Attention-related changes in short-term cortical plasticity help to explain fatigue in multiple sclerosis

Impairments of attention in RRMS patients: the role of disease duration

INTRODUCTION

The extent to which different types of attention are affected in RRMS based on disease duration has not been extensively analyzed. Therefore, the aim of this study was to determine whether MS patients differ compared to healthy individuals in a homogeneous sample of RRMS patients in terms of attention types and from which year of MS attention deficit starts. Another aim of the study was to examine the effect of MS duration and stimulus onset asynchrony on dual task performance.

METHODS

The sample consisted of RRMS patients (n = 53) and healthy participants (n = 30) between the ages of 20-49, who were at least primary school graduates. Healthy participants in the comparison group were reached by snowball sampling technique. Stroop Test, Cancellation Test, Paced Auditory Serial Addition Test, Coding Test, WMS-R Digit Span and Visual Memory Span subtests were administered to assess attention. Divided attention performance was assessed with a dual task developed based on psychological refractory period paradigm.

RESULTS

The results show that there is a significant difference between RRMS patients and healthy participants in terms of different types of attention (p < 0.05). Focused, sustained and divided attention of RRMS patients and the ability to resist interference showed a significant decline from the 7th year of the disease (p < 0.05); no significant difference was found between healthy participants and patients with 1-6 years of RRMS.

CONCLUSIONS

Although the results of the study are consistent with the literature which show that attention deficit develops in MS, it is important in terms of showing that attention deficit changes depending on the duration of the disease. Focused attention, sustained attention, interference resistance and divided attention performance of RRMS patients showed a significant decline after the 7th year of the disease.

Cortical plasticity in AQP4-positive NMOSD: a transcranial magnetic stimulation study

Aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD) is an autoimmune disease characterized by suboptimal recovery from attacks and long-term disability. Experimental data suggest that AQP4 antibodies can disrupt neuroplasticity, a fundamental driver of brain recovery. A well-established method to assess brain LTP is through intermittent theta-burst stimulation (iTBS). This study aimed to explore neuroplasticity in AQP4-NMOSD patients by examining long-term potentiation (LTP) through iTBS. We conducted a proof-of-principle study including 8 patients with AQP4-NMOSD, 8 patients with multiple sclerosis (MS), and 8 healthy controls (HC) in which iTBS was administered to induce LTP-like effects. iTBS-induced LTP exhibited significant differences among the 3 groups (p: 0.006). Notably, AQP4-NMOSD patients demonstrated impaired plasticity compared to both HC (p = 0.01) and pwMS (p = 0.02). This pilot study provides the first in vivo evidence supporting impaired neuroplasticity in AQP4-NMOSD patients. Impaired cortical plasticity may hinder recovery following attacks suggesting a need for targeted rehabilitation strategies.

Cerebellar Non-Invasive Brain Stimulation: A Frontier in Chronic Pain Therapy

Chronic pain poses a widespread and distressing challenge; it can be resistant to conventional therapies, often having significant side effects. Non-invasive brain stimulation (NIBS) techniques offer promising avenues for the safe and swift modulation of brain excitability. NIBS approaches for chronic pain management targeting the primary motor area have yielded variable outcomes. Recently, the cerebellum has emerged as a pivotal hub in human pain processing; however, the clinical application of cerebellar NIBS in chronic pain treatment remains limited. This review delineates the cerebellum's role in pain modulation, recent advancements in NIBS for cerebellar activity modulation, and novel biomarkers for assessing cerebellar function in humans. Despite notable progress in NIBS techniques and cerebellar activity assessment, studies targeting cerebellar NIBS for chronic pain treatment are limited in number. Nevertheless, positive outcomes in pain alleviation have been reported with cerebellar anodal transcranial direct current stimulation. Our review underscores the potential for further integration between cerebellar NIBS and non-invasive assessments of cerebellar function to advance chronic pain treatment strategies.

