TMS brain mapping of the pharyngeal cortical representation in healthy subjects

Repetitive Transcranial Magnetic Stimulation Combined with Sling Exercise Modulates the Motor Cortex in Patients with Chronic Low Back Pain

The study aims to explore the effects of combining repetitive transcranial magnetic stimulation (rTMS) with sling exercise (SE) intervention in patients with chronic low back pain (CLBP). This approach aims to directly stimulate brain circuits and indirectly activate trunk muscles to influence motor cortex plasticity. However, the impact of this combined intervention on motor cortex organization and clinical symptom improvement is still unclear, as well as whether it is more effective than either intervention alone. To investigate this, patients with CLBP were randomly assigned to three groups: SE/rTMS, rTMS alone, and SE alone. Motor cortical organization, numerical pain rating scale (NPRS), Oswestry Disability Index (ODI), and postural balance stability were measured before and after a 2-week intervention. The results showed statistically significant differences in the representative location of multifidus on the left hemispheres, as well as in NPRS and ODI scores, in the combined SE/rTMS group after the intervention. When compared to the other two groups, the combined SE/rTMS group demonstrated significantly different motor cortical organization, sway area, and path range from the rTMS alone group, but not from the SE alone group. These findings highlight the potential benefits of a combined SE/rTMS intervention in terms of clinical outcomes and neuroadaptive changes compared to rTMS alone. However, there was no significant difference between the combined intervention and SE alone. Therefore, our research does not support the use of rTMS as a standalone treatment for CLBP. Our study contributed to optimizing treatment strategies for individuals suffering from CLBP.

The Cortical and Subcortical Neural Control of Swallowing: A Narrative Review

Swallowing is a sophisticated process involving the precise and timely coordination of the central and peripheral nervous systems, along with the musculatures of the oral cavity, pharynx, and airway. The role of the infratentorial neural structure, including the swallowing central pattern generator and cranial nerve nuclei, has been described in greater detail compared with both the cortical and subcortical neural structures. Nonetheless, accumulated data from analysis of swallowing performance in patients with different neurological diseases and conditions, along with results from neurophysiological studies of normal swallowing have gradually enhanced understanding of the role of cortical and subcortical neural structures in swallowing, potentially leading to the development of treatment modalities for patients suffering from dysphagia. This review article summarizes findings about the role of both cortical and subcortical neural structures in swallowing based on results from neurophysiological studies and studies of various neurological diseases. In sum, cortical regions are mainly in charge of initiation and coordination of swallowing after receiving afferent information, while subcortical structures including basal ganglia and thalamus are responsible for movement control and regulation during swallowing through the cortico-basal ganglia-thalamo-cortical loop. This article also presents how cortical and subcortical neural structures interact with each other to generate the swallowing response. In addition, we provided the updated evidence about the clinical applications and efficacy of neuromodulation techniques, including both non-invasive brain stimulation and deep brain stimulation on dysphagia.

Effect of cerebellar transcranial magnetic stimulation with double-cone coil on dysphagia after subacute infratentorial stroke: A randomized, single-blinded, controlled trial

BACKGROUND

A 10-Hz cerebellar repetitive transcranial magnetic stimulation (rTMS) could increase corticobulbar tract excitability in healthy individuals. However, its clinical efficacy for poststroke dysphagia (PSD) remains unclear.

OBJECTIVE

To investigate the effectiveness of 10-Hz cerebellar rTMS in PSD patients with infratentorial stroke (IS).

METHODS

In this single-blinded, randomized controlled trial, 42 PSD patients with subacute IS were allocated to three groups: bilateral cerebellar rTMS (biCRB-rTMS), unilateral cerebellar rTMS (uniCRB-rTMS), or sham-rTMS. The stimulation parameters were 5 trains of 50 stimuli at 10 Hz with an interval of 10 s at 90% of the thenar resting motor threshold (RMT). The Functional Oral Intake Scale (FOIS) was assessed at T0 (baseline), T1 (day 0 after intervention), and T2 (day 14 after intervention), whereas the Dysphagia Outcome and Severity Scale (DOSS), Penetration Aspiration Scale (PAS), and neurophysiological parameters were evaluated at T0 and T1.

RESULTS

Significant time and intervention interaction effects were observed for the FOIS score (F = 3.045, p = 0.022). The changes in the FOIS scores at T1 and T2 were both significantly higher in the biCRB-rTMS group than in the sham-rTMS group (p < 0.05). The uniCRB-rTMS and biCRB-rTMS groups demonstrated greater changes in the DOSS and PAS at T1, compared with the sham-rTMS group (p < 0.05). Bilateral corticobulbar tract excitability partly increased in the biCRB-rTMS and uniCRB-rTMS groups at T1, compared with T0. The percent changes in corticobulbar tract excitability parameters at T1 showed no difference among three groups.

CONCLUSIONS

A 10-Hz bilateral cerebellar rTMS is a promising, noninvasive treatment for subacute infratentorial PSD.

