Recovery from a spinal cord injury: significance of compensation, neural plasticity, and repair

Temporal dynamics of gait function in acute cervical spinal cord injury

BACKGROUND

Following spinal cord injury (SCI), gait function reaches a post-recovery plateau that depends on the paralysis severity. However, the plateau dynamics during the recovery period are not known. This study aimed to examine the gait function temporal dynamics after traumatic cervical SCI (CSCI) based on paralysis severity.

METHODS

This retrospective cohort study included 122 patients with traumatic CSCI admitted to a single specialized facility within 2 weeks after injury. The Walking Index for Spinal Cord Injury II (WISCI II) was estimated at 2 weeks and 2, 4, 6, and 8 months postinjury for each American Spinal Injury Association Impairment Scale (AIS) grade, as determined 2 weeks postinjury. Statistical analysis was performed at 2 weeks to 2 months, 2-4 months, 4-6 months, and 6-8 months, and the time at which no significant difference was observed was considered the time at which the gait function reached a plateau.

RESULTS

In the AIS grade A and B groups, no significant differences were observed at any time point, while in the AIS grade C group, the mean WISCI II values continued to significantly increase up to 6 months. In the AIS grade D group, the improvement in gait function was significant during the entire observation period.

CONCLUSIONS

The plateau in gait function recovery was reached at 2 weeks postinjury in the AIS grade A and B groups and at 6 months in the AIS grade C group.

The Efficacy of Different Material Scaffold-Guided Cell Transplantation in the Treatment of Spinal Cord Injury in Rats: A Systematic Review and Network Meta-analysis

Cell transplantation is a promising treatment option for spinal cord injury (SCI). However, there is no consensus on the choice of carrier scaffolds to host the cells. This study aims to evaluate the efficacy of different material scaffold-mediated cell transplantation in treating SCI in rats. According to PRISMA's principle, Embase, PubMed, Web of Science, and Cochrane databases were searched, and relevant literature was referenced. Only original research on cell transplantation plus natural or synthetic scaffolds in SCI rats was included. Direct and indirect evidence for improving hind limb motor function was pooled through meta-analysis. A subgroup analysis of some factors that may affect the therapeutic effect was conducted to understand the results fully. In total, 25 studies met the inclusion criteria, in which 293 rats received sham surgery, 78 rats received synthetic material scaffolds, and 219 rats received natural materials scaffolds. The network meta-analysis demonstrated that although synthetic scaffolds were slightly inferior to natural scaffolds in terms of restoring motor function in cell transplantation of SCI rats, no statistical differences were observed between the two (MD: -0.35; 95% CI -2.6 to 1.9). Moreover, the subgroup analysis revealed that the type and number of cells may be important factors in therapeutic efficacy (P < 0.01). Natural scaffolds and synthetic scaffolds are equally effective in cell transplantation of SCI rats without significant differences. In the future, the findings need to be validated in multicenter, large-scale, randomized controlled trials in clinical practice. Trial registration: Registration ID CRD42024459674 (PROSPERO).

Changes in functional independence after inpatient rehabilitation in patients with spinal cord injury: A simultaneous evaluation of prognostic factors

OBJECTIVE

This study aimed to investigate the improvements of functional independence following inpatient rehabilitation and compare those improvements between different levels and severities of Spinal Cord Injury (SCI). Prognostic factors affecting the patient's outcomes were also studied.

SETTINGS

Rofeideh Rehabilitation Hospital.

OUTCOME MEASURES

Spinal Cord Independence Measure version III (SCIM III), and Functional Independence Measure (FIM).

METHOD

In this retrospective cohort study, 180 patients with SCI were enrolled to record their functional independence upon admission and discharge, and the changes were compared between different levels and severities of injury using non-parametric tests. The prognostic factors of outcomes were studied by generalized estimating equation (GEE) analysis.

RESULTS

The independence changes were significant for all the severities (American Spinal Injury Association Impairment Scale (AIS)) and levels of injury except for the patients with AIS A and B at upper cervical levels (P < 0.05). The level of injury, AIS, Length of Stay (LOS), and pressure ulcer had a significant prognostic value on patient's outcomes. Furthermore, there was a significant difference between different levels of injury with the same AIS grade in functional improvement (P < 0.05), while there was a significant difference between AIS groups with the same level of injury only at upper and middle cervical lesions (P < 0.05).

CONCLUSION

Recording the values of functional independence before and after rehabilitation in individuals with SCI can help clinicians approximately expect the outcomes of future patients. Moreover, a deeper study of the prognostic factors can provide a more logical expectation of rehabilitation outcomes.

Robotic Postural Training With Epidural Stimulation for the Recovery of Upright Postural Control in Individuals With Motor Complete Spinal Cord Injury: A Pilot Study

Activity-based training and lumbosacral spinal cord epidural stimulation (scES) have the potential to restore standing and walking with self-balance assistance after motor complete spinal cord injury (SCI). However, improvements in upright postural control have not previously been addressed in this population. Here, we implemented a novel robotic postural training with scES, performed with free hands, to restore upright postural control in individuals with chronic, cervical (n = 5) or high-thoracic (n = 1) motor complete SCI, who had previously undergone stand training with scES using a walker or a standing frame for self-balance assistance. Robotic postural training re-enabled and/or largely improved the participants' ability to control steady standing, self-initiated trunk movements and upper limb reaching movements while standing with free hands, receiving only external assistance for pelvic control. These improvements were associated with neuromuscular activation pattern adaptations above and below the lesion. These findings suggest that the human spinal cord below the level of injury can generate meaningful postural responses when its excitability is modulated by scES, and can learn to improve these responses. Upright postural control improvements can enhance functional motor recovery promoted by scES after severe SCI.

Pattern of neurological recovery in persons with an acute cervical spinal cord injury over the first 14 days post injury

Introduction

Following a traumatic spinal cord injury (SCI) it is critical to document the level and severity of injury. Neurological recovery occurs dynamically after injury and a baseline neurological exam offers a snapshot of the patient's impairment at that time. Understanding when this exam occurs in the recovery process is crucial for discussing prognosis and acute clinical trial enrollment. The objectives of this study were to: (1) describe the trajectory of motor recovery in persons with acute cervical SCI in the first 14 days post-injury; and (2) evaluate if the timing of the baseline neurological assessment in the first 14 days impacts the amount of motor recovery observed.

Methods

Data were obtained from the Rick Hansen Spinal Cord Injury Registry (RHSCIR) site in Vancouver and additional neurological data was extracted from medical charts. Participants with a cervical injury (C1-T1) who had a minimum of three exams (including a baseline and discharge exam) were included. Data on the upper-extremity motor score (UEMS), total motor score (TMS) and American Spinal Injury Association (ASIA) Impairment Scale (AIS) were included. A linear mixed-effect model with additional variables (AIS, level of injury, UEMS, time, time2, and TMS) was used to explore the pattern and amount of motor recovery over time.

Results

Trajectories of motor recovery in the first 14 days post-injury showed significant improvements in both TMS and UEMS for participants with AIS B, C, and D injuries, but was not different for high (C1-4) vs. low (C5-T1) cervical injuries or AIS A injuries. The timing of the baseline neurological examination significantly impacted the amount of motor recovery in participants with AIS B, C, and D injuries.

Discussion

Timing of baseline neurological exams was significantly associated with the amount of motor recovery in cervical AIS B, C, and D injuries. Studies examining changes in neurological recovery should consider stratifying by severity and timing of the baseline exam to reduce bias amongst study cohorts. Future studies should validate these estimates for cervical AIS B, C, and D injuries to see if they can serve as an "adjustment factor" to control for differences in the timing of the baseline neurological exam.

Adverse Effect of Neurogenic, Infective, and Inflammatory Fever on Acutely Injured Human Spinal Cord

This study aims to determine the effect of neurogenic, inflammatory, and infective fevers on acutely injured human spinal cord. In 86 patients with acute, severe traumatic spinal cord injuries (TSCIs; American Spinal Injury Association Impairment Scale (AIS), grades A-C) we monitored (starting within 72 h of injury, for up to 1 week) axillary temperature as well as injury site cord pressure, microdialysis (MD), and oxygen. High fever (temperature ≥38°C) was classified as neurogenic, infective, or inflammatory. The effect of these three fever types on injury-site physiology, metabolism, and inflammation was studied by analyzing 2864 h of intraspinal pressure (ISP), 1887 h of MD, and 840 h of tissue oxygen data. High fever occurred in 76.7% of the patients. The data show that temperature was higher in neurogenic than non-neurogenic fever. Neurogenic fever only occurred with injuries rostral to vertebral level T4. Compared with normothermia, fever was associated with reduced tissue glucose (all fevers), increased tissue lactate to pyruvate ratio (all fevers), reduced tissue oxygen (neurogenic + infective fevers), and elevated levels of pro-inflammatory cytokines/chemokines (infective fever). Spinal cord metabolic derangement preceded the onset of infective but not neurogenic or inflammatory fever. By considering five clinical characteristics (level of injury, axillary temperature, leukocyte count, C-reactive protein [CRP], and serum procalcitonin [PCT]), it was possible to confidently distinguish neurogenic from non-neurogenic high fever in 59.3% of cases. We conclude that neurogenic, infective, and inflammatory fevers occur commonly after acute, severe TSCI and are detrimental to the injured spinal cord with infective fever being the most injurious. Further studies are required to determine whether treating fever improves outcome. Accurately diagnosing neurogenic fever, as described, may reduce unnecessary septic screens and overuse of antibiotics in these patients.

