Utility of somatosensory and motor-evoked potentials in reflecting gross and fine motor functions after unilateral cervical spinal cord contusion injury

Effects of transcranial magnetic stimulation on axonal regeneration in the corticospinal tract of female rats with spinal cord injury

BACKGROUND

This study investigates the potential of transcranial magnetic stimulation (TMS) to enhance spinal cord axon regeneration by modulating corticospinal pathways and improving motor nerve function recovery in rats with spinal cord injury (SCI).

NEW METHOD

TMS is a non-invasive neuromodulation technique that generates a magnetic field to activate neurons in the brain, leading to depolarization and modulation of cortical activity. Initially utilized for brain physiology research, TMS has evolved into a diagnostic and prognostic tool in clinical settings, with increasing interest in its therapeutic applications. However, its potential for treating motor dysfunction in SCI has been underexplored.

RESULTS

The TMS intervention group exhibited significant improvements compared to the control group across behavioral assessments, neurophysiological measurements, pathological analysis, and immunological markers.

COMPARISON WITH EXISTING METHODS

Unlike most studies that focus on localized spinal cord injury or muscle treatments, this study leverages the non-invasive, painless, and highly penetrating nature of TMS to focus on the corticospinal tracts, exploring its therapeutic potential for SCI.

CONCLUSIONS

TMS enhances motor function recovery in rats with SCI by restoring corticospinal pathway integrity and promoting axonal regeneration. These findings highlight TMS as a promising therapeutic option for SCI patients with currently limited treatment alternatives.

Time varying characteristic in somatosensory evoked potentials as a biomarker of spinal cord ischemic-reperfusion injury in rat

Spinal cord ischemic-reperfusion injury (SCIRI) could occurs during surgical procedures without detection, presenting a complex course and an unfavorable prognosis. This may lead to postoperative sensory or motor dysfunction in areas innervated by the spinal cord, and in some cases, permanent paralysis. Timely detection of SCIRI and immediate waring can help surgeons implement remedial intervention to prevent irreversible spinal cord injury. Therefore, it is crucial to develop a precise and effective method for early detection of SCIRI. This study utilized rat models to simulate intraoperative SCIRI and employed somatosensory evoked potentials (SEP) for continuous monitoring during surgery. In this study, SEP signal changes were examined in six groups with varying severities of SCIRI and one normal control group. SEP signal changes were examined during operations in different groups and correlated with postoperative behavioral and histopathological data. The result demonstrated specific changes in SEP signals during SCIRI, termed as time-varying characteristics, which are associated with the duration of ischemia and subsequent reperfusion. Time-varying characteristics in SEP could potentially serve as a new biomarker for the intraoperative detection of SCIRI. This finding is significant for clinical surgeons to identify and guide early intervention of SCIRI timely. Additionally, this measurement is easily translatable to clinical application.

Evaluating somatosensory evoked potentials in predicting treatment outcomes for thoracolumbar spinal compression fractures using closed reduction and over-extension techniques

OBJECTIVE

To evaluate the predictive value of somatosensory evoked potentials (SEPs) for the efficacy of closed reduction combined with over-extension reduction technique (PVP) in managing thoracolumbar spinal compression fractures.

METHODS

Data were collected from 125 patients who underwent closed reduction with PVP and SEP monitoring from February 2021 to July 2023. We evaluated surgery success rates, incidence of bone cement leakage, and patient recovery outcomes including vertebral anterior height, Oswestry Disability Index (ODI), and Cobb angle restoration. SEP results were analyzed to categorize patients into effective and ineffective treatment groups. Differences in SEP waveforms between these groups were examined, and ROC analysis was used to assess the predictive value of these differences. Multivariate logistic regression was employed to identify risk factors affecting treatment efficacy.

RESULTS

Post-treatment assessments showed significant improvements in vertebral anterior height, ODI, and Cobb angle. SEP monitoring correlated well with intraoperative findings and physical examinations. During reduction, changes in SEP latency and amplitude were noted in 37 patients, with 7 patients meeting SEP amplitude alarm criteria, which normalized after adjustments. During PVP, 28 patients exhibited SEP amplitude fluctuations and 5 experienced a 30% reduction in amplitude following initial cement injection, with no significant latency changes. Treatment was deemed effective in 93 patients and ineffective in 32. SEP amplitudes during vertebral compression and PVP were significantly lower in the effective group (P<0.05). The AUC for predicting treatment efficacy was 0.819 and 0.859, respectively. Multivariate analysis revealed low preoperative vertebral compression ratio, number of fractures, and abnormal SEP amplitudes as independent risk factors for treatment outcomes.

