Identifying Neurophysiological Markers of Intermittent Theta Burst Stimulation in Treatment-Resistant Depression Using Transcranial Magnetic Stimulation-Electroencephalography

Classical, spaced, or accelerated transcranial magnetic stimulation of motor cortex for treating neuropathic pain: A 3-arm parallel non-inferiority study

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) at high frequency (HF) is an effective treatment of neuropathic pain. The classical HF-rTMS protocol (CHF-rTMS) includes a daily session for one week as an induction phase of treatment followed by more spaced sessions. Another type of protocol without an induction phase and based solely on spaced sessions of HF-rTMS (SHF-rTMS) has also been shown to produce neuropathic pain relief. However, CHF-rTMS and SHF-rTMS of M1 have never been compared regarding their analgesic potential. Another type of rTMS paradigm, called accelerated intermittent theta burst stimulation (ACC-iTBS), has recently been proposed for the treatment of depression, the other clinical condition for which HF-rTMS is proposed as an effective therapeutic strategy. ACC-iTBS combines a high number of pulses delivered in short sessions grouped into a few days of stimulation. This type of protocol has never been applied to M1 for the treatment of pain.

METHODS/DESIGN

The objective of this single-centre randomized study is to compare the efficacy of three different rTMS protocols for the treatment of chronic neuropathic pain: CHF-rTMS, SHF-rTMS, and ACC-iTBS. The CHF-rTMS will consists of 10 stimulation sessions, including 5 daily sessions of 10Hz-rTMS (3,000 pulses per session) over one week, then one session per week for 5 weeks, for a total of 30,000 pulses delivered in 10 stimulation days. The SHF-rTMS protocol will only include 4 sessions of 20Hz-rTMS (1,600 pulses per session), one every 15 days, for a total of 6,400 pulses delivered in 4 stimulation days. The ACC-iTBS protocol will comprise 5 sessions of iTBS (600 pulses per session) completed in half a day for 2 consecutive days, repeated 5 weeks later, for a total of 30,000 pulses delivered in 4 stimulation days. Thus, CHF-rTMS and ACC-iTBS protocols will share a higher total number of TMS pulses (30,000 pulses) compared to SHF-rTMS protocol (6,400 pulses), while CHF-rTMS protocol will include a higher number of stimulation days (10 days) compared to ACC-iTBS and SHF-rTMS protocols (4 days). In all protocols, the M1 target will be defined in the same way and stimulated at the same intensity using a navigated rTMS (nTMS) procedure. The evaluation will be based on clinical outcomes with various scales and questionnaires assessed every week, from two weeks before the 7-week period of therapeutic stimulation until 4 weeks after. Additionally, three sets of neurophysiological outcomes (resting-state electroencephalography (EEG), nTMS-EEG recordings, and short intracortical inhibition measurement with threshold tracking method) will be assessed the week before and after the 7-week period of therapeutic stimulation.

DISCUSSION

This study will make it possible to compare the analgesic efficacy of the CHF-rTMS and SHF-rTMS protocols and to appraise that of the ACC-iTBS protocol for the first time. This study will also make it possible to determine the respective influence of the total number of pulses and days of stimulation delivered to M1 on the extent of pain relief. Thus, if their analgesic efficacy is not inferior to that of CHF-rTMS, SHF-rTMS and especially the new ACC-iTBS protocol could be an optimal compromise of a more easy-to-perform rTMS protocol for the treatment of patients with chronic neuropathic pain.

Impact of high-frequency rTMS combined with pharmacotherapy on the left dorsolateral prefrontal cortex in treating major depressive disorder: A real-world study

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) combined with pharmacotherapy is a promising treatment method for depression. However, its treatment mechanism needs further research.

METHODS

This study recruited 38 healthy individuals (HC) and 52 patients with severe depression (MDD) and divided patients into two treatment groups: the rTMS combined antidepressant (rTMS+ADP) group and the single antidepressant (ADP) group. We used functional magnetic resonance imaging to calculate the fractional amplitude of low-frequency fluctuations (fALFF) in the left dorsolateral prefrontal cortex (DLPFC) to investigate the functional change after treatment.