A qualitative study to elicit user requirements for lower limb wearable exoskeletons for gait rehabilitation in spinal cord injury

OBJECTIVE

We aim to determine a comprehensive set of requirements, perceptions, and expectations that people with spinal cord injury (SCI) and the clinicians in charge of their rehabilitation have regarding the use of wearable robots (WR) for gait rehabilitation.

BACKGROUND

There are concerns due to the limited user acceptance of WR for gait rehabilitation. Developers need to emphasize understanding the needs and constraints of all stakeholders involved, including the real-life dynamics of rehabilitation centers.

METHODS

15 people with SCI, 9 without experience with WR and 6 with experience with these technologies, and 10 clinicians from 3 rehabilitation centers in Spain were interviewed. A directed content analysis approach was used.

RESULTS

78 codes grouped into 9 categories (physical results, usability, psychology-related codes, technical characteristics, activities, acquisition issues, context of use, development of the technologies and clinical rehabilitation context) were expressed by at least 20% of the users interviewed, of whom 16 were not found in the literature. The agreement percentage between each group and subgroup included in the study, calculated as the number of codes that more than 20% of both groups expressed, divided over the total amount of codes any of those two groups agreed on (≥ 20%), showed limited agreement between patients and clinicians (50.00%) and between both types of patients (55.77%). The limited accessibility and availability of lower limb exoskeletons for gait rehabilitation arose in most of the interviews.

CONCLUSIONS

The limited agreement percentage between patients and clinicians indicates that including both types of users in the design process of these technologies is important, given that their requirements are complementary. Engaging users with prior technology experience is recommended, as they often exhibit strong internal consensus and articulate well-defined requirements. This study adds up the knowledge available in the literature and the new codes found in our data, which enlighten important aspects that ought to be addressed in the field to develop technologies that respond to users' needs, are usable and feasible to implement in their intended contexts.

APPLICATION

The set of criteria summarized in our study will be useful to guide the design, development, and evaluation of WR for gait rehabilitation to meet user's needs and allow them to be implemented in their intended context of use.

Progress Report on the Spinal Cord Rehabilitation Research Initiatives Based on Registered Clinical Studies From 2000 to 2022

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Identify the most common trends and features of research studies on spinal cord rehabilitation, which were registered in the ClinicalTrials.gov Website between 2000 and 2022; (2) Discuss the main limitations of research on spinal cord rehabilitation, based on the protocols published on the ClinicalTrials.gov Website; and (3) Recognize important knowledge gaps in clinical studies on spinal cord rehabilitation that were registered in the ClinicalTrials.gov Website.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s) ™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

The evidence against somatotopic organization of function in the primate corticospinal tract

We review the spatial organization of corticospinal outputs from different cortical areas and how this reflects the varied functions mediated by the corticospinal tract. A long-standing question is whether the primate corticospinal tract shows somatotopical organization. Although this has been clearly demonstrated for corticofugal outputs passing through the internal capsule and cerebral peduncle, there is accumulating evidence against somatotopy in the pyramidal tract in the lower brainstem and in the spinal course of the corticospinal tract. Answering the question on somatotopy has important consequences for understanding the effects of incomplete spinal cord injury. Our recent study in the macaque monkey, using high-resolution dextran tracers, demonstrated a great deal of intermingling of fibres originating from primary motor cortex arm/hand, shoulder and leg areas. We quantified the distribution of fibres belonging to these different projections and found no significant difference in their distribution across different subsectors of the pyramidal tract or lateral corticospinal tract, arguing against somatotopy. We further demonstrated intermingling with corticospinal outputs derived from premotor and supplementary motor arm areas. We present new evidence against somatotopy for corticospinal projections from rostral and caudal cingulate motor areas and from somatosensory areas of the parietal cortex. In the pyramidal tract and lateral corticospinal tract, fibres from the cingulate motor areas overlap with each other. Fibres from the primary somatosensory cortex arm area completely overlap those from the leg area. There is also substantial overlap of both these outputs with those from posterior parietal sensorimotor areas. We argue that the extensive intermingling of corticospinal outputs from so many different cortical regions must represent an organizational principle, closely related to its mediation of many different functions and its large range of fibre diameters. The motor sequelae of incomplete spinal injury, such as central cord syndrome and 'cruciate paralysis', include much greater deficits in upper than in lower limb movement. Current teaching and text book explanations of these symptoms are still based on a supposed corticospinal somatotopy or 'lamination', with greater vulnerability of arm and hand versus leg fibres. We suggest that such explanations should now be finally abandoned. Instead, the clinical and neurobiological implications of the complex organization of the corticospinal tract need now to be taken into consideration. This leads us to consider the evidence for a greater relative influence of the corticospinal tract on upper versus lower limb movements, the former best characterized by skilled hand and digit movements.

Data-driven characterization of walking after a spinal cord injury using inertial sensors

BACKGROUND

An incomplete spinal cord injury (SCI) refers to remaining sensorimotor function below the injury with the possibility for the patient to regain walking abilities. However, these patients often suffer from diverse gait deficits, which are not objectively assessed in the current clinical routine. Wearable inertial sensors are a promising tool to capture gait patterns objectively and started to gain ground for other neurological disorders such as stroke, multiple sclerosis, and Parkinson's disease. In this work, we present a data-driven approach to assess walking for SCI patients based on sensor-derived outcome measures. We aimed to (i) characterize their walking pattern in more depth by identifying groups with similar walking characteristics and (ii) use sensor-derived gait parameters as predictors for future walking capacity.

METHODS

The dataset analyzed consisted of 66 SCI patients and 20 healthy controls performing a standardized gait test, namely the 6-min walking test (6MWT), while wearing a sparse sensor setup of one sensor attached to each ankle. A data-driven approach has been followed using statistical methods and machine learning models to identify relevant and non-redundant gait parameters.

RESULTS

Clustering resulted in 4 groups of patients that were compared to each other and to the healthy controls. The clusters did differ in terms of their average walking speed but also in terms of more qualitative gait parameters such as variability or parameters indicating compensatory movements. Further, using longitudinal data from a subset of patients that performed the 6MWT several times during their rehabilitation, a prediction model has been trained to estimate whether the patient's walking speed will improve significantly in the future. Including sensor-derived gait parameters as inputs for the prediction model resulted in an accuracy of 80%, which is a considerable improvement of 10% compared to using only the days since injury, the present 6MWT distance, and the days until the next 6MWT as predictors.

CONCLUSIONS

In summary, the work presented proves that sensor-derived gait parameters provide additional information on walking characteristics and thus are beneficial to complement clinical walking assessments of SCI patients. This work is a step towards a more deficit-oriented therapy and paves the way for better rehabilitation outcome predictions.

The Role of Transcranial Magnetic Stimulation, Peripheral Electrotherapy, and Neurophysiology Tests for Managing Incomplete Spinal Cord Injury

Efforts to find therapeutic methods that support spinal cord functional regeneration continue to be desirable. Natural recovery is limited, so high hopes are being placed on neuromodulation methods which promote neuroplasticity, such as repetitive transcranial magnetic stimulation (rTMS) and electrical stimulation used as treatment options for managing incomplete spinal cord injury (iSCI) apart from kinesiotherapy. However, there is still no agreement on the methodology and algorithms for treatment with these methods. The search for effective therapy is also hampered by the use of different, often subjective in nature, evaluation methods and difficulties in assessing the actual results of the therapy versus the phenomenon of spontaneous spinal cord regeneration. In this study, an analysis was performed on the database of five trials, and the cumulative data are presented. Participants (iSCI patients) were divided into five groups on the basis of the treatment they had received: rTMS and kinesiotherapy (N = 36), peripheral electrotherapy and kinesiotherapy (N = 65), kinesiotherapy alone (N = 55), rTMS only (N = 34), and peripheral electrotherapy mainly (N = 53). We present changes in amplitudes and frequencies of the motor units’ action potentials recorded by surface electromyography (sEMG) from the tibialis anterior—the index muscle for the lower extremity and the percentage of improvement in sEMG results before and after the applied therapies. The increase in values in sEMG parameters represents the better ability of motor units to recruit and, thus, improvement of neural efferent transmission. Our results indicate that peripheral electrotherapy provides a higher percentage of neurophysiological improvement than rTMS; however, the use of any of these additional stimulation methods (rTMS or peripheral electrotherapy) provided better results than the use of kinesiotherapy alone. The best improvement of tibialis anterior motor units’ activity in iSCI patients provided the application of electrotherapy conjoined with kinesiotherapy and rTMS conjoined with kinesiotherapy. We also undertook a review of the current literature to identify and summarise available works which address the use of rTMS or peripheral electrotherapy as neuromodulation treatment options in patients after iSCI. Our goal is to encourage other clinicians to implement both types of stimulation into the neurorehabilitation program for subjects after iSCI and evaluate their effectiveness with neurophysiological tests such as sEMG so further results and algorithms can be compared across studies. Facilitating the motor rehabilitation process by combining two rehabilitation procedures together was confirmed.

