Applications of transcranial magnetic stimulation in movement disorders

Distinct patterns of electrophysiologic-neuroimaging correlations between Parkinson's disease and multiple system atrophy

Due to a high degree of symptom overlap in the early stages, with movement disorders predominating, Parkinson's disease (PD) and multiple system atrophy (MSA) may exhibit a similar decline in motor areas, yet they differ in their spread throughout the brain, ultimately resulting in two distinct diseases. Drawing upon neuroimaging analyses and altered motor cortex excitability, potential diffusion mechanisms were delved into, and comparisons of correlations across distinct disease groups were conducted in a bid to uncover significant pathological disparities. We recruited thirty-five PD, thirty-seven MSA, and twenty-eight matched controls to conduct clinical assessments, electromyographic recording, and magnetic resonance imaging scanning during the "on medication" state. Patients with neurodegeneration displayed a widespread decrease in electrophysiology in bilateral M1. Brain function in early PD was still in the self-compensatory phase and there was no significant change. MSA patients demonstrated an increase in intra-hemispheric function coupled with a decrease in diffusivity, indicating a reduction in the spread of neural signals. The level of resting motor threshold in healthy aged showed broad correlations with both clinical manifestations and brain circuits related to left M1, which was absent in disease states. Besides, ICF exhibited distinct correlations with functional connections between right M1 and left middle temporal gyrus in all groups. The present study identified subtle differences in the functioning of PD and MSA related to bilateral M1. By combining clinical information, cortical excitability, and neuroimaging intuitively, we attempt to bring light on the potential mechanisms that may underlie the development of neurodegenerative disease.

The Lateralization of Resting Motor Threshold to Predict Medication-Mediated Improvement in Parkinson’s Disease

Cortical stimulation patterns in patients with Parkinson’s disease (PD) are asymmetric and get altered over time. This study examined cortical neurophysiological markers for PD and identified neurophysiological markers for lateralization in PD. We used transcranial magnetic stimulation (TMS) to study corticospinal and intracortical excitability in 21 patients with idiopathic PD. We used the Movement Disorder Society Unified Parkinson’s Disease Rating Scale for examination during on and off periods and evaluated inhibitory and facilitatory process markers using TMS, including resting motor thresholds (RMT), active motor thresholds, and motor evoked potential amplitude. The RMT in the more affected cortex was significantly shorter than in the less affected cortex, and was strongly correlated with improved motor function following medication. Patients in the tremor group exhibited significantly lower RMT compared to those in the akinetic-rigid group. Cortical electrophysiological laterality observed in patients with PD may be a useful marker for guiding treatment and identifying underlying compensatory mechanisms.

Dopaminergic Modulation of Local Non-oscillatory Activity and Global-Network Properties in Parkinson’s Disease: An EEG Study

Dopaminergic medication for Parkinson’s disease (PD) modulates neuronal oscillations and functional connectivity (FC) across the basal ganglia-thalamic-cortical circuit. However, the non-oscillatory component of the neuronal activity, potentially indicating a state of excitation/inhibition balance, has not yet been investigated and previous studies have shown inconsistent changes of cortico-cortical connectivity as a response to dopaminergic medication. To further elucidate changes of regional non-oscillatory component of the neuronal power spectra, FC, and to determine which aspects of network organization obtained with graph theory respond to dopaminergic medication, we analyzed a resting-state electroencephalography (EEG) dataset including 15 PD patients during OFF and ON medication conditions. We found that the spectral slope, typically used to quantify the broadband non-oscillatory component of power spectra, steepened particularly in the left central region in the ON compared to OFF condition. In addition, using lagged coherence as a FC measure, we found that the FC in the beta frequency range between centro-parietal and frontal regions was enhanced in the ON compared to the OFF condition. After applying graph theory analysis, we observed that at the lower level of topology the node degree was increased, particularly in the centro-parietal area. Yet, results showed no significant difference in global topological organization between the two conditions: either in global efficiency or clustering coefficient for measuring global and local integration, respectively. Interestingly, we found a close association between local/global spectral slope and functional network global efficiency in the OFF condition, suggesting a crucial role of local non-oscillatory dynamics in forming the functional global integration which characterizes PD. These results provide further evidence and a more complete picture for the engagement of multiple cortical regions at various levels in response to dopaminergic medication in PD.

Cortical excitability changes as a marker of cognitive impairment in Parkinson's disease

Cognitive impairment of different severity with eventual progression to dementia in Parkinson's disease (PD) appears during the course of the disease. In this study, transcranial magnetic stimulation (TMS) was used to assess cortical excitability changes in PD patients with varying cognitive impairment. We aimed to identify the TMS parameters that could serve as a non-invasive marker of cognitive impairment in patients with PD. Consecutive PD patients were recruited in the study. Detailed neuropsychological assessment was carried out to identify PD without cognitive impairment (PD-nC), PD with mild cognitive impairment (PD-MCI) and PD with dementia (PDD). Twenty patients of PDD (2 females and 18 males), 20 PD-MCI (4 females and 16 males), 18 PD-nC (5 females, 13 males) and 18 healthy controls (4 females, and 14 males) were included in the study. All the participants underwent TMS with recording of resting motor threshold, central motor conduction time, silent period, short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). All the groups were age matched. The SICI was present in all; however, significantly greater inhibition was noted in PDD (Mean±SD; 0.11±0.08) followed by PD-MCI (0.31±0.17), PD-nC (0.49±0.26) and controls (0.61±0.23; p<0.001). The ICF was significantly reduced in PDD (Mean±SD; 0.15±0.18), PD-MCI (0.55±0.31), PD-nC (0.96±0.59), when compared to healthy controls (1.81±0.83; p<0.001). Patients with PD-nC, PD-MCI and PDD had graded reduction in ICF and increasing intracortical inhibition as the disease progressed from PD-nC through PD-MCI to PDD. This suggests progressive overactivity of GABAergic transmission, glutaminergic deficiency with consequent reduction of cholinergic transmission leading to dementia.