RESULT

The fALFF in the left DLPFC was significantly lower in the MDD group than that in the HC group (p < 0.05). In addition, fALFF values of the left DLPFC negatively correlated with HAMD-24 scores (r = -0.294, p = 0.005). After treatment, both MDD groups showed a significant decrease in HAMD-24 scores, with a response rate of 88.89 % and a remission rate of 62.96 % in the rTMS+ADP group, compared to 64 % response and 56 % remission rates in the ADP group. The fALFF values in patients' left DLPFC significantly reduced in the rTMS+ADP group (p < 0.05), but not in the ADP group.

LIMITATIONS

Our study only focused on the treatment effect in the left DLPFC, without exploring the other brain regions or networks.

CONCLUSIONS

This study emphasizes the significance of the left DLPFC in MDD treatment. However, combined left DLPFC rTMS with ADP causes deviation from the normal resting brain function of the left DLPFC, indicating that future research should explore targeted treatment methods to normalize the left DLPFC.

Abnormal Global Cortical Responses in Drug-Naïve Patients With Schizophrenia Following Orbitofrontal Cortex Stimulation: A Concurrent Transcranial Magnetic Stimulation-Electroencephalography Study

BACKGROUND

Abnormalities in cortical excitability and plasticity have been considered to underlie the pathophysiology of schizophrenia. Transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) can provide a direct evaluation of cortical responses to TMS. Here, we employed TMS-EEG to investigate cortical responses to orbitofrontal cortex (OFC) stimulation in schizophrenia.

METHODS

In total, we recruited 92 drug-naïve patients with first-episode schizophrenia and 51 age- and sex-matched healthy individuals. For each participant, one session of 1-Hz repetitive TMS (rTMS) was delivered to the right OFC, and TMS-EEG data were obtained to explore the change in cortical-evoked activities before and immediately after rTMS during the eyes-closed state. The MATRICS Consensus Cognitive Battery was used to assess neurocognitive performance.

RESULTS

The cortical responses indexed by global mean field amplitudes (i.e., P30, N45, and P60) were larger in patients with schizophrenia than in healthy control participants at baseline. Furthermore, after one session of 1-Hz rTMS over the right OFC, the N100 amplitude was significantly reduced in the healthy control group but not in the schizophrenia group. In the healthy control participants, there was a significant correlation between modulation of P60 amplitude by rTMS and working memory; however, this correlation was absent in patients with schizophrenia.

CONCLUSIONS

Aberrant global cortical responses following right OFC stimulation were found in patients with drug-naïve first-episode schizophrenia, supporting its significance in the primary pathophysiology of schizophrenia.

Neurophysiological and neuroimaging markers of repetitive transcranial magnetic stimulation treatment response in major depressive disorder: A systematic review and meta-analysis of predictive modeling studies

Predicting repetitive transcranial magnetic stimulation (rTMS) treatment outcomes in major depressive disorder (MDD) could reduce the financial and psychological risks of treatment failure. We systematically reviewed and meta-analyzed studies that leveraged neurophysiological and neuroimaging markers to predict rTMS response in MDD. Five databases were searched from inception to May 25, 2023. The primary meta-analytic outcome was predictive accuracy pooled from classification models. Regression models were summarized qualitatively. A promising marker was identified if it showed a sensitivity and specificity of 80% or higher in at least two independent studies. Searching yielded 36 studies. Twenty-two classification modeling studies produced an estimated area under the summary receiver operating characteristic curve of 0.87 (95% CI = 0.83-0.92), with 86.8% sensitivity (95% CI = 80.6-91.2%) and 81.9% specificity (95% CI = 76.1-86.4%). Frontal theta cordance measured by electroencephalography is closest to proof of concept. Predicting rTMS response using neurophysiological and neuroimaging markers is promising for clinical decision-making. However, replications by different research groups are needed to establish rigorous markers.