Dynamic induction of the myelin-associated growth inhibitor Nogo-A in perilesional plasticity regions after human spinal cord injury

The myelin-associated inhibitor Nogo-A (Reticulon 4, RTN4) restricts axonal outgrowth, plasticity, and neural circuitry formation in experimental models of spinal cord injury (SCI) and is targeted in clinical interventions starting treatment within 4 weeks post-SCI. Specifically, Nogo-A expressed by oligodendroglia restricts compensatory neurite sprouting. To interrogate the hypothesis of an inducible, lesion reactive Nogo-A expression over time, we analyzed the spatiotemporal Nogo-A expression at the spinal lesion core (region of tissue necrosis and axonal damage/pruning) and perilesional rim (region of plasticity formation). Spinal cord specimens of SCI subjects (n = 22) were compared to neuropathologically unaltered controls (n = 9). Nogo-A expression was investigated ranging from acute (0-3 days), early subacute (4-21 days), late subacute (22-90 days) to early chronic-chronic (91 days to 1.5 years after SCI) stages after SCI. Nogo-A expression in controls is confined to motoneurons in the anterior horn and to oligodendrocytes in gray and white matter. After SCI, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes (i) inclined at the organizing perilesional rim specifically, (ii) increased further over time, and (iii) peaked at chronic stages after SCI. By contrast, at the lesion core, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes did not increase. Increasing numbers of Nogo-A+ oligodendrocytes coincided with oligodendrogenesis corroborated by Nogo-A coexpression of Ki67+ , TPPP/p25+ proliferating oligodendrocytes. Nogo-A oligodendrocyte expression emerges at perilesional (plasticity) regions over time and suggests an extended therapeutical window for anti-Nogo-A pathway targeting interventions beyond 4 weeks in patients after SCI.

Dynamics of progressive degeneration of major spinal pathways following spinal cord injury: A longitudinal study

BACKGROUND

Following spinal cord injury (SCI), disease processes spread gradually along the spinal cord forming a spatial gradient with most pronounced changes located at the lesion site. However, the dynamics of this gradient in SCI patients is not established.

OBJECTIVE

This study tracks the spatiotemporal dynamics of remote anterograde and retrograde spinal tract degeneration in the upper cervical cord following SCI over two years utilizing quantitative MRI.

METHODS

Twenty-three acute SCI patients (11 paraplegics, 12 tetraplegics) and 21 healthy controls were scanned with a T1-weighted sequence for volumetry and a FLASH sequence for myelin-sensitive magnetization transfer saturation (MTsat) of the upper cervical cord. We estimated myelin content from MTsat maps within the corticospinal tracts (CST) and dorsal columns (DC) and measured spinal cord atrophy by means of left-right width (LRW) and anterior-posterior width (APW) on the T1-weighted images across cervical levels C1-C3. MTsat in the CST and LRW were considered proxies for retrograde degeneration, while MTsat in the DC and APW provided evidence for anterograde degeneration, respectively. Using regression models, we compared the temporal and spatial trajectories of these MRI readouts between tetraplegics, paraplegics, and controls over a 2-year period and assessed their associations with clinical improvement.

RESULTS

Linear rates and absolute differences in myelin-sensitive MTsat indicated retrograde and anterograde neurodegeneration in the CST and DC, respectively. Changes in MTsat within the CST and in LRW progressively developed over time forming a gradient towards lower cervical levels by 2 years after injury, especially in tetraplegics (change per cervical level in MTsat: -0.247 p.u./level, p = 0.034; in LRW: -0.323 mm/level, p = 0.024). MTsat within the DC was already decreased at cervical levels C1-C3 at baseline (1.5 months after injury) in both tetra- and paraplegics, while linear decreases in APW over time were similar across C1-C3, preserving the spatial gradient. The relative improvement in light touch score was associated with MTsat within the DC at baseline (r_s = 0.575, p = 0.014).

CONCLUSION

Rostral and remote to the injury, the CST and DC show ongoing structural changes, indicative of myelin reductions and atrophy within 2 years after SCI. While anterograde degeneration in the DC was already detectable uniformly at C1-C3 early following SCI, retrograde degeneration in the CST developed over time revealing specific spatial and temporal neurodegenerative gradients. Disentangling and quantifying such dynamic pathological processes may provide biomarkers for regenerative and remyelinating therapies along entire spinal pathways.

A phase 1/2a dose-escalation study of oligodendrocyte progenitor cells in individuals with subacute cervical spinal cord injury

OBJECTIVE

The primary objective of this study was to evaluate the safety of 3 escalating doses of oligodendrocyte progenitor cells (LCTOPC1; previously known as GRNOPC1 and AST-OPC1) administered at a single time point between 21 and 42 days postinjury to participants with subacute cervical spinal cord injuries (SCIs). The secondary objective was to evaluate changes in neurological function following administration of LCTOPC1.

METHODS

This study was designed as an open-label, dose-escalation, multicenter clinical trial. Twenty-five participants with C4-7 American Spinal Injury Association Impairment Scale grade A or B injuries received a single dose of either 2 × 106, 1 × 107, or 2 × 107 LCTOPC1 delivered via intraparenchymal injection into the spinal cord at the site of injury using a custom-designed syringe positioning device. Low-dose tacrolimus was administered until day 60. Outcome measures included adverse event (AE) monitoring and neurological function as measured by the International Standards for Neurological Classification of Spinal Cord Injury.

RESULTS

All 25 participants experienced at least one AE, with a total of 534 AEs (32 study-related vs 502 study-unrelated anticipated complications of SCI) reported at the completion of 1-year follow-up. There were 29 serious AEs reported. Two grade 3 serious AEs (CSF leak in one participant and a bacterial infection in another) were considered related to the injection procedure and to immunosuppression with tacrolimus, respectively. The CSF leakage resolved with sequelae, including self-limited altered mental status, and the infection resolved with antibiotic therapy. For all participants, MRI scans demonstrated no evidence of an enlarging mass, spinal cord damage related to the injection procedure, inflammatory lesions in the spinal cord, or masses in the ventricular system. At 1-year follow-up, 21/22 (96%) of the intention-to-treat group recovered one or more levels of neurological function on at least one side of their body, and 7/22 (32%) recovered two or more levels of neurological function on at least one side of their body.

CONCLUSIONS

LCTOPC1 can be safely administered to participants in the subacute period after cervical SCI. The injection procedure, low-dose temporary immunosuppression regimen, and LCTOPC1 were well tolerated. The safety and neurological function data support further investigation to determine the efficacy of LCTOPC1 in the treatment of SCI. Clinical trial registration no.: NCT02302157 (ClinicalTrials.gov).

BCI system with lower-limb robot improves rehabilitation in spinal cord injury patients through short-term training: a pilot study

In the recent years, the increasing applications of brain-computer interface (BCI) in rehabilitation programs have enhanced the chances of functional recovery for patients with neurological disorders. We presented and validated a BCI system with a lower-limb robot for short-term training of patients with spinal cord injury (SCI). The cores of this system included: (1) electroencephalogram (EEG) features related to motor intention reported through experiments and used to drive the robot; (2) a decision tree to determine the training mode provided for patients with different degrees of injuries. Seven SCI patients (one American Spinal Injury Association Impairment Scale (AIS) A, three AIS B, and three AIS C) participated in the short-term training with this system. All patients could learn to use the system rapidly and maintained a high intensity during the training program. The strength of the lower limb key muscles of the patients was improved. Four AIS A/B patients were elevated to AIS C. The cumulative results indicate that clinical application of the BCI system with lower-limb robot is feasible and safe, and has potentially positive effects on SCI patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09801-6.

