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

The Muscle Shortening Maneuver: a noninvasive approach to the treatment of peroneal nerve injury. A case report

BACKGROUND

The treatment of peripheral nerve injuries is a debated topic. The Muscle Shortening Maneuver (MSM), a physiotherapy approach, is noninvasive and free of side effects; it consists of a muscle shortening and a solicitation in traction applied simultaneously.

OBJECTIVE

The focus of this report is to describe the effects of the MSM combined with walking retraining in a patient with incomplete injury of the peroneal nerve.

DESCRIPTION

The patient was a 17-year-old man, who underwent osteotomy surgery of the proximal two-thirds of the fibula, due to an Ewing sarcoma that caused a partial injury of the left peroneal nerve. Our assessment plan of the left ankle movement ability comprised range of movement, muscle strength, and surface electromyography (EMG); and a gait analysis was conducted by using an iPhone application. MSM and walking retraining were administered twice and once a week, respectively, for 4 weeks.

OUTCOMES

The active range of movement substantially improved in dorsiflexion (≥15°), whereas slightly decreased in plantar flexion (-5°). Aside from the tibialis anterior, an increase in muscle strength was detected. Surface EMG showed an increased activation, particularly in the peroneus longus. A decrease in gait speed and step length was recorded from the gait analysis, with a better bilateral symmetry.

CONCLUSIONS

Positive outcomes were reported without evidence of risk or adverse events for the participant.

Sensory re-education after free neurovascular toe pulp flap for digital pulp reconstruction

PURPOSE

To evaluate the effectiveness of a sensory re-education (SR) program after free neurovascular toe pulp flap for finger or thumb pulp defect reconstruction.

METHODS

From January 2015 to January 2020, 49 patients with finger or thumb pulp defects treated with free fibular side flaps of the great toe or tibial side flaps of the second toe were recruited. The patients were randomly divided into two groups one month after surgery. The training group received the SR program, and the control group underwent the traditional rehabilitation program. Clinical evaluation included Semmes-Weinstein Monofilament (SWM) tests, static two-point discrimination (2-PD), and sensibility grading, measured at 1, 3, 6, 9, and 12 months postoperatively.

RESULTS

A total of 42 patients completed the follow-up, including 22 (16 males) patients in the training group and 20 patients (12 males) in the control group. Compared with 1 month after the operation, significant improvements in sensory recovery were observed at 3, 6, 9, and 12 months postoperatively in both groups. In addition, earlier sensory recovery was seen in the SR group compared to the control group, showing significant differences at 3 and 6 months but not at 9 and 12 months postoperatively.

CONCLUSION

Although SR seemed to accelerate preliminary sensory recovery after free neurovascular toe pulp flaps for digital defect reconstruction, the program should be reconsidered as it offers no significant improvement over the control group at later follow-up stages.

Assessment, patient selection, and rehabilitation of nerve transfers

Peripheral nerve injuries are common and can have a devastating effect on physical, psychological, and socioeconomic wellbeing. Peripheral nerve transfers have become the standard of care for many types of peripheral nerve injury due to their superior outcomes relative to conventional techniques. As the indications for, and use of, nerve transfers expand, the importance of pre-operative assessment and post-operative optimization increases. There are two principal advantages of nerve transfers: (1) their ability to shorten the time to reinnervation of muscles undergoing denervation because of peripheral nerve injury; and (2) their specificity in ensuring proximal motor and sensory axons are directed towards appropriate motor and sensory targets. Compared to conventional nerve grafting, nerve transfers offer opportunities to reinnervate muscles affected by cervical spinal cord injury and to augment natural reinnervation potential for very proximal injuries. This article provides a narrative review of the current scientific knowledge and clinical understanding of nerve transfers including peripheral nerve injury assessment and pre- and post-operative electrodiagnostic testing, adjuvant therapies, and post-operative rehabilitation for optimizing nerve transfer outcomes.

