Peripheral Magnetic Stimulation Research Articles

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

Synergistic efficacy of repetitive peripheral magnetic stimulation on central intermittent theta burst stimulation for upper limb function in patients with stroke: a double-blinded, randomized controlled trial

BackgroundNon-invasive techniques such as central intermittent theta burst stimulation (iTBS) and repetitive peripheral magnetic stimulation (rPMS) have shown promise in improving motor function for patients with stroke. However, the combined efficacy of rPMS and central iTBS has not been extensively studied. This randomized controlled trial aimed to investigate the synergistic effects of rPMS and central iTBS in patients with stroke.MethodIn this study, 28 stroke patients were randomly allocated to receive either 1200 pulses of real or sham rPMS on the radial nerve of the affected limb, followed by 1200 pulses of central iTBS on the ipsilesional hemisphere. The patients received the intervention for 10 sessions over two weeks. The primary outcome measures were the Fugl-Meyer Assessment-Upper Extremity (FMA-UE) and the Action Research Arm Test (ARAT). Secondary outcomes for activities and participation included the Functional Independence Measure-Selfcare (FIM-Selfcare) and the Stroke Impact Scale (SIS). The outcome measures were assessed before and after the intervention.ResultsBoth groups showed significant improvement in FMA-UE and FIM-Selfcare after the intervention (p < 0.05). Only the rPMS + iTBS group had significant improvement in ARAT-Grasp and SIS-Strength and activity of daily living (p < 0.05). However, the change scores in all outcome measures did not differ between two groups.ConclusionsOverall, the study’s findings suggest that rPMS may have a synergistic effect on central iTBS to improve grasp function and participation. In conclusion, these findings highlight the potential of rPMS as an adjuvant therapy for central iTBS in stroke rehabilitation. Further large-scale studies are needed to fully explore the synergistic effects of rPMS on central iTBS.Trial registrationThis trial was registered under ClinicalTrials.gov ID No.NCT04265365, retrospectively registered, on February 11, 2020.

Repetitive peripheral magnetic stimulation for preventing shoulder subluxation after stroke: a randomized controlled trial.

Shoulder subluxation caused by paralysis after stroke is a serious issue affecting shoulder pain and functional prognosis. However, its preventive treatment has not been fully investigated. To investigate the effects of repetitive peripheral magnetic stimulation (rPMS) on the prevention of shoulder subluxation. A single-center, parallel-group, prospective randomized, open-blinded, end-point study. Convalescent rehabilitation ward. We included 50 inpatients in the convalescent rehabilitation ward with post-stroke, having upper limb paralysis, and the acromio-humeral interval (AHI) was within 1/2 finger-breadth. A blinded computer-based allocation system was used to randomly assign patients into two groups: 1) conventional rehabilitation plus rPMS therapy (rPMS group, N=25); and 2) conventional rehabilitation alone (control group, N=25). Blinded assessors evaluated the patients before the intervention (T0), 6 weeks after (T1), and 12 weeks after (T2). The primary outcome was the change in AHIs from T0 to T1 between the groups. In contrast, the secondary outcomes were shoulder pain, spasticity, active range of motion, and Fugl-Meyer Assessment upper extremity (FMA-UE) score. Twenty-two patients in the rPMS group and 24 in the control group completed T1, whereas 16 in the rPMS group and 11 in the control group completed T2. The change in AHI was significantly lower in the rPMS group than in the control group ([95% CI, -5.15 to -0.390], P=0.023). Within-group analysis showed that AHI in the rPMS group did not change significantly, whereas it increased in the control group (P=0.004). There were no significant differences between T1 and T2 within or between the groups. Moreover, AHI did not show differences in patients with severe impairment but decreased in the rPMS group in patients with mild impairment (P=0.001). The rPMS may be a new modality for preventing shoulder subluxation. The association between motor impairment and the sustained effect needs to be further examined. Applying rPMS to the muscles of the paralyzed shoulder after a stroke may prevent shoulder subluxation.