Surgical Efficacy and Prognostic Factors for Acute Traumatic Central Cord Syndrome Without Fracture and Dislocation

This study was undertaken to evaluate the effectiveness of surgical treatment of acute traumatic central cord syndrome (ATCCS) without fracture and dislocation and explore surgical timing and factors influencing postoperative recovery of spinal cord function. We retrospectively collected the general and clinical data of 112 patients with ATCCS (American Spinal Injury Association impairment scale grade C or D) without fracture and dislocation who underwent surgical treatment in our hospital from January 2013 to August 2019. We used statistical methods to evaluate the safety of the operation and explore the timing of surgery and the factors influencing postoperative recovery of spinal cord function. The mean age of the 112 patients was 60.64±12.91 years. The Japanese Orthopaedic Association score and the American Spinal Injury Association motor score (AMS) of the 112 patients were significantly higher at final follow-up than at admission. No significant difference in recovery of spinal cord function was seen between the early operation group (≤4 days) and the late operation group (>4 days). Comparison of patients with a good prognosis vs a poor prognosis showed that age, intrahand muscle strength at admission, maximum spinal cord compression, maximum canal compromise, length of high-intensity signal in the spinal cord on sagittal T2-weighted magnetic resonance imaging, AMS, and American Spinal Injury Association injury grade D/C at admission had a significant effect on recovery of spinal cord function. Surgical treatment of ATCCS without fracture and dislocation is safe and effective. Age, admission AMS and American Spinal Injury Association impairment scale score, intrinsic hand muscle strength, maximum canal compromise, maximum spinal cord compression, and length of high-intensity signal in the spinal cord can be used to predict postoperative recovery of spinal cord function. [Orthopedics. 2022;45(6):325-332.].

Comparing walking with knee-ankle-foot orthoses and a knee-powered exoskeleton after spinal cord injury: a randomized, crossover clinical trial

Recovering the ability to stand and walk independently can have numerous health benefits for people with spinal cord injury (SCI). Wearable exoskeletons are being considered as a promising alternative to conventional knee-ankle-foot orthoses (KAFOs) for gait training and assisting functional mobility. However, comparisons between these two types of devices in terms of gait biomechanics and energetics have been limited. Through a randomized, crossover clinical trial, this study compared the use of a knee-powered lower limb exoskeleton (the ABLE Exoskeleton) against passive orthoses, which are the current standard of care for verticalization and gait ambulation outside the clinical setting in people with SCI. Ten patients with SCI completed a 10-session gait training program with each device followed by user satisfaction questionnaires. Walking with the ABLE Exoskeleton improved gait kinematics compared to the KAFOs, providing a more physiological gait pattern with less compensatory movements (38% reduction of circumduction, 25% increase of step length, 29% improvement in weight shifting). However, participants did not exhibit significantly better results in walking performance for the standard clinical tests (Timed Up and Go, 10-m Walk Test, and 6-min Walk Test), nor significant reductions in energy consumption. These results suggest that providing powered assistance only on the knee joints is not enough to significantly reduce the energy consumption required by people with SCI to walk compared to passive orthoses. Active assistance on the hip or ankle joints seems necessary to achieve this outcome.

Integrated Neuroregenerative Techniques for Plasticity of the Injured Spinal Cord

On the slow path to improving the life expectancy and quality of life of patients post spinal cord injury (SCI), recovery remains controversial. The potential role of the regenerative capacity of the nervous system has led to numerous attempts to stimulate the SCI to re-establish the interrupted sensorimotor loop and to understand its potential in the recovery process. Numerous resources are now available, from pharmacological to biomolecular approaches and from neuromodulation to sensorimotor rehabilitation interventions based on the use of various neural interfaces, exoskeletons, and virtual reality applications. The integration of existing resources seems to be a promising field of research, especially from the perspective of improving living conditions in the short to medium term. Goals such as reducing chronic forms of neuropathic pain, regaining control over certain physiological activities, and enhancing residual abilities are often more urgent than complete functional recovery. In this perspective article, we provide an overview of the latest interventions for the treatment of SCI through broad phases of injury rehabilitation. The underlying intention of this work is to introduce a spinal cord neuroplasticity-based multimodal approach to promote functional recovery and improve quality of life after SCI. Nonetheless, when used separately, biomolecular therapeutic approaches have been shown to have modest outcomes.

Clinical electrodiagnostic evaluation for nerve transfer surgery in spinal cord injury: a new indication and clinical pearls

In this review, we highlight the important role of the clinical electrodiagnostic (EDX) evaluation after cervical spinal cord injury (SCI). Our discussion focuses on the need for timely, frequent, and accurate EDX evaluations in the context of nerve transfer surgery to restore critical upper limb functions, including elbow extension, hand opening, and hand closing. The EDX evaluation is crucial to define the extent of lower motor neuron lesions and determine candidacy for surgery. We also discuss the important role of the postoperative EDX evaluation in determining prognosis and supporting rehabilitation. We propose a practical framework for EDX evaluation in this clinical setting.

Is Graphene Shortening the Path toward Spinal Cord Regeneration?

Along with the development of the next generation of biomedical platforms, the inclusion of graphene-based materials (GBMs) into therapeutics for spinal cord injury (SCI) has potential to nourish topmost neuroprotective and neuroregenerative strategies for enhancing neural structural and physiological recovery. In the context of SCI, contemplated as one of the most convoluted challenges of modern medicine, this review first provides an overview of its characteristics and pathophysiological features. Then, the most relevant ongoing clinical trials targeting SCI, including pharmaceutical, robotics/neuromodulation, and scaffolding approaches, are introduced and discussed in sequence with the most important insights brought by GBMs into each particular topic. The current role of these nanomaterials on restoring the spinal cord microenvironment after injury is critically contextualized, while proposing future concepts and desirable outputs for graphene-based technologies aiming to reach clinical significance for SCI.

Multi-center, single-blind randomized controlled trial comparing functional electrical stimulation therapy to conventional therapy in incomplete tetraplegia

Background

Loss of upper extremity function after tetraplegia results in significant disability. Emerging evidence from pilot studies suggests that functional electrical stimulation (FES) therapy may enhance recovery of upper extremity function after tetraplegia. The aim of this trial was to determine the effectiveness of FES therapy delivered by the Myndmove stimulator in people with tetraplegia.

Methods

A multi-center, single-blind, parallel-group, two-arm, randomized controlled trial was conducted comparing FES to conventional therapy in adults (≥18 years) with C4–C7 traumatic incomplete tetraplegia between 4 and 96 months post-injury, and with a baseline spinal cord injury independence measure III -self-care (SCIM III-SC) score of ≤10. Participants were enrolled at four SCI-specialized neurorehabilitation centers in the U.S. and Canada. Participants were stratified by center and randomized in a 1:1 ratio to receive either 40 sessions of FES or conventional therapy targeting upper extremities over a 14-week period. Blinded assessors measured SCIM III, Toronto Rehabilitation Institute Hand Function Test, and Graded Redefined Assessment of Strength, Sensibility, and Prehension at baseline, after 20th session, after 40th session or 14 weeks after 1st session, and at 24 weeks after 1st session. The primary outcome measure was change in SCIM III-SC from baseline to end of the treatment. Based on the primary outcome measure, a sample size of 60 was calculated. Seventeen participants' progress in the study was interrupted due to the COVID-19 lockdown. The protocol was modified for these participants to allow them to complete the study.

Results

Between June 2019 to August 2021, 51 participants were randomized to FES (n = 27) and conventional therapy (n = 24). Both groups gained a mean of 2 points in SCIM-SC scores at the end of treatment, which was a clinically meaningful change. However, there was no statistically significant difference between the groups on any outcomes.

Conclusion

Forty sessions of FES therapy delivered by the MyndMove stimulator are as effective as conventional therapy in producing meaningful functional improvements that persist after therapy is completed. Limitations of this study include the impact of COVID-19 limiting the ability to recruit the target sample size and per-protocol execution of the study in one-third of the participants.

Registration

This trial is registered at www.ClinicalTrials.gov, NCT03439319.

Prevalence of spasticity in humans with spinal cord injury with different injury severity

Spasticity is one of the most common symptoms manifested following spinal cord injury (SCI). The aim of this study was to assess spasticity in individuals with subacute and chronic SCI with different injury severity, standardizing the time and assessments of spasticity. We tested 110 individuals with SCI classified by the American Spinal Injury Association Impairment Scale (AIS) as either motor complete (AIS A and B; subacute, n = 25; chronic, n = 33) or motor incomplete (AIS C and D; subacute, n = 23; chronic, n = 29) at a similar time after injury (subacute, ∼1 mo after injury during inpatient rehabilitation and chronic, ≥1 yr after injury) using clinical (modified Ashworth scale) and kinematic (pendulum test) outcomes to assess spasticity in the quadriceps femoris muscle. Using both methodologies, we found that among individuals with subacute motor complete injuries, only a minority showed spasticity, whereas the majority exhibited no spasticity. This finding stands in contrast to individuals with subacute motor incomplete injury, where both methodologies revealed that a majority exhibited spasticity, whereas a minority exhibited no spasticity. In chronic injuries, most individuals showed spasticity regardless of injury severity. Notably, when spasticity was present, its magnitude was similar across injury severity in both subacute and chronic injuries. Our results suggest that the prevalence, not the magnitude, of spasticity differs between individuals with motor complete and incomplete SCI in the subacute and chronic stages of the injury. We thus argue that considering the "presence of spasticity" might help the stratification of participants with motor complete injuries for clinical trials.NEW & NOTEWORTHY The prevalence of spasticity in humans with SCI remains poorly understood. Using kinematic and clinical outcomes, we examined spasticity in individuals with subacute and chronic injuries of different severity. We found that spasticity in the quadriceps femoris muscle was more prevalent among individuals with subacute motor incomplete than in those with motor complete injuries. However, in a different group of individuals with chronic injuries, no differences were found in the prevalence of spasticity across injury severity.