Reorganization of sensorimotor representations of the intact limb after upper but not lower limb traumatic amputation

It is becoming increasingly clear that limb loss induces wider spread reorganization of representations of the body that are nonadjacent to the affected cortical territory. Data from upper extremity amputees reveal intrusion of the representation of the ipsilateral intact limb into the former hand territory. Here we test for the first time whether this reorganization of the intact limb into the deprived cortex is specific to the neurological organization of the upper limbs or reflects large scale adaptation that is triggered by any unilateral amputation. BOLD activity was measured as human subjects with upper limb and lower limb traumatic amputation and their controls moved the toes on each foot, open and closed each hand and pursed their lips. Subjects with amputation were asked to imagine moving the missing limb while remaining still. Bayesian pattern component modeling of fMRI data showed that intact ipsilateral movements and contralateral movements of the hand and foot were distinctly represented in the deprived sensorimotor cortex years after upper limb amputation. In contrast, there was evidence reminiscent of contralateral specificity for hand and foot movements following lower limb amputation, like that seen in controls. We propose the cortical reorganization of the intact limb to be a function of use-dependent plasticity that is more specific to the consequence of upper limb loss of forcing an asymmetric reliance on the intact hand and arm. The contribution of this reorganization to phantom pain or a heightened risk of overuse and resultant maladaptive plasticity needs investigating before targeting such reorganization in intervention.

Altered Neural Pathways and Related Brain Remodeling: A Rat Study Using Different Nerve Reconstructions

BACKGROUND

Function recovery is related to cortical plasticity. The brain remodeling patterns induced by alterations in peripheral nerve pathways with different nerve reconstructions are unknown.

OBJECTIVE

To explore brain remodeling patterns related to alterations in peripheral neural pathways after different nerve reconstruction surgeries.

METHODS

Twenty-four female Sprague-Dawley rats underwent complete left brachial plexus nerve transection, together with the following interventions: no nerve repair (n = 8), grafted nerve repair (n = 8), and phrenic nerve transfer (n = 8). Resting-state functional MR images of brain were acquired at the end of seventh month postsurgery. Amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and functional connectivity (FC) were compared among 3 groups. Behavioral observation and electromyography assessed nerve regeneration.

RESULTS

Compared with brachial plexus injury group, ALFF and ReHo of left entorhinal cortex decreased in nerve repair and nerve transfer groups. The nerve transfer group showed increased ALFF and ReHo than nerve repair group in left caudate putamen, right accumbens nucleus shell (AcbSh), and right somatosensory cortex. The FC between right somatosensory cortex and bilateral piriform cortices and bilateral somatosensory cortices increased in nerve repair group than brachial plexus injury and nerve transfer groups. The nerve transfer group showed increased FC between right somatosensory cortex and areas including left corpus callosum, left retrosplenial cortex, right parietal association cortex, and right dorsolateral thalamus than nerve repair group.

CONCLUSION

Entorhinal cortex is a key brain area in recovery of limb function after nerve reconstruction. Nerve transfer related brain remodeling mainly involved contralateral sensorimotor areas, facilitating directional "shifting" of motor representation.

Review of rehabilitation protocols for brachial plexus injury

Brachial plexus injury (BPI) is one of the most serious peripheral nerve injuries, resulting in severe and persistent impairments of the upper limb and disability in adults and children alike. With the relatively mature early diagnosis and surgical technique of brachial plexus injury, the demand for rehabilitation treatment after brachial plexus injury is gradually increasing. Rehabilitation intervention can be beneficial to some extent during all stages of recovery, including the spontaneous recovery period, the postoperative period, and the sequelae period. However, due to the complex composition of the brachial plexus, location of injury, and the different causes, the treatment varies. A clear rehabilitation process has not been developed yet. Rehabilitation therapy that has been widely studied focusing on exercise therapy, sensory training, neuroelectromagnetic stimulation, neurotrophic factors, acupuncture and massage therapy, etc., while interventions like hydrotherapy, phototherapy, and neural stem cell therapy are less studied. In addition, rehabilitation methods in some special condition and group often neglected, such as postoperative edema, pain, and neonates. The purpose of this article is to explore the potential contributions of various methods to brachial plexus injury rehabilitation and to provide a concise overview of the interventions that have been shown to be beneficial. The key contribution of this article is to form relatively clear rehabilitation processes based on different periods and populations, which provides an important reference for the treatment of brachial plexus injuries.

Tactile Perception of the Hand in Children With an Upper Neonatal Brachial Plexus Palsy

OBJECTIVE

To investigate factors that cause impairment of hand function in children with an upper Neonatal Brachial Plexus Palsy (NBPP), we performed an in-depth analysis of tactile hand sensibility, especially the ability to correctly localize a sensory stimulus on their fingers.

DESIGN

A cross-sectional investigation of children with NBPP, compared with healthy controls. The thickest Semmes-Weinstein (SW) monofilament was pressed on the radial or ulnar part of each fingertip (10 regions), while a screen prevented seeing the hand.

SETTING

Tertiary referral center for nerve lesions in an academic hospital in The Netherlands. The control group was recruited at their school.