Effects of combination treatment with transcranial magnetic stimulation and bone marrow mesenchymal stem cell transplantation or Raf inhibition on spinal cord injury in rats

Spinal cord injury (SCI) remains a global challenge due to limited treatment strategies. Transcranial magnetic stimulation (TMS), bone marrow mesenchymal stem cell (BMSC) transplantation and downregulation of Raf/MEK/ERK signaling effectively improve SCI. The combination of BMSCs and TMS displays synergistic effects on vascular dementia. However, whether TMS displays a synergistic effect when combined with BMSC transplantation or Raf inhibitor (RafI) therapy for the treatment of SCI is not completely understood. The present study aimed to compare the therapeutic effect of monotherapy and combination therapy on SCI. In the present study, 8‑week‑old female Sprague Dawley rats were used to establish a model of SCI using the weight‑drop method followed by treatment with monotherapy (TMS, BMSCs or RafI) or combination therapy (TMS+BMSCs or TMS+RafI). The effect of monotherapy and combination therapy on locomotor function, pathological alterations, neuronal apoptosis and expression of axonal regeneration‑associated factors and Raf/MEK/ERK signaling‑associated proteins in the spinal cord was analyzed by Basso, Beattie and Bresnahan (BBB) scoring, hematoxylin and eosin staining, TUNEL‑neuronal nuclei (NeuN) staining and immunofluorescence or western blotting, respectively. The results demonstrated that compared with untreated SCI model rats, monotherapy significantly enhanced locomotor functional recovery, as evidenced by higher BBB scores, and slightly alleviated histopathological lesions of the spinal cord in SCI model rats. Furthermore, monotherapy markedly suppressed neuronal apoptosis and promoted axonal regeneration, as well as inhibiting astroglial activation in SCI model rats. The aforementioned results were demonstrated by significantly decreased numbers of apoptotic neurons, markedly decreased expression levels of glial fibrillary acidic protein (GFAP), significantly increased numbers of NeuN+ cells, markedly increased expression levels of growth‑associated protein 43 (GAP‑43) and significantly upregulated nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) expression levels in monotherapy groups (excluding the RafI monotherapy group) compared with untreated SCI model rats. In addition, monotherapy markedly suppressed activation of the Raf/MEK/ERK signaling pathway, as evidenced by significantly reduced p‑Raf/Raf, p‑MEK/MEK and p‑ERK/ERK protein expression levels in monotherapy groups (excluding the BMSC monotherapy group) compared with untreated SCI model rats. Notably, combination therapy further alleviated SCI‑induced spinal cord lesions and neuronal apoptosis, increased GAP‑43, NGF and BDNF expression levels, downregulated GFAP expression levels and inhibited activation of the Raf/MEK/ERK signaling pathway in SCI model rats compared with the corresponding monotherapy groups. Therefore, it was hypothesized that compared with monotherapy, combination therapy displayed an improved therapeutic effect on SCI by further suppressing Raf/MEK/ERK signaling. The results of the present study provided an important basis for the clinical application of combination therapy.

Clinical and Electrophysiological Hints to TMS in De Novo Patients with Parkinson's Disease and Progressive Supranuclear Palsy

BACKGROUND

Transcranial magnetic stimulation (TMS) can non-invasively probe cortical excitability in movement disorders, although clinical significance is still controversial, especially at early stages. We compare single-pulse TMS in two prototypic synucleinopathy and tauopathy-i.e., Parkinson's disease (PD) and Progressive Supranuclear Palsy (PSP), respectively-to find neurophysiological differences and identify early measures associated with cognitive impairment.

METHODS

28 PD and 23 PSP de novo patients were age-matched with 28 healthy controls, all right-handed and drug-free. Amplitude and latency of motor evoked potentials (MEP), central motor conduction time, resting motor threshold (rMT), and cortical silent period (CSP) were recorded through a figure-of-eight coil from the First Dorsal Interosseous muscle (FDI), bilaterally.

RESULTS

Mini Mental Examination and Frontal Assessment Battery (FAB) scored worse in PSP; PD had worse FAB than controls. Higher MEP amplitude from right FDI in PD and PSP than controls was found, without difference between them. CSP was bilaterally longer in patients than controls, but similar between patient groups. A positive correlation between FAB and rMT was observed in PSP, bilaterally.

CONCLUSIONS

Despite the small sample size, PD and PSP might share, at early stage, a similar global electrocortical asset. rMT might detect and possibly predict cognitive deterioration in PSP.

Clinical and Electrophysiological Hints to TMS in De Novo Patients with Parkinson's Disease and Progressive Supranuclear Palsy

BACKGROUND

Transcranial magnetic stimulation (TMS) can non-invasively probe cortical excitability in movement disorders, although clinical significance is still controversial, especially at early stages. We compare single-pulse TMS in two prototypic synucleinopathy and tauopathy-i.e., Parkinson's disease (PD) and Progressive Supranuclear Palsy (PSP), respectively-to find neurophysiological differences and identify early measures associated with cognitive impairment.

METHODS

28 PD and 23 PSP de novo patients were age-matched with 28 healthy controls, all right-handed and drug-free. Amplitude and latency of motor evoked potentials (MEP), central motor conduction time, resting motor threshold (rMT), and cortical silent period (CSP) were recorded through a figure-of-eight coil from the First Dorsal Interosseous muscle (FDI), bilaterally.

RESULTS

Mini Mental Examination and Frontal Assessment Battery (FAB) scored worse in PSP; PD had worse FAB than controls. Higher MEP amplitude from right FDI in PD and PSP than controls was found, without difference between them. CSP was bilaterally longer in patients than controls, but similar between patient groups. A positive correlation between FAB and rMT was observed in PSP, bilaterally.

CONCLUSIONS

Despite the small sample size, PD and PSP might share, at early stage, a similar global electrocortical asset. rMT might detect and possibly predict cognitive deterioration in PSP.

The Top 50 Most-Cited Articles in Orthostatic Tremor: A Bibliometric Review

Background

Article-level citation count is a hallmark indicating scientific impact. We aimed to pinpoint and evaluate the top 50 most-cited articles in orthostatic tremor (OT).