Spontaneous Motor Recovery after Cervical Spinal Cord Injury: Issues for Nerve Transfer Surgery Decision Making

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To quantify spontaneous upper extremity motor recovery between 6 and 12 months after spinal cord injury (SCI) to help guide timing of nerve transfer surgery to improve upper limb function in cervical SCI.

SETTING

Nineteen European SCI rehabilitation centers.

METHODS

Data was extracted from the European Multicenter Study of SCI database for individuals with mid-level cervical SCI (N = 268). Muscle function grades at 6 and 12 months post-SCI were categorized for analysis.

RESULTS

From 6 to 12 months after SCI, spontaneous surgically-relevant recovery was limited. Of all limbs (N = 263) with grade 0-2 elbow extension at 6 months, 4% regained grade 4-5 and 11% regained grade 3 muscle function at 12 months. Of all limbs (N = 380) with grade 0-2 finger flexion at 6 months, 3% regained grade 4-5 and 5% regained grade 3 muscle function at 12 months.

CONCLUSION

This information supports early (6 month) post-injury surgical consultation and evaluation. With this information, individuals with SCI can more fully engage in preference-based decision-making about surgical intervention versus continued rehabilitation and spontaneous recovery to gain elbow extension and/or hand opening and closing.

Activity-dependent plasticity and spinal cord stimulation for motor recovery following spinal cord injury

Spinal cord injuries lead to permanent physical impairment despite most often being anatomically incomplete disruptions of the spinal cord. Remaining connections between the brain and spinal cord create the potential for inducing neural plasticity to improve sensorimotor function, even many years after injury. This narrative review provides an overview of the current evidence for spontaneous motor recovery, activity-dependent plasticity, and interventions for restoring motor control to residual brain and spinal cord networks via spinal cord stimulation. In addition to open-loop spinal cord stimulation to promote long-term neuroplasticity, we also review a more targeted approach: closed-loop stimulation. Lastly, we review mechanisms of spinal cord neuromodulation to promote sensorimotor recovery, with the goal of advancing the field of rehabilitation for physical impairments following spinal cord injury.

A Therapeutic Approach Using the Combined Application of Virtual Reality with Robotics for the Treatment of Patients with Spinal Cord Injury: A Systematic Review

Spinal cord injury (SCI) has been associated with high mortality rates. Thanks to the multidisciplinary vision and approach of SCI, including the application of new technologies in the field of neurorehabilitation, people with SCI can survive and prosper after injury. The main aim of this systematic review was to analyze the effectiveness of the combined use of VR and robotics in the treatment of patients with SCI. The literature search was performed between May and July 2021 in the Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), PubMed, and Web of Science. The methodological quality of each study was assessed using the SCIRE system and the PEDro scale, whereas the risk of bias was analyzed using the Cochrane Collaboration’s tool. A total of six studies, involving 63 participants, were included in this systematic review. Relevant changes were found in the upper limbs, with improvements of shoulder and upper arm mobility, as well as the strengthening of weaker muscles. Combined rehabilitation may be a valuable approach to improve motor function in SCI patients. Nonetheless, further research is necessary, with a larger patient sample and a longer duration.

International surveillance study in acute spinal cord injury confirms viability of multinational clinical trials

BACKGROUND

The epidemiological international landscape of traumatic spinal cord injury (SCI) has evolved over the last decades along with given inherent differences in acute care and rehabilitation across countries and jurisdictions. However, to what extent these differences may influence neurological and functional recovery as well as the integrity of international trials is unclear. The latter also relates to historical clinical data that are exploited to inform clinical trial design and as potential comparative data.

METHODS

Epidemiological and clinical data of individuals with traumatic and ischemic SCI enrolled in the European Multi-Center Study about Spinal Cord Injury (EMSCI) were analyzed. Mixed-effect models were employed to account for the longitudinal nature of the data, efficiently handle missing data, and adjust for covariates. The primary outcomes comprised demographics/injury characteristics and standard scores to quantify neurological (i.e., motor and sensory scores examined according to the International Standards for the Neurological Classification of Spinal Cord Injury) and functional recovery (walking function). We externally validated our findings leveraging data from a completed North American landmark clinical trial.

RESULTS

A total of 4601 patients with acute SCI were included. Over the course of 20 years, the ratio of male to female patients remained stable at 3:1, while the distribution of age at injury significantly shifted from unimodal (2001/02) to bimodal distribution (2019). The proportional distribution of injury severities and levels remained stable with the largest percentages of motor complete injuries. Both, the rate and pattern of neurological and functional recovery, remained unchanged throughout the surveillance period despite the increasing age at injury. The findings related to recovery profiles were confirmed by an external validation cohort (n=791). Lastly, we built an open-access and online surveillance platform ("Neurosurveillance") to interactively exploit the study results and beyond.

CONCLUSIONS

Despite some epidemiological changes and considerable advances in clinical management and rehabilitation, the neurological and functional recovery following SCI has remained stable over the last two decades. Our study, including a newly created open-access and online surveillance tool, constitutes an unparalleled resource to inform clinical practice and implementation of forthcoming clinical trials targeting neural repair and plasticity in acute spinal cord injury.

Spinal Cord Injury and Loss of Cortical Inhibition

After spinal cord injury (SCI), the destruction of spinal parenchyma causes permanent deficits in motor functions, which correlates with the severity and location of the lesion. Despite being disconnected from their targets, most cortical motor neurons survive the acute phase of SCI, and these neurons can therefore be a resource for functional recovery, provided that they are properly reconnected and retuned to a physiological state. However, inappropriate re-integration of cortical neurons or aberrant activity of corticospinal networks may worsen the long-term outcomes of SCI. In this review, we revisit recent studies addressing the relation between cortical disinhibition and functional recovery after SCI. Evidence suggests that cortical disinhibition can be either beneficial or detrimental in a context-dependent manner. A careful examination of clinical data helps to resolve apparent paradoxes and explain the heterogeneity of treatment outcomes. Additionally, evidence gained from SCI animal models indicates probable mechanisms mediating cortical disinhibition. Understanding the mechanisms and dynamics of cortical disinhibition is a prerequisite to improve current interventions through targeted pharmacological and/or rehabilitative interventions following SCI.

Lack of somatotopy among corticospinal tract fibers passing through the primate craniovertebral junction and cervical spinal cord: pathoanatomical substrate of central cord syndrome and cruciate paralysis

OBJECTIVE

In some cases of incomplete cervical spinal cord injury (iSCI) there is marked paresis and dysfunction of upper-extremity movement but not lower-extremity movement. A continued explanation of such symptoms is a somatotopic organization of corticospinal tract (CST) fibers passing through the decussation at the craniovertebral junction (CVJ) and lateral CST (LCST). In central cord syndrome, it has been suggested that injury to the core of the cervical cord may include selective damage to medially located arm/hand LCST fibers, without compromising laterally located leg fibers. Because such somatotopic organization in the primate CST might contribute to the disproportionate motor deficits after some forms of iSCI, the authors made a systematic investigation of CST organization in the CVJ and LCST using modern neuroanatomical techniques.

METHODS

High-resolution anterograde tracers were used in 11 rhesus macaque monkeys to define the course of the corticospinal projection (CSP) through the CVJ and LCST from the arm/hand, shoulder, and leg areas of the primary motor cortex (M1). This approach labels CST fibers of all sizes, large and small, arising in these areas. The CSP from the dorsolateral and ventrolateral premotor cortex and supplementary motor area were also studied. A stereological approach was adapted to quantify labeled fiber distribution in 8 cases.

RESULTS

There was no evidence for somatotopic organization of CST fibers passing through the CVJ or contralateral LCST. Fiber labeling from each cortical representation was widespread throughout the CST at the CVJ and LCST and overlapped extensively with fibers from other representations. This study demonstrated no significant difference between medial versus lateral subsectors of the LCST in terms of number of fibers labeled from the M1 arm/hand area.

CONCLUSIONS

This investigation firmly rejects the concept of somatotopy among CST fibers passing through the CVJ and LCST, in contrast with the somatotopy in the cortex, corona radiata, and internal capsule. All CST fibers in the CVJ and LCST would thus appear to be equally susceptible to focal or diffuse injury, regardless of their cortical origin. The disproportionate impairment of arm/hand movement after iSCI must therefore be due to other factors, including greater dependence of hand/arm movements on the CST compared with the lower limb. The dispersed and intermingled nature of frontomotor fibers may be important in motor recovery after cervical iSCI.