PARTICIPANTS

Forty-one children with NBPP (mean age 10.0 y) and 25 controls (mean age 9.5 y; N=41).

INTERVENTIONS

Not applicable.

MAIN OUTCOMES MEASURES

Correct localization of the applied stimuli was evaluated, per region, per finger, and per dermatome with a test score. The affected side of the NBPP group was compared with the non-dominant hand of the controls.

RESULTS

The ability to localize stimuli on the tips of the fingers in children with an upper NBPP was significantly diminished in all fingers, except for the little finger, as compared with healthy controls. Mean localization scores were 6.6 (thumb) and 6.3 (index finger) in the NBPP group and 7.6 in both fingers for controls (maximum score possible is 8.0). Localization scores were significant lower in regions attributed to dermatomes C6 (P<.001) and C7 (P=.001), but not to C8 (P=.115).

CONCLUSION

Children with an upper NBPP showed a diminished and incorrect ability to localize sensory stimuli to their fingers. This finding is likely 1 of the factors underlying the impairment of hand function and should be addressed with sensory focused therapy.

Identifying Oscillations under Multi-site Sensory Stimulation for High-level Peripheral Nerve Injured Patients：A Pilot Study

OBJECTIVE

For high-level peripheral nerve injured (PNI) patients with severe sensory dysfunction of upper extremities, identifying the multi-site tactile stimulation is of great importance to provide neurorehabilitation with sensory feedback. In this pilot study, we showed the feasibility of identifying multi-site and multi-intensity tactile stimulation in terms of electroencephalography (EEG).

APPROACH

Three high-level PNI patients and eight non-PNI participants were recruited in this study. Four different sites over the upper arm, forearm, thumb finger and little finger were randomly stimulated at two intensities (both sensory-level) based on the transcutaneous electrical nerve stimulation (TENS). Meanwhile, 64-channel EEG signals were recorded during the passive tactile sense stimulation on each side.

MAIN RESULTS

The spatial-spectral distribution of brain oscillations underlying multi-site sensory stimulation showed dominant power attenuation over the somatosensory and prefrontal cortices in both alpha-band (8-12 Hz) and beta-band (13-30 Hz). But there was no significant difference among different stimulation sites in terms of the averaged power spectral density over the region of interest (ROI). By further identifying different stimulation sites using temporal-spectral features, we found the classification accuracies were all above 89% for the affected arm of PNI patients, comparable to that from their intact side and that from the non-PNI group. When the stimulation site-intensity combinations were treated as eight separate classes, the classification accuracies were ranging from 88.89% to 99.30% for the affected side of PNI subjects, similar to that from their non-affected side and that from the non-PNI group. Other performance metrics, including Specificity, Precision, and F1-Score, also showed a sound identification performance for both PNI patients and non-PNI subjects.

SIGNIFICANCE

These results suggest that reliable brain oscillations could be evoked and identified well, even though induced tactile sense could not be discerned by the PNI patients. This study have implication for facilitating bidirectional neurorehabilitation systems with sensory feedback.

Evidence-Based Approach to Timing of Nerve Surgery: A Review

ABSTRACT

Events causing acute stress to the health care system, such as the COVID-19 pandemic, place clinical decisions under increased scrutiny. The priority and timing of surgical procedures are critically evaluated under these conditions, yet the optimal timing of procedures is a key consideration in any clinical setting. There is currently no single article consolidating a large body of current evidence on timing of nerve surgery. MEDLINE and EMBASE databases were systematically reviewed for clinical data on nerve repair and reconstruction to define the current understanding of timing and other factors affecting outcomes. Special attention was given to sensory, mixed/motor, nerve compression syndromes, and nerve pain. The data presented in this review may assist surgeons in making sound, evidence-based clinical decisions regarding timing of nerve surgery.

