Historia y principios básicos de la estimulación magnética transcraneal

La estimulación magnética transcraneal (EMT) es una técnica no invasiva que consiste en la utilización de campos magnéticos para estimular a las neuronas de la corteza cerebral. Si bien la electricidad se ha pretendido emplear previamente en el campo de la medicina, la historia de la EMT se remonta al descubrimiento de la inducción electromagnética, por Faraday, en el siglo XIX. Sin embargo, no fue hasta la década de 1980 cuando Anthony Barker, en la Universidad de Sheffield, desarrolló el primer dispositivo de EMT. La EMT funciona mediante una bobina colocada en el cuero cabelludo, la cual produce un campo magnético que puede atravesar el cráneo y estimular las neuronas corticales. La intensidad y la frecuencia del campo magnético pueden ajustarse para dirigirse a zonas específicas del cerebro y producir efectos excitatorios e inhibitorios. Los principios de la EMT se basan en el concepto de neuroplasticidad, que se refiere a la capacidad del cerebro para cambiar y adaptarse en respuesta a nuevas experiencias y estímulos. Al estimular las neuronas del cerebro con la EMT, es posible inducir cambios en la actividad neuronal y la conectividad, lo que a su vez puede provocar cambios cognitivos y en el estado de ánimo.

Transcranial magnetic stimulation (TMS) is a noninvasive technique that uses magnetic fields to stimulate neurons in the cerebral cortex. While electricity has previously been intended to be used in the medical field, the history of TMS dates back to the discovery of electromagnetic induction by Faraday in the 19th century. However, it was not until the 1980s when Anthony Barker developed the first TMS device at the University of Sheffield. TMS works by means of a coil placed against the scalp, thereby producing a magnetic field. This magnetic field can pass through the skull and stimulate cortical neurons. The intensity and frequency of the magnetic field can be adjusted to target specific areas of the brain and produce excitatory and inhibitory effects. The principles of TMS are based on the concept of neuroplasticity, which refers to the brain's ability to change and adapt in response to new experiences and stimuli. By stimulating neurons in the brain with TMS, it is possible to cause changes in neuronal activity and connectivity, which in turn can lead to cognitive and mood changes.

Effect of Shugan Tiaoshen acupuncture combined with western medication on depression-insomnia comorbidity due to COVID-19 quarantine: a multi-central randomized controlled trial / 中国针灸

OBJECTIVE@#To observe the effect of Shugan Tiaoshen acupuncture (acupuncture for soothing the liver and regulating the mentality) combined with western medication on depression and sleep quality in the patients with depression-insomnia comorbidity due to COVID-19 quarantine, and investigate the potential mechanism from the perspective of cortical excitability.@*METHODS@#Sixty patients with depression-insomnia comorbidity due to COVID-19 quarantine were randomly divided into an acupuncture group and a sham-acupuncture group, 30 cases in each one. The patients of both groups were treated with oral administration of sertraline hydrochloride tablets. In the acupuncture group, Shugan Tiaoshen acupuncture was supplemented. Body acupuncture was applied to Yintang (GV 24+), Baihui (GV 20), Hegu (LI 4), Zhaohai (KI 6), Qihai (CV 6), etc. The intradermal needling was used at Xin (CO15), Gan (CO12) and Shen (CO10). In the sham-acupuncture group, the sham-acupuncture was given at the same points as the acupuncture group. The compensatory treatment was provided at the end of follow-up for the patients in the sham-acupuncture group. In both groups, the treatment was given once every two days, 3 times a week, for consecutive 8 weeks. The self-rating depression scale (SDS) and insomnia severity index (ISI) scores were compared between the two groups before and after treatment and 1 month after the end of treatment (follow-up) separately. The cortical excitability indexes (resting motor threshold [rMT], motor evoked potential amplitude [MEP-A], cortical resting period [CSP]) and the level of serum 5-hydroxytryptamine (5-HT) were measured before and after treatment in the two groups.@*RESULTS@#After treatment and in follow-up, SDS and ISI scores were decreased in both groups compared with those before treatment (P<0.05), and the scores in the acupuncture group were lower than those in the sham-acupuncture group (P<0.05), and the decrease range in the acupuncture group after treatment was larger than that in the sham-acupuncture group (P<0.05). After treatment, rMT was reduced (P<0.05), while MEP-A and CSP were increased (P<0.05) in the acupuncture group compared with that before treatment. The levels of serum 5-HT in both groups were increased compared with those before treatment (P<0.05). The rMT in the acupuncture group was lower than that in the sham-acupuncture group, while MEP-A and CSP, as well as the level of serum 5-HT were higher in the acupuncture group in comparison with the sham-acupuncture group (P<0.05).@*CONCLUSION@#Shugan Tiaoshen acupuncture combined with western medication can relieve depression and improve sleep quality in the patients with depression-insomnia comorbidity due to COVID-19 quarantine, which is probably related to rectifying the imbalanced excitatory and inhibitory neuronal functions.