Decreased short-latency afferent inhibition in individuals with mild cognitive impairment: A TMS-EEG study

TMS combined with EEG (TMS-EEG) is a tool to characterize the neurophysiological dynamics of the cortex. Among the TMS paradigms, short-latency afferent inhibition (SAI) allows the investigation of inhibitory effects mediated by the cholinergic system. The aim of this study was to compare cholinergic function in the DLPFC between individuals with mild cognitive impairment (MCI) and healthy controls (HC) using TMS-EEG with the SAI paradigm. In this study, 30 MCI and 30 HC subjects were included. The SAI paradigm consisted of 80 single pulse TMS and 80 SAI stimulations applied to the left DLPFC. N100 components, global mean field power (GMFP) and total power were calculated. As a result, individuals with MCI showed reduced inhibitory effects on N100 components and GMFP at approximately 100 ms post-stimulation and on β-band activity at 200 ms post-stimulation compared to HC. Individuals with MCI showed reduced SAI, suggesting impaired cholinergic function in the DLPFC compared to the HC group. We conclude that these findings underscore the clinical applicability of the TMS-EEG method as a powerful tool for assessing cholinergic function in individuals with MCI.

Transcranial Magnetic Stimulation-Electroencephalography for Biomarker Discovery in Psychiatry

Current diagnosis and treatment of psychiatric illnesses are still based on behavioral observations and self-reports, commonly leading to prolonged untreated illness. Biological markers (biomarkers) may offer an opportunity to revolutionize clinical psychiatry practice by helping provide faster and potentially more effective therapies. Transcranial magnetic stimulation concurrent with electroencephalography (TMS-EEG) is a noninvasive brain mapping methodology that can assess the functions and dynamics of specific brain circuitries in awake humans and aid in biomarker discovery. This article provides an overview of TMS-EEG-based biomarkers that may hold potential in psychiatry. The methodological readiness of the TMS-EEG approach and steps in the validation of TMS-EEG biomarkers for clinical utility are discussed. Biomarker discovery with TMS-EEG is in the early stages, and several validation steps are still required before clinical implementations are realized. Thus far, TMS-EEG predictors of response to magnetic brain stimulation treatments in particular have shown promise for translation to clinical practice. Larger-scale studies can confirm validation followed by biomarker-informed trials to assess added value compared to existing practice.

Transcranial magnetic stimulation neurophysiology in patients with non-Alzheimer's neurodegenerative diseases: A systematic review and meta-analysis

Non-Alzheimer's dementia (NAD) accounts for 30% of all neurodegenerative conditions and is characterized by cognitive decline beyond mere memory dysfunction. Diagnosing NAD remains challenging due to the lack of established biomarkers. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that enables the investigation of cortical excitability in the human brain. Paired-pulse TMS paradigms include short- and long-interval intracortical inhibition (SICI/LICI), intracortical facilitation (ICF), and short-latency afferent inhibition (SAI), which can assess neurophysiological functions of GABAergic, glutamatergic, and cholinergic neural circuits, respectively. We conducted the first systematic review and meta-analysis to compare these TMS indices among patients with NAD and healthy controls. Our meta-analyses indicated that TMS neurophysiological examinations revealed decreased glutamatergic function in patients with frontotemporal dementia (FTD) and decreased GABAergic function in patients with FTD, progressive supranuclear palsy, Huntington's disease, cortico-basal syndrome, and multiple system atrophy-parkinsonian type. In addition, decreased cholinergic function was found in dementia with Lewy body and vascular dementia. These results suggest the potential of TMS as an additional diagnostic tool to differentiate NAD.

TMS-evoked potential in the dorsolateral prefrontal cortex to assess the severity of depression disease: a TMS-EEG study

Objective: The combined use of transcranial magnetic stimulation and electroencephalography (TMS-EEG), as a powerful technique that can non-invasively probe the state of the brain, can be used as a method to study neurophysiological markers in the field of psychiatric disorders and discover potential diagnostic predictors. This study used TMS-evoked potentials (TEPs) to study the cortical activity of patients with major depressive disorder depression (MDD) and the correlation with clinical symptoms to provide an electrophysiological basis for the clinical diagnosis. Methods: A total of 41 patients and 42 healthy controls were recruited to study. Using TMS-EEG techniques to measure the left dorsolateral prefrontal cortex (DLPFC) 's TEP index and evaluate the clinical symptoms of MDD patients using the Hamilton Depression Scale-24 (HAMD-24). Results: MDD subjects performing TMS-EEG on the DLPFC showed lower cortical excitability P60 index levels than healthy controls. Further analysis revealed that the degree of P60 excitability within the DLPFC of MDD patients was significantly negatively correlated with the severity of depression. Conclusion: The low levels of P60 exhibited in DLPFC reflect low excitability in MDD; the P60 component can be used as a biomarker for MDD in clinical assessment tools.