The clinical diagnostic utility of transcranial magnetic stimulation: Report of an IFCN committee

Age-related differences in task-related modulation of cerebellar brain inhibition

Age-related reductions in cerebellar integrity predict motor impairments in older adults (OA), but the contribution of cerebro-cerebellar interactions to these impairments remains unclear. Understanding these interactions could reveal underlying mechanisms associated with age-related deficits in motor control. To explore this, twenty younger adults (YA) and twenty OA, all right-handed, participated in a dual-site transcranial magnetic stimulation protocol. Cerebellar brain inhibition (CBI) was measured at rest and during the anticipatory period of a bimanual tracking task (BTT). The results revealed that YA outperformed OA on the BTT. Both age groups demonstrated reduced CBI during the anticipatory period of the BTT compared to CBI at rest, with no differences in CBI levels between both groups. Notably, motor performance was influenced by CBI modulation, as learning progressed (early vs. slightly later short-term learning), and this influence differed between age groups. In summary, resting-state CBI and the task-related release of CBI were maintained in OA, challenging previous assumptions of reduced inhibitory function in OA. However, the modulation of CBI appears to influence short-term motor learning differently for both groups, suggesting potential functional reorganization of the cerebellar neural system.

Comparison of intermittent theta burst stimulation and high-frequency repetitive transcranial magnetic stimulation on spinal cord injury-related neuropathic pain: A sham-controlled study

OBJECTIVE

To compare the effects of intermittent theta burst stimulation (iTBS) and high-frequency repetitive transcranial magnetic stimulation (rTMS) on spinal cord injury-related neuropathic pain with sham controls, using neuropathic pain-specific evaluation tools.

DESIGN

A randomized, double-blind, sham-controlled trial.

SETTING

Rehabilitation medicine department of a university hospital.

PARTICIPANTS

Thirty-three patients with spinal cord injury-related neuropathic pain.

INTERVENTIONS

Patients were randomly allocated to one of three groups (real iTBS, real rTMS, and sham rTMS). Each patient underwent five sessions of assigned stimulation.

OUTCOME MEASURES

Before and after completion of the five sessions, patients were evaluated using the self-completed Leeds Assessment of Neuropathic Symptoms and Signs, Numeric Rating Scale, Neuropathic Pain Symptom Inventory, and Neuropathic Pain Scale.

RESULTS

Real iTBS and real rTMS reduced pain levels after stimulation according to all the evaluation tools, and the changes were significant when compared to the values of the sham rTMS group. No significant differences were found between the real iTBS and real rTMS groups.

CONCLUSION

Both iTBS and rTMS were effective in reducing spinal cord injury-related neuropathic pain. When safety, convenience, and compliance are considered, iTBS would have an advantage over rTMS in clinical situations with spinal cord injury-related neuropathic pain.Trial Registration: This trial was registered with the Clinical Research Information Service (registration no. KCT0004976).

Bridging the gap to clinical use: A systematic review on TMS-EEG test-retest reliability

BACKGROUND

Transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) can provide insight on cortical excitability and brain circuits. TMS-evoked potentials (TEPs) are phase-locked waveforms reflecting neural activity, with potential applications in psychiatry and neurology. However, the reliability of TEPs remains underexplored, hindering clinical standardization. This systematic review evaluates TEP reliability, focusing on commonly used measures and assessments.

METHODS

A systematic review was conducted on PubMed for studies from 2002 to October 10, 2024, using keywords combining TMS, EEG, and reliability terms. Systematic reviews and non-English articles were excluded.

RESULTS

Eighteen studies met inclusion criteria, mostly assessing young, healthy populations. Late TEP components demonstrated high relative reliability, while early components exhibited lower reliability and variability across sessions. Analytical methods like the intraclass and concordance correlation coefficients, and Pearson's correlations consistently favored late TEPs.

DISCUSSION

Late TEPs exhibit higher reliability, while early components require further research. TMS artifacts complicate interpretation, in both late and early responses. Formal reliability assessments, standardized protocols, and diverse populations are essential for advancing TEP reliability for clinical application.

CONCLUSIONS

A more comprehensive reliability assessments is needed before the implementation of clinical applications.

Neurophysiological assessment of cortical motor function: A direct comparison of methodologies

OBJECTIVE

Assessment of cortical function with threshold tracking transcranial magnetic stimulation (TT-TMS) has developed as a biomarker to inform disease pathophysiology, particularly in neurodegenerative disease and dementia. At present, a fully integrated testing system does not exist. To advance clinical utility, and to streamline software design to integrate with diagnostic approaches in an outpatient setting, the present series of studies assessed the effects of altering diagnostic paradigms to measure interstimulus interval (ISI) including serial ascending [T-SICIs] and parallel [T-SICIp] methodologies as measures of cortical motor function (the MagXite software).

METHODS

Cortical excitability was assessed in 30 healthy controls with a figure-of-eight coil, using an integrated approach compared to previously established experimental paradigms. Motor evoked responses were recorded over the contralateral abductor pollicis brevis muscle. Short interval intracortical inhibition (SICI) was recorded with each testing paradigm and validated in a healthy control cohort.

RESULTS

The integrated system determined a robust measure of T-SICIs between ISI 1-to-7 ms (16.6 ± 2.2 %) that was comparable to previously established testing paradigms (P = 0.34), but greater than T-SICIp (MagXite 10.7 ± 1.5 %, P = 0.016; Sydney TT-TMS 8.7 ± 1.4 %, P = 0.03). SICI peaks at ISI 1 and 2.5-to-3 ms were evident with both protocols. Significant correlations were evident between mean T-SICIs-MagXite and T-SICIp-MagXite (R = 0.599, P < 0.001).

CONCLUSION

The present series validates a fully integrated motor cortical functional assessment to provide reproducible measures of SICI, with data obtained for intracortical inhibition that is more prominent when assessed using the method of serial ascending order.

SIGNIFICANCE

An integrated system for transcranial magnetic stimulation of the human motor system has been validated for clinical practice, suitable for the assessment of cortical function in neurological disease in an outpatient clinic setting.

Attenuated afferent inhibition correlated with impaired gait performance in Parkinson's disease patients with freezing of gait

Background

The neural mechanisms underlying freezing of gait (FOG) in Parkinson's disease (PD) have not been completely comprehended. Sensory-motor integration dysfunction was proposed as one of the contributing factors. Here, we investigated short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI), and analyzed their association with gait performance in FOG PD patients, to further validate the role of sensorimotor integration in the occurrence of FOG in PD.

Methods

Twenty-five levodopa responsive-FOG PD patients (LR-FOG), fifteen levodopa unresponsive-FOG PD patients (LUR-FOG), twenty-eight PD patients without FOG (NO-FOG PD) and twenty-two healthy controls (HC) were included in the study. Clinical features such as PD motor symptoms, FOG severity and cognitive abilities were evaluated using clinical scales in subjects with PD. All participants underwent paired associative stimulation (PAS) to evaluate SAI and LAI in addition to regular input-output curve by transcranial magnetic stimulation. The performances of gait were assessed using a portable gait analyzing system in 10-meter timed Up and Go task. The correlations between the gait spatiotemporal parameters or the scores of FOG scale and the magnitudes of SAI or LAI were analyzed.

Results

Compared to HC and NO-FOG PD patients, SAI was decreased in FOG PD subgroups. LAI was also reduced in both LR-FOG PD and LUR-FOG PD in relative to HC; however, only LUR-FOG PD showed significant reduction of LAI in comparison to NO-FOG PD group. FOG PD patients showed poorer gait performance compared to HC and NO-FOG PD group. The reduction of SAI and LAI were correlated with the impaired gait spatiotemporal parameters or scores of FOG scale in PD with FOG.

Conclusion

The SAI and LAI were attenuated in PD patients with FOG, and the reduction of SAI or LAI were correlated to disturbed gait performance, indicating that sensory-motor integration dysfunction played a role in the development of FOG in PD.

A 12-week in-phase bilateral upper limb exercise protocol promoted neuroplastic and clinical changes in people with relapsing remitting multiple sclerosis: A registered report randomized single-case concurrent multiple baseline study

INTRODUCTION

Relapsing-Remitting Multiple Sclerosis manifests various motor symptoms including impairments in corticospinal tract integrity, whose symptoms can be assessed using transcranial magnetic stimulation. Several factors, such as exercise and interlimb coordination, can influence the plastic changes in corticospinal tract. Previous work in healthy and chronic stroke survivors showed that the greatest improvement in corticospinal plasticity occurred during in-phase bilateral exercises of the upper limbs. Altered corticospinal plasticity due to bilateral lesions in the central nervous system is common after Multiple Sclerosis, yet the effect of in-phase bilateral exercise on the bilateral corticospinal plasticity in this cohort remains unclear. Our aim was to investigate the effects of in-phase bilateral exercises on central motor conduction time, motor evoked potential amplitude and latency, motor threshold and clinical measures in people with Relapsing-Remitting Multiple Sclerosis.

METHODS

Five people were randomized and recruited in this single case concurrent multiple baseline design study. The intervention protocol lasted for 12 consecutive weeks (30-60 minutes /session x 3 sessions / week) and included in-phase bilateral upper limb movements, adapted to different sports activities and to functional motor training. To define the functional relation between the intervention and the results, we conducted a visual analysis. If a potential sizeable effect was observed, we subsequently performed a statistical analysis.

RESULTS

Results demonstrated bilateral reduction of the motor threshold alongside with improvement of all clinical measures, but not in any other corticospinal plasticity measures.

CONCLUSION

Our preliminary findings suggest that in-phase bilateral exercise affects motor threshold in people with Relapsing-Remitting Multiple Sclerosis. Therefore, this measure could potentially serve as a proxy for detecting corticospinal plasticity in this cohort. However, future studies with larger sample sizes should validate and potentially establish the effect of in-phase bilateral exercise on the corticospinal plasticity and clinical measures in this cohort.

TRIAL REGISTRATION

Clinical trial registration: ClinicalTrials.gov NCT05367947.