A systematic review of large animal and human studies of stem cell therapeutics for acute adult traumatic spinal cord injury

Background: Traumatic spinal cord injury (TSCI) is a devastating condition and the search for a cure remains one of the most tenacious healthcare challenges to date. Current therapies are limited in their efficacy to restore full neurological function – resulting in lifelong disability and loss of autonomy. Whilst there remains a necessity to refine therapeutic protocols, stem cell (SC) studies have shown promise in the mending and re-establishment of the spinal cord neuroanatomy. Objectives: We conducted a systematic review of functional outcomes in stem cell therapeutics over the last three decades in large animals and humans. Methods: Medline, Embase, Cochrane and SCOPUS databases were searched for potentially pertinent articles from 1990 to 2020. Studies published in English were included if the stem cells were directly injected into the intraspinal, epidural or intrathecal compartments within two weeks of a traumatic mechanism of injury, including acute intervertebral disc prolapse. The participants were either large animals – defined as canine, porcine or non-human primate in-vivo models – or human patients. Results: Nine studies were included in this review. Statistically significant improvements in motor function and deep pain perception were seen at 8 weeks to 6 months post-SC injection compared to controls. Limitations: Functional outcomes are variably measured across studies. Almost all studies used experimentally induced trauma, which may not accurately represent the complexity of human spinal cord injury. Due to the exclusion criteria, there were no non-human primate studies included, yet these animal models are considered a closer anatomical match to humans than other large mammals. No human studies were included. Conclusions and Implications: Autologous and allogeneic stem cells have been trialled for the reconstitution of damaged and lost cells, remyelination of axons and remodelling of the pathophysiological microenvironment within the injured spinal cord, with some promising outcome data. This may translate to more successful future Phase I/II human clinical trials into the use of stem cells after TSCI in adults.

Overground robotic training effects on walking and secondary health conditions in individuals with spinal cord injury: systematic review

Overground powered lower limb exoskeletons (EXOs) have proven to be valid devices in gait rehabilitation in individuals with spinal cord injury (SCI). Although several articles have reported the effects of EXOs in these individuals, the few reviews available focused on specific domains, mainly walking. The aim of this systematic review is to provide a general overview of the effects of commercial EXOs (i.e. not EXOs used in military and industry applications) for medical purposes in individuals with SCI. This systematic review was conducted following the PRISMA guidelines and it referred to MED-LINE, EMBASE, SCOPUS, Web of Science and Cochrane library databases. The studies included were Randomized Clinical Trials (RCTs) and non-RCT based on EXOs intervention on individuals with SCI. Out of 1296 studies screened, 41 met inclusion criteria. Among all the EXO studies, the Ekso device was the most discussed, followed by ReWalk, Indego, HAL and Rex devices. Since 14 different domains were considered, the outcome measures were heterogeneous. The most investigated domain was walking, followed by cardiorespiratory/metabolic responses, spasticity, balance, quality of life, human–robot interaction, robot data, bowel functionality, strength, daily living activity, neurophysiology, sensory function, bladder functionality and body composition/bone density domains. There were no reports of negative effects due to EXOs trainings and most of the significant positive effects were noted in the walking domain for Ekso, ReWalk, HAL and Indego devices. Ekso studies reported significant effects due to training in almost all domains, while this was not the case with the Rex device. Not a single study carried out on sensory functions or bladder functionality reached significance for any EXO. It is not possible to draw general conclusions about the effects of EXOs usage due to the lack of high-quality studies as addressed by the Downs and Black tool, the heterogeneity of the outcome measures, of the protocols and of the SCI epidemiological/neurological features. However, the strengths and weaknesses of EXOs are starting to be defined, even considering the different types of adverse events that EXO training brought about. EXO training showed to bring significant improvements over time, but whether its effectiveness is greater or less than conventional therapy or other treatments is still mostly unknown. High-quality RCTs are necessary to better define the pros and cons of the EXOs available today. Studies of this kind could help clinicians to better choose the appropriate training for individuals with SCI.

Differences in sensorimotor and functional recovery between the dominant and non-dominant upper extremity following cervical spinal cord injury

STUDY DESIGN

Post hoc analysis of prospective multi-national, multi-centre cohort study.

OBJECTIVE

Determine whether cerebral dominance influences upper extremity recovery following cervical spinal cord injury (SCI).

SETTING

A multi-national subset of the longitudinal GRASSP dataset (n = 127).

METHODS

Secondary analysis of prospective, longitudinal multicenter study of individuals with cervical SCI (n = 73). Study participants were followed for up to 12 months after a cervical SCI, and the following outcome measures were serially assessed - the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the International Standards for the Neurological Classification of SCI (ISNCSCI), including upper extremity motor and sensory scores. Observed recovery and relative (percent) recovery were then determined for both the GRASSP and ISNCSCI, based on change from initial to last available assessment.

RESULTS

With the exception of prehension performance (quantitative grasping) following complete cervical SCI, there were no significant differences (p < 0.05) for observed and relative (percent) recovery, between the dominant and non-dominant upper extremities, as measured using GRASSP subtests, ISNCSCI motor scores and ISNCSCI sensory scores.

CONCLUSION

Despite well documented differences between the cerebral hemispheres, cerebral dominance appears to play a limited role in upper extremity recovery following acute cervical SCI.

Strategies for interface issues and challenges of neural electrodes

Neural electrodes, as a bridge for bidirectional communication between the body and external devices, are crucial means for detecting and controlling nerve activity. The electrodes play a vital role in monitoring the state of neural systems or influencing it to treat disease or restore functions. To achieve high-resolution, safe and long-term stable nerve recording and stimulation, a neural electrode with excellent electrochemical performance (e.g., impedance, charge storage capacity, charge injection limit), and good biocompatibility and stability is required. Here, the charge transfer process in the tissues, the electrode-tissue interfaces and the electrode materials are discussed respectively. Subsequently, the latest research methods and strategies for improving the electrochemical performance and biocompatibility of neural electrodes are reviewed. Finally, the challenges in the development of neural electrodes are proposed. It is expected that the development of neural electrodes will offer new opportunities for the evolution of neural prosthesis, bioelectronic medicine, brain science, and so on.

Multisite Transcutaneous Spinal Stimulation for Walking and Autonomic Recovery in Motor-Incomplete Tetraplegia: A Single-Subject Design

OBJECTIVE

This study investigated the effect of cervical and lumbar transcutaneous spinal cord stimulation (tSCS) combined with intensive training to improve walking and autonomic function after chronic spinal cord injury (SCI).

METHODS

Two 64-year-old men with chronic motor incomplete cervical SCI participated in this single-subject design study. They each underwent 2 months of intensive locomotor training and 2 months of multisite cervical and lumbosacral tSCS paired with intensive locomotor training.

RESULTS

The improvement in 6-Minute Walk Test distance after 2 months of tSCS with intensive training was threefold greater than after locomotor training alone. Both participants improved balance ability measured by the Berg Balance Scale and increased their ability to engage in daily home exercises. Gait analysis demonstrated increased step length for each individual. Both participants experienced improved sensation and bowel function, and 1 participant eliminated the need for intermittent catheterization after the stimulation phase of the study.

CONCLUSION

These results suggest that noninvasive spinal cord stimulation might promote recovery of locomotor and autonomic functions beyond traditional gait training in people with chronic incomplete cervical SCI.

IMPACT

Multisite transcutaneous spinal stimulation may induce neuroplasticity of the spinal networks and confer functional benefits following chronic cervical SCI.

N-Acetylcysteine alleviates spinal cord injury in rats after early decompression surgery by regulating inflammation and apoptosis

OBJECTIVE

Decompression surgery in patients with spinal cord injury (SCI) has a neuroprotective effect by alleviating secondary injury and improving neurological outcomes. N-Acetylcysteine (NAC), a drug approved by the United States Food and Drug Administration, has been shown to play neuroprotective roles via attenuation of apoptosis and inflammation. The purpose of the present study was to investigate the effects of early or late decompression surgery in combination with NAC administration on acute SCI, as well as investigate the underlying mechanisms of its actions.

METHODS

In this study, an acute SCI model was established in rats. The rats were treated with decompression surgery 24/48 h post-SCI in combination with or without NAC.

RESULTS

The results showed that decompression surgery in combination with NAC lead to a better outcome than decompression alone, as demonstrated by the higher Basso, Beattie, and Bresnahan scores. Histopathological examination demonstrated that early decompression surgery in combination with NAC exerted the best therapeutic effect on spinal cord recovery, which was further confirmed by the extent of inflammation and apoptosis. Additionally, we found that NAC might compensate for a lack of late surgery.

CONCLUSIONS

Collectively, early decompression surgery and NAC could be a promising combination for the treatment of acute SCI, and its therapeutic effects may be associated with the regulation of inflammation and apoptosis.

Monitoring Spinal Cord Tissue Oxygen in Patients With Acute, Severe Traumatic Spinal Cord Injuries

Objectives

To determine the feasibility of monitoring tissue oxygen tension from the injury site (psctO2) in patients with acute, severe traumatic spinal cord injuries.

