A multimodal approach using TMS and EEG reveals neurophysiological changes in Parkinson's disease

Tms-evoked potentials: Neurophysiological biomarkers for diagnosis and prediction of response to ventriculoperitoneal shunt in normal pressure hydrocephalus

BACKGROUND

Current practice for normal pressure hydrocephalus (NPH) relies upon clinical presentation, imaging and invasive clinical procedures for indication of treatment with ventriculoperitoneal shunt (VPS). We aimed to assess the utility of a TMS-evoked potential (TEP)-based evaluation, for prediction of response to VPS in NPH, as an alternative for the cerebrospinal fluid tap test (CTT).

METHODS

37 "possible iNPH" patients and 16 age-matched healthy controls (HC) were included. All subjects performed Delphi (TMS-EEG and automated analysis of TEP), in response to primary motor cortex (M1) and dorsolateral prefrontal (DLPFC) stimulations. Sixteen patients underwent VPS and response was evaluated with change in modified Rankin Scale (MRS), clinical global impression of change (CGIC) regarding gait and the change on a repeated 3-meter timed up and Go (TUG) after 3 months.

RESULTS

TEP Delphi-NPH index was most successful in discrimination of iNPH responders to VPS (ROC-AUC of 0.91, p = 0.006) compared to other imaging (AUCEI = 0.58, p = 0.58; AUCTH = 0.65, p = 0.32; AUCCA = 0.83, p = 0.03) and TUG tests (AUCTUG = 0.63, p = 0.42; AUCCTT = 0.65, p = 0.35). The TEP M1 P60 and P180 latencies were earlier in responders compared to controls (pM1 P60 = 0.016, pM1 P180 = 0.009, respectively). Also, significant correlations of TEP Delphi measures were registered in comparison to the rank CGIC and magnitude of change in TUG times.

CONCLUSIONS

These initial results suggest that TEPs, may be an alternative for CTT, in prediction of response to VPS in patients suspected as iNPH, exhibiting higher efficacy with reduced patient discomfort and risks, given replication of results in a larger sample and longer follow up times.

Case Report: Peripheral combined central dual-target magnetic stimulation for non- motor symptoms of Parkinson's disease

This case report describes an innovative study using central combined vagus dual-target magnetic stimulation for treating non-motor symptoms of Parkinson's disease (PD). PD is a common neurodegenerative disease, and almost all PD patients experience varying degrees of non-motor symptoms. However, there aren't many targeted drugs for non-motor symptoms. Based on this clinical, we used left dorsolateral prefrontal cortex (DLPFC) and vagus nerve dual-target magnetic stimulation to treat PD non-motor symptoms. The choice of this combined stimulation method is based on the closed-loop rehabilitation theory of central-peripheral-central. Stimulation of DLPFC promoted the activation of brain functional areas and improved neuroplasticity, while stimulation of vagus nerve further enhanced the positive feedback and input to the central nervous system, forming a closed-loop information feedback, and synergically promoted the recovery of PD non-motor symptoms. The patient in this paper had non-motor symptoms such as constipation, short-term memory impairment, insomnia, depression, hallucinations. We had 10 sessions in total. The DLPFC stimulation was performed at 10Hz, 120% resting motor threshold (RMT) intensity, 1000 pulses per sequence for 10 minutes. The vagus nerve stimulation was performed at 10Hz, 100%RMT, with a total of 2000 pulses and a duration of 14 minutes. Assessment before treatment, after treatment, and at one month follow-up showed improvements in cognitive function, mood, and constipation symptoms. Therefore, we believe this treatment approach may represent a promising new option for treating non-motor symptoms of PD.