Methods

The ISI Web of Knowledge database and 2017 Journal Citation Report Science Edition were used to retrieve the 50 top-cited OT articles published from 1984 to April 2019. Information was collected by the Analyze Tool on the Web of Science, including number of citations, publication title, journal name, publication year, and country and institution of origin. Supplementary analyses were undertaken to clarify authorship, study design, level of evidence, and category.

Results

Up to 66% of manuscripts were recovered from five journals: Movement Disorders (n = 18), Brain (n = 4), Journal of Clinical Neurophysiology (n = 4), Neurology (n = 4), and Clinical Neurophysiology (n = 3). Articles were published between 1984 and 2018, with expert opinion as the predominant design (n = 22) and review as category (n = 17). Most articles had level 5 evidence (n = 26). According to their countries of origin, 34% of articles belonged to the United States (n = 17) leading the list, followed by United Kingdom (n = 15). University College London yielded the greater number of articles (n = 12), followed by the University of Kiel (n = 9). Most popular authors were G. Deuschl (n = 10), C.D. Marsden (n = 6), J. Jankovic (n = 5), P.D. Thompson (n = 5), J.C. Rothwell (n = 5), L.J. Findley (n = 4), and P. Brown (n = 4), who together accounted for 48% of them. All papers were in English.

Discussion

Publishing high-cited OT articles could be facilitated by source journal, study design, category, publication language, and country and institution of origin.

The use of transcranial magnetic stimulation as a treatment for movement disorders: A critical review

BACKGROUND

Transcranial magnetic stimulation is a safe and painless non-invasive brain stimulation technique that has been largely used in the past 30 years to explore cortical function in healthy participants and, inter alia, the pathophysiology of movement disorders. During the years, its use has evolved from primarily research purposes to treatment of a large variety of neurological and psychiatric diseases. In this article, we illustrate the basic principles on which the therapeutic use of transcranial magnetic stimulation is based and review the clinical trials that have been performed in patients with movement disorders.

METHODS

A search of the PubMed database for research and review articles was performed on therapeutic applications of transcranial magnetic stimulation in movement disorders. The search included the following conditions: Parkinson's disease, dystonia, Tourette syndrome and other chronic tic disorders, Huntington's disease and choreas, and essential tremor. The results of the studies and possible mechanistic explanations for the relatively minor effects of transcranial magnetic stimulation are discussed. Possible ways to improve the methodology and achieve greater therapeutic efficacy are discussed.

CONCLUSION

Despite the promising and robust rationales for the use of transcranial magnetic stimulations as a treatment tool in movement disorders, the results taken as a whole are not as successful as were initially expected. There is encouraging evidence that transcranial magnetic stimulation may improve motor symptoms and depression in Parkinson's disease, but the efficacy in other movement disorders is unclear. Possible improvements in methodology are on the horizon but have yet to be implemented in large clinical studies. © 2019 International Parkinson and Movement Disorder Society © 2019 International Parkinson and Movement Disorder Society.

An optimal protocol for measurement of corticospinal excitability, short intracortical inhibition and intracortical facilitation in the rectus femoris

The study aimed to determine the optimal application of single- and paired-pulse transcranial magnetic stimulation (TMS) in the rectus femoris. Twenty-nine male adults participated in the study, which involved 5 separate experiments. Experiments 1 to 3 assessed the effect of conditioning stimulus (CS) intensity (60, 70, 80 and 90% active motor threshold, AMT), contraction strength (5, 10, 20 and 50% maximum voluntary contraction, MVC), and inter-stimulus interval (ISI, 2-5 ms for short-interval intracortical inhibition, SICI and 10-15 ms for intracortical facilitation, ICF) on SICI and ICF. In Experiment 4, 30 measurements of corticospinal excitability (CSE), SICI and ICF were recorded, with the minimum number of consecutive measurements required as a probability of falling within the 95% CI determined. In Experiment 5, within- and between-day reliability of CSE, SICI and ICF was assessed. The results suggest that for SICI, a CS of 70% AMT, ISI of 2 ms, and contraction strength of 5 or 10% MVC induces the greatest level of inhibition. Negligible differences in ICF were seen across stimulus variables. The minimum number of measurements required to obtain an accurate estimate of CSE, SICI and ICF was 21, 18 and 17, respectively. Using the optimal stimulus variables and number of measurements, CSE, SICI and ICF can be measured reliably both within- and between-days (intraclass correlation coefficient, ICC ≥ 0.87, ≥0.74, and ≥0.61, respectively). The current findings can be used to guide future investigations using single- and paired-pulse TMS to elicit responses in the rectus femoris.

Effectiveness of allied health therapy in the symptomatic management of progressive supranuclear palsy: a systematic review

BACKGROUND

Progressive supranuclear palsy (PSP) is an adult onset neurodegenerative condition associated with mobility, balance, speech, swallowing, vision and cognitive changes. The condition is diagnosed using the National Institute for Neurological Disorders and Stroke (NINDS) and the Society of Progressive Supranuclear Palsy (SPSP) criteria. Therapeutic interventions for PSP are important, and a healthcare team should include a physiotherapist, occupational therapist and speech therapist. Mobility, speech and swallowing problems are commonly experienced, and aspiration pneumonia is the leading cause of death. A preliminary search of the literature has indicated that beyond small case series, there is very little evidence to guide specific allied health therapies in PSP. Many strategies for optimizing independence and function for PSP predominately rely on data extrapolated from the study of Parkinson's disease.

OBJECTIVES

The objective of this review was to examine the effectiveness of physical, occupational and speech therapy interventions in the symptomatic management of PSP.

INCLUSION CRITERIA TYPES OF PARTICIPANTS

This review included participants with PSP as per the NINDS and the SPSP criteria, aged over 40 years of age from all community and clinical settings.

TYPES OF INTERVENTIONS

This review included studies evaluating any allied health therapy that addressed mobility, vision, swallowing, communication or cognitive/neuropsychiatric difficulties experienced by patients with PSP. Studies examining interventions within the current scope of practice, and emerging interventions (non-invasive brain stimulation therapy) were eligible for inclusion.

