Effect of multisegmental electrical stimulation in combination with proprioceptive stimulation of the spinal cord on changes in reflex excitability of motor neurons

The study involved 15 men with movement disorders of central origin. We used percutaneous electrical stimulation of the spinal cord with the application of electrodes in the projection of the lumbar thickening, proprioceptive stimulation, and their combination. The data obtained showed the effectiveness of the combined course of percutaneous electrical stimulation of the spinal cord and proprioceptive stimulation on changes in the excitability of spinal locomotor neural networks. Key words: electrical stimulation, spinal cord, proprioceptive stimulation, rehabilitation, motor neuron.

Study of polysynaptic reflex excitability and somatosensory evoked potentials in patients with myofascial pain syndrome

Introduction. Myofascial pain syndrome (MFPS) is one of the most common pathologies of the musculoskeletal system that causes chronic pain. This type of pain reaches its peak in middle-aged people; women get sick 2,5 times more often than men. The disease leads to significant disability; it is not only a medical but also a social problem. Atthe same time, a number of authors still note the low clinical efficacy of the applied therapy regimens. In this situation there is in demand the further study of the MFPS pathogenesis, in particular, the clinical and electroneurophysiological characteristics of this pathology, in order to search for new, including pathogenetically proved, treatment methods.The aim of the research was to study the relationship between the indicators of the blinking reflex and somatosensory evoked potentials in patients with active and latent forms of MFPS.Materials and methods. In order to study the neurophysiological aspects of MFPS, a comprehensive clinical and electroneurophysiological examination was carried out in 92 patients of working age, including 78 women and 14 men, whose average age was 48,1±9,3) years, suffering from MFPS of the scapular area. The patients were subdivided into subgroups depending on the prevalence and severity of pain manifestations: the first subgroup — with an active form (58 people, 63 %), the second subgroup — with a latent form of MFPS (34 people, 37 %). The control group was formed from conditionally healthy volunteers in the amount of 35 people, comparable to the main group by age and sex.Results. The comparing of the study results, taking into account polysynaptic reflex excitability and the data of somatosensory evoked potentials, revealed the significant positive correlations of the indicators. The obtained results allowed to assess the excitability of spinal cord motor neurons as well as suprasegmental structures in MFPS, involved in the implementation of pain syndrome.Conclusion. The use of clinical electroneurophysiology methods makes it possible to assess the functional state of the CNS structures involved in the analysis of nociceptive afferentation. In the active form of MFPS, an increase in the excitability of stem and thalamic structures was mainly determined, which could potentially indicate the activation of adaptive processes on the one hand, and on the other hand, the predisposition of neuronal networks to a state of arousal. In the latent form of MFPS, a multidirectional change in reflex excitability was observed.

Low-Intensity and Short-Duration Continuous Cervical Transcutaneous Spinal Cord Stimulation Intervention Does Not Prime the Corticospinal and Spinal Reflex Pathways in Able-Bodied Subjects

Cervical transcutaneous spinal cord stimulation (tSCS) has been utilized in applications for improving upper-limb sensory and motor function in patients with spinal cord injury. Although therapeutic effects of continuous cervical tSCS interventions have been reported, neurophysiological mechanisms remain largely unexplored. Specifically, it is not clear whether sub-threshold intensity and 10-min duration continuous cervical tSCS intervention can affect the central nervous system excitability. Therefore, the purpose of this study was to investigate effects of sub-motor-threshold 10-min continuous cervical tSCS applied at rest on the corticospinal and spinal reflex circuit in ten able-bodied individuals. Neurophysiological assessments were conducted to investigate (1) corticospinal excitability via transcranial magnetic stimulation applied on the primary motor cortex to evoke motor-evoked potentials (MEPs) and (2) spinal reflex excitability via single-pulse tSCS applied at the cervical level to evoke posterior root muscle (PRM) reflexes. Measurements were recorded from multiple upper-limb muscles before, during, and after the intervention. Our results showed that low-intensity and short-duration continuous cervical tSCS intervention applied at rest did not significantly affect corticospinal and spinal reflex excitability. The stimulation duration and/or intensity, as well as other stimulating parameters selection, may therefore be critical for inducing neuromodulatory effects during cervical tSCS.