Quantifying Fatigue Using Electrophysiological Techniques and Non-invasive Brain Stimulation in People With Multiple Sclerosis- A Review and Discussion

Objective: The purpose of this literature review article is to provide a synthesis of recent research focused on the use of 3 techniques to evaluate MS-related fatigue: electroencephalography [EEG], transcranial direct-current stimulation (tDSC), and transcranial- magnetic stimulation (TMS). Method: We performed a literature search in the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCOhost), MEDLINE (OVID), APA PsycInfo (OVID), Scopus (Elsevier), and Web of Science (Clarivate) databases, limited to 2015 and after. Results: Our review revealed that fatigue in MS patients can be quantified and predicted using electrophysiological techniques. Such techniques, which yield objective data, are historically assessed in relation to subjective data, or perceived fatigue. We identified studies using EEG, TMS, and/or tDCS to study fatigue in people with MS. In total, 220 records were identified with 19 studies meeting inclusion criteria. Quality appraisal revealed that the level of evidence was generally graded "good". Conclusions: Despite the heterogenous nature of reviewed the studies and selected the varied self-report fatigue measures, our literature synthesis suggests promise for the use of EEG, TMS, and/or tDCS approaches in more accurately assessing fatigue in people with MS. Further research is needed in this arena.

The Cortical Silent Period and Its Association with Fatigue in Multiple Sclerosis: The Need for Standardized Data Collection

The cortical silent period (CSP), assessed with transcranial magnetic stimulation (TMS), provides insights into motor cortex excitability. Alterations in the CSP have been observed in multiple sclerosis (MS), although a comparison of the sometimes contradictory results is difficult due to methodological differences. The aim of this study is to provide a more profound neurophysiological understanding of fatigue's pathophysiology and its relationship to the CSP. Twenty-three patients with MS, along with a matched control group, underwent comprehensive CSP measurements at four intensities (125, 150, 175, and 200% resting motor threshold), while their fatigue levels were assessed using the Fatigue Scale for Motor and Cognitive Functions (FSMC) and its motor and cognitive subscore. MS patients exhibited a significantly increased CSP duration compared to controls (p = 0.02), but CSP duration was not associated with the total FSMC, or the motor or cognitive subscore. Our data suggest a systematic difference in MS patients compared to healthy controls in the CSP but no association with fatigue when measured with the FSMC. Based on these results, and considering the heterogeneous literature in the field, our study highlights the need for a more standardized approach to neurophysiological data collection and validation. This standardization is crucial for exploring the link between TMS and clinical impairments in diseases like MS.

Timing to be precise? An overview of spike timing-dependent plasticity, brain rhythmicity, and glial cells interplay within neuronal circuits

In the mammalian brain information processing and storage rely on the complex coding and decoding events performed by neuronal networks. These actions are based on the computational ability of neurons and their functional engagement in neuronal assemblies where precise timing of action potential firing is crucial. Neuronal circuits manage a myriad of spatially and temporally overlapping inputs to compute specific outputs that are proposed to underly memory traces formation, sensory perception, and cognitive behaviors. Spike-timing-dependent plasticity (STDP) and electrical brain rhythms are suggested to underlie such functions while the physiological evidence of assembly structures and mechanisms driving both processes continues to be scarce. Here, we review foundational and current evidence on timing precision and cooperative neuronal electrical activity driving STDP and brain rhythms, their interactions, and the emerging role of glial cells in such processes. We also provide an overview of their cognitive correlates and discuss current limitations and controversies, future perspectives on experimental approaches, and their application in humans.