TYPES OF COMPARATOR

The effectiveness of interventions of interest was compared with usual care and/or baseline measurements.

OUTCOMES

Outcomes of interest included the degree of change, or no change, in the symptoms experienced by patients with PSP relevant to allied health. These included difficulties with mobility, vision, swallowing, communication and cognition.

TYPES OF STUDIES

All types of quantitative study designs published in English from the time of development of the NINDS and the SPSP criteria in 1996-2014 were considered for inclusion.

SEARCH STRATEGY

A broad range of synonyms for PSP and a three-step search strategy was utilized to identify possible published and unpublished studies from 11 different databases. An initial limited search via MEDLINE (PubMed), CINAHL, Health Informit, PsycINFO, PEDRO, OTSeeker and SpeechBite was undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms was then undertaken across all included databases. Third, hand-searching was conducted and the reference list of all identified reports and articles was searched for additional studies.

METHODOLOGICAL QUALITY

Critical appraisal was conducted by two independent reviewers using standardized instruments.

DATA EXTRACTION

Quantitative data were extracted from articles included in the review using standardized data extraction tools.

DATA SYNTHESIS

As the quantitative articles examined different interventions, pooling of data was not appropriate. Instead, the findings were presented in narrative summary and tabular form.

RESULTS

Following methodological appraisal, six studies were included in the review. Aside from one small quasi-randomized control study, most studies were small case series and one was a case report. Five of the six studies examined the effectiveness of a range of different physiotherapy rehabilitation programs targeting gait, balance and physical capability, with one study also targeting gaze control. The sixth study examined non-invasive brain stimulation in improving gait and midline symptoms in PSP. No studies examined the effectiveness of occupational therapy or speech therapy interventions in PSP.

CONCLUSIONS

Research into the effectiveness of allied health therapeutic interventions for PSP symptoms is in its infancy. This review found preliminary evidence to support the use of various physiotherapy rehabilitation programs to improve balance, gait and gaze control in people affected by PSP. Further research is urgently required to identify effective interventions to manage mobility, vision, swallowing, communication and cognitive/neuropsychiatric symptoms associated with this devastating condition.

Effect of repetitive transcranial magnetic stimulation on action myoclonus: A pilot study in patients with EPM1

OBJECTIVE

The objective of this study was to explore the short-term effects of repetitive transcranial magnetic stimulation (rTMS) on action myoclonus.

METHODS

Nine patients with Unverricht-Lundborg (EPM1) progressive myoclonus epilepsy type underwent two series of 500 stimuli at 0.3Hz through round coil twice a day for five consecutive days. Clinical and neurophysiological examinations were performed two hours before starting the first rTMS session and two hours after the end of the last rTMS session.

RESULTS

Eight patients completed the protocol; one discontinued because of a transient increase in spontaneous jerks. The unified myoclonus rating scale indicated a 25% reduction in posttreatment myoclonus with action score associated with an increase in the cortical motor threshold and lengthening of the cortical silent period (CSP). The decrease in the myoclonus with action scores correlated with the prolongation of CSP.

CONCLUSIONS

Repetitive transcranial magnetic stimulation can be safely used in patients with EPM1, improves action myoclonus, and partially restores deficient cortical inhibition.

Transcallosal conduction in paroxysmal kinesigenic dyskinesia

OBJECTIVES

Detecting whether a possible disequilibrium between the excitatory and inhibitory interhemispheric interactions in paroxysmal kinesigenic dyskinesia (PKD) exists.

METHODS

This study assessed measures of motor threshold, motor evoked potential latency, the cortical silent period, the ipsilateral silent period and the transcallosal conduction time (TCT) in PKD patients. Data were compared between the clinically affected hemisphere (aH) and the fellow hemisphere (fH).

RESULTS

The transcallosal conduction time from the aH to the fH was 11.8 ms (range = 2.3-20.7) and 13.6 ms (range = 2.8-67.7) from the fH to the aH. The difference in TCT in the affected side was significant (p = .019).

CONCLUSION

The findings demonstrated that, although inhibitory interneurons act normally and symmetrically between the motor cortices and transcallosal inhibition was normal and symmetrical between both sides, the onset of transcallosal inhibition was asymmetrical. The affected hemisphere's inhibition toward the unaffected hemisphere is faster compared to the inhibition provided by the fellow hemisphere. These results are consistent with an inhibitory deficit in the level of interhemispheric interactions.

SIGNIFICANCE

This study revealed a defect in inhibition of the motor axis could be responsible in the pathological mechanisms of kinesigenic dyskinesia.

Cortical involvement in celiac disease before and after long-term gluten-free diet: A Transcranial Magnetic Stimulation study

OBJECTIVE

Transcranial Magnetic Stimulation in de novo patients with Celiac Disease previously revealed an imbalance in the excitability of cortical facilitatory and inhibitory circuits. After a median period of 16 months of gluten-free diet, a global increase of cortical excitability was reported, suggesting a glutamate-mediated compensation for disease progression. We have now evaluated cross-sectionally the changes of cortical excitability to TMS after a much longer gluten-free diet.

METHODS

Twenty patients on adequate gluten-free diet for a mean period of 8.35 years were enrolled and compared with 20 de novo patients and 20 healthy controls. Transcranial Magnetic Stimulation measures, recorded from the first dorsal interosseous muscle of the dominant hand, consisted of: resting motor threshold, cortical silent period, motor evoked potentials, central motor conduction time, mean short-latency intracortical inhibition and intracortical facilitation.

RESULTS

The cortical silent period was shorter in de novo patients, whereas in gluten-free diet participants it was similar to controls. The amplitude of motor responses was significantly smaller in all patients than in controls, regardless of the dietary regimen. Notwithstanding the diet, all patients exhibited a statistically significant decrease of mean short-latency intracortical inhibition and enhancement of intracortical facilitation with respect to controls; more intracortical facilitation in gluten-restricted compared to non-restricted patients was also observed. Neurological examination and celiac disease-related antibodies were negative.