Study on the Effect of Repetitive Peripheral Magnetic Stimulation Combined with Conventional Rehabilitation Measures on Shoulder Dysfunction in Early Stroke

Objective: To study the effect of repetitive peripheral magnetic stimulation (rPMS) combined with conventional rehabilitation measures on shoulder dysfunction in early stroke. Methods: 60 patients with shoulder dysfunction in early stroke were selected, and all of them were admitted to our hospital from August 2021 to August 2023. The patients were randomly grouped into a control group (conventional rehabilitation measures intervention, 30 cases) and an intervention group (rPMS and conventional rehabilitation measures intervention, 30 cases) according to the lottery method. The pain scores, shoulder mobility, and motor function scores of the two groups were compared. Results: The pain score was lower in the intervention group, and the shoulder mobility and motor function scores were higher in the intervention group (P &lt; 0.05) as compared to that of the control group. Conclusion: The effect of combining rPMS and conventional rehabilitation measures in treating shoulder dysfunction in early stroke was remarkable and should be popularized.

Sensory Stimulation of the Triceps Surae Muscle Complex Modulates Spinal Reflex Responses-A Comparison between Tapotement Massage and Repetitive Peripheral Magnetic Stimulation (rPMS).

The reduction of muscular hypertonia is important in the treatment of various diseases or rehabilitation. This study aims to test the efficacy of a 5 Hz mechanical muscle stimulation (tapotement massage) in comparison to a 5 Hz repetitive peripheral magnetic stimulation (rPMS) on the neuromuscular reflex response. In a randomized control trial, 15 healthy volunteers were administered with either 5 Hz rPMS, tapotement massage, or rPMS sham stimulation. The posterior tibial nerve was stimulated with rPMS and sham stimulation. The Achilles tendon was exposed to a mechanically applied high-amplitude 5 Hz repetitive tendon tapotement massage (rTTM). The tendon reflex (TR) was measured for the spinal response of the soleus muscle. After rPMS, there was a reduction of the TR response (-9.8%, p ≤ 0.034) with no significant changes after sham stimulation. Likewise, TR decreased significantly (-17.4%, p ≤ 0.002) after Achilles tendon tapotement intervention. These findings support the hypothesis that both afferent 5 Hz sensory stimulations contributed to a modulation within the spinal and/or supraspinal circuits, which resulted in a reduction of the spinal reflex excitability. The effects could be beneficial for patients with muscle hypertonia and could improve the functional results of rehabilitation programs.

Repetitive Peripheral Magnetic Stimulation to Improve Upper Limb Spasticity and Function in a Chronic Stroke Patient. A Single Case Study.

Hombre blanco de 69 años que se le diagnosticó un accidente cerebrovascular isquémico de la arteria cerebral media en julio del 2020. El procedimiento consistió en dos semanas de tratamiento control mediante entrenamiento robótico y orientado a tareas, seguido de cuatro semanas de tratamiento experimental aplicando rPMS, añadiendo el tratamiento control. Finalmente se aplicó el tratamiento control durante 2 semanas más. Se llevaron a cabo  evaluaciones de espasticidad utilizando rPMS y un goniometro, función motora con la preuba de Nine Hole Peg Test y Finger Taping Test. A nivel estadístico se aplico el método de banda descriptica de dos desviaciones estándar (DTSD) para ver el efecto del tratamiento aplicado

Long-Term Outcomes of Management of Inferior Alveolar Neuropathy Following Orthognatic Surgeries in Patients with Mandibular Anomalies and Deformities