Neural bases of motor fatigue in multiple sclerosis: A multimodal approach using neuromuscular assessment and TMS-EEG

Motor fatigue is one of the most common symptoms in multiple sclerosis (MS) patients. Previous studies suggested that increased motor fatigue in MS may arise at the central nervous system level. However, the mechanisms underlying central motor fatigue in MS are still unclear. This paper investigated whether central motor fatigue in MS reflects impaired corticospinal transmission or suboptimal primary motor cortex (M1) output (supraspinal fatigue). Furthermore, we sought to identify whether central motor fatigue is associated with abnormal M1 excitability and connectivity within the sensorimotor network. Twenty-two patients affected by relapsing-remitting MS and 15 healthy controls (HCs) performed repeated blocks of contraction at different percentages of maximal voluntary contraction with the right first dorsal interosseus muscle until exhaustion. Peripheral, central, and supraspinal components of motor fatigue were quantified by a neuromuscular assessment based on the superimposed twitch evoked by peripheral nerve and transcranial magnetic stimulation (TMS). Corticospinal transmission, excitability and inhibition during the task were tested by measurement of motor evoked potential (MEP) latency, amplitude, and cortical silent period (CSP). M1 excitability and connectivity was measured by TMS-evoked electroencephalography (EEG) potentials (TEPs) elicited by M1 stimulation before and after the task. Patients completed fewer blocks of contraction and showed higher values of central and supraspinal fatigue than HCs. We found no MEP or CSP differences between MS patients and HCs. Patients showed a post-fatigue increase in TEPs propagation from M1 to the rest of the cortex and in source-reconstructed activity within the sensorimotor network, in contrast to the reduction observed in HCs. Post-fatigue increase in source-reconstructed TEPs correlated with supraspinal fatigue values. To conclude, MS-related motor fatigue is caused by central mechanisms related explicitly to suboptimal M1 output rather than impaired corticospinal transmission. Furthermore, by adopting a TMS-EEG approach, we proved that suboptimal M1 output in MS patients is associated with abnormal task-related modulation of M1 connectivity within the sensorimotor network. Our findings shed new light on the central mechanisms of motor fatigue in MS by highlighting a possible role of abnormal sensorimotor network dynamics. These novel results may point to new therapeutical targets for fatigue in MS.

The borderland of multiple sclerosis and functional neurological disorder: A call for clinical research and vigilance

BACKGROUND AND PURPOSE

Functional neurological disorders (FNDs) have attracted much attention from the neurological medical community over the last decades as new developments in neurosciences have reduced stigma around these by showing brain network dysfunctions. An overlap with other neurological conditions such as multiple sclerosis (MS) is well known by clinicians but there is a lack of clinical and fundamental research in this field to better define diagnosis and therapeutic decisions, as well as a lack of deep understanding of the underlying pathophysiology.

AIM

We aimed to provide a critical commentary on the state of knowledge about the borderland between FNDs and MS.

METHODS

We based our commentary on a joint point of view between an FND specialist and an MS expert.

RESULTS

A brief review of the previous literature and relevant new studies covering the overlap between FNDs and MS is presented, along with suggestions for future research directions.

CONCLUSION

There are clear diagnostic criteria for both FNDs and MS and a strict application of these will help better diagnosis and prevent unnecessary treatment escalation in MS or absence of referral to multimodal therapy in FND. Better teaching of younger neurologists is needed as well as prospective research focusing on pathophysiology.

Fatigue in Multiple Sclerosis: A Review of the Exploratory and Therapeutic Potential of Non-Invasive Brain Stimulation

Fatigue is the most commonly reported symptom in patients with multiple sclerosis (MS). It is a worrisome, frequent, and debilitating manifestation that could occur at any time during the course of MS and in all its subtypes. It could engender professional, familial, and socioeconomic consequences and could severely compromise the patients' quality of life. Clinically, the symptom exhibits motor, cognitive, and psychosocial facets. It is also important to differentiate between perceived or subjective self-reported fatigue and fatigability which is an objective measure of decrement in the performance of cognitive or motor tasks. The pathophysiology of MS fatigue is complex, and its management remains a challenge, despite the existing body of literature on this matter. Hence, unraveling its neural mechanisms and developing treatment options that target the latter might constitute a promising field to explore. A PubMed/Medline/Scopus search was conducted to perform this review which aims (a) to reappraise the available electrophysiological studies that explored fatigue in patients with MS with a particular focus on corticospinal excitability measures obtained using transcranial magnetic stimulation and (b) to assess the potential utility of employing neuromodulation (i.e., non-invasive brain stimulation techniques) in this context. A special focus will be put on the role of transcranial direct current stimulation and transcranial magnetic stimulation. We have provided some suggestions that will help overcome the current limitations in upcoming research.