CONCLUSIONS

In this new investigation, the length of dietary regimen was able to modulate the electrocortical changes in celiac disease. Nevertheless, an intracortical synaptic dysfunction, mostly involving excitatory and inhibitory interneurons within the motor cortex, may persist. The clinical significance of subtle neurophysiological changes in celiac disease needs to be further investigated.

The duration of the cortical silent period is not abnormal in Restless Legs Syndrome/Willis-Ekbom Disease

OBJECTIVE

To compare the duration of the cortical silent period (CSP) measured in a hand muscle in subjects with primary Restless Legs Syndrome (RLS/WED) and controls, using four different methods of analysis.

METHODS

The CSP to transcranial magnetic stimulation of the dominant motor cortex was assessed in the abductor digiti minimi of 33 subjects with RLS/WED and 24 controls. CSP duration was measured by an automated and three visually-guided methods.

RESULTS

There were significant differences between absolute values of CSP duration according to the method of analysis. However, irrespectively of the method used for CSP assessment, no differences were found between measurements performed in subjects with RLS/WED and subjects from the control group.

CONCLUSIONS

Absolute values of CSP durations analyzed by different methods should not be directly compared, because significantly different results can be obtained from the same data set.

SIGNIFICANCE

The CSP assessed from a hand muscle is unlikely to be a biomarker of primary RLS/WED. Our results highlight the importance of standardizing the definition of CSP onset and offset, as well as of describing in detail the methodology chosen to record and measure CSP duration, in order to enable comparisons between studies.

Cortical involvement in celiac disease before and after long-term gluten-free diet: A Transcranial Magnetic Stimulation study

OBJECTIVE

Transcranial Magnetic Stimulation in de novo patients with Celiac Disease previously revealed an imbalance in the excitability of cortical facilitatory and inhibitory circuits. After a median period of 16 months of gluten-free diet, a global increase of cortical excitability was reported, suggesting a glutamate-mediated compensation for disease progression. We have now evaluated cross-sectionally the changes of cortical excitability to TMS after a much longer gluten-free diet.

METHODS

Twenty patients on adequate gluten-free diet for a mean period of 8.35 years were enrolled and compared with 20 de novo patients and 20 healthy controls. Transcranial Magnetic Stimulation measures, recorded from the first dorsal interosseous muscle of the dominant hand, consisted of: resting motor threshold, cortical silent period, motor evoked potentials, central motor conduction time, mean short-latency intracortical inhibition and intracortical facilitation.

RESULTS

The cortical silent period was shorter in de novo patients, whereas in gluten-free diet participants it was similar to controls. The amplitude of motor responses was significantly smaller in all patients than in controls, regardless of the dietary regimen. Notwithstanding the diet, all patients exhibited a statistically significant decrease of mean short-latency intracortical inhibition and enhancement of intracortical facilitation with respect to controls; more intracortical facilitation in gluten-restricted compared to non-restricted patients was also observed. Neurological examination and celiac disease-related antibodies were negative.

CONCLUSIONS

In this new investigation, the length of dietary regimen was able to modulate the electrocortical changes in celiac disease. Nevertheless, an intracortical synaptic dysfunction, mostly involving excitatory and inhibitory interneurons within the motor cortex, may persist. The clinical significance of subtle neurophysiological changes in celiac disease needs to be further investigated.

cSPider - Evaluation of a Free and Open-Source Automated Tool to Analyze Corticomotor Silent Period

Background

The corticomotor silent period (CSP), as assessed noninvasively by transcranial magnetic stimulation (TMS) in the primary motor cortex, has been found to reflect intracortical inhibitory mechanisms. Analysis of CSP is mostly conducted manually. However, this approach is time-consuming, and comparison of results from different laboratories may be compromised by inter-rater variability in analysis. No open source program for automated analysis is currently available.

Methods/Results

Here, we describe cross-validation with the manual analysis of an in-house written automated tool to assess CSP (cSPider). Results from automated routine were compared with results of the manual evaluation. We found high inter-method reliability between automated and manual analysis (p<0.001), and significantly reduced time for CSP analysis (median = 10.3 sec for automated analysis of 10 CSPs vs. median = 270 sec for manual analysis of 10 CSPs). cSPider can be downloaded free of charge.

Conclusion

cSPider allows automated analysis of CSP in a reliable and time-efficient manner. Use of this open-source tool may help to improve comparison of data from different laboratories.

Transcranial magnetic stimulation to understand pathophysiology and as potential treatment for neurodegenerative diseases

Common neurodegenerative diseases include Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD). Transcranial magnetic stimulation (TMS) is a noninvasive and painless method to stimulate the human brain. Single- and paired-pulse TMS paradigms are powerful ways to study the pathophysiological mechanisms of neurodegenerative diseases. Motor evoked potential studied with single-pulse TMS is increased in PD, AD and ALS, but is decreased in HD. Changes in motor cortical excitability in neurodegenerative diseases may be related to functional deficits in cortical circuits or to compensatory mechanisms. Reduction or even absence of short interval intracortical inhibition induced by paired-pulse TMS is common in neurodegenerative diseases, suggesting that there are functional impairments of inhibitory cortical circuits. Decreased short latency afferent inhibition in AD, PD and HD may be related to the cortical cholinergic deficits in these conditions. Cortical plasticity tested by paired associative stimulation or theta burst stimulation is impaired in PD, AD and HD. Repetitive TMS (rTMS) refers to the application of trains of regularly repeating TMS pulses. High-frequency facilitatory rTMS may improve motor symptoms in PD patients whereas low-frequency inhibitory stimulation is a potential treatment for levodopa induced dyskinesia. rTMS delivered both to the left and right dorsolateral prefrontal cortex improves memory in AD patients. Supplementary motor cortical stimulation in low frequency may be useful for HD patients. However, the effects of treatment with multiple sessions of rTMS for neurodegenerative diseases need to be tested in large, sham-controlled studies in the future before they can be adopted for routine clinical practice.