Concurrent TMS-EEG to characterize cortical responses in the motor and prefrontal cortices in Parkinson's disease

Patients with Parkinson's disease (PD) experience both motor and non-motor symptoms. However, it remains unclear the full spectrum of PD, which requires a comprehensive assessment of both motor and non-motor cortical regions. The use of combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) allows the examination of neural circuit beyond motor cortex. In this study, TMS-EEG data were collected over the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) in 46 patients with PD and 27 healthy controls (HC). We analyzed TMS-evoked potentials and oscillatory powers to identify differences in cortical excitability and neural connectivity dynamics between the two cohorts. Patients with PD exhibited higher P30 amplitude following M1 stimulation compared to HCs, and there was a positive correlation between P30 amplitude and the severity of motor symptoms. DLPFC stimulation revealed an increased global mean field amplitude area under the curve (GMFA-AUC) at P30 and P60 in the PD group compared to HCs. A significant correlation was also observed within the PD group between P30 and P60 with depression scores. In addition, PD showed a significant power reduction in the alpha and beta bands during stimulation and distinct patterns emerged for each stimulation site. These findings provide novel insights into cortical network abnormalities and contribute to a better understanding of the mechanisms underlying PD.

Non-invasive brain stimulation to modulate neural activity in Parkinson's disease

Despite its potential to modulate brain and network activity, non-invasive brain stimulation is not yet clinically applied for treating Parkinson's disease. We here review recent findings that illustrate how various non-invasive stimulation techniques can modify pathological and compensatory activities. Due to unavoidable heterogeneities and low effect sizes of the reviewed studies, a deeper understanding of the mechanisms of action will be critical for refining clinical effectiveness and generating consistent results.

TMS-evoked potentials provide novel neurophysiological features of Tourette syndrome

INTRODUCTION

Gilles de la Tourette syndrome (TS) is a neuropsychiatric disorder associated with abnormal activation of the cortico-striatal-thalamo-cortical circuits and dopaminergic system. We sought to examine changes in neurotransmission relating to cortical excitation/inhibition of TS by measuring TMS-evoked potentials (TEPs) of selected networks.

METHODS

Thirty-three adult TS patients and 18 healthy controls underwent evaluation of symptom severity using the YGTSS (tics), PUTS (premonitory urge), Y-BOCS (OCD), CAARS (ADHD), BDI (depression), and BAI (anxiety). TMS-EEG was performed to measure TEPs obtained from the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), and primary visual cortex (V1).

RESULTS

TEP analysis revealed a delayed P180 latency in M1 for TS patients compared to controls (p = 0.006). Lower early amplitude of TEP in response to stimulation of DLPFC (50-70 ms), and delayed DLPFC P180 latency were associated with higher tic severity (p = 0.001 and p = 0.003, respectively). M1 early amplitude (50-70 ms) also effectively differentiated TS with mild-moderate from severe tics (p = 0.003). Significant correlation was found between TEP V1 early amplitude (15-45 ms) and severity of TS anxiety.

CONCLUSION

Distinct TEP patterns registered in response to DLPFC, M1, and V1 stimulation may shed light on the underlying pathophysiology of TS and are associated with tic severity and comorbidities.

Utilization of Single-Pulse Transcranial-Evoked Potentials in Neurological and Psychiatric Clinical Practice: A Narrative Review

Background: The utility of single-pulse TMS (transcranial magnetic stimulation)-evoked EEG (electroencephalograph) potentials (TEPs) has been extensively studied in the past three decades. TEPs have been shown to provide insights into features of cortical excitability and connectivity, reflecting mechanisms of excitatory/inhibitory balance, in various neurological and psychiatric conditions. In the present study, we sought to review and summarize the most studied neurological and psychiatric clinical indications utilizing single-pulse TEP and describe its promise as an informative novel tool for the evaluation of brain physiology. Methods: A thorough search of PubMed, Embase, and Google Scholar for original research utilizing single-pulse TMS-EEG and the measurement of TEP was conducted. Our review focused on the indications and outcomes most clinically relevant, commonly studied, and well-supported scientifically. Results: We included a total of 55 publications and summarized them by clinical application. We categorized these publications into seven sub-sections: healthy aging, Alzheimer's disease (AD), disorders of consciousness (DOCs), stroke rehabilitation and recovery, major depressive disorder (MDD), Parkinson's disease (PD), as well as prediction and monitoring of treatment response. Conclusions: TEP is a useful measurement of mechanisms underlying neuronal networks. It may be utilized in several clinical applications. Its most prominent uses include monitoring of consciousness levels in DOCs, monitoring and prediction of treatment response in MDD, and diagnosis of AD. Additional applications including the monitoring of stroke rehabilitation and recovery, as well as a diagnostic aid for PD, have also shown encouraging results but require further evidence from randomized controlled trials (RCTs).