Effects of low frequency repetitive transcranial magnetic stimulation on motor recovery in subacute stroke patients with different motor evoked potential status: a randomized controlled trial

Objectives

To explore the effects of low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) on motor function and cortical excitability in stroke patients with different motor evoked potential (MEP) status.

Methods

A total of 80 stroke patients were enrolled in this randomized controlled trial and divided into two groups according to MEP status (- or +) of lesioned hemisphere. Then, each group was randomly assigned to receive either active or sham LF-rTMS. In addition to conventional rehabilitation, all participants received 20 sessions of rTMS at 1 Hz frequency through the active or the sham coil over 4 weeks. Fugl-Meyer Assessment (FMA), National Institutes of Health Stroke Scale (NIHSS), Shoulder Abduction Finger Extension (SAFE) and Barthel Index (BI), bilateral resting motor threshold (rMT), amplitude of Motor evoked potential (MEP) and Central Motor Conduction Time (CMCT), and Interhemispheric asymmetry (IHA) were blindly assessed at baseline, 4 weeks and 8 weeks after treatment, respectively.

Results

At 4 weeks after intervention, FMA and NIHSS changed scores in 1 Hz MEP(+) group were significantly higher than those in the other three groups (p < 0.001). After receiving 1 Hz rTMS, stroke patients with MEP(+) showed significant changes in their bilateral cortical excitability (p < 0.05). At 8 weeks after intervention, 1 Hz MEP(+) group experienced higher changes in NIHSS, FMA, SAFE, and BI scores than other groups (p < 0.001). Furthermore, 1 Hz rTMS intervention could decrease unaffected cortical excitability and enhance affected cortical excitability of stroke patients with MEP(+) (p < 0.05). The correlation analysis revealed that FMA motor change score was associated with decreased unaffected MEP amplitude (r = -0.401, p = 0.010) and decreased affected rMT (r = -0.584, p < 0.001) from baseline, which was only observed in the MEP(+) group.

Conclusion

The effects of LF-rTMS on motor recovery and cortical excitability were more effective in stroke patients with MEP than those with no MEP.

Imagining Speeds up the Effect of Motor Imagery on Central Motor Conduction Time

INTRODUCTION

Although motor imagery (MI) has been reported to increase motor cortical excitability, its effect on central motor conduction time (CMCT), a widely used neurophysiological diagnostic method, has not been investigated. In this study, we sought to determine the effect of MI on CMCT.

METHODS

In this cross-sectional study, 21 healthy volunteers (11 females, 10 males) aged 24 to 67 years (mean age: 38.8 years) were recruited between April 2022 and June 2023. CMCT was calculated during MI from the abductor digiti minimi (ADM) and tibialis anterior (TA) muscles. Measurements were also performed with conventional measurement methods, such as resting and voluntary contraction, to compare the effect of MI on CMCT.

RESULTS

The ANOVA test revealed that the CMCT session (rest, MI, and voluntary contraction) was a significant factor (p < 0.05). In both muscles, CMCT was shorter in the imagery state than in the resting state but longer than in the voluntary contraction state (p < 0.05). Similarly, motor-evoked potential (MEP) latencies obtained during imagery were shorter for both muscles than the resting state but longer for the voluntary contraction state.

CONCLUSION

The study's findings suggest that MI is a mental activity that modulates CMCT measurement. MI shows a voluntary contraction-like effect on CMCT and MEP latency, although the effect is more uncertain.

TMS assessment of corticospinal tract integrity after stroke: broadening the concept to inform neurorehabilitation prescription

Upper limb actions require intersegmental coordination of the scapula, shoulders, elbows, forearms, wrists, and hand muscles. Stroke hemiparesis, presenting as an impairment of an intersegmentally coordinated voluntary movement, is associated with altered integrity of corticospinal tract (CST) transmission from the motor cortex (M1) to muscles. Motor evoked potentials (MEPs) elicited by M1 transcranial magnetic stimulation (TMS) of "at rest" muscles, or as a backup, during muscle contraction have been used to identify CST integrity and predict the outcome after hemiparesis, under the implicit assumption that MEPs present in only one or two muscles are manifest surrogates of CST integrity for other muscles of the upper limbs. This study presents a method for applying TMS during motor tasks that involve proximal and distal muscles. It focuses on evaluating multi-muscle electromyography (EMG) and MEPs across all task-relevant limb segments. Protocols are presented for assessing voluntary motor behavior in individuals with hemiparetic stroke using isometric, unimanual, bimanual, and "REST" conditions that broaden the concept of the degree of CST integrity in order to inform clinical prescription for neurorehabilitation and distinguish its potential as a prognostic tool. Data describing the recordings of multi-muscle transcranial magnetic stimulation induced motor evoked potentials (TMS-MEP) will be presented in a case of subacute hemiparetic stroke to elucidate our perspective.

Water and brain function: effects of hydration status on neurostimulation with transcranial magnetic stimulation

Neurostimulation/neurorecording are tools to study, diagnose, and treat neurological/psychiatric conditions. Both techniques depend on volume conduction between scalp and excitable brain tissue. Here, we examine how neurostimulation with transcranial magnetic stimulation (TMS) is affected by hydration status, a physiological variable that can influence the volume of fluid spaces/cells, excitability, and cellular/global brain functioning. Normal healthy adult participants (32, 9 males) had common motor TMS measures taken in a repeated-measures design from dehydrated (12-h overnight fast/thirst) and rehydrated (identical dehydration protocol followed by rehydration with 1 L water in 1 h) testing days. The target region was left primary motor cortex hand area. Response at the target muscle was recorded with electromyography. Urinalysis confirmed hydration status. Motor hotspot shifted in half of participants. Motor threshold decreased in rehydration, indicating increased excitability. Even after redosing/relocalizing TMS to the new threshold/hotspot, rehydration still showed evidence of increased excitability: recruitment curve measures generally shifted upward and the glutamate-dependent paired-pulse protocol, short intracortical facilitation (SICF), was increased. Short intracortical inhibition (SICI), long intracortical inhibition (LICI), long intracortical facilitation (LICF), and cortical silent period (CSP) were relatively unaffected. The hydration perturbations were mild/subclinical based on the magnitude/speed and urinalysis. Motor TMS measures showed evidence of expected physiological changes of osmotic challenges. Rehydration showed signs of macroscopic and microscopic volume changes including decreased scalp-cortex distance (brain closer to stimulator) and astrocyte swelling-induced glutamate release. Hydration may be a source of variability affecting any techniques dependent on brain volumes/volume conduction. These concepts are important for researchers/clinicians using such techniques or dealing with the wide variety of disease processes involving water balance.NEW & NOTEWORTHY Hydration status can affect brain volumes and excitability, which should affect techniques dependent on electrical volume conduction, including neurostimulation/recording. We test the previously unknown effects of hydration on neurostimulation with TMS and briefly review relevant physiology of hydration. Rehydration showed lower motor threshold, shifted motor hotspot, and generally larger responses even after compensating for threshold/hotspot changes. This is important for clinical and research applications of neurostimulation/neurorecording and the many clinical disorders related to water balance.

Neurophysiological effects of acute aerobic exercise in young adults: a systematic review and meta-analysis

Evidence continues to accumulate that acute aerobic exercise (AAE) impacts neurophysiological excitability as measured by transcranial magnetic stimulation (TMS). Yet, uncertainty exists about which TMS measures are modulated after AAE in young adults. The influence of AAE intensity and duration of effects are also uncertain. This pre-registered meta-analysis (CRD42017065673) addressed these uncertainties by synthesizing data from 23 studies (including 474 participants) published until February 2024. Meta-analysis was run using a random-effects model and Hedge's g used as effect size. Our results demonstrated a decrease in short-interval intracortical inhibition (SICI) following AAE (g = 0.27; 95 % CI [0.16-0.38]; p <.0001), particularly for moderate (g = 0.18; 95 % CI [0.05-0.31]; p <.01) and high (g = 0.49; 95 % CI [0.27-0.71]; p <.0001) AAE intensities. These effects remained for 30 minutes after AAE. Additionally, increased corticospinal excitability was only observed for high intensity AAE (g = 0.28; 95 % CI, [0.07-0.48]; p <.01). Our results suggest potential mechanisms for inducing a more susceptible neuroplastic environment following AAE.

Immediate Effects of Preconditioning Intermittent Theta Burst Stimulation on Lower Extremity Motor Cortex Excitability in Healthy Participants

BACKGROUND

Previous studies have found that inhibitory priming with continuous theta burst stimulation (cTBS) can enhance the effect of subsequent excitatory conditioning stimuli with intermittent theta burst stimulation (iTBS) in the upper limbs. However, whether this combined stimulation approach elicits a comparable compensatory response in the lower extremities remains unclear. This study aimed to investigate how cTBS preconditioning modulated the effect of iTBS on motor cortex excitability related to the lower limb in healthy individuals.

METHODS

Using a randomised cross-over design, a total of 25 healthy participants (19 females, mean age = 24.80 yr) were recruited to undergo three different TBS protocols (cTBS + iTBS, sham cTBS + iTBS, sham cTBS + sham iTBS) in a random order. Each TBS intervention was administered with one-week intervals. cTBS and iTBS were administered at an intensity of 80% active motor threshold (AMT) delivering a total of 600 pulses. Before intervention (T0), immediately following intervention (T1), and 20 min after intervention (T2), the corticomotor excitability was measured for the tibialis anterior muscle of participants' non-dominant leg using a Magneuro100 stimulator and matched double-cone coil. The average amplitude of the motor-evoked potential (MEP) induced by applying 20 consecutive monopulse stimuli at an intensity of 130% resting motor threshold (RMT) was collected and analysed.

RESULTS

Compare with T0 time, the MEP amplitude (raw and normalised) at T1 and T2 showed a statistically significant increase following the cTBS + iTBS protocol (p < 0.01), but no significant differences were observed in amplitude changes following other protocols (sham cTBS + iTBS and sham cTBS + sham iTBS) (p > 0.05). Furthermore, no statistically significant difference was found among the three protocols at any given time point (p > 0.05).