Distinctive patterns of cortical excitability to transcranial magnetic stimulation in obstructive sleep apnea syndrome, restless legs syndrome, insomnia, and sleep deprivation

Altered responses to transcranial magnetic stimulation (TMS) in obstructive sleep apnea syndrome (OSAS), restless legs syndrome (RLS), insomnia, and sleep-deprived healthy subjects have been reported. We have reviewed the relevant literature in order to identify eventual distinctive electrocortical profiles based on single and paired-pulse TMS, sensorimotor modulation, plasticity-related and repetitive TMS measures. Although obtained from heterogeneous studies, the detected changes might be the result of the different pathophysiological substrates underlying OSAS, RLS, insomnia and sleep deprivation rather than reflect the general effect of non-specific sleep loss and instability. OSAS tends to exhibit an increased motor cortex inhibition, which is reduced in RLS; intracortical excitability seems to be in favor of an "activating" profile in chronic insomnia and in sleep-deprived healthy individuals. Abnormal plasticity-related TMS phenomena have been demonstrated in OSAS and RLS. This review provides a perspective of TMS techniques by further understanding the role of neurotransmission pathways and plastic remodeling of neuronal networks involved in common sleep disorders. TMS might be considered a valuable tool in the assessment of sleep disorders, the evaluation of the effect of therapy and the design of non-pharmacological approaches.

Treatment and physiology in Parkinson's disease and dystonia: using transcranial magnetic stimulation to uncover the mechanisms of action

Transcranial magnetic stimulation (TMS) has served as an important technological breakthrough in the field of the physiology of movement disorders over the last three decades. TMS has grown popular owing to the ease of application as well as its painless and noninvasive character. The technique has provide important insights into understanding the pathophysiology of movement disorders, particularly Parkinson's disease and dystonia. The basic applications have included the study of motor cortex excitability, functioning of excitatory and inhibitory circuits, study of interactions between sensory and motor systems, and the plasticity response of the brain. TMS has also made important contributions to understanding the response to treatments such as dopaminergic medications, botulinum toxin injections, and deep brain stimulation surgery. This review summarizes the knowledge gained to date with TMS in Parkinson's disease and dystonia, and highlights the current challenges in the use of TMS technology.

Modulation of cortical-subcortical networks in Parkinson's disease by applied field effects

Studies suggest that endogenous field effects may play a role in neuronal oscillations and communication. Non-invasive transcranial electrical stimulation with low-intensity currents can also have direct effects on the underlying cortex as well as distant network effects. While Parkinson’s disease (PD) is amenable to invasive neuromodulation in the basal ganglia by deep brain stimulation (DBS), techniques of non-invasive neuromodulation like transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) are being investigated as possible therapies. tDCS and tACS have the potential to influence the abnormal cortical-subcortical network activity that occurs in PD through sub-threshold changes in cortical excitability or through entrainment or disruption of ongoing rhythmic cortical activity. This may allow for the targeting of specific features of the disease involving abnormal oscillatory activity, as well as the enhancement of potential cortical compensation for basal ganglia dysfunction and modulation of cortical plasticity in neurorehabilitation. However, little is currently known about how cortical stimulation will affect subcortical structures, the size of any effect, and the factors of stimulation that will influence these effects.

Magnetic Fields in Noninvasive Brain Stimulation

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d’Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985.

Motor evoked potentials by transcranial magnetic stimulation in healthy elderly people

INTRODUCTION

Transcranial magnetic stimulation (TMS) is a non-invasive, safe, and painless method for evaluating the corticospinal pathway. The population of older adults is growing, along with the prevalence of neurological diseases common to this group. Latency and amplitude of motor evoked potentials (MEPs) vary among healthy subjects and no reference normal values for MEPs in healthy older adults are available.

OBJECTIVE

To create a reference value for MEPs by TMS for healthy older adults.

METHODS

Descriptive study in 36 healthy 70-year-old and older subjects. A 90-mm circular coil Magstim® magnetic stimulator was applied over Cz and Fz. Recording was done in the abductor pollicis brevis and tibialis anterior muscles, at rest and during sustained tonic contraction. Central motor conduction time (CMCT) was derived from MEP latency and peripheral motor conduction time (PMCT). Values were related to age, gender, standing height, and knee height.

RESULTS

Mean age was 73.3 ± 2.4 years (58% female). In the upper extremity, average MEP latency was 23.3 ± 1.9 ms at rest and 19.9 ± 1.9 ms during tonic contraction. In the lower extremity, average MEP latency was 30.6 ± 2.5 ms at rest and 27.2 ± 2.3 ms during tonic contraction. There was a significant correlation between MEP latency and standing height, greater in the lower extremities. Female gender appeared as an independent factor determining lower MEP latency, but not CMCT, in upper and lower extremities.

CONCLUSION

We have provided clinically useful reference values for MEPs by TMS in healthy adults older than 70 years of age. As in the younger population, standing height is important in defining normal MEPs. The difference between genders might be due to the lower height of women.

Combination of rTMS and Treadmill Training Modulates Corticomotor Inhibition and Improves Walking in Parkinson Disease

Background. Repetitive transcranial magnetic stimulation (rTMS) of the brain has been shown to modulate cortical excitability. Combinations of rehabilitation therapies with rTMS might enhance the therapeutic effects. Objective. The purpose of this study was to investigate the effects of high-frequency rTMS followed by treadmill training on cortical inhibition and walking function in individuals with Parkinson disease (PD). Methods. A total of 20 patients with PD were randomized into an experimental group and a control group. Participants received rTMS (experimental group) or sham rTMS (control group) followed by treadmill training (30 minutes) for 12 sessions over 4 weeks. Repetitive TMS was applied at a 5-Hz frequency over the leg area of the motor cortex contralaterally to the more affected side for 6 minutes. Outcomes, including corticomotor inhibition and walking performance, were measured before and after training. Results. The results showed significant time effects on almost all corticomotor and functional variables. There are significant interaction effects between group and time of evaluation on the motor threshold, duration of the cortical silent period, and short interval intracortical inhibition of the contralateral hemisphere relatively to the more affected side as well as on the fast walking speed and timed up and go. Conclusions. The findings suggested that combination of rTMS and treadmill training enhances the effect of treadmill training on modulation of corticomotor inhibition and improvement of walking performance in those with PD.

