oberlin nerve transfer.

Methods

A focus group discussion ( n = 6) allowed participants to give their accounts of successful restoration of active elbow flexion. Qualitative analysis of the transcript identified ‘significant statements’ which were used to generate themes and capture participants’ lived experience.

Results

Four main themes were identified as being important components of the lived experience: ‘pain’, ‘patience and positive thought’, ‘functionality and daily lifestyle’ and ‘the biceps muscle’ itself. Each theme was identified to have several subthemes and constituent parts.

Conclusions

The lived experience of motor recovery is complex, multifaceted and individual to the patient. This study has identified areas where clinicians may be able to better tailor their care to the individual and suggested adjuncts to therapy have been included.

Novel method for restoration of anorectal function following spinal cord injury via nerve transfer in rats

OBJECTIVES

Nerve transfer has been developed to restore partial function after serious nerve injuries, for example, restoring bladder control after spinal cord injury (SCI). Our aim here was to establish a preclinical proof-of-concept model using nerve transfer for restoring anorectal function after SCI.

SETTING

We used laminectomy to model SCI, and bilateral spinal ventral and dorsal nerve root anastomosis to re-establish connectivity to the anorectal musculature.

METHODS

Multidisciplinary methods were used to assess the anatomical and functional integrity of the alternative spinal-to-anorectal nerve circuit. Adult rats were used to establish the model. Bilateral anterior and posterior L5 nerve roots were surgically matched with anterior and posterior of S1 nerve roots by microscopic anastomosis to establish an artificial rectal reflex arc with complete sensory and motor pathways. Twelve weeks later, we used retrograde nerve tracing and neurohistomorphological analysis to assess anatomical integrity of the new artificial rectal reflex arc. Anorectal manometry was used to assess the function of the new nerve circuit.

RESULTS

Retrograde tracing with recombinant attenuated pseudo rabies virus indicated that the new neural pathway was successfully established to the anorectal musculature after experimental SCI. Toluidine blue-stained sections of the anastomosis site revealed normal-appearing nerve fiber morphology and regeneration, and transmission electron microscopy revealed myelinated axons. Anorectal manometry revealed significant anorectal functional recovery.

CONCLUSION

These results suggest that our model is a feasible first step in developing an alternative reflex pathway after laminectomy at L4 to S2 and shows promise for effective restoration of anorectal function.

Evaluation of the Neo-umbilicus Cutaneous Sensitivity Following Abdominoplasty

BACKGROUND

Abdominal cutaneous sensitivity loss after abdominoplasty is an undesirable outcome. However, little is known in the literature about sensitivity changes of the neo-umbilicus after abdominoplasty. The aim of this study was to evaluate post-abdominoplasty cutaneous sensitivity of the neo-umbilicus using clinical, quantitative, and reproducible methods.

METHODS

Patients who underwent abdominoplasty were included, whereas the control group consisted of healthy volunteers with similar demographic characteristics but who did not undergo abdominoplasty. The umbilicus was divided into five zones, and superficial tactile sensitivity and spatial orientation were assessed subjectively (score 1-4) and objectively (Semmes-Weinstein monofilament examination).

RESULTS

Twenty patients (45 ± 12 years) operated on consecutively between April 2012 and May 2016 and 14 healthy volunteers in the control group (39 ± 9 years) could be included. Although there were statistically significant differences (p = 0.0005) in the average cutaneous pressure thresholds between the control group (0.4 g/mm², range 0.07-2 g/mm²) and the study group (0.4 g/mm², range 0.07-4 g/mm²), patient satisfaction after a mean follow-up of 33 ± 16 months (range 10-62 months) was acceptable (mean satisfaction score 1.8 ± 0.7). Furthermore, spatial perceptions were precise in all patients and similar to the control group.

CONCLUSION

Our long-term results indicate that spontaneous reinnervation of the neo-umbilicus after abdominoplasty together with accurate spatial orientation can occur.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A longitudinal study of pain, personality, and brain plasticity following peripheral nerve injury

We do not know precisely why pain develops and becomes chronic after peripheral nerve injury (PNI), but it is likely due to biological and psychological factors. Here, we tested the hypotheses that (1) high Pain Catastrophizing Scale (PCS) scores at the time of injury and repair are associated with pain and cold sensitivity after 1-year recovery and (2) insula gray matter changes reflect the course of injury and improvements over time. Ten patients with complete median and/or ulnar nerve transections and surgical repair were tested ∼3 weeks after surgical nerve repair (time 1) and ∼1 year later for 6 of the 10 patients (time 2). Patients and 10 age-/sex-matched healthy controls completed questionnaires that assessed pain (patients) and personality and underwent quantitative sensory testing and 3T MRI to assess cortical thickness. In patients, pain intensity and neuropathic pain correlated with pain catastrophizing. Time 1 pain catastrophizing trended toward predicting cold pain thresholds at time 2, and at time 1 cortical thickness of the right insula was reduced. At time 2, chronic pain was related to the time 1 pain-PCS relationship and cold sensitivity, pain catastrophizing correlated with cold pain threshold, and insula thickness reversed to control levels. This study highlights the interplay between personality, sensory function, and pain in patients following PNI and repair. The PCS-pain association suggests that a focus on affective or negative components of pain could render patients vulnerable to chronic pain. Cold sensitivity and structural insula changes may reflect altered thermosensory or sensorimotor awareness representations.