CONCLUSIONS

Preconditioning the lower extremity motor cortex with cTBS prior to iTBS intervention can promptly enhance its excitability in healthy participants. This effect persists for a minimum duration of 20 min.

CLINICAL TRIAL REGISTRATION

No: ChiCTR2300069315. Registered 13 March, 2023, https://www.chictr.org.cn.

Physiological Biomarkers of Upper Motor Neuron Dysfunction in ALS

Upper motor neuron (UMN) dysfunction is an important feature of amyotrophic lateral sclerosis (ALS) for the diagnosis and understanding of pathogenesis. The identification of UMN signs forms the basis of ALS diagnosis, although may be difficult to discern, especially in the setting of severe muscle weakness. Transcranial magnetic stimulation (TMS) techniques have yielded objective physiological biomarkers of UMN dysfunction in ALS, enabling the interrogation of cortical and subcortical neuronal networks with diagnostic, pathophysiological, and prognostic implications. Transcranial magnetic stimulation techniques have provided pertinent pathogenic insights and yielded novel diagnostic and prognostic biomarkers. Cortical hyperexcitability, as heralded by a reduction in short interval intracortical inhibition (SICI) and an increase in short interval intracortical facilitation (SICF), has been associated with lower motor neuron degeneration, patterns of disease evolution, as well as the development of specific ALS clinical features including the split hand phenomenon. Reduction in SICI has also emerged as a potential diagnostic aid in ALS. More recently, physiological distinct inhibitory and facilitatory cortical interneuronal circuits have been identified, which have been shown to contribute to ALS pathogenesis. The triple stimulation technique (TST) was shown to enhance the diagnostic utility of conventional TMS measures in detecting UMN dysfunction. Resting-state EEG is a novel neurophysiological technique developed for directly interrogating cortical neuronal networks in ALS, that have yielded potentially useful physiological biomarkers of UMN dysfunction. The present review discusses physiological biomarkers of UMN dysfunction in ALS, encompassing conventional and novel TMS techniques developed to interrogate the functional integrity of the corticomotoneuronal system, focusing on pathogenic, diagnostic, and prognostic utility.

Challenges and opportunities in testing sensorimotor processing with tendon vibration and transcranial magnetic stimulation in subacromial impingement syndrome: A case series

BACKGROUND

Non-invasive neurostimulation like muscle tendon vibration (VIB) and transcranial magnetic stimulation (TMS) can provide valuable insights on mechanisms underlying sensorimotor dysfunctions. However, their feasibility in the context of painful musculoskeletal disorders like shoulder impingement syndrome (SIS) remain uncertain.

METHODS

The present work used a case series design including 15 participants with SIS, as well as a secondary group-based analysis comparing participants with SIS to 15 healthy counterparts. Proprioceptive processing was tested by VIB-induced kinesthetic illusions of shoulder abduction, and TMS tested corticospinal excitability of the upper trapezius. Detailed individual data were collected, including any technical challenges and feasibility issues encountered.

RESULTS

VIB was in general well-tolerated and elicited a perceptible kinesthetic illusion in 13 participants with SIS and 14 controls. TMS presented with several challenges related to discomfort, fear-related behaviors, technical problems and high motor thresholds, especially in participants with SIS. It was only possible to collect all TMS measures in 5 participants with SIS (for both the painful and non/less-painful sides), in 7 controls on their dominant side and 10 controls on the non-dominant side. The only significant group-based analysis was a lower illusion speed/amplitude on the painful versus non-painful side in persons with SIS (p = 0.035).

CONCLUSION

Our study provides preliminary data on challenges encountered with TMS and VIB of trunk/proximal muscle in persons with SIS and healthy counterparts. It might help future studies to better address those challenges beforehand and improve the overall feasibility and impact of neurostimulation tools in musculoskeletal disorders.

Novel approaches to assessing upper motor neuron dysfunction in motor neuron disease/amyotrophic lateral sclerosis: IFCN handbook chapter

Identifying upper motor neuron (UMN) dysfunction is fundamental to the diagnosis and understanding of disease pathogenesis in motor neuron disease (MND). The clinical assessment of UMN dysfunction may be difficult, particularly in the setting of severe muscle weakness. From a physiological perspective, transcranial magnetic stimulation (TMS) techniques provide objective biomarkers of UMN dysfunction in MND and may also be useful to interrogate cortical and network function. Single, paired- and triple pulse TMS techniques have yielded novel diagnostic and prognostic biomarkers in MND, and have provided important pathogenic insights, particularly pertaining to site of disease onset. Cortical hyperexcitability, as heralded by reduced short interval intracortical inhibition (SICI) and increased short interval intracortical facilitation, has been associated with the onset of lower motor neuron degeneration, along with patterns of disease spread, development of specific clinical features such as the split hand phenomenon, and may provide an indication about the rate of disease progression. Additionally, reduction of SICI has emerged as a potential diagnostic aid in MND. The triple stimulation technique (TST) was shown to enhance the diagnostic utility of conventional TMS measures in detecting UMN dysfunction in MND. Separately, sophisticated brain imaging techniques have uncovered novel biomarkers of neurodegeneration that have bene associated with progression. The present review will discuss the utility of TMS and brain neuroimaging derived biomarkers of UMN dysfunction in MND, focusing on recently developed TMS techniques and advanced neuroimaging modalities that interrogate structural and functional integrity of the corticomotoneuronal system, with an emphasis on pathogenic, diagnostic, and prognostic utility.

The effect of real versus sham intermittent theta burst transcranial magnetic stimulation combined with conventional treatment on poststroke dysphagia: a randomized controlled trial

Repetitive transcranial magnetic stimulation to the pharyngeal motor cortex has shown beneficial effects on poststroke dysphagia. Previous studies, however, using intermittent theta burst stimulation (iTBS) for dysphagia have targeted the suprahyoid motor cortex. This study aimed to investigate the effects of iTBS to the pharyngeal motor cortex in patients with poststroke dysphagia, using ultrasound and videofluoroscopic swallowing studies (VFSS). A randomized controlled trial was conducted on patients with dysphagia due to a first-time unilateral stroke. Patients who had signs and symptoms of dysphagia and showed aspiration or penetration on VFSS were included. Twenty-eight patients were randomly assigned to either real or sham iTBS groups, and each patient underwent five sessions of iTBS to the ipsilesional pharyngeal motor cortex. Each iTBS session was followed by conventional dysphagia treatment for 30 min. The hyoid-larynx approximation measured by ultrasound, penetration-aspiration scale (PAS) and functional dysphagia scale (FDS) assessed by VFSS were evaluated before and after completion of iTBS. There were no significant differences between the two groups in terms of demographic and clinical characteristics, including age and type of stroke. The hyoid-larynx approximation ratio increased in the real iTBS group and decreased in the sham iTBS group (median values of pre-post differences were 0.27 vs. -0.01, P  < 0.001). The PAS and FDS showed greater improvements in the real iTBS group than in the sham iTBS group (median values of pre-post differences of the PAS were -2.50 vs. 0.00, P  = 0.004; median values of pre-post differences of the FDS were -12.50 vs. -2.50, P  < 0.001). No adverse effects were reported during or after iTBS sessions. Five-session iTBS to the pharyngeal motor cortex combined with conventional treatment led to a significant improvement in poststroke dysphagia in terms of hyoid-larynx approximation which is related to the suprahyoid muscle. Considering the short duration of one iTBS session, this can be an efficient and effective treatment tool for patients with this condition.

Alteration of Interhemispheric Inhibition in Patients With Lateral Epicondylalgia

Patients with lateral epicondylalgia (LE) show alterations in the primary motor cortex (M1) contralateral to the affected side. Cortical alterations have been investigated by measuring intracortical facilitation/inhibition; however, their association with pain remains controversial. Furthermore, no studies have investigated changes in interhemispheric inhibition (IHI). IHI can be assessed using the ipsilateral silent period (iSP) known as the temporary inhibition of electromyographic activity evoked by transcranial magnetic stimulation in the ipsilateral M1 of the contracting muscle. To better understand the relationship between cortical alterations and pain in LE, this observational study investigated the relationship between iSP and pain in LE. Twenty-seven healthy volunteers and 21 patients with LE were recruited. The duration of iSP in the extensor carpi radialis brevis was measured. The IHI asymmetry ratio was calculated to determine the IHI balance. Pain and disability were scored using the Japanese version of the patient-rated elbow evaluation. We observed increased inhibitory input from the ipsilateral M1 on the affected side to the contralateral M1 in LE. Additionally, the IHI balance correlated with pain severity. Hence, regulating imbalanced IHI can potentially decrease lateral elbow pain in LE. PERSPECTIVE: Patients with lateral epicondylalgia (LE) experience persistent pain and cortical alterations. However, there is no established relationship between cortical alterations and pain. This study demonstrated that the interhemispheric inhibition (IHI) balance is correlated with pain. Regulating imbalanced IHI can potentially decrease lateral elbow pain in patients with LE.

Corticospinal inhibition investigated in relation to upper extremity motor function in cervical spinal cord injury

OBJECTIVE

Corticospinal inhibitory mechanisms are relevant to functional recovery but remain poorly understood after spinal cord injury (SCI). Post-injury characteristics of contralateral silent period (CSP), a measure of corticospinal inhibition evaluated using transcranial magnetic stimulation (TMS), is inconsistent in literature. We envisioned that investigating CSP across muscles with varying degrees of weakness may be a reasonable approach to resolve inconsistencies and elucidate the relevance of corticospinal inhibition for upper extremity function following SCI.

METHODS

We studied 27 adults with chronic C1-C8 SCI (age 48.8 ± 16.1 years, 3 females) and 16 able-bodied participants (age 33.2 ± 11.8 years, 9 females). CSP characteristics were assessed across biceps (muscle power = 3-5) and triceps (muscle power = 1-3) representing stronger and weaker muscles, respectively. We assessed functional abilities using the Capabilities of the Upper Extremity Test (CUE-T).

