Restorative Neurology and Neuroscience - Volume 39, issue 5

Authors: Roumengous, Thibault | Reutter, Alec B. | Peterson, Carrie L.

Article Type: Research Article

Abstract: Background: Transcranial magnetic stimulation (TMS) can monitor or modulate brain excitability. However, reliability of TMS outcomes depends on consistent coil placement during stimulation. Neuronavigated TMS systems can address this issue, but their cost limits their use outside of specialist research environments. Objective: The objective was to evaluate the performance of a low-cost navigated TMS approach in improving coil placement consistency and its effect on motor evoked potentials (MEPs) when targeting the biceps brachii at rest and during voluntary contractions. Methods: We implemented a navigated TMS system using a low-cost 3D camera system and open-source software environment …programmed using the Unity 3D engine. MEPs were collected from the biceps brachii at rest and during voluntary contractions across two sessions in ten non-disabled individuals. Motor hotspots were recorded and targeted via two conditions: navigated and conventional. Results: The low-cost navigated TMS system reduced coil orientation error (pitch: 1.18°±1.2°, yaw: 1.99°±1.9°, roll: 1.18°±2.2° with navigation, versus pitch: 3.7°±5.7°, yaw: 3.11°±3.1°, roll: 3.8°±9.1° with conventional). The improvement in coil orientation had no effect on MEP amplitudes and variability. Conclusions: The low-cost system is a suitable alternative to expensive systems in tracking the motor hotspot between sessions and quantifying the error in coil placement when delivering TMS. Biceps MEP variability reflects physiological variability across a range of voluntary efforts, that can be captured equally well with navigated or conventional approaches of coil locating. Show more

Keywords: Neuronavigation, corticomotor excitability, navigated brain stimulation, voluntary contraction, proximal muscles, upper limb

DOI: 10.3233/RNN-211207

Citation: Restorative Neurology and Neuroscience, vol. 39, no. 5, pp. 319-328, 2021

Authors: Butler, John T. | Robinson, Tobias J. | Edwards, Jared R. | Grafe, Marjorie R. | Kirsch, Jeffrey R.

Article Type: Research Article

Abstract: Background/Objective: Peripheral-nerve blocks (PNBs) using continuous-infusion of local anesthetics are used to provide perioperative analgesia. Yet little research exists to characterize the histopathological effects of continuous long-duration PNBs. Herein we test the hypothesis that continuous peri-neural bupivacaine infusion (3-day vs. 7-day infusion) contributes to histologic injury in a duration-dependent manner using an in vivo model of rat sciatic nerves. Methods: We placed indwelling catheters in 22 rats for infusion with low-dose (0.5mg/kg/hr) bupivacaine or normal saline proximal to the right sciatic nerves for 3 or 7 consecutive days. Hind-limb analgesia was measured using Von-Frey nociceptive testing. At …infusion end, rats were sacrificed, bilateral nerves were sectioned and stained with hematoxylin and eosin and CD68 for evaluation of inflammatory response, and eriochrome to assess damage to myelin. Results: Animals receiving continuous infusion of bupivacaine maintained analgesia as demonstrated by significant decrease (50% on average) in nociceptive response in bupivacaine-infused limbs across time points. Both 7-day saline and bupivacaine-infused sciatic nerves showed significantly-increased inflammation by H&E staining compared to untreated native nerve controls (P  = 0.0001, P  < 0.0001). Extent of inflammation did not vary significantly based on infusate (7-day saline vs. 7-day bupivacaine P  > 0.99) or duration (3-day bupivacaine vs 7-day bupivacaine P  > 0.99). No significant change in sciatic nerve myelin was found in bupivacaine-infused animals compared to saline-infused controls, regardless of duration. Conclusions: Long-duration (7-day) bupivacaine infusion provided durable post-operative analgesia, yet contributed to equivalent neural inflammation as short duration (3-day) infusion of bupivacaine or saline with no evidence of demyelination. Show more

Keywords: Continuous, peripheral, nerve, block, bupivacaine

DOI: 10.3233/RNN-211170

Citation: Restorative Neurology and Neuroscience, vol. 39, no. 5, pp. 329-338, 2021