WITHDRAWN: Mechanisms Underlying Inhibitory and Facilitatory Transcranial Magnetic Stimulation Abnormalities in a Large Sample of Patients with Parkinson's Disease

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A practical guide to diagnostic transcranial magnetic stimulation: report of an IFCN committee

Transcranial magnetic stimulation (TMS) is an established neurophysiological tool to examine the integrity of the fast-conducting corticomotor pathways in a wide range of diseases associated with motor dysfunction. This includes but is not limited to patients with multiple sclerosis, amyotrophic lateral sclerosis, stroke, movement disorders, disorders affecting the spinal cord, facial and other cranial nerves. These guidelines cover practical aspects of TMS in a clinical setting. We first discuss the technical and physiological aspects of TMS that are relevant for the diagnostic use of TMS. We then lay out the general principles that apply to a standardized clinical examination of the fast-conducting corticomotor pathways with single-pulse TMS. This is followed by a detailed description of how to examine corticomotor conduction to the hand, leg, trunk and facial muscles in patients. Additional sections cover safety issues, the triple stimulation technique, and neuropediatric aspects of TMS.

Combining functional imaging with brain stimulation in Parkinson's disease

Brain stimulation techniques such as deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS) constitute promising clinical and research tools to investigate neural mechanisms underlying neurological and psychiatric diseases. They have enormous potential in modifying brain activity and subsequent function. However, it is still a matter of debate how either of these stimulation approaches operates to produce the clinical outcomes observed in patients. The combination of these techniques with functional neuroimaging is contributing significantly to disentangle the mechanisms through which brain stimulation affects neuronal activity and related networks. In the present review we outline the research done to date on the effects of DBS and TMS on motor, cognition and behaviour in Parkinson's disease (PD) with particular emphasis on neuroimaging.

Silent period-dentate, edentulous, and patients with craniomandibular dysfunction

BACKGROUND

The record of electrical activity of elevator muscles in mandible is important for the evaluation of muscular potency and diagnosis of neuromuscular pathologies, which allows prevention and treatment. The aim of this study was to define silent periods (SPs) and the importance in dentistry and compare the SPs in masticatory muscles of dentate and edentulous patients wearing prosthesis considering the presence or absence of craniomandibular dysfunction (CMD).

MATERIALS AND METHODS

Literature review in PubMed database.

DISCUSSION

Silent periods are isolated pulses of transcranial magnetic stimulation in the primary motor cortex during voluntary muscular activity that generates an interruption of muscular activity for hundredths of milliseconds. The SP duration depends on the patient (dentate or edentulous), type of stimulus, and presence of CMD.

CONCLUSIONS

The SP is higher in complete edentulous patients and in individuals with occlusal disharmonies than in dentate patients without CMDs. The treatment of CMDs through occlusal therapy decreases SP duration.

Role of Neurostimulation and Neuroplasticity in the Rehabilitation of Dysphagia After Stroke

Swallowing problems are common after brain injury, and can affect as many as 50% of patients in the period immediately after stroke. In some cases this can lead to serious morbidity, in particular malnutrition and pulmonary aspiration. Despite this, swallowing therapies remain controversial, with limited evidence base and little in the way of objective scientific criteria. Moreover, swallowing can recover in some patients to a safe level within weeks, making it an interesting model for understanding brain recovery and cortical plasticity. A better understanding of these adaptive processes as seen in spontaneous recovery therefore may help in developing therapeutic interventions that can drive plasticity and so encourage the recovery process. In this article, I will examine present knowledge about the recovery mechanisms for swallowing after brain injury, particularly from investigations with Transcranial Magnetic Stimulation, and explore what aspects are important for compensating for recovery after damage. In addition, I will describe novel approaches to swallowing therapy, based on objective neurophysiological models that may be useful in speeding up the process of recovery and encouraging cortical plasticity that may form the basis for future clinical trials of dysphagia after brain injury.

Substantia nigra echomorphology and motor cortex excitability

The aim of our study was to investigate the relation between substantia nigra (SN) echomorphology and indices of motor cortex excitability. Nigral hyperechogenicity in healthy individuals is thought to represent an SN abnormality or predisposition to Parkinson's disease (PD) and its prevalence is greater in the very old. Our study involved 20 old healthy subjects (aged 72-84 years) known to have normal (n=10) or abnormal (n=10) SN echomorphology. All were in good health with no overt neurological signs. SN morphology was assessed with transcranial sonography through the pre-auricular bone window. Motor cortical excitability and intracortical inhibition were assessed with transcranial magnetic stimulation (TMS) over the first dorsal interosseus motor area. Single stimuli were delivered during relaxation and voluntary contraction and paired stimuli were delivered during relaxation. Each cortical hemisphere was analysed separately. The response to single-pulse TMS (in motor cortex ipsilateral to the target SN) did not differ between groups. However, a significant difference between groups was observed in the paired pulse paradigm (conditioning stimulus intensity: 70% resting motor threshold; interstimulus interval: 2 ms). The conditioned motor evoked potential amplitude was significantly larger ipsilateral to the hyperechogenic SN than in controls (P=0.014). Thus, healthy subjects with SN hyperechogenicity exhibit significantly less intracortical inhibition within the motor cortex than subjects with normal echomorphology. Decreased intracortical inhibition is also observed in PD patients. This study provides further evidence that SN hyperechogenicity in healthy individuals is associated with changes characteristic of PD supporting a role for this feature as a vulnerability marker or state marker for subtle nigral dopaminergic dysfunction.