RESULTS

Participants with chronic SCI had prolonged CSPs for biceps but delayed and diminished CSPs for triceps compared to able-bodied participants. Early-onset CSPs for biceps and longer, deeper CSPs for triceps correlated with better CUE-T scores.

CONCLUSIONS

Corticospinal inhibition is pronounced for stronger biceps but diminished for weaker triceps muscle in SCI indicating innervation relative to the level of injury matters in the study of CSP.

SIGNIFICANCE

Nevertheless, corticospinal inhibition or CSP holds relevance for upper extremity function following SCI.

Contribution of neurophysiology to the diagnosis and monitoring of ALS

This chapter describes the role of neurophysiological techniques in diagnosing and monitoring amyotrophic lateral sclerosis (ALS). Despite many advances, electromyography (EMG) remains a keystone investigation from which to build support for a diagnosis of ALS, demonstrating the pathophysiological processes of motor unit hyperexcitability, denervation and reinnervation. We consider development of the different diagnostic criteria and the role of EMG therein. While not formally recognised by established diagnostic criteria, we discuss the pioneering studies that have demonstrated the diagnostic potential of transcranial magnetic stimulation (TMS) of the motor cortex and highlight the growing evidence for TMS in the diagnostic process. Finally, accurately monitoring disease progression is crucial for the successful implementation of clinical trials. Neurophysiological measures of disease state have been incorporated into clinical trials for over 20 years and we review prominent techniques for assessing disease progression.

M2M-InvNet: Human Motor Cortex Mapping From Multi-Muscle Response Using TMS and Generative 3D Convolutional Network

Transcranial magnetic stimulation (TMS) is often applied to the motor cortex to stimulate a collection of motor evoked potentials (MEPs) in groups of peripheral muscles. The causal interface between TMS and MEP is the selective activation of neurons in the motor cortex; moving around the TMS 'spot' over the motor cortex causes different MEP responses. A question of interest is whether a collection of MEP responses can be used to identify the stimulated locations on the cortex, which could potentially be used to then place the TMS coil to produce chosen sets of MEPs. In this work we leverage our previous report on a 3D convolutional neural network (CNN) architecture that predicted MEPs from the induced electric field, to tackle an inverse imaging task in which we start with the MEPs and estimate the stimulated regions on the motor cortex. We present and evaluate five different inverse imaging CNN architectures, both conventional and generative, in terms of several measures of reconstruction accuracy. We found that one architecture, which we propose as M2M-InvNet, consistently achieved the best performance.

Neurofilament Light Chain Levels Interact with Neurodegenerative Patterns and Motor Neuron Dysfunction in Amyotrophic Lateral Sclerosis

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease involving rapid motor neuron degeneration leading to brain, primarily precentral, atrophy. Neurofilament light chains are a robust prognostic biomarker highly specific to ALS, yet associations between neurofilament light chains and MR imaging outcomes are not well-understood. We investigated the role of neurofilament light chains as mediators among neuroradiologic assessments, precentral neurodegeneration, and disability in ALS.

MATERIALS AND METHODS

We retrospectively analyzed a prospective cohort of 29 patients with ALS (mean age, 56 [SD, 12] years; 18 men) and 36 controls (mean age, 49 [SD, 11] years; 18 men). Patients underwent 3T (n = 19) or 7T (n = 10) MR imaging, serum (n = 23) and CSF (n = 15) neurofilament light chains, and clinical (n = 29) and electrophysiologic (n = 27) assessments. The control group had equivalent 3T (n = 25) or 7T (n = 11) MR imaging. Two trained neuroradiologists performed blinded qualitative assessments of MR imaging anomalies (n = 29 patients, n = 36 controls). Associations between precentral cortical thickness and neurofilament light chains and clinical and electrophysiologic data were analyzed.

RESULTS

We observed extensive cortical thinning in patients compared with controls. MR imaging analyses showed significant associations between precentral cortical thickness and bulbar or arm impairment following distributions corresponding to the motor homunculus. Finally, uncorrected results showed positive interactions among precentral cortical thickness, serum neurofilament light chains, and electrophysiologic outcomes. Qualitative MR imaging anomalies including global atrophy (P = .003) and FLAIR corticospinal tract hypersignal anomalies (P = .033), correlated positively with serum neurofilament light chains.

CONCLUSIONS

Serum neurofilament light chains may be an important mediator between clinical symptoms and neuronal loss according to cortical thickness. Furthermore, MR imaging anomalies might have underestimated prognostic value because they seem to indicate higher serum neurofilament light chain levels.

Transcranial magnetic stimulation enhances the specificity of multiple sclerosis diagnostic criteria: a critical narrative review

Background

Multiple sclerosis (MS) is an immune-mediated neurodegenerative disease that involves attacks of inflammatory demyelination and axonal damage, with variable but continuous disability accumulation. Transcranial magnetic stimulation (TMS) is a noninvasive method to characterize conduction loss and axonal damage in the corticospinal tract. TMS as a technique provides indices of corticospinal tract function that may serve as putative MS biomarkers. To date, no reviews have directly addressed the diagnostic performance of TMS in MS. The authors aimed to conduct a critical narrative review on the diagnostic performance of TMS in MS.

Methods

The authors searched the Embase, PubMed, Scopus, and Web of Science databases for studies that reported the sensitivity and/or specificity of any reported TMS technique compared to established clinical MS diagnostic criteria. Studies were summarized and critically appraised for their quality and validity.

Results

Seventeen of 1,073 records were included for data extraction and critical appraisal. Markers of demyelination and axonal damage-most notably, central motor conduction time (CMCT)-were specific, but not sensitive, for MS. Thirteen (76%), two (12%), and two (12%) studies exhibited high, unclear, and low risk of bias, respectively. No study demonstrated validity for TMS techniques as diagnostic biomarkers in MS.

Conclusions

CMCT has the potential to: (1) enhance the specificity of clinical MS diagnostic criteria by "ruling in" true-positives, or (2) revise a diagnosis from relapsing to progressive forms of MS. However, there is presently insufficient high-quality evidence to recommend any TMS technique in the diagnostic algorithm for MS.

Transcranial Magnetic Stimulation Across the Lifespan: Impact of Developmental and Degenerative Processes

Transcranial magnetic stimulation (TMS) has emerged as a pivotal noninvasive technique for investigating cortical excitability and plasticity across the lifespan, offering valuable insights into neurodevelopmental and neurodegenerative processes. In this review, we explore the impact of TMS applications on our understanding of normal development, healthy aging, neurodevelopmental disorders, and adult-onset neurodegenerative diseases. By presenting key developmental milestones and age-related changes in TMS measures, we provide a foundation for understanding the maturation of neurotransmitter systems and the trajectory of cognitive functions throughout the lifespan. Building on this foundation, the paper delves into the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder, attention-deficit/hyperactivity disorder, Tourette syndrome, and adolescent depression. Highlighting recent findings on altered neurotransmitter circuits and dysfunctional cortical plasticity, we underscore the potential of TMS as a valuable tool for unraveling underlying mechanisms and informing future therapeutic interventions. We also review the emerging role of TMS in investigating and treating the most common adult-onset neurodegenerative disorders and late-onset depression. By outlining the therapeutic applications of noninvasive brain stimulation techniques in these disorders, we discuss the growing body of evidence supporting their use as therapeutic tools for symptom management and potentially slowing disease progression. The insights gained from TMS studies have advanced our understanding of the underlying mechanisms in both healthy and disease states, ultimately informing the development of more targeted diagnostic and therapeutic strategies for a wide range of neuropsychiatric conditions.

The paired-pulse TMS paradigm of short intracortical inhibition is mediated by a reduction of repetitive motor neuron discharges

Transcranial magnetic stimulation (TMS) causes repetitive spinal motoneuron discharges (repMNDs), but the effects of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) on repMNDs remain unknown. Triple stimulation technique (TST) and the extended TST-protocols that include a fourth and fifth stimulation, the Quadruple (QuadS) and Quintuple (QuintS) stimulation, respectively, offer a precise estimate of cortical and spinal motor neuron discharges, including repMNDs. The objective of our study was to explore the effects of SICI and ICF on repMNDs. We explored conventional paired-pulse TMS protocols of SICI and ICF with the TMS, TST, the QuadS, and the QuintS protocols, in a randomized study design in 20 healthy volunteers. We found significantly less repMNDs in the SICI paradigm compared with a single-pulse TMS (SP-TMS). No significant difference was observed in the ICF paradigm. There was a significant inter- and intrasubject variability in both SICI and ICF. We demonstrate a significant reduction of repMNDs in SICI, which may result from the suppression of later I-waves and mediate the inhibition of motor-evoked potential (MEP). There is no increase in repMNDs in ICF suggesting another mechanism underlying facilitation. This study provides the proof that a reduction of repMNDs mediates the inhibition seen in SICI.NEW & NOTEWORTHY Significant reduction of repetitive motor neuron discharges (repMNDs) in short-interval intracortical inhibition (SICI) may result from the suppression of later I-waves and mediate the inhibition of motor-evoked potential (MEP). There is no change in the number of repMNDs in intracortical facilitation (ICF). There was a significant variability in SICI and ICF in healthy subjects.

Novel Therapeutic Strategies of Non-Invasive Brain Stimulation and Nanomedicine in Pediatric Cerebral Palsy Patients

Infantile central palsy (CP) is caused due to damage to the immature developing brain usually before birth, leading to altered topography and biochemical milieu. CP is a life-limiting disorder, which causes changes in sensory, motor, cognitive, and behavioral functioning. Understanding its pathophysiology is complex, and current therapeutic modalities, oral medication, surgical treatment, physical therapy, and rehabilitation provide minimal relief. As the brain is plastic, it has an inherent capacity to adapt to altered activity; thus, non-invasive brain stimulation (NIBS) strategies, like repetitive transcranial magnetic stimulation, which can modulate the neuronal activity and its function, may lead to recovery in CP patients. Further, in recent years, nanomedicine has shown a promising approach in pre-clinical studies for the treatment of central nervous system disorder because it can cross the blood-brain barrier, improve penetration, and provide sustained release of the drug. The review focuses on the principles and mechanisms of various NIBS techniques used in CP. We have also contemplated the effect of rehabilitation and nanomedicine in CP children, which will definitely lead to advancing our diagnostic as well as therapeutic abilities, in a vulnerable group of little ones.

