P 230. Third generation controllable pulse parameter transcranial magnetic stimulation device

Commercially available transcranial magnetic stimulation (TMS) devices provide very limited control over the pulse parameters. We present a third generation controllable pulse parameter device (cTMS3) that uses a novel full-bridge circuit topology with two energy storage capacitors and incorporates a number of implementation and functionality advantages over conventional TMS devices and previous cTMS devices. cTMS3 is implemented with transistors with lower voltage rating than previous cTMS devices. It provides more flexible pulse shaping since the circuit topology allows four coil voltage levels during a pulse, including zero voltage. The zero coil voltage level enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse bursts (<; 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage. These features enhance the advantages of cTMS and could extend the utility of TMS as a research, diagnostic, and therapeutic tool.

Transcranial magnetic stimulation (TMS) is a method of Non-Invasive Brain Stimulation that is based on electro-physical principles discovered by Michael Faraday. A TMS device is made of one or two copper coils, positioned superficially to a site of interest in the brain, to non-invasively produce a brief magnetic pulse to an estimated depth from the surface of the scalp with the following axonal depolarization. This axonal depolarization activates cortical and subcortical networks with multiple effects. There are different methods of TMS used, all with different mechanisms of action. TMS is well tolerated with very few side effects. TMS is now approved for major depression disorder and obsessive-compulsive disorder. There is significant data to consider approval of TMS for many neurological disorders. This is a review of the uses of TMS in diverse neurological conditions, including stroke and spasticity, migraine, and dementia. TMS is a device that utilizes non-invasive brain stimulation, and it has shown promising results with objective clinical and basic science data. Its ability to trigger neuronal plasticity and potentiating synaptic transmission gives it incredible therapeutic potential. There are diverse mechanisms of action, and this could be troublesome in elaborating clinical trials and standardization of therapy.

Electrical stimulation involving visual areas of the brain produces artificial light percepts called phosphenes. These visual percepts have been extensively investigated in previous studies involving intracortical microsimulation (ICMS) and serve as the basis for developing a visual prosthesis for the blind. Although advances have been achieved, many challenges still remain with implementing a functional ICMS for visual rehabilitation purposes. Transcranial magnetic stimulation (TMS) over the primary occipital lobe offers an alternative method to produce phosphenes non-invasively. A main challenge facing blind individuals involves navigation. Within the scientific community, methods to evaluate the ability of a visual prosthesis to facilitate in navigation has been neglected. In this study, we investigate the effectiveness of evoking lateralized phosphenes to navigate a computer simulated virtual environment. More importantly, we demonstrate how virtual environments along with the development of a visual prosthesis share a mutual relationship benefiting both patients and researchers. Using two TMS devices, a pair of 40mm figure-of-eight coils were placed over each occipital hemisphere resulting in lateralized phosphene perception. Participants were tasked with making a series of left and right turns using peripheral devices depending on the visual hemifield in which a phosphene is present. If a participant was able to accurately perceive all ten phosphenes, the simulated target is able to advance and fully exit the virtual environment. Our findings demonstrate that participants can interpret lateralized phosphenes while highlighting the integration of computer based virtual environments to evaluate the capability of a visual prosthesis during navigation.