Authors: Begenisic, Tatjana | Pavese, Chiara | Aiachini, Beatrice | Nardone, Antonio | Rossi, Daniela

Article Type: Research Article

Abstract: 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. Show more

Keywords: Spinal cord injury, neural plasticity, biomarkers, neurotrophic factors, cytokines

DOI: 10.3233/RNN-211169

Citation: Restorative Neurology and Neuroscience, vol. 39, no. 5, pp. 339-366, 2021

Authors: Mackay, Christopher P. | Brauer, Sandra G. | Kuys, Suzanne S. | Schaumberg, Mia A. | Leow, Li-Ann

Article Type: Research Article

Abstract: Background: Sensorimotor adaptation, or the capacity to adapt movement to changes in the moving body or environment, is a form of motor learning that is important for functional independence (e.g., regaining stability after slips or trips). Aerobic exercise can acutely improve many forms of motor learning in healthy adults. It is not known, however, whether acute aerobic exercise has similar positive effects on sensorimotor adaptation in stroke survivors as it does in healthy individuals. Objective: The aim of this study was to determine whether acute aerobic exercise promotes sensorimotor adaptation in people post stroke. Methods: A …single-blinded crossover study. Participants attended two separate sessions, completing an aerobic exercise intervention in one session and a resting control condition in the other session. Sensorimotor adaptation was assessed before and after each session, as was brain derived neurotrophic factor. Twenty participants with chronic stroke completed treadmill exercise at moderate to high intensity for 30 minutes. Results: Acute aerobic exercise in chronic stroke survivors significantly increased sensorimotor adaptation from pre to post treadmill intervention. The 30-minute treadmill intervention resulted in an averaged 2.99 ng/ml increase in BDNF levels (BDNF pre-treadmill = 22.31 + /–2.85 ng/ml, post-treadmill was = 25.31 + /–2.46 pg/ml; t(16) = 2.146, p  = 0.048, cohen’s d  = 0.521, moderate effect size). Conclusions: These results indicate a potential role for aerobic exercise to promote the recovery of sensorimotor function in chronic stroke survivors. Show more

Keywords: Sensorimotor adaptation, aerobic exercise, stroke

DOI: 10.3233/RNN-211175

Citation: Restorative Neurology and Neuroscience, vol. 39, no. 5, pp. 367-377, 2021

Authors: Gardi, Adam Z. | Vogel, Amanda K. | Dharia, Aastha K. | Krishnan, Chandramouli

Article Type: Research Article

Abstract: Background: There is a growing concern among the scientific community that the effects of transcranial direct current stimulation (tDCS) are highly variable across studies. The use of different tDCS devices and electrode sizes may contribute to this variability; however, this issue has not been verified experimentally. Objective: To evaluate the effects of tDCS device and electrode size on quadriceps motor cortical excitability. Methods: The effect of tDCS device and electrode size on quadriceps motor cortical excitability was quantified across a range of TMS intensities using a novel evoked torque approach that has been previously shown to …be highly reliable. In experiment 1, anodal tDCS-induced excitability changes were measured in twenty individuals using two devices (Empi and Soterix) on two separate days. In experiment 2, anodal tDCS-induced excitability changes were measured in thirty individuals divided into three groups based on the electrode size. A novel Bayesian approach was used in addition to the classical hypothesis testing during data analyses. Results: There were no significant main or interaction effects, indicating that cortical excitability did not differ between different tDCS devices or electrode sizes. The lack of pre-post time effect in both experiments indicated that cortical excitability was minimally affected by anodal tDCS. Bayesian analyses indicated that the null model was more favored than the main or the interaction effects model. Conclusions: Motor cortical excitability was not altered by anodal tDCS and did not differ by devices or electrode sizes used in the study. Future studies should examine if behavioral outcomes are different based on tDCS device or electrode size. Show more

Keywords: Corticospinal excitability, MEP, knee, evoked torque, bayes factor, rehabilitation

DOI: 10.3233/RNN-211210

Citation: Restorative Neurology and Neuroscience, vol. 39, no. 5, pp. 379-391, 2021