Normal Values of Central, Peripheral, and Root Motor Conduction Times in a Healthy Korean Population

PURPOSE

Central, peripheral, and root motor conduction times (CMCTs, PMCTs, and RMCTs, respectively) are valuable diagnostic tools for spinal cord and motor nerve root lesions. We investigated the normal values and the effects of age and height on each motor conduction time.

METHODS

This study included 190 healthy Korean subjects who underwent magnetic stimulation of the cortex and spinous processes at the C7 and L1 levels. Recording muscles were abductor pollicis brevis and abductor digiti minimi in the unilateral upper limb and extensor digitorum brevis and abductor hallucis in the contralateral lower limb. F-wave and compound motor nerve action potentials were also recorded. Central motor conduction time was evaluated as the difference between cortical motor evoked potential onset latency and PMCT using calculation and spinal stimulation methods. Root motor conduction time was computed as the difference between spinal stimulated and calculated CMCTs.

RESULTS

The average age and height of the participants were 41.21 ± 14.39 years and 164.64 ± 8.27 cm, respectively; 39.5% (75/190) patients were men. In the linear regression analyses, upper limb CMCTs showed a significant and weak positive relationship with height. Lower limb CMCTs demonstrated a significant and weak positive relationship with age and height. Peripheral motor conduction times were significantly and positively correlated with age and height. Root motor conduction times showed no significant relationship with age and height, except for abductor pollicis brevis-RMCT, which had a weak negative correlation with height.

CONCLUSIONS

This study provides normal values of CMCTs, PMCTs, and RCMTs, which have potential clinical applications. When interpreting CMCTs, age and height should be considered.

Effects of sleep deprivation on cortical excitability: A threshold-tracking TMS study and review of the literature

Objective

Insufficient sleep is linked to several health problems. Previous studies on the effects of sleep deprivation on cortical excitability using conventional transcranial magnetic stimulation (TMS) included a limited number of modalities, and few inter-stimulus intervals (ISIs) and showed conflicting results. This study aimed to investigate the effects of sleep deprivation on cortical excitability through threshold-tracking TMS, using a wide range of protocols at multiple ISIs.

Methods

Fifteen healthy subjects (mean age ± SD: 36 ± 3.34 years) were included. The following tests were performed before and after 24 h of sleep deprivation using semi-automated threshold-tacking TMS protocols: short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) at 11 ISIs between 1 and 30 ms, short interval intracortical facilitation (SICF) at 14 ISIs between 1 and 4.9 ms, long interval intracortical inhibition (LICI) at 6 ISIs between 50 and 300 ms, and short-latency afferent inhibition (SAI) at 12 ISIs between 16 and 30 ms.

Results

No significant differences were observed between pre- and post-sleep deprivation measurements for SICI, ICF, SICF, or LICI at any ISIs (p < 0.05). As for SAI, we found a difference at 28 ms (p = 0.007) and 30 ms (p = 0.04) but not at other ISIs.

Conclusions

Sleep deprivation does not affect cortical excitability except for SAI.

Significance

This study confirms some of the previous studies while contradicting others.

Parkinson's Disease-related Pains are Not Equal: Clinical, Somatosensory and Cortical Excitability Findings in Individuals With Nociceptive Pain

Chronic pain is a frequent and burdensome nonmotor symptom of Parkinson's disease (PD). PD-related chronic pain can be classified as nociceptive, neuropathic, or nociplastic, the former being the most frequent subtype. However, differences in neurophysiologic profiles between these pain subtypes, and their potential prognostic and therapeutic implications have not been explored yet. This is a cross-sectional study on patients with PD (PwP)-related chronic pain (ie, started with or was aggravated by PD). Subjects were assessed for clinical and pain characteristics through questionnaires and underwent quantitative sensory tests and motor corticospinal excitability (CE) evaluations. Data were then compared between individuals with nociceptive and non-nociceptive (ie, neuropathic or nociplastic) pains. Thirty-five patients were included (51.4% male, 55.7 ± 11.0 years old), 20 of which had nociceptive pain. Patients with nociceptive PD-related pain had lower warm detection threshold (WDT, 33.34 ± 1.39 vs 34.34 ± 1.72, P = .019) and mechanical detection threshold (MDT, 2.55 ± 1.54 vs 3.86 ± .97, P = .007) compared to those with non-nociceptive pains. They also presented a higher proportion of low rest motor threshold values than the non-nociceptive pain ones (64.7% vs 26.6%, P = .048). In non-nociceptive pain patients, there was a negative correlation between WDT and non-motor symptoms scores (r = -.612, P = .045) and a positive correlation between MDT and average pain intensity (r = .629, P = .038), along with neuropathic pain symptom scores (r = .604, P = .049). It is possible to conclude that PD-related chronic pain subtypes have distinctive somatosensory and CE profiles. These preliminary data may help better frame previous contradictory findings in PwP and may have implications for future trial designs aiming at developing individually-tailored therapies. PERSPECTIVE: This work showed that PwP-related nociceptive chronic pain may have distinctive somatosensory and CE profiles than those with non-nociceptive pain subtypes. These data may help shed light on previous contradictory findings in PwP and guide future trials aiming at developing individually-tailored management strategies.

Methodological approach for assessing motor cortical excitability changes with single-pulse transcranial magnetic stimulation

Transcranial Magnetic Stimulation (TMS) serves as a crucial tool in evaluating motor cortex excitability by applying short magnetic pulses to the skull, inducing neuron depolarization in the cerebral cortex through electromagnetic induction. This technique leads to the activation of specific skeletal muscles recorded as Motor-Evoked Potentials (MEPs) through electromyography. Although various methodologies assess cortical excitability with TMS, measuring MEP amplitudes offers a straightforward approach, especially when comparing excitability states pre- and post-interventions designed to alter cortical excitability. Despite TMS's widespread use, the absence of a standardized procedure for such measurements in existing literature hinders the comparison of results across different studies. This paper proposes a standardized procedure for assessing changes in motor cortical excitability using single-pulse TMS pre- and post-intervention. The recommended approach utilizes an intensity equating to half of the MEP's maximum amplitude, thereby ensuring equal likelihood of amplitude increase or decrease, providing a consistent basis for future studies and facilitating meaningful comparisons of results.•A method for assessing changes in motor cortical excitability using single-pulse TMS before and after a specified intervention.•We recommend using an intensity equal to half of the MEP's maximum amplitude during evaluations to objectively assess motor cortical excitability changes post-intervention.

Cortical excitability changes in patients of vascular parkinsonism with cognitive impairment

INTRODUCTION

Vascular parkinsonism (VaP), type of lower body parkinsonism, occurs in relation to ischemic cerebrovascular disease. It can be associated with cognitive impairment. We aimed to study the cortical excitability changes in these patients using transcranial magnetic stimulation (TMS).

METHODS

We included 20 patients with VaP and 22 healthy controls (HC). All subjects underwent TMS over left motor cortex with recording of resting motor threshold (RMT), central motor conduction time (CMCT), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), contralateral and ipsilateral silent period (SP) along with RMT and CMCT in the contralateral lower limb. Cognitive assessments were done using Montreal cognitive assessment (MoCA) and Addenbrooke's cognitive evaluation III (ACE III).

RESULTS

Mean age of patients (63.90 ± 7.36 years) was comparable with controls (59.77 ± 6.94 years; p = 0.07). Duration of disease was 2.58 ± 2.57 years. The upper and lower limb RMT of patients (32.45 ± 4.81%; 57.20 ± 11.54%) was significantly low compared to HC (43.64 ± 7.73%; 69.18 ± 14.27%; p < 0.001). There was a significant reduction in SICI in patients (1.87 ± 2.03) compared to HC (0.38 ± 0.29; p < 0.001). In addition, there was a significant prolongation of ipsilateral SP in patients (48.49 ± 24.49) compared to controls (32.04 ± 12.26, p = 0.01). However, there was no significant difference in contralateral SP (p = 0.66) and ICF (p = 0.25) between the two groups. There was a significant prolongation of lower limb CMCT in patients (p < 0.01). There was a positive correlation of SICI with MoCA (r = 0.45, p < 0.05) and ACE-III (r = 0.33, p < 0.05) scores.

CONCLUSION

Reduction in RMT and SICI in patients with VaP suggests abnormalities in GABAergic neurotransmission that may underlie cognitive impairment observed in them.

Corticospinal adaptations following resistance training and its relationship with strength: A systematic review and multivariate meta-analysis

Neural adaptations to resistance training (RT) and their correlation with muscle strength remain partially understood. We conducted a systematic review and multivariate meta-analysis to examine the effects of metronome-paced (MP), self-paced (SP), and isometric (IM) training on M1 and corticospinal pathway activity. Following MP RT, a significant increase in corticospinal excitability was observed, correlating with increased strength. Conversely, no significant relationship was found after SP or IM training. RT also reduced the duration of the cortical silent period, but this change did not predict strength changes and was not specific to any training modality. No significant effects were found for short-interval intracortical inhibition. Our findings suggest that changes in corticospinal excitability may contribute to strength gains after RT. Furthermore, the relationship between these adaptations and strength appears dependent on the type of training performed.