CONCLUSION

SEP monitoring provides an accurate reflection of spinal cord function during closed reduction with PVP, aiding in predicting treatment safety and efficacy. The use of SEP monitoring is thus recommended for clinical application in this context.

Positive effect of microvascular proliferation on functional recovery in experimental cervical spondylotic myelopathy

Background and purpose

Cervical Spondylotic Myelopathy (CSM), the most common cause of spinal cord dysfunction globally, is a degenerative disease that results in non-violent, gradual, and long-lasting compression of the cervical spinal cord. The objective of this study was to investigate whether microvascular proliferation could positively affect neural function recovery in experimental cervical spondylotic myelopathy (CSM).

Methods

A total of 60 male adult Sprague-Dawley (SD) were randomly divided into four groups: Control (CON), Compression (COM), Angiostasis (AS), and Angiogenesis (A G),with 15 rats in each group. Rats in the AS group received SU5416 to inhibit angiogenesis, while rats in the AG group received Deferoxamine (DFO) to promote angiogenesis. Motor and sensory functions were assessed using the Basso Beattie Bresnahan (BBB) scale and somatosensory evoked potential (SEP) examination. Neuropathological degeneration was evaluated by the number of neurons, Nissl bodies (NB), and the de-myelination of white matter detected by Hematoxylin & Eosin(HE), Toluidine Blue (TB), and Luxol Fast Blue (LFB) staining. Immunohistochemical (IHC) staining was used to observe the Neurovascular Unit (NVU).

Results

Rats in the CON group exhibited normal locomotor function with full BBB score, normal SEP latency and amplitude. Among the other three groups, the AG group had the highest BBB score and the shortest SEP latency, while the AS group had the lowest BBB score and the most prolonged SEP latency. The SEP amplitude showed an opposite performance to the latency. Compared to the COM and AS groups, the AG group demonstrated significant neuronal restoration in gray matter and axonal remyelination in white matter. DFO promoted microvascular proliferation, especially in gray matter, and improved the survival of neuroglial cells. In contrast, SU-5416 inhibited the viability of neuroglial cells by reducing micro vessels.

Conclusion

The microvascular status was closely related to NVU remodeling an-d functional recovery. Therefore, proliferation of micro vessels contributed to function -al recovery in experimental CSM, which may be associated with NVU remodeling.

Chronic demyelination and myelin repair after spinal cord injury in mice: A potential link for glutamatergic axon activity

Our prior work examining endogenous repair after spinal cord injury (SCI) in mice revealed that large numbers of new oligodendrocytes (OLs) are generated in the injured spinal cord, with peak oligodendrogenesis between 4 and 7 weeks post-injury (wpi). We also detected new myelin formation over 2 months post-injury (mpi). Our current work significantly extends these results, including quantification of new myelin through 6 mpi and concomitant examination of indices of demyelination. We also examined electrophysiological changes during peak oligogenesis and a potential mechanism driving OL progenitor cell (OPC) contact with axons. Results reveal peak in remyelination occurs during the 3rd mpi, and that myelin generation continues for at least 6 mpi. Further, motor evoked potentials significantly increased during peak remyelination, suggesting enhanced axon potential conduction. Interestingly, two indices of demyelination, nodal protein spreading and Nav1.2 upregulation, were also present chronically after SCI. Nav1.2 was expressed through 10 wpi and nodal protein disorganization was detectable throughout 6 mpi suggesting chronic demyelination, which was confirmed with EM. Thus, demyelination may continue chronically, which could trigger the long-term remyelination response. To examine a potential mechanism that may initiate post-injury myelination, we show that OPC processes contact glutamatergic axons in the injured spinal cord in an activity-dependent manner. Notably, these OPC/axon contacts were increased 2-fold when axons were activated chemogenetically, revealing a potential therapeutic target to enhance post-SCI myelin repair. Collectively, results show the surprisingly dynamic nature of the injured spinal cord over time and that the tissue may be amenable to treatments targeting chronic demyelination.

