Changes in corticospinal excitability with short-duration high-frequency electrical muscle stimulation: a transcranial magnetic stimulation study

Beneficial Effect of Repetitive Transcranial Magnetic Stimulation Combined With Physiotherapy After Cervical Spondylotic Myelopathy Surgery

PURPOSE

Cervical spondylotic myelopathy (CSM) is one of the most notable causes of spinal cord impairment among elderly people worldwide. Little is written about the influence of postoperative rehabilitation on recovery of function in patients with CSM. In this study, we assessed the combined effects of repetitive transcranial magnetic stimulation (rTMS) combined with physiotherapy and physiotherapy alone on motor and sensory improvement assessed after spinal cord decompression in patients with CSM.

METHODS

This prospective study comprised 52 patients with CSM; they were divided into two randomized groups after spinal cord decompression. The first group (group Ι) includes 26 patients, received a combination of rTMS and physiotherapy. The second group (group ΙΙ) of 26 patients underwent only physiotherapy. The neurologic assessment measures, including American Spinal Cord Injury Association score, modified Japanese Orthopaedic Association score, Ashworth scale, and Nurick grade, were recorded before and after rehabilitation interventions for each patient.

RESULTS

According to the neurologic assessment measures, physiotherapy with/without rTMS after surgical decompression corresponded to significant improvement of motor function ( P < 0. 01) without significant restoration of sensory function ( P > 0. 01). Recovery rates of motor function were significantly better in group Ι than in group ΙΙ ( P < 0. 01). There was no significant difference between two groups with respect to age ( P = 0.162) and sex ( P = 1.00).

CONCLUSIONS

Although physiotherapy with/without rTMS improves motor function recovery after CSM surgery, rTMS in combination with physiotherapy leads to a more rapid motor function recovery than physiotherapy alone.

High-Frequency External Muscle Stimulation Reduces Depressive Symptoms in Older Male Veterans: A Pilot Study

OBJECTIVE

Late-life depression (LLD) is a severe public health problem. Given that pharmacological treatments for LLD are limited by their side effects, development of efficient and tolerable nonpharmacological treatment for LLD is urgently required. This study investigated whether high-frequency external muscle stimulation could reduce depressive symptoms in LLD.

METHODS

Twenty-two older male veterans with major depression were recruited and randomized into a treatment (n = 9) or sham control group (n = 13). The groups received high-frequency external muscle stimulation or sham intervention 3 times per week for 12 weeks. Clinical symptoms and muscle strength were evaluated at baseline and every 2 weeks.

RESULTS

The 2 groups were homogeneous in age, baseline clinical symptoms, and muscle strength. The treatment group showed significant improvement in depression and anxiety scores and muscle strength (all P < .01), whereas the control group showed no significant change after the 12-week follow-up. Compared to the control group, the treatment group showed significant improvements in depression (Geriatric Depression Scale, P = .009; Hamilton Depression Rating Scale, P = .007) and anxiety scores (HAMA, P = .008) and muscle strength (all P < .001). Changes in depression and anxiety levels were significantly correlated with changes in muscle strength after the study. In the treatment group, we observed a trend of correlation between the reduction in depression and muscle strength gains.

CONCLUSION

High-frequency external muscle stimulation appears to be an effective treatment for older patients with LLD. Large studies with more tests and/or conducted in different populations are warranted to validate these preliminary findings.

Modulation of Corticospinal Excitability by Two Different Somatosensory Stimulation Patterns; A Pilot Study

Following amputation, almost two-thirds of amputees experience unpleasant to painful sensations in the area of the missing limb. Whereas the mechanism of phantom limb pain (PLP) remains unknown, it has been shown that maladaptive cortical plasticity plays a major role in PLP. Transcutaneous electrical nerve stimulation (TENS) generating sensory input is believed to be beneficial for PLP relief. TENS effect may be caused by possible reversing reorganization at the cortical level that can be evaluated by changes in the excitability of the corticospinal (CS) pathway. Excitability changes are dependent on the chosen stimulation patterns and parameters. The aim of this study was to investigate the effect of two TENS patterns on the excitability of the CS tract among healthy subjects. We compared a non-modulated TENS as a conventional pattern with pulse width modulated TENS pattern. Motor evoked potentials (MEPs) from APB muscles of stimulated arm (TENS-APB) and contralateral arm (Control-APB) were recorded. We applied single TMS pulses on two subjects for each TENS pattern. The results showed that both patterns increase the CS excitability, while the effects of the conventional TENS is stronger. However, the amplitude of MEPs from control-APB after TENS delivery remained almost the same.Clinical Relevance- The primary results revealed changes in the activity of CS pathway for both patterns. A future study on a larger population is needed to provide strong evidence on the changes in CS excitability. The evaluation part with more factors such as changes in intracortical inhibition (ICI) may be beneficial to find an optimal modulated TENS pattern to enhance pain alleviation process in PLP.