The degree of cortical plasticity correlates with cognitive performance in patients with Multiple Sclerosis

BACKGROUND

Cortical reorganization and plasticity may compensate for structural damage in Multiple Sclerosis (MS). It is important to establish sensitive methods to measure these compensatory mechanisms, as they may be of prognostic value.

OBJECTIVE

To investigate the association between the degree of cortical plasticity and cognitive performance and to compare plasticity between MS patients and healthy controls (HCs).

METHODS

The amplitudes of the motor evoked potential (MEP) pre and post quadripulse stimulation (QPS) applied over the contralateral motor cortex served as measure of the degree of cortical plasticity in 63 patients with relapsing-remitting MS (RRMS) and 55 matched HCs. The main outcomes were the correlation coefficients between the difference of MEP amplitudes post and pre QPS and the Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test-Revised (BVMT-R), and the QPS^xgroup interaction in a mixed model predicting the MEP amplitude.

RESULTS

SDMT and BVMT-R correlated significantly with QPS-induced cortical plasticity in RRMS patients. Plasticity was significantly reduced in patients with cognitive impairment compared to patients with preserved cognitive function and the degree of plasticity differentiated between both patient groups. Interestingly, the overall RRMS patient cohort did not show reduced plasticity compared to HCs.

CONCLUSIONS

We provide first evidence that QPS-induced plasticity may inform about the global synaptic plasticity in RRMS which correlates with cognitive performance as well as clinical disability. Larger longitudinal studies on patients with MS are needed to investigate the relevance and prognostic value of this measure for disease progression and recovery.

The Signature of Primary Writing Tremor Is Dystonic

BACKGROUND

It has been debated for decades whether primary writing tremor is a form of dystonic tremor, a variant of essential tremor, or a separate entity. We wished to test the hypothesis that primary writing tremor and dystonia share a common pathophysiology.

OBJECTIVES

The objective of the present study was to investigate the pathophysiological hallmarks of dystonia in patients affected by primary writing tremor.

METHODS

Ten patients with idiopathic dystonic tremor syndrome, 7 with primary writing tremor, 10 with essential tremor, and 10 healthy subjects were recruited. They underwent eyeblink classic conditioning, blink recovery cycle, and transcranial magnetic stimulation assessment, including motor-evoked potentials and short- and long-interval intracortical inhibition at baseline. Transcranial magnetic stimulation measures were also recorded after paired-associative plasticity protocol.

RESULTS

Primary writing tremor and dystonic tremor syndrome had a similar pattern of electrophysiological abnormalities, consisting of reduced eyeblink classic conditioning learning, reduced blink recovery cycle inhibition, and a lack of effect of paired-associative plasticity on long-interval intracortical inhibition. The latter 2 differ from those obtained in essential tremor and healthy subjects. Although not significant, slightly reduced short-interval intracortical inhibition and a larger effect of paired-associative plasticity in primary writing tremor and dystonic tremor syndrome, compared with essential tremor and healthy subjects, was observed.

CONCLUSIONS

Our initial hypothesis of a common pathophysiology between dystonia and primary writing tremor has been confirmed. Primary writing tremor might be considered a form of dystonic tremor. © 2021 International Parkinson and Movement Disorder Society.

Motor disability in patients with multiple sclerosis: transcranial magnetic stimulation study

Background

Transcranial magnetic stimulation (TMS) is a non-invasive procedure used in a small targeted region of the brain via electromagnetic induction and used diagnostically to measure the connection between the central nervous system (CNS) and skeletal muscle to evaluate the damage that occurs in MS.