Electroacupuncture improves swallowing function in a post-stroke dysphagia mouse model by activating the motor cortex inputs to the nucleus tractus solitarii through the parabrachial nuclei

As a traditional medical therapy, stimulation at the Lianquan (CV23) acupoint, located at the depression superior to the hyoid bone, has been shown to be beneficial in dysphagia. However, little is known about the neurological mechanism by which this peripheral stimulation approach treats for dysphagia. Here, we first identified a cluster of excitatory neurons in layer 5 (L5) of the primary motor cortex (M1) that can regulate swallowing function in male mice by modulating mylohyoid activity. Moreover, we found that focal ischemia in the M1 mimicked the post-stroke dysphagia (PSD) pathology, as indicated by impaired water consumption and electromyographic responses in the mylohyoid. This dysfunction could be rescued by electroacupuncture (EA) stimulation at the CV23 acupoint (EA-CV23) in a manner dependent on the excitatory neurons in the contralateral M1 L5. Furthermore, neuronal activation in both the parabrachial nuclei (PBN) and nucleus tractus solitarii (NTS), which was modulated by the M1, was required for the ability of EA-CV23 treatment to improve swallowing function in male PSD model mice. Together, these results uncover the importance of the M1-PBN-NTS neural circuit in driving the protective effect of EA-CV23 against swallowing dysfunction and thus reveal a potential strategy for dysphagia intervention.

Swallowing function after acute ischemic stroke: Development and validation of a novel clinical prognostic model

Background

Predicting the duration of dysphagia after acute ischemic stroke (AIS) is important for clinical treatment decisions.

Objective

The purpose of this study is to assess the swallowing function of AIS patients and to develop and validate a prognostic model for the need for nasogastric tube (NGT) in these patients.

Materials and methods

We included 554 AIS patients during 2018–2019 as the development group and had 186 AIS patients as the external validation group. The primary end point of the study was the retention of NGT in patients 1 week after admission (Functional Oral Intake Scale ≤ 4). Swallowing function and stroke-associated pneumonia (SAP) at 1 month post-onset were also the objectives of this study. The volume-viscosity swallow test (V-VST) was used to assess the patient’s impaired swallowing function. The Predictive model was built by logistic regression.

Results

Overall, a total of 104 patients required indwelling NGT at 1 week of AIS onset in development group. The final prognostic model includes 5 variables: age (OR: 1.085, 95%CI: 1.049–1.123), neutrophil-to-lymphocyte ratio (NLR) (OR: 1.332, 95%CI: 1.090–1.626), NIHSS (OR: 1.092, 95%CI: 1.025–1.164), history of drinking (OR: 2.532, 95%CI: 1.452–4.417) and stroke location (Subtentorial vs. Supratentorial, OR: 1.954, 95%CI: 1.088–3.509). The prediction model had an AUC of 0.810, while the external validation group was 0.794.

Conclusion

In stroke patients, it is very important to decide early whether to indwell a NGT. The nomogram will support decision making for NGT insertion and help these patients recover from their condition.

Estimation of the Motor Threshold for Near-Rectangular Stimuli Using the Hodgkin-Huxley Model

The motor threshold measurement is a standard in preintervention probing in TMS experiments. We aim to predict the motor threshold for near-rectangular stimuli to efficiently determine the motor threshold size before any experiments take place. Estimating the behavior of large-scale networks requires dynamically accurate and efficient modeling. We utilized a Hodgkin-Huxley (HH) type model to evaluate motor threshold values and computationally validated its function with known true threshold data from 50 participants trials from state-of-the-art published datasets. For monophasic, bidirectional, and unidirectional rectangular stimuli in posterior-anterior or anterior-posterior directions as generated by the cTMS device, computational modeling of the HH model captured the experimentally measured population-averaged motor threshold values at high precision (maximum error ≤ 8%). The convergence of our biophysically based modeling study with experimental data in humans reveals that the effect of the stimulus shape is strongly correlated with the activation kinetics of the voltage-gated ion channels. The proposed method can reliably predict motor threshold size using the conductance-based neuronal models and could therefore be embedded in new generation neurostimulators. Advancements in neural modeling will make it possible to enhance treatment procedures by reducing the number of delivered magnetic stimuli to participants.

Cortical Representations of Transversus Abdominis and Multifidus Muscles Were Discrete in Patients with Chronic Low Back Pain: Evidence Elicited by TMS

Introduction

The transversus abdominis (TVA) and multifidus (MF) muscles are the main segmental spinal stabilizers that are controlled by the primary motor cortex of the brain. However, relocations of the muscle representation in the motor cortex may occur after chronic lower back pain (cLBP); it still needs more evidence to be proven. The current study was aimed at applying transcranial magnetic stimulation (TMS) to investigate the changes of representation of TVA and MF muscles at the cortical network in individuals with cLBP.

Methods

Twenty-four patients with cLBP and 12 age-matched healthy individuals were recruited. Responses of TVA and MF to TMS during muscle contraction were monitored and mapped over the contralateral cortex using a standardized grid cap. Maps of the center of gravity (CoG), area, volume, and latency were analyzed, and the asymmetry index was also computed and compared.

Results

The locations of MF CoG in cLBP individuals were posterior and lateral to the CoG locations in healthy individuals. In the healthy group, the locations of TVA and MF CoG were closed to each other in both the left and right hemispheres. In the cLBP group, these two locations were next to each other in the right hemisphere but discrete in the left hemisphere. In the cLBP group, the cortical motor map of TVA and MF were mutually symmetric in five out of eleven (45.5%) subjects and leftward asymmetric in four out of ten (40.0%) subjects.

Conclusions

Neural representations of TVA and MF muscles were closely organized in both the right and left motor cortices in the healthy group but were discretely organized in the left motor cortex in the cLBP group. This provides strong support for the neural basis of pathokinesiology and clinical treatment of cLBP.