Introduction. Orthognatic surgery is a routine method to manage mandibular anomalies and deformities.&#x0D; Objective: To assess long-term outcomes of rhythmic peripheral magnetic stimulation (rPMS) in patients with neuropathy of the inferior alveolar nerve (IAN) resulting from the surgical treatment of mandibular anomalies and deformities.&#x0D; Materials and methods. The study included 8 males and 16 females aged 32 ± 12 years with IAN neuropathy following the surgical treatment of mandibular anomalies and deformities. Therapeutic rPMS was performed with the Neuro-MS magnetic stimulator (Neurosoft, Ivanovo, Ivanovo Region, Russian Federation). Trigeminal and brainstem acoustic evoked potentials (EPs) were registered with Neuro-MVP (Neurosoft) to assess rPMS both at baseline (in 10 days) and in long term (in 18 ± 2 months).&#x0D; Results. Sensory disorders and pain prevailed in postoperative IAN neuropathy. Sensory disorders improved in 20 patients following 10-day rPMS. The clinical effect persisted in re-assessment. In long term, acoustic brainstem EPs normalized and trigeminal EPs did not change negatively.&#x0D; Conclusion. The use of rPMS in IAN neuropathy following orthognatic surgeries contributes to the functional improvement and stabilization of the peripheral and central brainstem and the trigeminal system.

Effect of repetitive peripheral magnetic stimulation of the common fibular nerve on the soleus muscle Hoffmann reflex.

[Purpose] This study aimed to investigate the effects of repetitive peripheral magnetic stimulation of the common fibular nerve on the modification of neural circuit function as measured through the soleus muscle Hoffmann reflex. [Participants and Methods] Twenty-four healthy adult males were randomly and equally divided into the magnetic stimulation (experimental) and control groups. The Hoffmann reflex of the soleus muscle was analyzed before and after 10 min of repetitive peripheral magnetic stimulation for the experimental group and before and after 10 min of rest for the control group. The averages of the values for the maximum amplitude and latency of the Hoffman reflex across twenty repetitions were recorded and compared. [Results] The Hoffmann reflex amplitude decreased following stimulation in the experimental group, and significant variations were observed between the experimental and control groups. [Conclusion] The change in the Hoffmann reflex amplitude may have been caused by the magnetic stimulation to I-a sensory fibers on the common fibular nerve, suggesting that magnetic stimulation induces reciprocal inhibition of motor neurons through synapses in the spinal cord.

Peripheral Sacral Magnetic Stimulation in Patients with Idiopathic Overactive Bladder: a Single Blind Prospective Randomized Comparative Clinical Study

INTRODUCTION. Overactive bladder (OAB) is a symptom complex that includes urgency, frequent urination, imperative urinary incontinence and nocturia. The idiopathic form of OAB is associated with dysfunction of sensory signal transmission at the level of the peripheral and central nervous system, which leads to bladder hypersensitivity. The low level of patients’ compliance to OAB drug therapy and the high level of refusal to take drugs emphasize the urgency of finding new effective methods of influencing the lower urinary tract. Magnetic stimulation (MS) is a non-drug treatment for lower urinary tract dysfunction.&#x0D; AIM. To study the efficacy and safety of the sacral MS method in women with idiopathic detrusor overactivity (DO) and OAB symptoms.&#x0D; MATERIALS AND METHODS. A single blind prospective randomized comparative study included 55 female patients with urodynamically confirmed idiopathic DO. The patients were divided by simple randomization into the main group (n = 29), which received MS 3 times a week for 5 weeks with a frequency of 5 Hz per sacral root area (S2–S4), and the placebo group (n = 26), in which sham stimulation was performed.&#x0D; RESULTS AND DISCUSSION. The study revealed that sacral MS is reliably effective against the clinical symptoms of OAB in idiopathic DO. The dynamics of clinical symptoms is confirmed by changes in urodynamic parameters. The effect of sacral MS significantly exceeds placebo. MS is a safe procedure and is well tolerated by patients.&#x0D; CONCLUSION. The sacral MS method, the effectiveness of which has been proven in comparison with placebo, is recommended to be included in the treatment regimen of patients with idiopathic OAB. The mechanism of action of sacral MS is associated with the activation of sympathetic and inhibition of parasympathetic influences, as well as changes in supraspinal control and cerebral activity.

Efficacy of repetitive transcranial magnetic stimulation at different sites for peripheral facial paralysis: a prospective cohort study.