Methodological Choices Matter: A Systematic Comparison of TMS-EEG Studies Targeting the Primary Motor Cortex

Transcranial magnetic stimulation (TMS) triggers time-locked cortical activity that can be recorded with electroencephalography (EEG). Transcranial evoked potentials (TEPs) are widely used to probe brain responses to TMS. Here, we systematically reviewed 137 published experiments that studied TEPs elicited from TMS to the human primary motor cortex (M1) in healthy individuals to investigate the impact of methodological choices. We scrutinized prevalent methodological choices and assessed how consistently they were reported in published papers. We extracted amplitudes and latencies from reported TEPs and compared specific TEP peaks and components between studies using distinct methods. Reporting of methodological details was overall sufficient, but some relevant information regarding the TMS settings and the recording and preprocessing of EEG data were missing in more than 25% of the included experiments. The published TEP latencies and amplitudes confirm the "prototypical" TEP waveform following stimulation of M1, comprising distinct N15, P30, N45, P60, N100, and P180 peaks. However, variations in amplitude were evident across studies. Higher stimulation intensities were associated with overall larger TEP amplitudes. Active noise masking during TMS generally resulted in lower TEP amplitudes compared to no or passive masking but did not specifically impact those TEP peaks linked to long-latency sensory processing. Studies implementing independent component analysis (ICA) for artifact removal generally reported lower TEP magnitudes. In summary, some aspects of reporting practices could be improved in future TEP studies to enable replication. Methodological choices, including TMS intensity and the use of noise masking or ICA, introduce systematic differences in reported TEP amplitudes. Further investigation into the significance of these and other methodological factors and their interactions is warranted.

TMS-evoked potentials unveil occipital network involvement in patients diagnosed with Parkinson's disease within 5 years of inclusion

Distinguishing Parkinson's disease (PD) subgroups may be achieved by observing network responses to external stimuli. We compared TMS-evoked potential (TEP) measures from stimulation of bilateral motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), and visual cortex (V1) between 62 PD patients (age: 69.9 ± 7.5) and 76 healthy controls (age: 69.2 ± 4.3) using a TMS-EEG protocol. TEP measures were analyzed using two-way ANCOVA adjusted for MOCA. PD patients were divided into tremor dominant (TD), non-tremor dominant (NTD) and rapid disease progression (RDP) subgroups. PD patients showed lower wide-waveform adherence (wWFA) (p = 0.025) and interhemispheric connectivity (IHCCONN) (p < 0.001) compared to healthy controls. Lower occipital IHCCONN correlated with advanced disease stage (r = -0.37, p = 0.0039). The RDP and NTD groups showed lower wWFA in response to occipital stimulation than the TD group (p = 0.005). Occipital TEP measures identified RDP patients with 85% accuracy. These findings demonstrate occipital network involvement in early PD stages, suggesting that TEP measures offer insights into altered networks in PD subgroups.

Neuromodulation techniques - From non-invasive brain stimulation to deep brain stimulation

Over the past 30 years, the field of neuromodulation has witnessed remarkable advancements. These developments encompass a spectrum of techniques, both non-invasive and invasive, that possess the ability to both probe and influence the central nervous system. In many cases neuromodulation therapies have been adopted into standard care treatments. Transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and transcranial ultrasound stimulation (TUS) are the most common non-invasive methods in use today. Deep brain stimulation (DBS), spinal cord stimulation (SCS), and vagus nerve stimulation (VNS), are leading surgical methods for neuromodulation. Ongoing active clinical trials using are uncovering novel applications and paradigms for these interventions.