Changes in Spinal-Reflex Excitability during Static Stretch and/or Explosive Contraction

To examine individual or combined effects of static stretch and explosive contraction on quadriceps spinal-reflex excitability (the peak Hoffmann’s reflex normalized by the peak motor-response) and the latency times of the Hoffmann’s reflex and motor-response. Fourteen healthy young males randomly experienced four conditions (stretch, contraction, stretch + contraction, and control—no intervention). For the stretch condition, three sets of a 30 s hold using the modified Thomas test on each leg were performed. For the contraction condition, three trials of maximal countermovement vertical jump were performed. Quadriceps spinal-reflex excitability and the latent period of each value on the right leg were compared at pre- and post-condition. All measurement values across conditions were not changed at any time point (condition × time) in spinal-reflex excitability (F6,143 = 1.10, p = 0.36), Hoffmann’s reflex latency (F6,143 = 0.45, p = 0.84), motor-response latency (F6,143 = 0.37, p = 0.90), and vertical jump heights (F2,65 = 1.82, p = 0.17). A statistical trend was observed in the contraction condition that spinal-reflex excitability was increased by 42% (effect size: 0.63). Neither static stretch nor explosive contraction changed the quadriceps spinal-reflex excitability, latency of Hoffmann’s reflex, and motor-response. Since our stretch protocol did not affect jumping performance and our contraction protocol induced the post-activation potentiation effect, either protocol could be used as pre-exercise activity.

Neuronal Actions of Transspinal Stimulation on Locomotor Networks and Reflex Excitability During Walking in Humans With and Without Spinal Cord Injury

This study investigated the neuromodulatory effects of transspinal stimulation on soleus H-reflex excitability and electromyographic (EMG) activity during stepping in humans with and without spinal cord injury (SCI). Thirteen able-bodied adults and 5 individuals with SCI participated in the study. EMG activity from both legs was determined for steps without, during, and after a single-pulse or pulse train transspinal stimulation delivered during stepping randomly at different phases of the step cycle. The soleus H-reflex was recorded in both subject groups under control conditions and following single-pulse transspinal stimulation at an individualized exactly similar positive and negative conditioning-test interval. The EMG activity was decreased in both subject groups at the steps during transspinal stimulation, while intralimb and interlimb coordination were altered only in SCI subjects. At the steps immediately after transspinal stimulation, the physiological phase-dependent EMG modulation pattern remained unaffected in able-bodied subjects. The conditioned soleus H-reflex was depressed throughout the step cycle in both subject groups. Transspinal stimulation modulated depolarization of motoneurons over multiple segments, limb coordination, and soleus H-reflex excitability during assisted stepping. The soleus H-reflex depression may be the result of complex spinal inhibitory interneuronal circuits activated by transspinal stimulation and collision between orthodromic and antidromic volleys in the peripheral mixed nerve. The soleus H-reflex depression by transspinal stimulation suggests a potential application for normalization of spinal reflex excitability after SCI.

Neuromuscular Function of the Knee Joint Following Knee Injuries: Does It Ever Get Back to Normal? A Systematic Review with Meta-Analyses

Background Neuromuscular deficits are common following knee injuries and may contribute to early-onset post-traumatic osteoarthritis, likely mediated through quadriceps dysfunction. Objective To identify how peri-articular neuromuscular function changes over time after knee injury and surgery. Design Systematic review with meta-analyses. Data Sources PubMed, Web of Science, Embase, Scopus, CENTRAL (Trials). Eligibility Criteria for Selecting Studies Moderate and high-quality studies comparing neuromuscular function of muscles crossing the knee joint between a knee-injured population (ligamentous, meniscal, osteochondral lesions) and healthy controls. Outcomes included normalized isokinetic strength, muscle size, voluntary activation, cortical and spinal-reflex excitability, and other torque related outcomes. Results A total of 46 studies of anterior cruciate ligament (ACL) and five of meniscal injury were included. For ACL injury, strength and voluntary activation deficits were evident (moderate to strong evidence). Cortical excitability was not affected at < 6 months (moderate evidence) but decreased at 24+ months (moderate evidence). Spinal-reflex excitability did not change at < 6 months (moderate evidence) but increased at 24+ months (strong evidence). We also found deficits in torque variability, rate of torque development, and electromechanical delay (very limited to moderate evidence). For meniscus injury, strength deficits were evident only in the short-term. No studies reported gastrocnemius, soleus or popliteus muscle outcomes for either injury. No studies were found for other ligamentous or chondral injuries. Conclusions Neuromuscular deficits persist for years post-injury/surgery, though the majority of evidence is from ACL injured populations. Muscle strength deficits are accompanied by neural alterations and changes in control and timing of muscle force, but more studies are needed to fill the evidence gaps we have identified. Better characterisation and therapeutic strategies addressing these deficits could improve rehabilitation outcomes, and potentially prevent PTOA. Trial Registration Number PROSPERO CRD42019141850.