There are very few studies on transcranial magnetic stimulation (TMS) therapy for facial paralysis and no studies comparing the efficacy of central and peripheral TMS in the treatment of peripheral facial paralysis (PFP). To observe the therapeutic effect and security of central and peripheral repetitive transcranial magnetic stimulation (rTMS) on PFP. Patients with unilateral onset of peripheral facial paralysis within 1 month were prospectively recruited, 97 patients with PFP were divided into the peripheral group, central group, and control group. The control group was given common treatment (drug therapy and acupuncture), and the peripheral and central groups received rTMS in addition to conventional treatment. After 2 weeks of treatment, the House-Brackmann (HB) grading scale, Sunnybrook facial grading system (SFGS), and modified Portmann scale (MPS) were used to evaluate the facial muscle function of patients in the three groups. After 2 weeks of rTMS treatment, the HBGS/SFGS/MPS scores of the three groups were significantly better than before (p < 0.05), and the mean change values of HBGS, SFGS, and MPS scores were significantly higher in participants in Peripheral Group (p < 0.001; p < 0.001; p = 0.003; respectively) and Central Group (p = 0.004; p = 0.003; p = 0.009; respectively) than in Control Group. But the mean change values of HBGS, SFGS, and MPS scores showed no significant differences in participants in the Peripheral Group than in the Central Group (p = 0.254; p = 0.139; p = 0.736; respectively) after 2 weeks of treatment (p > 0.05). Our study shows that rTMS can be a safe and effective adjuvant therapy for patients with PFP. Preliminary studies have shown that both peripheral and central stimulation can effectively improve facial nerve function, but there is no significant difference in the efficacy of the two sites.

Repetitive peripheral magnetic stimulation for improving upper limb function in post-stroke hemiparesis

BackgroundStroke is one of the leading causes of disability worldwide, with hand and arm weakness, affecting the patients’ daily activities and quality of life. Recently, repetitive peripheral magnetic stimulation (rPMS) was found to enhance neuroplasticity and motor recovery post-stroke hemiparesis via its deep proprioceptive stimulation and simulation of lost voluntary movement.ObjectiveTo determine the therapeutic effect of rPMS on the functional improvement of upper limb in patients with hemiparesis following cerebrovascular insult and to compare the effect of therapy in subacute and chronic cases.ResultsPost-rehabilitation program both the Fugl-Meyer-Upper Extremity scale (FM-UE) and Functional Independence Measures (FIM) scale showed highly significant improvement in the active group, compared to controls. Regarding active range of motion (AROM) of the shoulder abductors, triceps, wrist extensors and supinators, significant differences were also found in the active group in comparison to controls. Modified Ashworth scale showed also significant change in the active group. When dividing our patients according to the duration post-stroke, into subacute group (6 weeks to 6 months post-stroke) and chronic group (more than 6-month post-stroke), the subacute group showed significant improvements in the FM-UE scale, and in the AROM of wrist extensors and supinators but not in the chronic group. Ultrasonographic measurements showed a significant decrease in cross sectional area of the control group.ConclusionrPMS is potentially effective in improving motor recovery post-stroke, especially in the subacute stage.

Emerging theory of sensitization in post-stroke muscle spasticity.

Spasticity, characterized by a velocity-dependent increase in muscle tone and exaggerated reflexes, is a common complication in individuals with upper motor neuron syndrome, such as stroke survivors. Sensitization, the heightened responsiveness of the nervous system to sensory stimuli, has emerged as a potential cause of spasticity. This perspective article explores three emerging treatments targeting sensitization. Recent studies have investigated novel treatment modalities for spasticity, including Extracorporeal Shockwave Therapy (ESWT), repetitive peripheral magnetic stimulation (rPMS), and needling. ESWT has shown promising results in reducing spasticity in both the upper and lower extremities, potentially through mechanisms such as nitric oxide production, rheological property changes, and neuromuscular transmission dysfunction. rPMS offers a non-invasive approach that may reduce spasticity by increasing sensory input, enhancing cortical activation, and exerting tissue-softening effects. Needling has also demonstrated positive effects on spasticity reduction. The high heterogeneity observed indicates the need for more rigorous research to confirm these findings. Recently, mechanical needling and sterile water injection invented by the author is also promising for reducing spasticity through removing sensitization. In conclusion, the emerging treatment options discussed in this perspective article provide promising avenues for addressing sensitization in spasticity and improving motor function. However, further research is needed to validate their findings, optimize treatment protocols, and investigate their long-term effects on motor recovery and overall quality of life in individuals with spasticity.