Electrical Stimulation of the Motor Cortex or Paretic Muscles Improves Strength Production in Stroke Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

Transcranial direct current stimulation (tDCS) and functional electrical stimulation (FES) are two widely applied methods of electrical stimulation for motor recovery among stroke patients. This systematic review and meta-analysis investigated the efficacy of tDCS and FES for strength production in stroke patients. TYPE: Systematic review.

LITERATURE SURVEY

Studies that explored the effects of tDCS or FES on the strength production of paralyzed muscles in stroke patients were retrieved on a comprehensive set of three databases: (1) Google Scholar, (2) PubMed, and (3) the Cochrane Database of Systematic Reviews until July 2019.

METHODOLOGY

Systematic study retrieval led to the inclusion of 15 studies that reported on strength production effects after tDCS and FES interventions among stoke patients. A sham control group and randomization were used in each study. The 15 studies included 20 comparisons with sham controls, 7 of which involved tDCS and 13 of which involved FES.

SYNTHESIS

Random-effects models showed that strength production was improved after tDCS (effect size [ES] = 0.52, 95% confidence interval [CI] = 0.35-0.69, P < .001, Z = 6.05) and FES (ES = 0.47, 95% CI = 0.16-0.78, P < .003, Z = 2.99). Additionally, tDCS was shown to improve strength production in the acute (ES = 0.52, 95% CI = 0.24-0.80, P < .001, Z = 3.65), subacute (ES = 0.85, 95% CI = 0.37-1.32, P < .001, Z = 3.51), but not chronic (ES = 0.06, 95% CI = -0.47-0.60, P = .82, Z = 0.23) phases of stroke recovery. Out of the 13 studies involving FES, 12 investigated strength production in the chronic phase and one investigated in the acute phase, showing a positive effect in these two stages.

CONCLUSIONS

The results of the meta-analysis showed that tDCS and FES successfully improved strength production in stroke patients.

Randomising stimulus intensity improves the variability and reliability of the assessment of corticospinal excitability

BACKGROUND

Advances in the control of transcranial magnetic stimulation (TMS) have enabled greater randomisation of stimulus intensity. It is unclear if such randomisation improves assessments of corticospinal excitability.

NEW METHOD

We recorded the amplitude of TMS-induced motor evoked potentials (MEPs) from the first dorsal interosseous muscle of eleven participants, during three TMS protocols: blocks of increasing intensity (IB), randomised blocks (RB) and inter-stimulus randomisation (IR). Stimulus intensities from 90 to 140% of active motor threshold described corticospinal input-output (I/O) properties. The experiment was repeated in five participants.

RESULTS

Although MEP amplitudes did not differ between IB, RB and IR stimulation protocols, variability was lowest in the IR protocol, compared to IB and RB protocols. Reliability was highest in the IR protocol, compared to IB and IR protocols.

COMPARISON WITH EXISTING METHODS

Randomising TMS intensity between each trial produces less variable and more reliable estimates of corticospinal excitability than previously used blocked protocols and produces the same I/O measures.

CONCLUSIONS

Inter-trial randomization of TMS intensities appears to be the most reliable method for constructing I/O curves at multiple time points and decreases the variability of responses.

Insights About the Neuroplasticity State on the Effect of Intramuscular Electrical Stimulation in Pain and Disability Associated With Chronic Myofascial Pain Syndrome (MPS): A Double-Blind, Randomized, Sham-Controlled Trial