Objectives

The study aims to investigate whether single-pulse TMS measures differ between patients with MS and healthy controls and to consider if these measures are associated with clinical disability.

Patients and methods

Single-pulse TMS was performed in 26 patients with MS who hand an Expanded Disability Status Scale (EDSS) score between 0 and 9.5 and in 26 normal subjects. Different TMS parameters from upper and lower limbs were investigated.

Results

TMS disclosed no difference in all MEP parameters between the right and left side of the upper and lower limbs in patients with MS and controls. In all patients, TMS parameters were different from the control group. Upper limb central motor conduction time (CMCT) was prolonged in MS patients with pyramidal signs. Upper and lower limb CMCT and CMCT-f wave (CMCT-f) were prolonged in patients with ataxia. Moreover, CMCT and CMCT-f were prolonged in MS patients with EDSS of 5–9.5 as compared to those with a score of 0–4.5. EDSS correlated with upper and lower limb cortical latency (CL), CMCT, and CMCT-f whereas motor evoked potential (MEP) amplitude not.

Conclusion

TMS yields objective data to evaluate clinical disability and its parameters correlated well with EDSS.

Blunted sweating does not alter the rise in core temperature in people with multiple sclerosis exercising in the heat

The purpose of this study is to determine whether thermoregulatory capacity is altered by multiple sclerosis (MS) during exercise in the heat. Sixteen MS participants (EDSS: 2.9 ± 0.9; 47 ± 8 yr; 77.6 ± 14.0 kg) and 14 healthy control (CON) participants (43 ± 11 yr; 78.6 ± 17.0 kg) cycled at a heat production of 4 W·kg^-1 for 60 min at 30°C, 30% relative humidity (RH) (Warm). A subset of eight MS (EDSS: 2.6 ± 0.5; 44 ± 8 yr; 82.3 ± 18.2 kg) and 8 CON (44 ± 12 yr; 81.2 ± 21.1 kg) also exercised at 35°C, 30% RH (Hot). Rectal temperature (T_re), mean skin (T_sk) temperature, and local sweat rate (LSR) on the upper back (LSR_back) and forearm (LSR_arm) were measured. All CON, and only 9 of 16 and 7 of 8 MS participants completed 60 min of exercise in Warm and Hot trials, respectively. All MS participants who were unable to complete exercise stopped with a ΔT_re between 0.2 and 0.5°C. The time to reach a ΔT_re of 0.2°C was similar (MS: 28 ± 15 min, CON: 32 ± 18 min; P = 0.51). For MS participants, completing 60-min of exercise in Warm, ΔT_re (P = 0.13), ΔT_sk (P = 0.45), LSR_back (P = 0.69), and LSR_arm (P = 0.54) was similar to CON, but ΔT_b (body temperature) (MS: 0.16 ± 0.13°C, CON: 0.07 ± 0.06°C; P = 0.02) and onset time (MS: 16 ± 10 min, CON: 8 ± 5 min; P = 0.02) for sweating were greater in MS. Similarly, in Hot, ΔT_re (P = 0.52), ΔT_sk (P = 0.06), LSR_back (P = 0.59), and LSR_arm (P = 0.08) were similar, but ΔT_b (MS: 0.19 ± 0.16°C, CON: 0.06 ± 0.04°C; P = 0.04) and onset time (MS: 13 ± 7 min, CON: 6 ± 3 min; P = 0.02) for sweating were greater in MS. Even at 35°C, a delayed sweating onset did not alter heat loss to sufficiently affect exercise-induced rises in core temperature. Heat intolerance with MS does not seem attributable to thermoregulatory impairments.