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.

Characterizing cortical responses to short-term multidisciplinary intensive rehabilitation treatment in patients with Parkinson’s disease: A transcranial magnetic stimulation and electroencephalography study

Combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) is a powerful non-invasive tool for qualifying the neurophysiological effects of interventions by recording TMS-induced cortical activation with high temporal resolution and generates reproducible and reliable waves of activity without participant cooperation. Cortical dysfunction contributes to the pathogenesis of the clinical symptoms of Parkinson’s disease (PD). Here, we examined changes in cortical activity in patients with PD following multidisciplinary intensive rehabilitation treatment (MIRT). Forty-eight patients with PD received 2 weeks of MIRT. The cortical response was examined following single-pulse TMS over the primary motor cortex by 64-channel EEG, and clinical symptoms were assessed before and after MIRT. TMS-evoked potentials were quantified by the global mean field power, as well as oscillatory power in theta, alpha, beta, and gamma bands, and their clinical correlations were calculated. After MIRT, motor and non-motor symptoms improved in 22 responders, and only non-motor function was enhanced in 26 non-responders. Primary motor cortex stimulation reduced global mean field power amplitudes in responders but not significantly in non-responders. Oscillations exhibited attenuated power in the theta, beta, and gamma bands in responders but only reduced gamma power in non-responders. Associations were observed between beta oscillations and motor function and between gamma oscillations and non-motor symptoms. Our results suggest that motor function enhancement by MIRT may be due to beta oscillatory power modulation and that alterations in cortical plasticity in the primary motor cortex contribute to PD recovery.

Layer recurrent neural network-based diagnosis of Parkinson’s disease using voice features

Parkinson’s disease (PD), a slow-progressing neurological disease, affects a large percentage of the world’s elderly population, and this population is expected to grow over the next decade. As a result, early detection is crucial for community health and the future of the globe in order to take proper safeguards and have a less arduous treatment procedure. Recent research has begun to focus on the motor system deficits caused by PD. Because practically most of the PD patients suffer from voice abnormalities, researchers working on automated diagnostic systems investigate vocal impairments. In this paper, we undertake extensive experiments with features extracted from voice signals. We propose a layer Recurrent Neural Network (RNN) based diagnosis for PD. To prove the efficiency of the model, different network models are compared. To the best of our knowledge, several neural network topologies, namely RNN, Cascade Forward Neural Networks (CFNN), and Feed Forward Neural Networks (FFNN), are used and compared for voice-based PD detection for the first time. In addition, the impacts of data normalization and feature selection (FS) are thoroughly examined. The findings reveal that normalization increases classifier performance and Laplacian-based FS outperforms. The proposed RNN model with 300 voice features achieves 99.74% accuracy.

Bridging the gap: TMS-EEG from Lab to Clinic

The combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) has reached technological maturity and has been an object of significant scientific interest for over two decades. Ιn parallel, accumulating evidence highlights the potential of TMS-EEG as a useful tool in the field of clinical neurosciences. Nevertheless, its clinical utility has not yet been established, partly because technical and methodological limitations have created a gap between an evolving scientific tool and standard clinical practice. Here we review some of the identified gaps that still prevent TMS-EEG moving from science laboratories to clinical practice. The principal and partly overlapping gaps include: 1) complex and laborious application, 2) difficulty in obtaining high-quality signals, 3) suboptimal accuracy and reliability, and 4) insufficient understanding of the neurobiological substrate of the responses. All these four aspects need to be satisfactorily addressed for the method to become clinically applicable and enter the diagnostic and therapeutic arena. In the current review, we identify steps that might be taken to address these issues and discuss promising recent studies providing tools to aid bridging the gaps.