[Research progress on rodent models of cervical spinal cord injury]

Objective

To summarize the research progress on rodent models of cervical spinal cord injury (SCI).

Methods

The relevant domestic and foreign literature in recent years was reviewed, the methods of establishing the rodent models of cervical SCI and the evaluation methods of behavior, imaging, neuroelectrophysiology, and histology were summarized.

Results

Cervical SCI involves primary and secondary injuries. Primary cervical SCI can be simulated with contusion, contusion compression, fracture dislocation, spinal cord traction, and spinal cord transection; scondary cervical SCI can be simulated with photochemical model and excitotoxicity model. Certain evaluation methods such as behavior, imaging, neuroelectrophysiology, and histology are used to evaluation during model building and research.

Conclusion

Different rodent models of cervical SCI have different advantages and application directions, and it is critical importance for the study of cervical SCI to establish effective animal models.

Anatomical and behavioral outcomes following a graded hemi-contusive cervical spinal cord injury model in mice

BACKGROUND

A graded hemi-contusion spinal cord injury produces complex anatomical deformation of the spinal cord parenchyma. The relationship between lesion severity and behavioral consequences in a novel contusion mouse model remains unknown.

PURPOSE

We aimed to establish a graded cervical hemi-contusion spinal cord injury model in mice and investigate the correlation between graded anatomical damage to the spinal cord and resulting behavioral impairments.

METHODS

Thirty-two mice were divided into groups of 1.2 mm, 1.5 mm and sham. The tip of an impactor with a diameter of 1 mm was utilized to compress the left dorsal cord of C5 by 1.2 mm or 1.5 mm at a speed of 300 mm/s. Forelimb motor function was evaluated using rearing, grooming and grip-strength tests before and after the injuries. Histologically the area of white matter sparing, gray matter sparing and lesion area were quantified at 6-week-post-injury.

RESULTS

Behavioral assessments showed a more severe forelimb functional deficit in 1.5 mm contusion displacements relative to 1.2 mm contusion displacements after injury. The 1.2 mm hemi-contusion mainly caused damage to the dorsal fasciculus, ventral and dorsal horn, while the 1.5 mm hemi-contusion lead to additional damage extending to ventral fasciculus. Sparing of the gray and white matter at the epicenter was 36.8 ± 2.4% and 12.4 ± 2.6% in the 1.2 mm group, and 27.6 ± 4.0% and 4.1 ± 2.2% in the 1.5 mm group, respectively. Furthermore, the lesion area was 20.8 ± 3.0% and 36.0 ± 2.1% in the 1.2 mm and 1.5 mm groups, respectively. There was a significant correlation between the performance in the grooming test and white matter sparing, and between grip-test strength and gray matter sparing.

CONCLUSION

The present study demonstrates that a hemi-contusion cervical spinal cord injury in mice can be graded by contusion displacement and that there is a correlation between anatomical and behavioral outcomes. This study provides a means for determining the severity of lesions in a contusion mouse model.

Improving reproducibility of motor evoked potentials in mice

BACKGROUND

In preclinical research involving murine models of neurological diseases, Motor Evoked Potentials (MEPs) can detect pathological alterations in nerve conduction throughout the cortico-spinal tract. In mice, MEPs elicited by electrical stimulation of the motor cortex can be performed with epicranial or subdermal electrodes such as implanted screws or removable needles, which are associated with invasive surgery and variability in placement of the stimulating electrodes, respectively.

METHODS

We compared MEPs induced by epicranial or subcutaneous stimulation with a non-invasive surface cup electrode over five recording sessions, in healthy C57BL/6 mice. Additionally, using surface stimulation, we examined the recordings obtained with intramuscular needles or surface electrodes to understand if MEP reproducibility could be improved.