Chronic low back pain (CLBP) is a global burden with an unknown etiology. Reorganization of the cortical representation of paraspinal muscles in the primary motor cortex (M1) may be related to the pathology. Single-pulse transcranial magnetic stimulation (TMS), commonly used to map the functional organization of M1, is not potent enough to stimulate the cortical maps of paraspinal muscles in M1 in CLBP patients with reduced corticospinal excitability (CSE) with intensities even as high as maximum stimulator output (100% MSO). This makes TMS mapping impractical for these patients. The aim of this study was to increase the practicality of TMS mapping for people with CLBP. This study included eight men and ten women who had CLBP for over three months. A biphasic paired-pulse TMS paradigm, conjunct anticipatory postural adjustment (APA), and maximal voluntary activation of paraspinal muscles (MVC) were used to facilitate TMS mapping. TMS mapping was possible in all CLBP participants, with TMS intensities <50% of the MSO. Reorganization in terms of an anterior and lateral shift of the center of gravity (COG) of the cortical maps of paraspinal muscles was observed in all participants with CLBP, and a reduced number of discrete peaks was found in 33%. The facilitation of the CSE to paraspinal muscles makes TMS mapping more practical and tolerable in people with CLBP, lowering the risk of seizure and discomfort associated with high-intensity TMS pulses. Conventional transcranial magnetic stimulation (TMS) brain mapping is not optimal for patients with Chronic low back pain (CLBP).Paired-pulse TMS dramatically lessens the energy needed for brain mapping.Maximal voluntary contraction of back muscles facilitates TMS mapping.Anticipatory postural activity of back muscles enhances the efficacy of TMS mapping. Chronic low back pain (CLBP) is a social, emotional, and economic burden and the leading cause of disability worldwide. Yet the etiology of the CLBP is unknown. The persistence of aberrant or antalgic movement patterns observed in people with CLBP has been suggested as a possible cause of pain chronification by inducing continuous damage to sensitive structures of the lumbar spine. It is well known that the brain is in charge of the production and planning of movements, so it is likely that abnormal movement patterns also stem from the abnormalities in the brain. However, until recently, human knowledge about the structure and function of the brain has been very limited. The invention of noninvasive and painless brain imaging and stimulating techniques such as transcranial magnetic stimulation (TMS) during the last decades has augmented our knowledge about the structure and function of the brain. Modification in terms of shift, shrinkage, or expansion of areas of the brain devoted to movement control or sensation of the back muscles has been documented in CLBP via these techniques, which are argued to relate to pain chronification but need further clarification. Yet monitoring the course of CLBP via TMS, despite its many potentials, is challenging. This could be due to the reduced cortical drive to back muscles in CLBP patients and the small area devoted to control of back muscles in the brain in general that increases the brain threshold to TMS in people with CLBP. The aim of this study was to tailor an approach to make TMS more applicable for CLBP patients by reducing the threshold to TMS. This could be achieved by engaging back muscles in anticipatory postural activity in combination with maximal voluntary activation of these muscles, along with TMS paradigms that induce intracortical facilitation.

The paired-pulse (PP) transcranial magnetic stimulation (TMS) paradigms allow the exploration of the motor cortex physiology. The triple stimulation technique (TST) improves conventional TMS by reducing effects of desynchronization of motor neuron discharges allowing a precise evaluation of the corticospinal conduction. The objective of our study was to explore PP TMS paradigms combined with the TST to study whether the desynchronization contributes to these phenomena and whether the combined TMS-TST protocol could improve the consistency of responses. We investigated the PP paradigms of short intracortical inhibition (SICI) with 2 ms interstimulus interval (ISI) and of intracortical facilitation (ICF) with 10 ms ISI in 22 healthy subjects applying either conventional TMS alone or combined with the TST protocol. The results of the PP paradigms combined with the TST of SICI and ICF do not differ from those with conventional TMS. However, combining the PP paradigm with the TST reduces their variability. These results speak against a contribution of the desynchronization of motor neuron discharges to the PP paradigms of SICI and ICF. Combining the PP TMS paradigm with the TST may improve their consistency, but the interindividual variability remains such that it precludes their utility for clinical practice.NEW & NOTEWORTHY Combining the triple stimulation technique with the paired-pulse stimulation paradigm improves the consistency of short intracortical inhibition and facilitation and could be useful in research, but the interindividual variability precludes their utility for clinical practice. Our findings do not suggest that desynchronization of descending discharges following transcranial magnetic stimulation contributes to short intracortical inhibition or intracortical facilitation.