Design

We inserted at the injury site a pressure probe, a microdialysis catheter, and an oxygen electrode to monitor for up to a week intraspinal pressure (ISP), spinal cord perfusion pressure (SCPP), tissue glucose, lactate/pyruvate ratio (LPR), and psctO2. We analyzed 2,213 hours of such data. Follow-up was 6-28 months postinjury.

Setting

Single-center neurosurgical and neurocritical care units.

Subjects

Twenty-six patients with traumatic spinal cord injuries, American spinal injury association Impairment Scale A-C. Probes were inserted within 72 hours of injury.

Interventions

Insertion of subarachnoid oxygen electrode (Licox; Integra LifeSciences, Sophia-Antipolis, France), pressure probe, and microdialysis catheter.

Measurements and Main Results

psctO2 was significantly influenced by ISP (psctO2 26.7 +/- 0.3 mm Hg at ISP > 10 mmHg vs psctO2 22.7 +/- 0.8 mm Hg at ISP <= 10 mm Hg), SCPP (psctO2 26.8 +/- 0.3 mm Hg at SCPP < 90 mm Hg vs psctO2 32.1 +/- 0.7 mm Hg at SCPP >= 90 mm Hg), tissue glucose (psctO2 26.8 +/- 0.4 mm Hg at glucose < 6 mM vs 32.9 +/- 0.5 mm Hg at glucose >= 6 mM), tissue LPR (psctO2 25.3 +/- 0.4 mm Hg at LPR > 30 vs psctO2 31.3 +/- 0.3 mm Hg at LPR <= 30), and fever (psctO2 28.8 +/- 0.5 mm Hg at cord temperature 37-38[degrees]C vs psctO2 28.7 +/- 0.8 mm Hg at cord temperature >= 39[degrees]C). Tissue hypoxia also occurred independent of these factors. Increasing the FIO2 by 0.48 increases psctO2 by 71.8% above baseline within 8.4 minutes. In patients with motor-incomplete injuries, fluctuations in psctO2 correlated with fluctuations in limb motor score. The injured cord spent 11% (39%) hours at psctO2 less than 5 mm Hg (< 20 mm Hg) in patients with motor-complete outcomes, compared with 1% (30%) hours at psctO2 less than 5 mm Hg (< 20 mm Hg) in patients with motor-incomplete outcomes. Complications were cerebrospinal fluid leak (5/26) and wound infection (1/26).

Conclusions

This study lays the foundation for measuring and altering spinal cord oxygen at the injury site. Future studies are required to investigate whether this is an effective new therapy.

Association of age with the timing of acute spine surgery-effects on neurological outcome after traumatic spinal cord injury

PURPOSE

To investigate the association of age with delay in spine surgery and the effects on neurological outcome after traumatic spinal cord injury (SCI).

METHODS

Ambispective cohort study (2011-2017) in n = 213 patients consecutively enrolled in a Level I trauma center with SCI care in a metropolitan region in Germany. Age-related differences in the injury to surgery interval and conditions associated with its delay (> 12 h after SCI) were explored using age categories or continuous variables and natural cubic splines. Effects of delayed surgery or age with outcome were analyzed using multiple logistic regression.

RESULTS

The median age of the study population was 58.8 years (42.0-74.6 IQR). Older age (≥ 75y) was associated with a prolonged injury to surgery interval of 22.8 h (7.2-121.3) compared to 6.6 h (4.4-47.9) in younger patients (≤ 44y). Main reasons for delayed surgery in older individuals were secondary referrals and multimorbidity. Shorter time span to surgery (≤ 12 h) was associated with higher rates of ASIA impairment scale (AIS) conversion (OR 4.22, 95%CI 1.85-9.65), as mirrored by adjusted spline curves (< 20 h 20-25%, 20-60 h 10-20%, > 60 h < 10% probability of AIS conversion). In incomplete SCI, the probability of AIS conversion was lower in older patients [e.g., OR 0.09 (0.02-0.44) for'45-59y' vs.' ≤ 44y'], as confirmed by spline curves (< 40y 20-80%, ≥ 40y 5-20% probability).

CONCLUSION

Older patient age complexifies surgical SCI care and research. Tackling secondary referral to Level I trauma centers and delayed spine surgery imposes as tangible opportunity to improve the outcome of older SCI patients.

Evaluation of the Clinical Efficacy of Stem Cell Transplantation in the Treatment of Spinal Cord Injury: A Systematic Review and Meta-analysis

Stem cell transplantation has been applied to treat spinal cord injury (SCI) in clinical trials for many years. However, the clinical efficacies of stem cell transplantation in SCI have been quite diverse. The purpose of our study was to systematically investigate the efficacy of stem cell transplantation in patients with SCI. The PubMed, Web of Science, Ovid-Medline, Cochrane Library, China National Knowledge Infrastructure, VIP, Wanfang, and SinoMed databases were searched until October 27, 2020. Quantitative and qualitative data were analyzed by Review Manager 5.3 and R. Nine studies (n = 328) were included, and the overall risk of bias was moderate. The ASIA Impairment Scale (AIS) grading improvement rate was analyzed in favor of stem cell transplantation group [odds ratio (OR) = 6.06, 95% confidence interval (CI): 3.16–11.62, P < 0.00001]. Urodynamic indices also showed improvement in bladder function. In subgroup analyses, the results indicated that in patients with complete (AIS A) SCI, with the application of cell numbers between n*(10⁷–10⁸), two cell types (i.e., bone marrow–derived mesenchymal stem cells and bone marrow mononuclears), and treatment time of more than 6 months, stem cell transplantation was more beneficial for sensorimotor function (P < 0.05 for all groups). The risk of fever incidence in the stem cell transplantation group was 4.22 (95% CI: 1.7–10.22, P = 0.001), and principal component analysis (PCA) suggested it was more related to transplanted cell numbers. Thus, stem cell transplantation can promote functional recovery in SCI patients. Moreover, the type and quantity of transplanted stem cells and treatment time are important factors affecting the therapeutic effect of stem cell transplantation in SCI. Further studies are needed to evaluate the effects and elucidate the mechanisms of these factors on stem cell therapy in SCI.

The Study of Cerebrospinal Fluid microRNAs in Spinal Cord Injury and Neurodegenerative Diseases: Methodological Problems and Possible Solutions

Despite extensive research on neurological disorders, unanswered questions remain regarding the molecular mechanisms underpinning the course of these diseases, and the search continues for effective biomarkers for early diagnosis, prognosis, or therapeutic intervention. These questions are especially acute in the study of spinal cord injury (SCI) and neurodegenerative diseases. It is believed that the changes in gene expression associated with processes triggered by neurological disorders are the result of post-transcriptional gene regulation. microRNAs (miRNAs) are key regulators of post-transcriptional gene expression and, as such, are often looked to in the search for effective biomarkers. We propose that cerebrospinal fluid (CSF) is potentially a source of biomarkers since it is in direct contact with the central nervous system and therefore may contain biomarkers indicating neurodegeneration or damage to the brain and spinal cord. However, since the abundance of miRNAs in CSF is low, their isolation and detection is technically difficult. In this review, we evaluate the findings of recent studies of CSF miRNAs as biomarkers of spinal cord injury (SCI) and neurodegenerative diseases. We also summarize the current knowledge concerning the methods of studying miRNA in CSF, including RNA isolation and normalization of the data, highlighting the caveats of these approaches and possible solutions.

Characterizing Natural Recovery of People With Initial Motor Complete Tetraplegia

OBJECTIVE

To determine the differences in neurologic recovery in persons with initial cervical American Spinal Cord Injury Association Impairment Scale (AIS) grades A and B over time.

DESIGN

Retrospective analysis of data from people with traumatic cervical spinal cord injury (SCI) enrolled in the National Spinal Cord Injury Model Systems (SCIMS) database from 2011-2019.

SETTING

SCIMS centers.

PARTICIPANTS

Individuals (N=187) with traumatic cervical (C1-C7 motor level) SCI admitted with initial AIS grade A and B injuries within 30 days of injury, age 16 years or older, upper extremity motor score (UEMS) ≤20 on both sides, and complete neurologic data at admission and follow-up between 6 months and 2 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Conversion in AIS grades, UEMS and lower extremity motor scores (LEMS), and sensory scores.

RESULTS

Mean time to initial and follow-up examinations were 16.1±7.3 days and 377.5±93.4 days, respectively. Conversion from an initial cervical AIS grades A and B to motor incomplete status was 13.4% and 50.0%, respectively. The mean UEMS change for people with initial AIS grades A and B did not differ (7.8±6.5 and 8.8±6.1; P=.307), but people with AIS grade B experienced significantly higher means of LEMS change (2.3±7.4 and 8.8±13.9 (P≤.001). The increased rate of conversion to motor incomplete status from initial AIS grade B appears to be the primary driving factor of increased overall motor recovery. Individuals with initial AIS grade B had greater improvement in sensory scores.