Impaired Automatic Arm Movements in Obstetric Brachial Plexus Palsy Suggest a Central Disorder

The authors aimed to find evidence for a central component of the impairment of movement of the affected arm in children with obstetric brachial plexus palsy. The authors performed a cross-sectional study in 19 children (median age 5 years) with obstetric brachial plexus palsy who were able to voluntarily abduct their affected arm beyond 90 degrees. They were asked to perform 4 tasks designed to provoke automatic arm movements to maintain balance. The authors assumed automatic motor programming to be impaired when 2 of 3 investigators agreed using video recordings that the affected arm did not abduct beyond 90 degrees while the unaffected arm did. Children abducted the affected arm less often than the healthy one (generalized binary logistic model of all 4 tasks, P = .001). The deficit during automatic arm abduction was not observed during voluntary movements and therefore cannot be explained by a peripheral deficit, suggesting a central component.

Free Functional Muscle Transfers to Restore Upper Extremity Function

Free functional muscle transfer provides an option for functional restoration when nerve reconstruction and tendon transfers are not feasible. To ensure a successful outcome, many factors need to be optimized, including proper patient selection, timing of intervention, donor muscle and motor nerve selection, optimal microneurovascular technique and tension setting, proper postoperative management, and appropriate rehabilitation. Functional outcomes of various applications to the upper extremity and the authors' algorithm for the use of free functional muscle transfer are also included in this article.

Primary Motor Cortex Representation of Handgrip Muscles in Patients with Leprosy

BACKGROUND

Leprosy is an endemic infectious disease caused by Mycobacterium leprae that predominantly attacks the skin and peripheral nerves, leading to progressive impairment of motor, sensory and autonomic function. Little is known about how this peripheral neuropathy affects corticospinal excitability of handgrip muscles. Our purpose was to explore the motor cortex organization after progressive peripheral nerve injury and upper-limb dysfunction induced by leprosy using noninvasive transcranial magnetic stimulation (TMS).

METHODS

In a cross-sectional study design, we mapped bilaterally in the primary motor cortex (M1) the representations of the hand flexor digitorum superficialis (FDS), as well as of the intrinsic hand muscles abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM). All participants underwent clinical assessment, handgrip dynamometry and motor and sensory nerve conduction exams 30 days before mapping. Wilcoxon signed rank and Mann-Whitney tests were performed with an alpha-value of p<0.05.

FINDINGS

Dynamometry performance of the patients' most affected hand (MAH), was worse than that of the less affected hand (LAH) and of healthy controls participants (p = 0.031), confirming handgrip impairment. Motor threshold (MT) of the FDS muscle was higher in both hemispheres in patients as compared to controls, and lower in the hemisphere contralateral to the MAH when compared to that of the LAH. Moreover, motor evoked potential (MEP) amplitudes collected in the FDS of the MAH were higher in comparison to those of controls. Strikingly, MEPs in the intrinsic hand muscle FDI had lower amplitudes in the hemisphere contralateral to MAH as compared to those of the LAH and the control group. Taken together, these results are suggestive of a more robust representation of an extrinsic hand flexor and impaired intrinsic hand muscle function in the hemisphere contralateral to the MAH due to leprosy.

CONCLUSION

Decreased sensory-motor function induced by leprosy affects handgrip muscle representation in M1.

Rehabilitation of the upper extremity following nerve and tendon reconstruction: when and how

Following upper extremity nerve and tendon reconstruction, rehabilitation is necessary to achieve optimal function and outcome. In this review, the authors present current evidence and literature regarding the strategies and techniques of rehabilitation following peripheral nerve and tendon reconstruction.

Advances in nerve transfer surgery

Peripheral nerve injuries are devastating injuries and can result in physical impairments, poor functional outcomes and high levels of disability. Advances in our understanding of peripheral nerve regeneration and nerve topography have lead to the development of nerve transfers to restore function. Over the past two decades, nerve transfers have been performed and modified. With the advancements in surgical management and recognition of importance of cortical plasticity, motor-reeducation and perioperative rehabilitation, nerve transfers are producing improved functional outcomes in patients with nerve injuries. This manuscript explores the recent literature as it relates to current nerve transfer techniques and advances in post-operative rehabilitation protocols, with a focus on indications, techniques and outcomes.