Factors Involved in Higher Knee Extension Torque Induced by Repetitive Peripheral Magnetic Stimulation.

The study aimed to determine the relationship between knee extension torque induced by repetitive peripheral magnetic stimulation and the characteristics of the participants. This was a basic study with noninvasive intervention. Knee extension torque induced by repetitive peripheral magnetic stimulation (repetitive peripheral magnetic stimulation-induced torque) and maximum voluntary contraction were measured. Stepwise method of multiple regression was performed to determine the factors affecting repetitive peripheral magnetic stimulation-induced torque at 100% intensity and repetitive peripheral magnetic stimulation-induced torque divided by maximum voluntary contraction (percent maximum voluntary contraction). Subcutaneous fat thickness, vastus lateralis muscle thickness measured by ultrasound, maximum voluntary contraction, and mean power frequency of electromyography during maximum voluntary contraction were selected as independent variables. Repetitive peripheral magnetic stimulation was applied to the right vastus lateralis of 30 young healthy adults (average age, 21.1 ± 0.3 yrs). In the multiple regression analysis, repetitive peripheral magnetic stimulation-induced torque ( P < 0.001) was shown to be independently and significantly associated with maximum voluntary contraction (β = 0.510), subcutaneous fat thickness (β = -0.358), and vastus lateralis muscle thickness (β = 0.208), while percent maximum voluntary contraction value ( P < 0.05) was independently and significantly associated with vastus lateralis muscle thickness (β = 1.059). Repetitive peripheral magnetic stimulation-induced torque decreases with thicker subcutaneous fat and increases with stronger maximum voluntary contraction or with thicker muscle.

Low energy magnetic stimulation of the phrenic nerve - a simulation study

Peripheral magnetic stimulation is a promising assistive technique for rehabilitation. Today’s magnetic stimulation devices, designed for transcranial stimulation, operate at currents of 6 kA and higher. This makes them expensive and bulky. Many motor neurons in peripheral nerves are more accessible, have large diameters, and require significantly lower field strengths for stimulation. In this work, we present a simulation environment to determine the threshold current required to trigger an action potential in phrenic nerve motor neurons for different coil geometries. An anatomical model was used for coil placement and realistic field calculations. The field distribution was calculated using the finite integration technique and then applied to a neuronal model to simulate the axon membrane dynamics. For general applicability, the coil-nerve distance and the axon diameter were varied. We show that the required current was approximately 1.3 kA for a nerve-coil distance of 35 mm, which corresponds to 20% of the available power of a commercial TMS device. By including the nearby vagus nerve in the simulations, we showed that accidental stimulation of this nerve is highly unlikely. Our results pave the way for the development of smaller, less complex, and more affordable stimulators and promise to increase the use of peripheral magnetic stimulators in clinical settings.

Top-down and bottom-up stimulation techniques combined with action observation treatment in stroke rehabilitation: a perspective.

Stroke is a central nervous system disease that causes structural lesions and functional impairments of the brain, resulting in varying types, and degrees of dysfunction. The bimodal balance-recovery model (interhemispheric competition model and vicariation model) has been proposed as the mechanism of functional recovery after a stroke. We analyzed how combinations of motor observation treatment approaches, transcranial electrical (TES) or magnetic (TMS) stimulation and peripheral electrical (PES) or magnetic (PMS) stimulation techniques can be taken as accessorial physical therapy methods on symptom reduction of stroke patients. We suggest that top-down and bottom-up stimulation techniques combined with action observation treatment synergistically might develop into valuable physical therapy strategies in neurorehabilitation after stroke. We explored how TES or TMS intervention over the contralesional hemisphere or the lesioned hemisphere combined with PES or PMS of the paretic limbs during motor observation followed by action execution have super-additive effects to potentiate the effect of conventional treatment in stroke patients. The proposed paradigm could be an innovative and adjunctive approach to potentiate the effect of conventional rehabilitation treatment, especially for those patients with severe motor deficits.