Background: Major depressive disorder (MDD) is a leading global cause of disability, with a substantial proportion of patients failing to respond to pharmacotherapy or psychotherapy. Theta burst stimulation (TBS), a newer form of transcranial magnetic stimulation (TMS), offers the advantage of shorter treatment duration, but its comparative efficacy against conventional TMS and sham remains uncertain. Despite growing clinical interest, prior reviews have lacked sufficient data to establish TBS as a frontline neuromodulatory option. Objective: This study aimed to conduct an updated systematic review and meta-analysis evaluating the efficacy and safety of TBS compared to both sham stimulation and conventional TMS in adults with MDD, focusing on categorical response, percent symptom reduction, remission, and adverse events. Methods: This systematic review and meta-analysis included randomized controlled trials (RCTs) comparing TBS with sham or standard TMS in adult patients diagnosed with MDD. A comprehensive search of PubMed, CENTRAL, and EBSCO/CINAHL was performed through March 28, 2025. Primary outcome was defined as ≥50% reduction in Hamilton Rating Scale for Depression (HRSD) scores. Secondary outcomes included percent change in HRSD, remission (HRSD &lt;11), Beck Depression Inventory (BDI) scores, and adverse events. Data were pooled using a random-effects model in Review Manager (RevMan) 5.4, with quality assessed via the Cochrane Risk of Bias tool and GRADE. Ethical approval was not applicable due to the nature of secondary data synthesis The protocol for this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number CRD420251008712. Results: Fourteen RCTs met inclusion criteria. TBS showed significantly higher response rates than sham (RR = 2.40, 95% CI: 1.27–4.55, p = 0.007) and was comparable to standard TMS (RR = 1.02, p = 0.80). Percent change in HRSD and MADRS outcomes favored TBS, while adverse event rates did not differ significantly between groups. Conclusion: TBS is a clinically effective and time-efficient intervention for MDD, offering comparable or superior outcomes to conventional TMS and significantly outperforming sham. Its favorable tolerability and shorter session duration support broader clinical application and integration into psychiatric care settings.

Conventional or threshold-hunting TMS? A tale of two SICIs

This paper proposes an efficient algorithm for automatic and optimal tuning of pulse amplitude and width for sequential parameter estimation (SPE) of the neural membrane time constant and input-output (IO) curve parameters in closed-loop electromyography-guided (EMG-guided) controllable transcranial magnetic stimulation (cTMS). The proposed SPE is performed by administering a train of optimally tuned TMS pulses and updating the estimations until a stopping rule is satisfied or the maximum number of pulses is reached. The pulse amplitude is computed by the Fisher information maximization. The pulse width is chosen by maximizing a normalized depolarization factor, which is defined to separate the optimization and tuning of the pulse amplitude and width. The normalized depolarization factor maximization identifies the critical pulse width, which is an important parameter in the identifiability analysis, without any prior neurophysiological or anatomical knowledge of the neural membrane. The effectiveness of the proposed algorithm is evaluated through simulation. The results confirm satisfactory estimation of the membrane time constant and IO curve parameters for the simulation case. By defining the stopping rule based on the satisfaction of the convergence criterion with tolerance of 0.01 for 5 consecutive times for all parameters, the IO curve parameters are estimated with 52 TMS pulses, with absolute relative estimation errors (AREs) of less than 7%. The membrane time constant is estimated with 0.67% ARE, and the pulse width value tends to the critical pulse width with 0.16% ARE with 52 TMS pulses. The results confirm that the pulse width and amplitude can be tuned optimally and automatically to estimate the membrane time constant and IO curve parameters in real-time with closed-loop EMG-guided cTMS.

A waveform-controlled, power-efficient, monophasic repetitive transcranial magnetic stimulation (rTMS) device is presented. Unlike conventional designs, the power efficiency is improved by recycling the energy used to generate monophasic stimulation pulses. Such enhanced power efficiency enables a monophasic rTMS device to eliminate an extra cooling system. The slope and width of the stimulation pulse is made programmable in the digital domain for user-friendliness. The energy-recycling circuitry is reconfigured to function as a buck-boost converter with a single additional switch, allowing the proposed device to be low-voltage battery operated. In addition, the pulse width in the DC-DC conversion process is adjusted dynamically to eliminate current accumulation in the inductor, which reduces ohmic dissipation in parasitic resistors and further improves the power efficiency.