Low frequency (0.5Hz) rTMS over the right (non-dominant) motor cortex does not affect ipsilateral hand performance in healthy humans

Reduction of excitability of the dominant primary motor cortex (M1) improves ipsilateral hand function in healthy subjects. In analogy, inhibition of non-dominant M1 should also improve ipsilateral performance. In order to investigate this hypothesis, we have used slow repetitive transcranial magnetic stimulation (rTMS) and the Purdue Pegboard test. Twenty-eight volunteers underwent 10 minutes of either 0.5Hz rTMS over right M1 or sham rTMS (coil perpendicular to scalp). The motor task was performed before, immediately after, and 20 minutes after rTMS. In both groups, motor performance improved significantly throughout the sessions. rTMS inhibition of the non-dominant M1 had no significant influence over ipsilateral or contralateral manual dexterity, even though the results were limited by unequal performance between groups at baseline. This is in contrast to an improvement in left hand function previously described following slow rTMS over left M1, and suggests a less prominent physiological transcallosal inhibition from right to left M1.

Brain function decline in healthy retired athletes who sustained their last sports concussion in early adulthood

Recent studies have shown that the detrimental effects of sports concussions on cognitive and motor function may persist up to a few years post-injury. The present study sought to investigate the effects of having sustained a sports concussion more than 30 years prior to testing on cognitive and motor functions. Nineteen healthy former athletes, in late adulthood (mean age = 60.79; SD = 5.16), who sustained their last sport-related concussion in early adulthood (mean age = 26.05; SD = 9.21) were compared with 21 healthy former athletes with no history of concussion (mean age = 58.89; SD = 9.07). Neuropsychological tests sensitive to age-related changes in cognition were administered. An auditory oddball paradigm was used to evoke P3a and P3b brain responses. Four TMS paradigms were employed to assess motor cortex excitability: (i) resting motor threshold; (ii) paired-pulse intracortical inhibition and intracortical facilitation; (iii) input/output curve and (iv) cortical silent period (CSP). A rapid alternating movement task was also used to characterize motor system dysfunctions. Relative to controls, former athletes with a history of concussion had: (i) lower performance on neuropsychological tests of episodic memory and response inhibition; (ii) significantly delayed and attenuated P3a/P3b components; (iii) significantly prolonged CSP and (iv) significantly reduced movement velocity (bradykinesia). The finding that the P3, the CSP as well as neuropsychological and motor indices were altered more than three decades post-concussion provides evidence for the chronicity of cognitive and motor system changes consecutive to sports concussion.

Muscles in "concert": study of primary motor cortex upper limb functional topography

Background

Previous studies with Transcranial Magnetic Stimulation (TMS) have focused on the cortical representation of limited group of muscles. No attempts have been carried out so far to get simultaneous recordings from hand, forearm and arm with TMS in order to disentangle a ‘functional’ map providing information on the rules orchestrating muscle coupling and overlap. The aim of the present study is to disentangle functional associations between 12 upper limb muscles using two measures: cortical overlapping and cortical covariation of each pair of muscles. Interhemispheric differences and the influence of posture were evaluated as well.

Methodology/Principal Findings

TMS mapping studies of 12 muscles belonging to hand, forearm and arm were performed. Findings demonstrate significant differences between the 66 pairs of muscles in terms of cortical overlapping: extremely high for hand-forearm muscles and very low for arm vs hand/forearm muscles. When right and left hemispheres were compared, overlapping between all possible pairs of muscles in the left hemisphere (62.5%) was significantly higher than in the right one (53.5% ).

The arm/hand posture influenced both measures of cortical association, the effect of Position being significant [p = .021] on overlapping, resulting in 59.5% with prone vs 53.2% with supine hand, but only for pairs of muscles belonging to hand and forearm, while no changes occurred in the overlapping of proximal muscles with those of more distal districts.

Conclusions/Significance

Larger overlapping in the left hemisphere could be related to its lifetime higher training of all twelve muscles studied with respect to the right hemisphere, resulting in larger intra-cortical connectivity within primary motor cortex. Altogether, findings with prone hand might be ascribed to mechanisms facilitating coupling of muscles for object grasping and lifting -with more proximal involvement for joint stabilization- compared to supine hand facilitating actions like catching. TMS multiple-muscle mapping studies permit a better understanding of motor control and ‘plastic’ reorganization of motor system.

Transcranial magnetic stimulation reduces masseter motoneuron pool excitability throughout the cortical silent period

OBJECTIVE

To evaluate the time-course of changes in masseter motoneuron pool excitability following transcranial magnetic stimulation of motor cortex, and relate this to the duration of the masseter cortical silent period (CSP).

METHODS

Surface EMG was recorded bilaterally from masseter and digastric muscles in 13 subjects. Focal TMS was applied at 1.3x active motor threshold (AMT) to motor cortex of one hemisphere to elicit a muscle evoked potential (MEP) and silent period bilaterally in masseter as subjects maintained an isometric bite at approximately 10% maximum. With jaw muscles relaxed, a servo-controlled stretcher evoked a stretch reflex in masseter which was conditioned by TMS (1.3x AMT) at 14 different conditioning-testing intervals. There were 20 trials at each interval, in random order. TMS evoked no MEP in resting masseter, but often produced a small MEP in digastric.

RESULTS

Mean (+/-SE) masseter CSP was 67+/-3ms. The masseter stretch reflex was facilitated when stretch preceded TMS by 8 and 10ms, which we attribute to spatial summation of corticobulbar and Ia-afferent excitatory inputs to masseter. Masseter stretch reflex amplitude was reduced when TMS was given up to 75ms before stretch, and for up to 2ms afterwards.

CONCLUSIONS

We conclude that descending corticobulbar activity evoked by TMS acts bilaterally on brainstem interneurons that either inhibit masseter motoneurons or increase pre-synaptic inhibition of Ia-afferent terminals for up to 75ms after TMS. The reduction of masseter motoneuron pool excitability following TMS has a similar time-course to the CSP.

SIGNIFICANCE

In contrast to the situation for spinal and facial (CN VII) muscles, the masseter CSP appears to have no component that can be attributed exclusively to cortical mechanisms. Abnormalities in the masseter cortical silent period observed in neurological conditions may be due to pathophysiological changes at cortical and/or sub-cortical levels.