Quantitative assessment of spasticity: a narrative review of novel approaches and technologies.

Spasticity is a complex neurological disorder, causing significant physical disabilities and affecting patients' independence and quality of daily lives. Current spasticity assessment methods are questioned for their non-standardized measurement protocols, limited reliabilities, and capabilities in distinguishing neuron or non-neuron factors in upper motor neuron lesion. A series of new approaches are developed for improving the effectiveness of current clinical used spasticity assessment methods with the developing technology in biosensors, robotics, medical imaging, biomechanics, telemedicine, and artificial intelligence. We investigated the reliabilities and effectiveness of current spasticity measures employed in clinical environments and the newly developed approaches, published from 2016 to date, which have the potential to be used in clinical environments. The new spasticity scales, taking advantage of quantified information such as torque, or echo intensity, the velocity-dependent feature and patients' self-reported information, grade spasticity semi-quantitatively, have competitive or better reliability than previous spasticity scales. Medical imaging technologies, including near-infrared spectroscopy, magnetic resonance imaging, ultrasound and thermography, can measure muscle hemodynamics and metabolism, muscle tissue properties, or temperature of tissue. Medical imaging-based methods are feasible to provide quantitative information in assessing and monitoring muscle spasticity. Portable devices, robotic based equipment or myotonometry, using information from angular, inertial, torque or surface EMG sensors, can quantify spasticity with the help of machine learning algorithms. However, spasticity measures using those devices are normally not physiological sound. Repetitive peripheral magnetic stimulation can assess patients with severe spasticity, which lost voluntary contractions. Neuromusculoskeletal modeling evaluates the neural and non-neural properties and may gain insights into the underlying pathology of spasticity muscles. Telemedicine technology enables outpatient spasticity assessment. The newly developed spasticity methods aim to standardize experimental protocols and outcome measures and enable quantified, accurate, and intelligent assessment. However, more work is needed to investigate and improve the effectiveness and accuracy of spasticity assessment.

Effectiveness of Repetitive Peripheral Magnetic Stimulation for Treatment of Mild to Moderate Carpal Tunnel Syndrome: A Randomized Controlled Trial

Objective: This study aimed to evaluate the effectiveness of active repetitive peripheral magnetic stimulation (rPMS) compared to sham rPMS on symptoms severity and functional status among patients with mild to moderate carpal tunnel syndrome. Materials and Methods: A randomized controlled trial was conducted. Participants were randomly allocated (1:1) to either intervention (active rPMS) or control (sham rPMS) groups. Both groups received rPMS (A20 mode of OPTIMUS Pro) for 10 min, once a week for four weeks (four sessions). Symptom severity scales (SSS) and functional status scales (FSS) of Boston Carpal Tunnel Questionnaire were measured at baseline (before session one) and at the end of treatment (after session four). The relative changes in SSS and FSS scores were calculated as a clinical outcome. Results: Forty-two participants were enrolled and randomly allocated to either the intervention (n = 21) or control group (n = 21). There were no statistically significant differences in the median (interquartile range) of relative changes in SSS [0.05 (0.15) vs 0 (0.27), P = 0.41] or FSS [0 (0.25) vs 0 (0.11), P = 0.97] between the intervention and control groups. Conclusion: Active rPMS did not improve clinical outcome compared to sham rPMS among patients with mild to moderate CTS. A greater number of subjects and treatment sessions might be required for the future study.

Impact of Repetitive Peripheral Magnetic Stimulation on Post-Stroke Patients with Upper Limb Spasticity - A Randomized Controlled Trial

Impact of Repetitive Peripheral Magnetic Stimulation on Post-Stroke Patients with Upper Limb Spasticity - A Randomized Controlled Trial

Combined Peripheral Nerve Stimulation and Controllable Pulse Parameter Transcranial Magnetic Stimulation to Probe Sensorimotor Control and Learning.