CONCLUSIONS

While UEMS recovery is similar in persons with initial AIS grades A and B, the rate of conversion to motor incomplete status, LEMS, and sensory recovery are significantly different. This information is important for clinical as well as research considerations.

Rehabilitation of Acute Vs. Chronic Patients With Spinal Cord Injury With a Neurologically Controlled Hybrid Assistive Limb Exoskeleton: Is There a Difference in Outcome?

This study aimed to assess the outcome of acute and chronic participants with spinal cord injury (SCI) after 12 weeks of bodyweight supported treadmill training (BWSTT) with a hybrid assistive limb exoskeleton (HAL). Acute participants were defined as ≤12 months between SCI and training, chronic participants >12 months between SCI and training. We assessed whether HAL-assisted BWSTT is advantageous for acute and chronic participants and if length of time post injury impacts the outcome of HAL-assisted BWSTT. As the primary outcome, we assessed the time needed for the 10 meter walk test (10MWT). Hundred and twenty-one individuals participated in a 12-week HAL-assisted BWSTT five times a week. We regularly conducted a 10MWT, a 6 minute walk test (6MWT), and assessed the walking index for spinal cord injury (WISCI II) and lower extremity motor score (LEMS) to evaluate the gait performance without the exoskeleton. Distance and time were recorded by the treadmill while the participant was walking with the exoskeleton. All participants benefit from the 12-week HAL-assisted BWSTT. A significant difference between acute and chronic participants' outcomes was found in 6MWT, LEMS, and WISCI II, though not in 10MWT. Although chronic participants improved significantly lesser than acute participants, they did improve their outcome significantly compared to the beginning. Hybrid assistive limb-assisted BWSTT in the rehabilitation of patients with SCI is advantageous for both acute and chronic patients. We could not define a time related cut-off threshold following SCI for effectiveness of HAL-assisted BWSTT.

Dynamics of biomarkers across the stages of traumatic spinal cord injury - implications for neural plasticity and repair

BACKGROUND

Traumatic spinal cord injury (SCI) is a complex medical condition causing significant physical disability and psychological distress. While the adult spinal cord is characterized by poor regenerative potential, some recovery of neurological function is still possible through activation of neural plasticity mechanisms. We still have limited knowledge about the activation of these mechanisms in the different stages after human SCI.

OBJECTIVE

In this review, we discuss the potential role of biomarkers of SCI as indicators of the plasticity mechanisms at work during the different phases of SCI.

METHODS

An extensive review of literature related to SCI pathophysiology, neural plasticity and humoral biomarkers was conducted by consulting the PubMed database. Research and review articles from SCI animal models and SCI clinical trials published in English until January 2021 were reviewed. The selection of candidates for humoral biomarkers of plasticity after SCI was based on the following criteria: 1) strong evidence supporting involvement in neural plasticity (mandatory); 2) evidence supporting altered expression after SCI (optional).

RESULTS

Based on selected findings, we identified two main groups of potential humoral biomarkers of neural plasticity after SCI: 1) neurotrophic factors including: Brain derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrofin-3 (NT-3), and Insulin-like growth factor 1 (IGF-1); 2) other factors including: Tumor necrosis factor-alpha (TNF-α), Matrix Metalloproteinases (MMPs), and MicroRNAs (miRNAs). Plasticity changes associated with these biomarkers often can be both adaptive (promoting functional improvement) and maladaptive. This dual role seems to be influenced by their concentrations and time-window during SCI.

CONCLUSIONS

Further studies of dynamics of biomarkers across the stages of SCI are necessary to elucidate the way in which they reflect the remodeling of neural pathways. A better knowledge about the mechanisms underlying plasticity could guide the selection of more appropriate therapeutic strategies to enhance positive spinal network reorganization.

The intractable problems with brain death and possible solutions

Brain death has been accepted worldwide medically and legally as the biological state of death of the organism. Nevertheless, the literature has described persistent problems with this acceptance ever since brain death was described. Many of these problems are not widely known or properly understood by much of the medical community. Here we aim to clarify these issues, based on the two intractable problems in the brain death debates. First, the metaphysical problem: there is no reason that withstands critical scrutiny to believe that BD is the state of biological death of the human organism. Second, the epistemic problem: there is no way currently to diagnose the state of BD, the irreversible loss of all brain functions, using clinical tests and ancillary tests, given potential confounders to testing. We discuss these problems and their main objections and conclude that these problems are intractable in that there has been no acceptable solution offered other than bare assertions of an 'operational definition' of death. We present possible ways to move forward that accept both the metaphysical problem - that BD is not biological death of the human organism - and the epistemic problem - that as currently diagnosed, BD is a devastating neurological state where recovery of sentience is very unlikely, but not a confirmed state of irreversible loss of all [critical] brain functions. We argue that the best solution is to abandon the dead donor rule, thus allowing vital organ donation from patients currently diagnosed as BD, assuming appropriate changes are made to the consent process and to laws about killing.

Tracking White and Gray Matter Degeneration along the Spinal Cord Axis in Degenerative Cervical Myelopathy

This study aims to determine tissue-specific neurodegeneration across the spinal cord in patients with mild-moderate degenerative cervical myelopathy (DCM). Twenty-four mild-moderate DCM and 24 healthy subjects were recruited. In patients, a T2-weighted scan was acquired at the compression site, whereas in all participants a T2*-weighted and diffusion-weighted scan was acquired at the cervical level (C2-C3) and in the lumbar enlargement (i.e., rostral and caudal to the site of compression). We quantified intramedullary signal changes, maximal canal and cord compression, white (WM) and gray matter (GM) atrophy, and microstructural indices from diffusion-weighted scans. All patients underwent clinical (modified Japanese Orthopaedic Association; mJOA) and electrophysiological assessments. Regression analysis assessed associations between magnetic resonance imaging (MRI) readouts and electrophysiological and clinical outcomes. Twenty patients were classified with mild and 4 with moderate DCM using the mJOA scale. The most frequent site of compression was at the C5-C6 level, with maximum cord compression of 38.73% ± 11.57%. Ten patients showed imaging evidence of cervical myelopathy. In the cervical cord, WM and GM atrophy and WM microstructural changes were evident, whereas in the lumbar cord only WM showed atrophy and microstructural changes. Remote cervical cord WM microstructural changes were pronounced in patients with radiological myelopathy and associated with impaired electrophysiology. Lumbar cord WM atrophy was associated with lower limb sensory impairments. In conclusion, tissue-specific neurodegeneration revealed by quantitative MRI is already apparent across the spinal cord in mild-moderate DCM before the onset of severe clinical impairments. WM microstructural changes are particularly sensitive to remote pathologically and clinically eloquent changes in DCM.

Restoration of motor function after CNS damage: is there a potential beyond spontaneous recovery?

What determines the effectiveness of neurorehabilitation approaches on the outcome of function in stroke or spinal cord injured subjects? Many studies claim that an improvement of function is based on the intensity of training, while some actual studies indicate no additional gain in function by a more intensive training after a stroke. Inherent factors seem to determine outcome, such as damage of specific tracts in stroke and level of lesion in spinal cord injured subjects, while the improvement of function achieved by an intensive training is small in relation to the spontaneous recovery. It is argued that an individual capacity of recovery exists depending on such factors. This capacity can be exploited by a repetitive execution of functional movements (supported as far as required), irrespective of the intensity and technology applied. Elderly subjects have difficulties to translate the recovery of motor deficit into function. Alternative, non-training approaches to restore motor function, such as epidural or deep brain stimulation as well as CNS repair are still in an early clinical or in a translational stage.

Improving Diagnostic Workup Following Traumatic Spinal Cord Injury: Advances in Biomarkers

PURPOSE OF REVIEW

Traumatic spinal cord injury (SCI) is a life-changing event with drastic implications for patients due to sensorimotor impairment and autonomous dysfunction. Current clinical evaluations focus on the assessment of injury level and severity using standardized neurological examinations. However, they fail to predict individual trajectories of recovery, which highlights the need for the development of advanced diagnostics. This narrative review identifies recent advances in the search of clinically relevant biomarkers in the field of SCI.

RECENT FINDINGS

Advanced neuroimaging and molecular biomarkers sensitive to the disease processes initiated by the SCI have been identified. These biomarkers range from advanced neuroimaging techniques, neurophysiological readouts, and molecular biomarkers identifying the concentrations of several proteins in blood and CSF samples. Some of these biomarkers improve current prediction models based on clinical readouts. Validation with larger patient cohorts is warranted. Several biomarkers have been identified-ranging from imaging to molecular markers-that could serve as advanced diagnostic and hence supplement current clinical assessments.

The Natural History of Spinal Cord Injury

The natural history of spinal cord injury is in a state of flux. Our knowledge about the prevalence, epidemiology, and natural history spinal cord injury is in evolution. In this article, we summarize these considerations to provide a state-of-the-art synopsis of the neurologic outcomes of this condition.