Clinical diagnostic utility of transcranial magnetic stimulation in neurological disorders. Updated report of an IFCN committee

The review provides a comprehensive update (previous report: Chen R, Cros D, Curra A, Di Lazzaro V, Lefaucheur JP, Magistris MR, et al. The clinical diagnostic utility of transcranial magnetic stimulation: report of an IFCN committee. Clin Neurophysiol 2008;119(3):504-32) on clinical diagnostic utility of transcranial magnetic stimulation (TMS) in neurological diseases. Most TMS measures rely on stimulation of motor cortex and recording of motor evoked potentials. Paired-pulse TMS techniques, incorporating conventional amplitude-based and threshold tracking, have established clinical utility in neurodegenerative, movement, episodic (epilepsy, migraines), chronic pain and functional diseases. Cortical hyperexcitability has emerged as a diagnostic aid in amyotrophic lateral sclerosis. Single-pulse TMS measures are of utility in stroke, and myelopathy even in the absence of radiological changes. Short-latency afferent inhibition, related to central cholinergic transmission, is reduced in Alzheimer's disease. The triple stimulation technique (TST) may enhance diagnostic utility of conventional TMS measures to detect upper motor neuron involvement. The recording of motor evoked potentials can be used to perform functional mapping of the motor cortex or in preoperative assessment of eloquent brain regions before surgical resection of brain tumors. TMS exhibits utility in assessing lumbosacral/cervical nerve root function, especially in demyelinating neuropathies, and may be of utility in localizing the site of facial nerve palsies. TMS measures also have high sensitivity in detecting subclinical corticospinal lesions in multiple sclerosis. Abnormalities in central motor conduction time or TST correlate with motor impairment and disability in MS. Cerebellar stimulation may detect lesions in the cerebellum or cerebello-dentato-thalamo-motor cortical pathways. Combining TMS with electroencephalography, provides a novel method to measure parameters altered in neurological disorders, including cortical excitability, effective connectivity, and response complexity.

Dependence of cortical neuronal strength-duration properties on TMS pulse shape

OBJECTIVE

The aim of present study was to explore the effects of different combinations of transcranial magnetic stimulation (TMS) pulse width and pulse shape on cortical strength-duration time constant (SDTC) and rheobase measurements.

METHODS

Resting motor thresholds (RMT) at pulse widths (PW) of 30, 45, 60, 90 and 120 µs and M-ratios of 0.2, 0.1 and 0.025 were determined using figure-of-eight coil with initial posterior-to-anterior induced current. The M-ratio indicates the relative phases of the induced current with lower values signifying a more unidirectional stimulus. Strength-duration time constant (SDTC) and rheobase were estimated for each M-ratio and various PW combinations. Simulations of biophysically realistic cortical neuron models assessed underlying neuronal populations and physiological mechanisms mediating pulse shape effects on strength-duration properties.

RESULTS

The M-ratio exerted significant effect on SDTC (F(2,44) = 4.386, P = 0.021), which was longer for M-ratio of 0.2 (243.4 ± 61.2 µs) compared to 0.025 (186.7 ± 52.5 µs, P = 0.034). Rheobase was significantly smaller when assessed with M-ratio 0.2 compared to 0.025 (P = 0.026). SDTC and rheobase values were most consistent with pulse width sets of 30/45/60/90/120 µs, 30/60/90/120 µs, and 30/60/120 µs. Simulation studies indicated that isolated pyramidal neurons in layers 2/3, 5, and large basket-cells in layer 4 exhibited SDTCs comparable to experimental results. Further, simulation studies indicated that reducing transient Na+ channel conductance increased SDTC with larger increases for higher M-ratios.

CONCLUSIONS

Cortical strength-duration curve properties vary with pulse shape, and the modulating effect of the hyperpolarising pulse phase on cortical axonal transient Na+ conductances could account for these changes, although a shift in the recruited neuronal populations may contribute as well.

SIGNIFICANCE

The dependence of the cortical strength-duration curve properties on the TMS pulse shape and pulse width selection underscores the need for consistent measurement methods across studies and the potential to extract information about pathophysiological processes.

Individualized closed-loop TMS synchronized with exoskeleton for modulation of cortical-excitability in patients with stroke: a proof-of-concept study

Background

Repetitive TMS is used in stroke rehabilitation with predefined passive low and high-frequency stimulation. Brain State-Dependent Stimulation (BSDS)/Activity-Dependent Stimulation (ADS) using bio-signal has been observed to strengthen synaptic connections. Without the personalization of brain-stimulation protocols, we risk a one-size-fits-all approach.

Methods

We attempted to close the ADS loop via intrinsic-proprioceptive (via exoskeleton-movement) and extrinsic-visual-feedback to the brain. We developed a patient-specific brain stimulation platform with a two-way feedback system, to synchronize single-pulse TMS with exoskeleton along with adaptive performance visual feedback, in real-time, for a focused neurorehabilitation strategy to voluntarily engage the patient in the brain stimulation process.

Results

The novel TMS Synchronized Exoskeleton Feedback (TSEF) platform, controlled by the patient's residual Electromyogram, simultaneously triggered exoskeleton movement and single-pulse TMS, once in 10 s, implying 0.1 Hz frequency. The TSEF platform was tested for a demonstration on three patients (n = 3) with different spasticity on the Modified Ashworth Scale (MAS = 1, 1+, 2) for one session each. Three patients completed their session in their own timing; patients with (more) spasticity tend to take (more) inter-trial intervals. A proof-of-concept study on two groups-TSEF-group and a physiotherapy control-group was performed for 45 min/day for 20-sessions. Dose-matched Physiotherapy was given to control-group. Post 20 sessions, an increase in ipsilesional cortical-excitability was observed; Motor Evoked Potential increased by ~48.5 μV at a decreased Resting Motor Threshold by ~15.6%, with improvement in clinical scales relevant to the Fugl-Mayer Wrist/Hand joint (involved in training) by 2.6 units, an effect not found in control-group. This strategy could voluntarily engage the patient.

Conclusion

A brain stimulation platform with a real-time two-way feedback system was developed to voluntarily engage the patients during the brain stimulation process and a proof-of-concept study on three patients indicates clinical gains with increased cortical excitability, an effect not observed in the control-group; and the encouraging results nudge for further investigations on a larger cohort.

Reversed Mirror Therapy (REMIT) after Stroke-A Proof-of-Concept Study

In mirror training (MIT), stroke patients strive to move their hands while looking at the reflected image of the unaffected one. The recruitment of the mirror neurons and visual-proprioceptive conflict are expected to facilitate the paretic voluntary movement. Here, a reversed MIT (REMIT) is presented, which requires moving hands while looking at the reflected image of the paretic one, giving the illusion of being unable to move the unimpaired hand. This study compares MIT and REMIT on post-stroke upper-limb recovery to gain clues on the mechanism of action of mirror therapies. Eight chronic stroke patients underwent two weeks of MIT and REMIT (five sessions each) in a crossover design. Upper-limb Fugl-Meyer, Box and Block and handgrip strength tests were administered at baseline and treatments end. The strength of the mirror illusion was evaluated after each session. MIT induced a larger illusory effect. The Fugl-Meyer score improved to the same extent after both treatments. No changes occurred in the Box and Block and the handgrip tests. REMIT and MIT were equally effective on upper-limb dexterity, challenging the exclusive role of mirror neurons. Contrasting learned nonuse through an intersensory conflict might provide the rationale for both forms of mirror-based rehabilitation after stroke.

Cortical inhibition and facilitation are mediated by distinct physiological processes

A complex interaction of inhibitory and facilitatory interneuronal processes may underlie development of cortical excitability in the human motor cortex. To determine whether distinct interneuronal processes mediated cortical excitability, threshold tracking transcranial magnetic stimulation was utilised to assess cortical excitability, with figure-of-eight coil oriented in posterior-anterior (PA), anterior-posterior (AP) and latero-medial (LM) directions. Motor evoked potential (MEP) responses were recorded over the contralateral abductor pollicis brevis. Resting motor threshold (RMT), short interval intracortical inhibition (SICI), short interval intracortical facilitation (SICF) and intracortical facilitation were recorded. Significant effects of coil orientation were evident on SICI (F = 8.560, P = 0.002) and SICF (F = 7.132, P = 0.003). SICI was greater when recorded with PA (9.7 ± 10.9%, P = 0.029) and AP (13.1 ± 7.0%, P = 0.003) compared to LM (5.2 ± 7.3%) directed currents. SICF was significantly greater with PA (-14.7 ± 8.1%, P = 0.016) and LM (-14.7 ± 8.8%, P = 0.005) compared to AP (-9.1 ± 7.2%) coil orientations. SICI recorded with LM and PA coil orientations were correlated (R = 0.7, P = 0.002), as was SICF recorded with AP vs LM (R = 0.60, P = 0.019) and LM vs PA (R = 0.69, P = 0.002) coil orientations. RMT was significantly smaller with PA compared to AP (P < 0.001) and LM (P = 0.018) stimulation. Recruitment of distinct interneuronal processes with variable cortical orientation and thresholds underlies short interval intracortical inhibition and facilitation.

Investigation of in-phase bilateral exercise effects on corticospinal plasticity in relapsing remitting multiple sclerosis: A registered report single-case concurrent multiple baseline design across five subjects

Relapsing-remitting Multiple Sclerosis is the most common demyelinating neurodegenerative disease and is characterized by periods of relapses and generation of various motor symptoms. These symptoms are associated with the corticospinal tract integrity, which is quantified by means of corticospinal plasticity which can be probed via transcranial magnetic stimulation and assessed with corticospinal excitability measures. Several factors, such as exercise and interlimb coordination, can influence corticospinal plasticity. Previous work in healthy and in chronic stroke survivors showed that the greatest improvement in corticospinal plasticity occurred during in-phase bilateral exercises of the upper limbs. During in-phase bilateral movement, both upper limbs are moving simultaneously, activating the same muscle groups and triggering the same brain region respectively. Altered corticospinal plasticity due to bilateral cortical lesions is common in MS, yet, the impact of these type of exercises in this cohort is unclear. The aim of this concurrent multiple baseline design study is to investigate the effects of in-phase bilateral exercises on corticospinal plasticity and on clinical measures using transcranial magnetic stimulation and standardized clinical assessment in five people with relapsing-remitting MS. The intervention protocol will last for 12 consecutive weeks (30-60 minutes /session x 3 sessions/week) and include in-phase bilateral movements of the upper limbs, adapted to different sports activities and to functional training. To define functional relation between the intervention and the results on corticospinal plasticity (central motor conduction time, resting motor threshold, motor evoked potential amplitude and latency) and on clinical measures (balance, gait, bilateral hand dexterity and strength, cognitive function), we will perform a visual analysis and if there is a potential sizeable effect, we will perform statistical analysis. A possible effect from our study, will introduce a proof-of-concept for this type of exercise that will be effective during disease progression. Trial registration: ClinicalTrials.gov NCT05367947.