Background: There is limited evidence concerning the effect of intramuscular electrical stimulation (EIMS) on the neural mechanisms of pain and disability associated with chronic Myofascial Pain Syndrome (MPS). Objectives: To provide new insights into the EIMS long-term effect on pain and disability related to chronic MPS (primary outcomes). To assess if the neuroplasticity state at baseline could predict the long-term impact of EIMS on disability due to MPS we examined the relationship between the serum brain-derived-neurotrophic-factor (BDNF) and by motor evoked potential (MEP). Also, we evaluated if the EIMS could improve the descending pain modulatory system (DPMS) and the cortical excitability measured by transcranial magnetic stimulation (TMS) parameters. Methods: We included 24 right-handed female with chronic MPS, 19-65 years old. They were randomically allocated to receive ten sessions of EIMS, 2 Hz at the cervical paraspinal region or a sham intervention (n = 12). Results: A mixed model analysis of variance revealed that EIMS decreased daily pain scores by -73.02% [95% confidence interval (CI) = -95.28 to -52.30] and disability due to pain -43.19 (95%CI, -57.23 to -29.39) at 3 months of follow up. The relative risk for using analgesics was 2.95 (95% CI, 1.36 to 6.30) in the sham group. In the EIMS and sham, the change on the Numerical Pain Scale (NPS0-10) throughout CPM-task was -2.04 (0.79) vs. -0.94 (1.18), respectively, (P = 0.01). EIMS reduced the MEP -28.79 (-53.44 to -4.15), while improved DPMS and intracortical inhibition. The MEP amplitude before treatment [(Beta = -0.61, (-0.58 to -0.26)] and a more significant change from pre- to post-treatment on serum BDNF) (Beta = 0.67; CI95% = 0.07 to 1.26) were predictors to EIMS effect on pain and disability due to pain. Conclusion: These findings suggest that a bottom-up effect induced by the EIMS reduced the analgesic use, improved pain, and disability due to chronic MPS. This effect might be mediated by an enhancing of corticospinal inhibition as seen by an increase in IC and a decrease in MEP amplitude. Likewise, the MEP amplitude before treatment and the changes induced by the EIMS in the serum BDNF predicted it's long-term clinical impact on pain and disability due MPS. The trial is recorded in ClinicalTrials.gov: NCT02381171.

High-frequency neuromuscular electrical stimulation modulates interhemispheric inhibition in healthy humans

High-frequency neuromuscular electrical stimulation (HF NMES) induces muscular contractions through neural mechanisms that partially match physiological motor control. Indeed, a portion of the contraction arises from central mechanisms, whereby spinal motoneurons are recruited through the evoked sensory volley. However, the involvement of supraspinal centers of motor control during such stimulation remains poorly understood. Therefore, we tested whether a single HF NMES session applied to the upper limb influences interhemispheric inhibition (IHI) from left to right motor cortex (M1). Using noninvasive electrophysiology and transcranial magnetic stimulation, we evaluated the effects of a 10-min HF NMES session applied to a right wrist flexor on spinal and corticospinal excitability of both arms, as well as IHI, in healthy subjects. HF NMES induced a rapid decline in spinal excitability on the right stimulated side that closely matched the modulation of evoked force during the protocol. More importantly, IHI was significantly increased by HF NMES, and this increase was correlated to the electromyographic activity within the contralateral homologous muscle. Our study highlights a new neurophysiological mechanism, suggesting that HF NMES has an effect on the excitability of the transcallosal pathway probably to regulate the lateralization of the motor output. The data suggest that HF NMES can modify the hemispheric balance between both M1 areas. These findings provide important novel perspectives for the implementation of HF NMES in sport training and neurorehabilitation.

NEW & NOTEWORTHY

High-frequency neuromuscular electrical stimulation (HF NMES) induces muscular contractions that partially match physiological motor control. Here, we tested whether HF NMES applied to the upper limb influences interhemispheric inhibition. Our results show that interhemispheric inhibition was increased after HF NMES and that this increase was correlated to the electromyographic activity within the contralateral homologous muscle. This opens up original perspectives for the implementation of HF NMES in sport training and neurorehabilitation.

Effect of high-frequency repetitive transcranial magnetic stimulation on motor cortical excitability and sensory nerve conduction velocity in subacute-stage incomplete spinal cord injury patients

[Purpose] The aim of the present study was to determine whether repetitive transcranial magnetic stimulation can improve sensory recovery of the lower extremities in subacute-stage spinal cord injury patients. [Subjects and Methods] This study was conducted on 20 subjects with diagnosed paraplegia due to spinal cord injury. These 20 subjects were allocated to an experimental group of 10 subjects that underwent active repetitive transcranial magnetic stimulation or to a control group of 10 subjects that underwent sham repetitive transcranial magnetic stimulation. The SCI patients in the experimental group underwent active repetitive transcranial magnetic stimulation and conventional rehabilitation therapy, whereas the spinal cord injury patients in the control group underwent sham repetitive transcranial magnetic stimulation and conventional rehabilitation therapy. Participants in both groups received therapy five days per week for six-weeks. Latency, amplitude, and sensory nerve conduction velocity were assessed before and after the six week therapy period. [Results] A significant intergroup difference was observed for posttreatment velocity gains, but no significant intergroup difference was observed for amplitude or latency. [Conclusion] repetitive transcranial magnetic stimulation may be improve sensory recovery of the lower extremities in subacute-stage spinal cord injury patients.