Plastic Changes in Pain and Motor Network Induced by Chronic Burn Pain

Musculoskeletal diseases with chronic pain are difficult to control because of their association with both central as well as the peripheral nervous system. In burn patients, chronic pain is one of the major complications that cause persistent discomfort. The peripheral mechanisms of chronic pain by burn have been greatly revealed through studies, but the central mechanisms have not been identified. Our study aimed to characterize the cerebral plastic changes secondary to electrical burn (EB) and non-electrical burn (NEB) by measuring cerebral blood volume (CBV). Sixty patients, twenty with electrical burn (EB) and forty with non-electrical burn (NEB), having chronic pain after burn, along with twenty healthy controls, participated in the study. Voxel-wise comparisons of relative CBV maps were made among EB, NEB, and control groups over the entire brain volume. The CBV was measured as an increase and decrease in the pain and motor network including postcentral gyrus, frontal lobe, temporal lobe, and insula in the hemisphere associated with burned limbs in the whole burn group. In the EB group, CBV was decreased in the frontal and temporal lobes in the hemisphere associated with the burned side. In the NEB group, the CBV was measured as an increase or decrease in the pain and motor network in the postcentral gyrus, precentral gyrus, and frontal lobe of the hemisphere associated with the burn-affected side. Among EB and NEB groups, the CBV changes were not different. Our findings provide evidence of plastic changes in pain and motor network in patients with chronic pain by burn.

The role of mirror mechanism in the recovery, maintenance, and acquisition of motor abilities

While it is well documented that the motor system is more than a mere implementer of motor actions, the possible applications of its cognitive side are still under-exploited, often remaining as poorly organized evidence. Here, we will collect evidence showing the value of action observation treatment (AOT) in the recovery of impaired motor abilities for a vast number of clinical conditions, spanning from traumatological patients to brain injuries and neurodegenerative diseases. Alongside, we will discuss the use of AOT in the maintenance of appropriate motor behavior in subjects at risk for events with dramatic physical consequences, like fall prevention in elderly people or injury prevention in sports. Finally, we will report that AOT can help to tune existing motor competencies in fields requiring precise motor control. We will connect all these diverse dots into the neurophysiological scenario offered by decades of research on the human mirror mechanism, discussing the potentialities for individualization. Empowered by modern technologies, AOT can impact individuals' safety and quality of life across the whole lifespan.

Impaired Limb Functional Outcome of Peripheral Nerve Regeneration Is Marked by Incomplete Recovery of Paw Muscle Atrophy and Brain Functional Connectivity in a Rat Forearm Nerve Repair Model

Skilled sensorimotor deficit is an unsolved problem of peripheral nerve injury (PNI) led by limb trauma or malignancies, despite the improvements in surgical techniques of peripheral nerve anastomosis. It is now accepted that successful functional recovery of PNI relies tremendously on the multilevel neural plasticity from the muscle to the brain. However, animal models that recapitulate these processes are still lacking. In this report, we developed a rat model of PNI to longitudinally assess peripheral muscle reinnervation and brain functional reorganization using noninvasive imaging technology. Based on such model, we compared the longitudinal changes of the rat forepaw intrinsic muscle volume and the seed-based functional connectivity of the sensorimotor cortex after nerve repair. We found that the improvement of skilled limb function and the recovery of paw intrinsic muscle following nerve regeneration are incomplete, which correlated with the functional connectivity between the primary motor cortex and dorsal striatum. Our results were highly relevant to the clinical observations and provided a framework for future investigations that aim to study the peripheral central sensorimotor circuitry underlying skilled limb function recovery after PNI.

Transcranial Direct Current Stimulation and Mirror Therapy for Neuropathic Pain After Brachial Plexus Avulsion: A Randomized, Double-Blind, Controlled Pilot Study

Introduction: Although transcranial direct current stimulation (tDCS) and mirror therapy (MT) have benefits in combating chronic pain, there is still no evidence of the effects of the simultaneous application of these techniques in patients with neuropathic pain. This study aims to assess the efficacy of tDCS paired with MT in neuropathic pain after brachial plexus injury. Methods: In a sham controlled, double-blind, parallel-group design, 16 patients were randomized to receive active or sham tDCS administered during mirror therapy. Each patient received 12 treatment sessions, 30 min each, during a period of 4 weeks over M1 contralateral to the side of the injury. Outcome variables were evaluated at baseline and post-treatment using the McGill questionnaire, Brief Pain Inventory, and Medical Outcomes Study 36-Item Short-Form Health Survey. Long-term effects of treatment were evaluated at a 3-month follow-up. Results: An improvement in pain relief and quality of life were observed in both groups (p ≤ 0.05). However, active tDCS and mirror therapy resulted in greater improvements after the endpoint (p ≤ 0.02). No statistically significant differences in the outcome measures were identified among the groups at follow-up (p ≥ 0.12). A significant relationship was found between baseline pain intensity and outcome measures (p ≤ 0.04). Moreover, the results showed that state anxiety is closely linked to post-treatment pain relief (p ≤ 0.05). Conclusion: Active tDCS combined with mirror therapy has a short-term effect of pain relief, however, levels of pain and anxiety at the baseline should be considered. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT04385030.