Assessing the mechanisms of brain plasticity by transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is a non-invasive technique for focal brain stimulation based on electromagnetic induction where a fluctuating magnetic field induces a small intracranial electric current in the brain. For more than 35 years, TMS has shown promise in the diagnosis and treatment of neurological and psychiatric disorders in adults. In this review, we provide a brief introduction to the TMS technique with a focus on repetitive TMS (rTMS) protocols, particularly theta-burst stimulation (TBS), and relevant rTMS-derived metrics of brain plasticity. We then discuss the TMS-EEG technique, the use of neuronavigation in TMS, the neural substrate of TBS measures of plasticity, the inter- and intraindividual variability of those measures, effects of age and genetic factors on TBS aftereffects, and then summarize alterations of TMS-TBS measures of plasticity in major neurological and psychiatric disorders including autism spectrum disorder, schizophrenia, depression, traumatic brain injury, Alzheimer's disease, and diabetes. Finally, we discuss the translational studies of TMS-TBS measures of plasticity and their therapeutic implications.

Effects of Bihemispheric Transcranial Direct Current Stimulation Combined With Repetitive Peripheral Nerve Stimulation in Acute Stroke Patients

PURPOSE

Transcranial direct current stimulation (tDCS) can change the excitability of the central nervous system and contribute to motor recovery of stroke patients. The aim of our study was to examine the short- and long-term effects of real versus sham bihemispheric tDCS combined with repetitive peripheral nerve stimulation in patients with acute stroke and a severe motor impairment.

METHODS

The study was prospective, randomized, double blind, and placebo controlled. Nineteen acute stroke patients (ischemic and hemorrhagic) with upper limb Fugl-Meyer mean score of <19 were randomized in two groups: one group received five consecutive daily sessions of anodal tDCS over the affected hemisphere and cathodal over unaffected hemisphere combined with repetitive peripheral nerve stimulation and the other received sham tDCS associated to repetitive peripheral nerve stimulation. Clinical and neurophysiological assessment was applied before tDCS, 5 days after tDCS, and 3, 6, and 12 months after tDCS.

RESULTS

There were significant time-related changes in both groups of patients in motor evoked potentials, somatosensory evoked potentials, Hmax:Mmax ratio, upper limb Fugl-Meyer scores, and Modified Ashworth scales scores ( P < 0.05). However, no significant differences between groups were present at any time ( P > 0.05).

CONCLUSIONS

Bihemispheric tDCS and repetitive peripheral nerve stimulation with the parameters of our study did not add significant short- or long-term clinical improvement or change in neurophysiological data in severe acute stroke patients in comparison to sham stimulation. The severity of motor impairment in stroke patients may influence a possible response to an interventional tDCS treatment.

Normal parameters for diagnostic transcranial magnetic stimulation using a parabolic coil with biphasic pulse stimulation

BACKGROUND

TMS is being used to aid in the diagnosis of central nervous system (CNS) illnesses. It is useful in planning rehabilitation programs and setting appropriate goals for patients. We used a parabolic coil with biphasic pulse stimulation to find normal values for diagnostic TMS parameters.

OBJECTIVES

1. To determine the normal motor threshold (MT), motor evoked potentials (MEP), central motor conduction time (CMCT), intracortical facilitation (ICF), short-interval intracortical inhibition (SICI), and silent period (SP) values. 2. To measure the MEP latencies of abductor pollicis brevis (APB) and extensor digitorum brevis (EDB) at various ages, heights, and arm and leg lengths.

STUDY DESIGN

Descriptive Study.

SETTING

Department of Rehabilitation Medicine, Chiang Mai University, Thailand.

SUBJECTS

Forty-eight healthy participants volunteered for the study.

METHODS

All participants received a single diagnostic TMS using a parabolic coil with biphasic pulse stimulation on the left primary motor cortex (M1). All parameters: MT, MEP, CMCT, ICF, SICI, and SP were recorded through surface EMGs at the right APB and EDB. Outcome parameters were reported by the mean and standard deviation (SD) or median and interquartile range (IQR), according to data distribution. MEP latencies of APB and EDB were also measured at various ages, heights, and arm and leg lengths.

RESULTS

APB-MEP latencies at 120% and 140% MT were 21.77 ± 1.47 and 21.17 ± 1.44 ms. APB-CMCT at 120% and 140% MT were 7.81 ± 1.32 and 7.19 ± 1.21 ms. APB-MEP amplitudes at 120% and 140% MT were 1.04 (0.80-1.68) and 2.24 (1.47-3.52) mV. EDB-MEP latencies at 120% and 140% MT were 37.14 ± 2.85 and 36.46 ± 2.53 ms. EDB-CMCT at 120% and 140% MT were 14.33 ± 2.50 and 13.63 ± 2.57 ms. EDB-MEP amplitudes at 120% and 140% MT were 0.60 (0.38-0.98) and 0.95 (0.69-1.55) mV. ICF amplitudes of APB and EDB were 2.26 (1.61-3.49) and 1.26 (0.88-1.98) mV. SICI amplitudes of APB and EDB were 0.21 (0.13-0.51) and 0.18 (0.09-0.29) mV. MEP latencies of APB at 120% and 140% MT were different between heights < 160 cm and ≥ 160 cm (p < 0.001 and p < 0.001) and different between arm lengths < 65 and ≥ 65 cm (p = 0.022 and p = 0.002).

CONCLUSION

We established diagnostic TMS measurements using a parabolic coil with a biphasic pulse configuration. EDB has a higher MT than APB. The 140/120 MEP ratio of APB and EDB is two-fold. The optimal MEP recording for APB is 120%, whereas EDB is 140% of MT. CMCT by the F-wave is more convenient and tolerable for patients. ICF provides a twofold increase in MEP amplitude. SICI provides a ¼-fold of MEP amplitude. SP from APB and EDB are 121.58 ± 21.50 and 181.01 ± 40.99 ms, respectively. Height and MEP latencies have a modest relationship, whereas height and arm length share a strong positive correlation.

Reduced Short-Latency Afferent Inhibition in Parkinson's Disease Patients with L-dopa-Unresponsive Freezing of Gait

BACKGROUND

Freezing of gait (FOG) in Parkinson's disease (PD), especially the "L-dopa-unresponsive" subtype, is associated with the dysfunction of non-dopaminergic circuits.

OBJECTIVE

We sought to determine whether cortical sensorimotor inhibition evaluated by short-latency afferent inhibition (SAI) related to cholinergic and gamma-aminobutyric acid (GABA)-ergic activities is impaired in PD patients with L-dopa-unresponsive FOG (ONOFF-FOG).

METHODS

SAI protocol was performed in 28 PD patients with ONOFF-FOG, 15 PD patients with "off" FOG (OFF-FOG), and 25 PD patients without FOG during medication "on" state. Additionally, 10 ONOFF-FOG patients underwent SAI testing during both "off" and "on" states. Twenty healthy controls participated in this study. Gait was measured objectively using a portable Inertial Measurement Unit system, and participants performed 5-meter Timed Up and Go single- and dual-task conditions. Spatiotemporal gait characteristics and their variability were determined. FOG manifestations and cognition were assessed with clinical scales.

RESULTS

Compared to controls, PD patients without FOG and with OFF-FOG, ONOFF-FOG PD patients showed significantly reduced SAI. Further, dopaminergic therapy had no remarkable effect on this SAI alterations in ONOFF-FOG. Meanwhile, OFF-FOG patients presented decreased SAI only relative to controls. PD patients with ONOFF-FOG exhibited decreased gait speed, stride length, and increased gait variability relative to PD patients without FOG and controls under both walking conditions. For ONOFF-FOG patients, significant associations were found between SAI and FOG severity, gait characteristics and variability.

CONCLUSION

Reduced SAI was associated with severe FOG manifestations, impaired gait characteristics and variability in PD patients with ONOFF-FOG, suggesting the impaired thalamocortical cholinergic-GABAergic SAI pathways underlying ONOFF-FOG.

Neurophysiology tools to lower the stroke onset to treatment time during the golden hour: microwaves, bioelectrical impedance and near infrared spectroscopy

Reperfusion therapy administration timing in acute ischaemic stroke is the main determinant of patients' mortality and long-term disability. Indeed, the first hour from the stroke onset is defined the "golden hour", in which the treatment has the highest efficacy and lowest side effects. Delayed ambulance transport, inappropriate triage and difficulty in accessing CT scans lead to delayed onset to treatment time (OTT) in clinical practice. To date brain CT scan is needed to rule out intracranial haemorrhage, which is a major contraindication to thrombolytic therapy. The availability, dimension and portability make CT suitable mainly for intrahospital use, determining further delays in the therapies administration. This review aims at evaluating portable neurophysiology technologies developed with the scope of speeding up the diagnostic phase of acute stroke and, therefore, the initiation of intravenous thrombolysis. Medline databases were explored for studies concerning near infrared spectroscopy (NIRS), bioelectrical impedance spectroscopy (BIS) and Microwave imaging (MWI) as methods for stroke diagnosis. A total of 1368 articles were found, and 12 of these fit with our criteria and were included in the review. For each technology, the following parameters were evaluated: diagnostic accuracy, ability to differentiate ischaemic and haemorrhagic stroke, diagnosis time from stroke onset, portability and technology readiness level (TRL). All the described methods seem to be able to identify acute stroke even though the number of studies is very limited. Low cost and portability make them potentially usable during ambulance transport, possibly leading to a reduction of stroke OTT along with the related huge benefits in terms of patients outcome and health care costs. In addition, unlike standard imaging techniques, neurophysiological techniques could allow continuous monitoring of patients for timely intrahospital stroke diagnosis.KEY MESSAGESFirst hour from the stroke onset is defined the "golden hour", in which the treatment has the highest efficacy and lowest side effects.The delay for stroke onset to brain imaging time is one of the major reasons why only a minority of patients with acute ischaemic stroke are eligible to reperfusion therapies.Neurophysiology techniques (NIRS, BIS and MWI) could have a potential high impact in reducing the time to treatment in stroke patients.