Skilled motor ability depends on efficiently integrating sensory afference into the appropriate motor commands. Afferent inhibition provides a valuable tool to probe the procedural and declarative influence over sensorimotor integration during skilled motor actions. This manuscript describes the methodology and contributions of short-latency afferent inhibition (SAI) for understanding sensorimotor integration. SAI quantifies the effect of a convergent afferent volley on the corticospinal motor output evoked by transcranial magnetic stimulation (TMS). The afferent volley is triggered by the electrical stimulation of a peripheral nerve. The TMS stimulus is delivered to a location over the primary motor cortex that elicits a reliable motor-evoked response in a muscle served by that afferent nerve. The extent of inhibition in the motor-evoked response reflects the magnitude of the afferent volley converging on the motor cortex and involves central GABAergic and cholinergic contributions. The cholinergic involvement in SAI makes SAI a possible marker of declarative-procedural interactions in sensorimotor performance and learning. More recently, studies have begun manipulating the TMS current direction in SAI to tease apart the functional significance of distinct sensorimotor circuits in the primary motor cortex for skilled motor actions. The ability to control additional pulse parameters (e.g., the pulse width) with state-of-the-art controllable pulse parameter TMS (cTMS) has enhanced the selectivity of the sensorimotor circuits probed by the TMS stimulus and provided an opportunity to create more refined models of sensorimotor control and learning. Therefore, the current manuscript focuses on SAI assessment using cTMS. However, the principles outlined here also apply to SAI assessed using conventional fixed pulse width TMS stimulators and other forms of afferent inhibition, such as long-latency afferent inhibition (LAI).

Effects of transcranial combined with peripheral repetitive magnetic stimulation on limb spasticity and resting-state brain activity in stroke patients.

Transcranial magnetic stimulation and peripheral repetitive magnetic stimulation (rPMS), as non-invasive neuromodulation techniques, can promote functional recovery in patients with post-stroke spasticity (PSS), but the effects of transcranial magnetic stimulation combined with peripheral magnetic stimulation on PSS remain largely unknown. Therefore, we examined the effects of low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) combined with rPMS on PSS patients and its potential neural correlates to behavioral improvements. Forty-nine PSS patients were divided randomly into three groups: a combined group (n = 20), a LF-rTMS group (n = 15), and a control group (n = 14). The combined group received LF-rTMS and rPMS treatment, the rTMS group received LF-rTMS treatment, and the control group received only routine rehabilitation. All patients underwent Ashworth Spasm Scale (MAS), upper extremity Fugl-Meyer (FMA-UE), and modified Barthel Index (MBI) assessments before and after intervention. In addition, resting-state functional magnetic resonance imaging data were collected pre- and post-treatment to observe changes in the amplitude of low-frequency fluctuation (ALFF). The MAS score was decreased, FMA-UE score and MBI scores were increased in the three groups after therapy than before therapy (all P < 0.05). In particular, the combined group showed significant effect on improved motor function and relieved spasticity in PSS (P < 0.01). Moreover, the combined treatment increased ALFF values mainly in the right supplementary motor area, right middle frontal gyrus, and right cerebellum, while reduced ALFF values mainly in the right post-central gyrus compared with pre-treatment. Compared with the LF-rTMS and control groups, the combined treatment increased ALFF values in the right cerebellum and reduced ALFF values mainly in the frontoparietal cortex. Improvements in the MAS score were positively correlated with the change in ALFF values in the right cerebellum (r = 0.698, P = 0.001) and the right supplementary motor area (r = 0.700, P = 0.001) after combined treatment. Transcranial combined with peripheral repetitive magnetic stimulation could improve spastic state and motor function in PSS patients, and this effect may be associated with altered cerebellar and frontoparietal cortical activity. http://www.chictr.org.cn/index.aspx, identifier ChiCTR1800019452.