On the Use of TMS to Investigate the Pathophysiology of Neurodegenerative Diseases

Neurodegenerative diseases are a collection of disorders that result in the progressive degeneration and death of neurons. They are clinically heterogenous and can present as deficits in movement, cognition, executive function, memory, visuospatial awareness and language. Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation tool that allows for the assessment of cortical function in vivo. We review how TMS has been used for the investigation of three neurodegenerative diseases that differ in their neuroanatomical axes: (1) Motor cortex-corticospinal tract (motor neuron diseases), (2) Non-motor cortical areas (dementias), and (3) Subcortical structures (parkinsonisms). We also make four recommendations that we hope will benefit the use of TMS in neurodegenerative diseases. Firstly, TMS has traditionally been limited by the lack of an objective output and so has been confined to stimulation of the motor cortex; this limitation can be overcome by the use of concurrent neuroimaging methods such as EEG. Given that neurodegenerative diseases progress over time, TMS measures should aim to track longitudinal changes, especially when the aim of the study is to look at disease progression and symptomatology. The lack of gold-standard diagnostic confirmation undermines the validity of findings in clinical populations. Consequently, diagnostic certainty should be maximized through a variety of methods including multiple, independent clinical assessments, imaging and fluids biomarkers, and post-mortem pathological confirmation where possible. There is great interest in understanding the mechanisms by which symptoms arise in neurodegenerative disorders. However, TMS assessments in patients are usually carried out during resting conditions, when the brain network engaged during these symptoms is not expressed. Rather, a context-appropriate form of TMS would be more suitable in probing the physiology driving clinical symptoms. In all, we hope that the recommendations made here will help to further understand the pathophysiology of neurodegenerative diseases.

Early diagnosis of secondary progressive multiple sclerosis: focus on fluid and neurophysiological biomarkers

BACKGROUND AND AIMS

Most patients with multiple sclerosis presenting with a relapsing-remitting disease course at diagnosis transition to secondary progressive multiple sclerosis (SPMS) 1-2 decades after onset. SPMS is characterized by predominant neurodegeneration and atrophy. These pathogenic hallmarks result in unsatisfactory treatment response in SPMS patients. Therefore, early diagnosis of SPMS is necessary for prompt treatment decisions. The aim of this review was to assess neurophysiological and fluid biomarkers that have the potential to monitor disease progression and support early SPMS diagnosis.

METHODS

We performed a systematic review of studies that analyzed the role of neurophysiological techniques and fluid biomarkers in supporting SPMS diagnosis using the preferred reporting items for systematic reviews and meta-analyses statement.

RESULTS

From our initial search, we selected 24 relevant articles on neurophysiological biomarkers and 55 articles on fluid biomarkers.

CONCLUSION

To date, no neurophysiological or fluid biomarker is sufficiently validated to support the early diagnosis of SPMS. Neurophysiological measurements, including short interval intracortical inhibition and somatosensory temporal discrimination threshold, and the neurofilament light chain fluid biomarker seem to be the most promising. Cross-sectional studies on an adequate number of patients followed by longitudinal studies are needed to confirm the diagnostic and prognostic value of these biomarkers. A combination of neurophysiological and fluid biomarkers may be more sensitive in detecting SPMS conversion.

The Potential Role of Neurophysiology in the Management of Multiple Sclerosis-Related Fatigue

Fatigue is a very common symptom among people with multiple sclerosis (MS), but its management in clinical practice is limited by the lack of clear evidence about the pathogenic mechanisms, objective tools for diagnosis, and effective pharmacological treatments. In this scenario, neurophysiology could play a decisive role, thanks to its ability to provide objective measures and to explore the peripheral and the central structures of the nervous system. We hereby review and discuss current evidence about the potential role of neurophysiology in the management of MS-related fatigue. In the first part, we describe the use of neurophysiological techniques for exploring the pathogenic mechanisms of fatigue. In the second part, we review the potential application of neurophysiology for monitoring the response to pharmacological therapies. Finally, we show data about the therapeutic implications of neurophysiological techniques based on non-invasive brain stimulation.