Free Muscle Transfer in Posttraumatic Plexopathies Part II: The Elbow

The indications for free muscle transfer in brachial plexopathies are prolonged denervation time or inadequate upper extremity function after primary nerve reconstruction. The purpose of this study is to analyze the outcomes of free muscle transfer for elbow flexion and extension in brachial plexopathies in relation to the different muscles used and the respective motor donors. Seventy-three muscles were transferred for elbow flexion and ten for elbow extension. Latissimus dorsi (LD) was used in 37 cases, gracilis in 28, rectus femoris (RF) in seven, and vastus lateralis in one. Five LD and five gracilis were transferred for elbow extension. Patients younger than 15 years yielded better results than older patients for elbow flexion. When LD was transferred, the mean muscle grading (MG) was 3.33 ± 0.25 when the neurotization was from intercostals; these outcomes were statistically significant when compared with outcomes of free gracilis transfer (MG 2.25 ± 0.6). There was also a statistically significant difference when free LD was neurotized with three intercostals as compared with two intercostals nerves. RF yielded also good results when neurotized from contralateral C7 (cC7; MG 3.67 ± 0.6). For elbow extension, the better outcomes of LD were not statistically significant. Among all the free muscle transfers for upper extremity reconstruction, elbow reanimation yielded the most rewarding outcomes. The selection of powerful muscle units was more important than the effect of neurotization which was not as strong as it was in muscle transfers for facial or hand reanimation.

Rehabilitation following motor nerve transfers

Cortical mapping and relearning are key factors in optimizing patient outcome following motor nerve transfers. To maximize function following nerve transfers, the rehabilitation program must include motor reeducation to initiate recruitment of the weak reinnervated muscles and to establish new motor patterns and cortical mapping. Patient education and a home program are essential to obtain the optimal functional result.

Cortical plasticity following nerve transfer in the upper extremity

With increasing clinical experience, peripheral nerve surgeons have come to appreciate the important role that cortical plasticity and motor relearning play in functional recovery following a nerve transfer. Neurostimulation (transcranial magnetic stimulation), and neuroimaging (functional MRI, structural MRI, magnetoencephalography) measure different aspects of cortical physiology and when used together are powerful tools in the study of cortical plasticity. The mechanisms of cortical plasticity, according to current and widely accepted opinions, involve the unmasking of previously ineffective connections or the sprouting of intact afferents from adjacent cortical or subcortical territories. Although significant strides have been made in our understanding of cortical plasticity following nerve transfer and during motor relearning, a great deal remains that we do not understand. Cortical plasticity and its manipulation may one day become important contributors to improve functional outcome following nerve transfer.

TRAUMATIC LESIONS OF THE BRACHIAL PLEXUS

OBJECTIVE

To analyze retrospectively the outcomes of primary as well as secondary functional reconstructions in 49 patients with traumatic brachial plexus lesions from a single service. Guidelines for treatment might be extracted from this analysis.

METHODS

Among 152 cases of traumatic lesion of the brachial plexus presented to our clinic, 58 underwent primary brachial plexus reconstructive surgery. On exploration, all patients showed stretching and scarring of plexus elements; root avulsions were found in 28 patients (48%). Outcome evaluation was carried out in 49 of these patients with a follow-up period of 1 year or longer (mean follow-up, 27.9 mo; range, 12–72 mo). A total of 43 secondary reconstructive procedures to improve functionality of the involved arm were performed at a later stage in 25 of 58 patients. Outcomes of the secondary functional restorative procedures were evaluated (mean follow-up, 11.5 mo; range, 3–60 mo in 43 procedures).

RESULTS

Patients with neurolysis as a stand-alone procedure (11 patients) showed an outcome grade of 4 or 5. The average outcome of the 19 patients with C5, C6, and C7 grafting was Grade 3, the same as in patients with nerve transfers to the upper plexus elements (C5–C6 root avulsions, 13 patients). Patients with multiple root avulsions (five cases) showed an overall poor outcome (Grades 0–2). Secondary functional restorative surgery was performed in 43% of the patients and helped improve individual outcomes, providing a favorable effect on the general functionality of the arm. Among the restorative operations performed, the Steindler procedure, wrist extension restoration, claw hand correction, and free functional muscle flap transfer to the arm and forearm were the most rewarding.

CONCLUSION

A combination of primary brachial plexus reconstruction and carefully evaluated, selected, and planned function-restorative secondary procedures might offer favorable outcomes in patients with partial or total brachial plexus lesions.