Transcranial magnetic stimulation maps the neurophysiology of chronic noncancer pain: A scoping review

BACKGROUND

Chronic noncancer pain is a global public health challenge. It is imperative to identify biological markers ("biomarkers") to understand the mechanisms underlying chronic pain and to monitor pain over time and after interventions. Transcranial magnetic stimulation (TMS) is a promising method for this purpose.

OBJECTIVES

To examine differences in TMS-based outcomes between persons with chronic pain and healthy controls (HCs) and/or before versus after pain-modulating interventions and relationships between pain measures and TMS outcomes; To summarize the neurophysiological mechanisms underlying chronic pain as identified by TMS.

METHODS

We searched the PubMed database for literature from January 1, 1985, to June 9, 2020, with the keywords "pain" and "transcranial magnetic stimulation." Eligible items included original studies of adult human participants with pain lasting for ≥ 6 months. We completed a narrative synthesis of the study findings stratified by chronic pain etiology (primary pain, neuropathic pain, and secondary musculoskeletal pain).

RESULTS

The search yielded 1265 records. The final 12 articles included 244 patients with chronic pain (192 females, aged 35-65 years) and 169 HCs (89 females, aged 28-59 years). Abnormalities in TMS outcomes that reflect GABAergic and glutamatergic activities were associated with many of the disorders studied and were distinct for each pain etiology. Chronic primary pain is characterized by reduced intracortical inhibition and corticospinal excitability, chronic neuropathic pain shows evidence of increased excitation and disinhibition, and chronic secondary musculoskeletal pain involves low corticospinal excitability.

DISCUSSION

TMS could be a useful tool for delineating the neurophysiological underpinnings of chronic pain syndromes.

Alzheimer's disease and epilepsy: An increasingly recognized comorbidity

Both Alzheimer's disease (AD) and epilepsy are common chronic diseases in older people. Seizures and epileptiform discharges are very prevalent in AD and can occur since any stage of AD. Increasing evidence indicates that AD and epilepsy may be comorbid. Several factors may be related to the underlying mechanism of the comorbidity. Identifying seizures in patients with AD is a challenge because seizures are often clinically non-motor and may overlap with some AD symptoms. Not only seizures but also epileptiform discharges may exacerbate the cognitive decline in AD patients, highlighting the importance of early recognition and treatment. This review provides a comprehensive overview of seizures in AD from multiple aspects to provide more insight.

Cortical hyperexcitability and plasticity in Alzheimer's disease: developments in understanding and management

INTRODUCTION

Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that provides important insights into Alzheimer's Disease (AD). A significant body of work utilizing TMS techniques has explored the pathophysiological relevance of cortical hyperexcitability and plasticity in AD and their modulation in novel therapies.

AREAS COVERED

This review examines the technique of TMS, the use of TMS to examine specific features of cortical excitability and the use of TMS techniques to modulate cortical function. A search was performed utilizing the PubMed database to identify key studies utilizing TMS to examine cortical hyperexcitability and plasticity in Alzheimer's dementia. We then translate this understanding to the study of Alzheimer's disease pathophysiology, examining the underlying neurophysiologic links contributing to these twin signatures, cortical hyperexcitability and abnormal plasticity, in the cortical dysfunction characterizing AD. Finally, we examine utilization of TMS excitability to guide targeted therapies and, through the use of repetitive TMS (rTMS), modulate cortical plasticity.

EXPERT OPINION

The examination of cortical hyperexcitability and plasticity with TMS has potential to optimize and expand the window of therapeutic interventions in AD, though remains at relatively early stage of development.

Utility of transcranial magnetic stimulation in the assessment of spinal cord injury: Current status and future directions

Comprehensive assessment following traumatic spinal cord injury (SCI) is needed to improve prognostication, advance the understanding of the neurophysiology and better targeting of clinical interventions. The International Standards for Neurological Classification of Spinal Cord Injury is the most common clinical examination recommended for use after a SCI. In addition, there are over 30 clinical assessment tools spanning across different domains of the International Classification of Functioning, Disability, and Health that have been validated and recommended for use in SCI. Most of these tools are subjective in nature, have limited value in predicting neurologic recovery, and do not provide insights into neurophysiological mechanisms. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiology technique that can supplement the clinical assessment in the domain of body structure and function during acute and chronic stages of SCI. TMS offers a better insight into neurophysiology and help in better detection of residual corticomotor connectivity following SCI compared to clinical assessment alone. TMS-based motor evoked potential and silent period duration allow study of excitatory and inhibitory mechanisms following SCI. Changes in muscle representations in form of displacement of TMS-based motor map center of gravity or changes in the map area can capture neuroplastic changes resulting from SCI or following rehabilitation. Paired-pulse TMS measures help understand the compensatory reorganization of the cortical circuits following SCI. In combination with peripheral stimulation, TMS can be used to study central motor conduction time and modulation of spinal reflexes, which can be used for advanced diagnostic and treatment purposes. To strengthen the utility of TMS in SCI assessment, future studies will need to standardize the assessment protocols, address population-specific concerns, and establish the psychometric properties of TMS-based measurements in the SCI population.

A comprehensive review of transcranial magnetic stimulation in secondary dementia

Although primary degenerative diseases are the main cause of dementia, a non-negligible proportion of patients is affected by a secondary and potentially treatable cognitive disorder. Therefore, diagnostic tools able to early identify and monitor them and to predict the response to treatment are needed. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological technique capable of evaluating in vivo and in "real time" the motor areas, the cortico-spinal tract, and the neurotransmission pathways in several neurological and neuropsychiatric disorders, including cognitive impairment and dementia. While consistent evidence has been accumulated for Alzheimer's disease, other degenerative cognitive disorders, and vascular dementia, to date a comprehensive review of TMS studies available in other secondary dementias is lacking. These conditions include, among others, normal-pressure hydrocephalus, multiple sclerosis, celiac disease and other immunologically mediated diseases, as well as a number of inflammatory, infective, metabolic, toxic, nutritional, endocrine, sleep-related, and rare genetic disorders. Overall, we observed that, while in degenerative dementia neurophysiological alterations might mirror specific, and possibly primary, neuropathological changes (and hence be used as early biomarkers), this pathogenic link appears to be weaker for most secondary forms of dementia, in which neurotransmitter dysfunction is more likely related to a systemic or diffuse neural damage. In these cases, therefore, an effort toward the understanding of pathological mechanisms of cognitive impairment should be made, also by investigating the relationship between functional alterations of brain circuits and the specific mechanisms of neuronal damage triggered by the causative disease. Neurophysiologically, although no distinctive TMS pattern can be identified that might be used to predict the occurrence or progression of cognitive decline in a specific condition, some TMS-associated measures of cortical function and plasticity (such as the short-latency afferent inhibition, the short-interval intracortical inhibition, and the cortical silent period) might add useful information in most of secondary dementia, especially in combination with suggestive clinical features and other diagnostic tests. The possibility to detect dysfunctional cortical circuits, to monitor the disease course, to probe the response to treatment, and to design novel neuromodulatory interventions in secondary dementia still represents a gap in the literature that needs to be explored.

The central-peripheral coupling effect of ocular acupuncture kinesitherapy in post-stroke dyskinesia: A functional neuroimaging and neurotic electrophysiology study protocol

Background

Dyskinesia is a common manifestation after stroke. Motor functional rehabilitation after stroke is of great significance to the maintenance of national health. Ocular Acupuncture Kinesitherapy (OAKT) can repair nerve injuries, improve motor function, reduce rehabilitation time, and promote dyskinesia recovery after stroke. The mechanism, however, remains a mystery, necessitating urgent research. The M1-thalamus-spinal cord neural signaling pathway is linked to limb motor function. Bold-fMRI can represent the cerebral functional state, and TMS-MEP is of certain practical utility for assessing motor neural function and prognosis. Combining fMRI scanning with TMS-MEP detection is predicted to advance brain-spinal cord regulation and muscle response linkage control mechanism research, as well as completely investigate the central-peripheral coupling effect of Ocular Acupuncture Kinesitherapy on dyskinesia after stroke (PSD).

Methods

This is a prospective functional neuroimaging and neurotic electrophysiological study with a case-control design between the PSD with the HC groups and a randomized controlled design within the 3 PSD groups (OAKT group, ocular acupuncture group, and kinesitherapy group). Using fMRI scans and TMS-MEP approach, we will assess the central-peripheral neural function alterations in PSD as well as the coupling effects of OAKT on PSD. We plan to enroll 90 participants at the Hospital of Chengdu University of Traditional Chinese Medicine from Aug 31, 2022, to Dec 31, 2023, including 45 PSD and 45 HC subjects. After enrollment and on the last day after 4-weeks of waiting (HC subjects) or intervention (PSD subjects), all eligible subjects will be evaluated using fMRI scanning, TMS-MEP detection, and the MMT and Fugl-Mayer scales assessment. The MMT and Fugl-Meyer scores will be recorded, and a Pearson correlation analysis will be performed to assess the correlation between clinical and imaging outcomes.

Discussion

Findings of this study will help to explain the central-peripheral coupling effect of OAKT on PSD and to further provide the neural processing of acupuncture kinesitherapy covering the entire pathway from peripheral to central nervous system.

Clinical trial registration

This study is registered with an identifier (ChiCTR2200060483) at the Chinese Clinical Trial Registry in June 2022. http://www.chictr.org.cn/index.aspx.