Transcranial Magnetic Stimulation as a Potential Biomarker in Multiple Sclerosis: A Systematic Review with Recommendations for Future Research

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system. Disease progression is variable and unpredictable, warranting the development of biomarkers of disease status. Transcranial magnetic stimulation (TMS) is a noninvasive method used to study the human motor system, which has shown potential in MS research. However, few reviews have summarized the use of TMS combined with clinical measures of MS and no work has comprehensively assessed study quality. This review explored the viability of TMS as a biomarker in studies of MS examining disease severity, cognitive impairment, motor impairment, or fatigue. Methodological quality and risk of bias were evaluated in studies meeting selection criteria. After screening 1603 records, 30 were included for review. All studies showed high risk of bias, attributed largely to issues surrounding sample size justification, experimenter blinding, and failure to account for key potential confounding variables. Central motor conduction time and motor-evoked potentials were the most commonly used TMS techniques and showed relationships with disease severity, motor impairment, and fatigue. Short-latency afferent inhibition was the only outcome related to cognitive impairment. Although there is insufficient evidence for TMS in clinical assessments of MS, this review serves as a template to inform future research.

Deep grey matter involvement and altered sensory gating in multiple sclerosis

BACKGROUND

Somatosensory temporal discrimination threshold (STDT) is altered in multiple sclerosis (MS). In healthy subjects (HS), voluntary movement modulates the STDT through mechanisms of subcortical sensory gating.

OBJECTIVE

With neurophysiological and magnetic resonance imaging (MRI) techniques, we investigated sensory gating and sensorimotor integration in MS.

METHODS

We recruited 38 relapsing-remitting multiple sclerosis (RR-MS) patients with no-to-mild disability and 33 HS. We tested STDT at rest and during index finger abductions and recorded the movement kinematics. Participants underwent a 3T MRI protocol.

RESULTS

Patients exhibited higher STDT values and performed slower finger movements than HS. During voluntary movement, STDT values increased in both groups, albeit to a lesser extent in patients, while the mean angular velocity of finger movements decreased in patients alone. Patients had a smaller volume of the thalamus, pallidum and caudate nucleus, and displayed higher mean diffusivity in the putamen, pallidum and thalamus. STDT correlated with thalamic volume while mean angular velocity correlated with putaminal volume. Changes in mean angular velocity during sensorimotor integration inversely correlated with mean diffusivity in the thalamus and pallidum. Changes in STDT and velocity were associated with fatigue score.

CONCLUSION

Altered STDT and sensorimotor integration are related to structural damage in the thalamus and basal ganglia in MS and likely to affect motor performance.

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.

Abnormal Resting-State Neural Activity and Connectivity of Fatigue in Parkinson's Disease

AIMS

Fatigue is a common burdensome problem in patients with Parkinson's disease (PD), but its pathophysiological mechanisms are poorly understood. This study aimed at investigating the neural substrates of fatigue in patients with PD.

METHODS

A total of 17 PD patients with fatigue, 32 PD patients without fatigue, and 25 matched healthy controls were recruited. The 9-item fatigue severity scale (FSS) was used for fatigue screening and severity rating. Resting-state functional magnetic resonance imaging (RS-fMRI) data were obtained from all subjects. Amplitude of low-frequency fluctuations (ALFF) was used to measure regional brain activity, and functional connectivity (FC) was applied to investigate functional connectivity at a network level.

RESULTS

PD-related fatigue was associated with ALFF changes in right middle frontal gyrus within the attention network and in left insula as well as right midcingulate cortex within the salience network. FC analysis revealed that above three regions showing ALFF differences had altered functional connectivity mainly in the temporal, parietal, and motor cortices.

CONCLUSION

Our findings do reveal that abnormal regional brain activity within attention and salience network and altered FC of above abnormal regions are involved in neural mechanism of fatigue in patients with PD.