RESULTS

Resting motor threshold (RMT), MEP latency and amplitude were comparable among the different stimulation methods. Epicranial, subcutaneous and surface stimulation techniques presented good repeatability over time, with surface stimulation showing a significantly reduced inter-session variability. Compared with intramuscular needles, MEPs recorded with surface electrode showed reduced peak-to-peak amplitude at all timepoints. RMT and MEP latency were comparable with both recording methods. On the other hand, amplitudes recorded with the surface electrode presented a significantly lower inter-session variance, resulting in improved repeatability.

CONCLUSION

Overall, there is evidence for highly reproducible results using different stimulating methods, with indication for reduced inter-session variability for surface stimulation. Moreover, MEP recording with surface electrode provided a decrease in amplitude variability over time, indicating improved measurement stability when considering amplitude as functional outcome in longitudinal studies.

Cotransplantation with RADA16-PRG-Self-Assembled Nanopeptide Scaffolds, Bone Mesenchymal Stem Cells and Brain-Derived Neurotrophic Factor-Adeno-Associated Virus Promote Functional Repair After Acute Spinal Cord Injury in Rats

We transplanted RADA16-PRG self-assembled nanopeptide scaffolds (SAPNSs), bone mesenchymal stem cells (BMSCs), and a brain-derived neurotrophic factor (BDNF)-expressing adeno-associated virus (AAV) into rats subjected to acute spinal cord injury (SCI) to investigate the effects of these transplantations on acute SCI repair and explore their mechanisms. Forty-eight SCI rats were randomly divided into four groups: BBR, BR, B, and NC groups. Seven and 28 days after SCI, evoked potentials (EPs) and BBB scores were assessed to evaluate the recovery of rats' motor behavior and sensory function after injury. HE and toluidine blue staining were performed to investigate the histological structure of the spinal cord tissue of rats from each group, and immunofluorescence staining was used to observe the red fluorescent protein (RFP) intensity of BMSCs and glial fibrillary acidic protein (GFAP) and neurofilament (NF) in the damaged area in each group. RT-PCR was utilized to detect the expression levels of the BDNF, GFAP, and neuron-specific enolase (NSE) genes in the injured area in each group. The results showed that cotransplantation of RADA16-PRG-SAPNs, BMSCs, and BDNF-AVV promoted the spinal cord's motor and sensory function of SCI rats; increased levels of BMSCs, inhabited glial cells proliferation, and promoted neurons proliferations in the injured area; and increased NF, BDNF, and NSE levels and decreased its GFAP in the injured area. Thus, cotransplantation of RADA16-PRG-SAPNS, BMSCs, and BDNF-AAV can prolong the survival time of BMSCs in rats, reduce the postoperative scarring caused by glial proliferation, and promote the migration and proliferation of neurons in the injured area, resulting in the promotion of functional repair after acute SCI.

MRI metrics at the epicenter of spinal cord injury are correlated with the stepping process in rhesus monkeys

Clinical evaluations of long-term outcomes in the early-stage spinal cord injury (SCI) focus on macroscopic motor performance and are limited in their prognostic precision. This study was designed to investigate the sensitivity of the magnetic resonance imaging (MRI) indexes to the data-driven gait process after SCI. Ten adult female rhesus monkeys were subjected to thoracic SCI. Kinematics-based gait examinations were performed at 1 (early stage) and 12 (chronic stage) months post-SCI. The proportion of stepping (PS) and gait stability (GS) were calculated as the outcome measures. MRI metrics, which were derived from structural imaging (spinal cord cross-sectional area, SCA) and diffusion tensor imaging (fractional anisotropy, FA; axial diffusivity, λ_//), were acquired in the early stage and compared with functional outcomes by using correlation analysis and stepwise multivariable linear regression. Residual tissue SCA at the injury epicenter and residual tissue FA/remote normal-like tissue FA were correlated with the early-stage PS and GS. The extent of lesion site λ_///residual tissue λ_// in the early stage after SCI was correlated with the chronic-stage GS. The ratios of lesion site λ_// to residual tissue λ_// and early-stage GS were predictive of the improvement in the PS at follow-up. Similarly, the ratios of lesion site λ_// to residual tissue λ_// and early-stage PS best predicted chronic GS recovery. Our findings demonstrate the predictive power of MRI combined with the early data-driven gait indexes for long-term outcomes. Such an approach may help clinicians to predict functional recovery accurately.