Real-time electric-field neuronavigation on realistic head models for conventional and multi-locus TMS.

Med Check

Transcranial magnetic stimulation (TMS) makes use of electromagnetic induction principle to induce electrical fields in the neuronal tissues and has an effect on neuromodulation. Theta burst stimulation (TBS) as a novel pattern of TMS has been shown to have advantages over conventional repetitive TMS (crTMS) in modulating brain cortical excitability. However, to date little is known about the potential of TBS of acupuncture point (acupoint) in modifying the brain activity. An acupoint is a specific point in the human body with nerve trunk and nerve ending through it, which is sensitive to various stimuli. In this paper, different-mode magnetic stimulations including crTMS, continuous TBS (cTBS), intermittent TBS (iTBS), and corresponding Sham iTBS were used to stimulate the Neiguan acupoint (PC6). Electroencephalogram characteristics induced by different-mode magnetic stimulations were compared to investigate whether the mode of magnetic stimulation of acupoint would impact stimulation effects. The results showed that iTBS of acupoint could induce a remarkable evoked potential of P80 component, activate more brain functional areas compared to crTMS, cTBS, and Sham stimulation, which suggested that iTBS of acupoint could induce a powerful brain response and produce a plastic reorganization of the cortical network. This paper proved that iTBS of acupoint with lower stimulation intensity and fewer stimulation pulses may be one more effective stimulation mode than crTMS, which may be clinically useful.

Commonly used repetitive transcranial magnetic stimulation (rTMS) protocols, including regular rTMS, intermittent and continuous theta-burst stimulation (TBS) and quadripulse stimulation (QPS) are presented with respect to their induced neuromodulatory after-effects and the underlying cellular and synaptic neurophysiological mechanisms. The anatomical target is typically primary motor cortex since motor evoked potentials (MEPs) before and after the intervention can be used to assess effects of the respective rTMS protocol. High-frequency regular rTMS and intermittent TBS protocols tend to increase corticospinal excitability as indexed by MEP amplitude, whereas low-frequency regular rTMS and continuous TBS protocols tend to reduce corticospinal excitability. These effects are primarily due to LTP-like and LTD-like synaptic changes mediated by GABA and NMDA receptors. Changes in the balance between excitatory and inhibitory cortical microcircuits play a secondary role, with inconsistent effects as determined by paired-pulse TMS protocols. Finally, the challenge of large inter-subject response variability, and current directions of research to optimize rTMS effects through EEG-dependent personalized TMS are discussed.

The Neuronetics NeuroStar Transcranial Magnetic Stimulation (TMS) System is a class II medical device that produces brief duration, pulsed magnetic fields. These rapidly alternating fields induce electrical currents within localized, targeted regions of the cortex which are associated with various physiological and functional brain changes. In 2007, O'Reardon et al., utilizing the NeuroStar device, published the results of an industry-sponsored, multisite, randomized, sham-stimulation controlled clinical trial in which 301 patients with major depression, who had previously failed to respond to at least one adequate antidepressant treatment trial, underwent either active or sham TMS over the left dorsolateral prefrontal cortex (DLPFC). The patients, who were medication-free at the time of the study, received TMS five times per week over 4-6 weeks. The results demonstrated that a sub-population of patients (those who were relatively less resistant to medication, having failed not more than two good pharmacologic trials) showed a statistically significant improvement on the Montgomery-Asberg Depression Scale (MADRS), the Hamilton Depression Rating Scale (HAMD), and various other outcome measures. In October 2008, supported by these and other similar results, Neuronetics obtained the first and only Food and Drug Administration (FDA) approval for the clinical treatment of a specific form of medication-refractory depression using a TMS Therapy device (FDA approval K061053). In this paper, we will explore the specified FDA approved NeuroStar depression treatment protocol (to be administered only under prescription and by a licensed medical profession in either an in- or outpatient setting).

Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research.