Advance in Neural Control in Eccentric Exercise (review) / 中国康复理论与实践

The nervous system controls eccentric exercise in a special way. During eccentric exercise, excitability increases in cortex, and inhibition decreases, causing excitability decrease in spinal cords. In another hand, increased cortical excitability results in extra excitatory compensation for spinal inhibition. The excitability of the corticospinal pathway depends on the balance between excitability and inhibition of the spinal cord level finally, which usually decreases. Many factors, such as the intensity of contraction, can affect the balance of corticospinal excitability. There is a cross-over effect in eccentric exercise, which promotes corticospinal excitability in untrained limbs. However, the effects and mechanisms of muscle length, fatigue and training duration are still unclear, and current researches have focused in the healthy populations. More researches are needed to explore the effects of eccentric exercise on ill populations.

Effect of electroacupuncture combined with motor training on motor learning and motor cortex excitability / 中国针灸

OBJECTIVE@#To compare the effect of electroacupuncture (EA), motor training (MT) and EA combined with MT on motor learning and motor cortex excitability in healthy subjects, and to explore the effect of EA combined with MT on synaptic metaplasticity.@*METHODS@#Using self-control design, 12 healthy subjects were assigned into an EA group, a motor training group (MT group) and an EA plus motor training group (EA+MT group) successively, wash-out period of at least 2 weeks was required between each group. EA was applied at left Hegu (LI 4) in the EA group for 30 min, with continuous wave, 2 Hz in frequency and 0.5-1 mA in density. Motor training of left hand was adopted in the MT group for 30 min. EA and motor training were adopted in the EA+MT group successively. The time of finishing grooved pegboard test (GPT) was observed, and the average amplitude of motor evoked potentials (MEPs), the rest motor threshold (rMT) and the latency were recorded by transcranial magnetic stimulation technique before intervention (T0), after intervention (T1) and 30 min after EA (T3) in the EA group and the EA+MT group, T0 and T1 in the MT group.@*RESULTS@#Compared with T0, the time of finishing GPT was shortened at T1 in the MT group and at T2 in the EA group and the EA+MT group (@*CONCLUSION@#In physiological state, electroacupuncture combined with motor training have a synergistic effect on motor learning, while have no such effect on excitability of cerebral motor cortex.

Correlating cognition and cortical excitability with pain in fibromyalgia: a case control study

Abstract Background: Fibromyalgia is a chronic pain disorder characterized by widespread musculoskeletal symptoms, primarily attributed to sensitization of somatosensory system carrying pain. Few reports have investigated the impact of fibromyalgia symptoms on cognition, corticomotor excitability, sleepiness, and the sleep quality — all of which can deteriorate the quality of life in fibromyalgia. However, the existing reports are underpowered and have conflicting directions of findings, limiting their generalizability. Therefore, the present study was designed to compare measures of cognition, corticomotor excitability, sleepiness, and sleep quality using standardized instruments in the recruited patients of fibromyalgia with pain-free controls. Methods: Diagnosed cases of fibromyalgia were recruited from the Rheumatology department for the cross-sectional, case-control study. Cognition (Mini-Mental State Examination, Stroop color-word task), corticomotor excitability (Resting motor threshold, Motor evoked potential amplitude), daytime sleepiness (Epworth sleepiness scale), and sleep quality (Pittsburgh sleep quality index) were studied according to the standard procedure. Results: Thirty-four patients of fibromyalgia and 30 pain-free controls were recruited for the study. Patients of fibromyalgia showed decreased cognitive scores (p = 0.05), lowered accuracy in Stroop color-word task (for color: 0.02, for word: 0.01), and prolonged reaction time (< 0.01, < 0.01). Excessive daytime sleepiness in patients were found (< 0.01) and worsened sleep quality (< 0.01) were found. Parameters of corticomotor excitability were comparable between patients of fibromyalgia and pain-free controls. Conclusions: Patients of fibromyalgia made more errors, had significantly increased reaction time for cognitive tasks, marked daytime sleepiness, and impaired quality of sleep. Future treatment strategies may include cognitive deficits and sleep disturbances as an integral part of fibromyalgia management.(AU)

Effect of Repetitive Transcranial Magnetic Stimulation in Post-stroke Patients with Severe Upper-Limb Motor Impairment

Repetitive transcranial magnetic stimulation (rTMS) has been known to improve the motor function through modulation of excitability in the cerebral cortex. However, most studies with rTMS were limited to post-stroke patients with mild to moderate motor impairments. The effect of rTMS on severe upper-limb motor impairment remains unclear. Therefore, this study investigated the effects of rTMS on the upper extremity function in post-stroke patients with severe upper-limb motor impairment. Subjects were divided into 3 groups, low-, high-frequency rTMS and control group were received stimulation 10 times for 2 weeks. The motor scale of Fugl-Meyer Assessment (FMA) and cortical excitability on the unaffected hemisphere were measured before and after performing 10 rTMS sessions. The motor scale of upper extremity FMA (UE-FMA) and shoulder component of the UE-FMA were significantly improved in both low- and high-frequency rTMS groups. However, no significant improvement was observed in the wrist and hand components. No significant differences were noted in low- and high-frequency rTMS groups. The amplitude of motor evoked potential on the unaffected hemisphere showed a significant decrease in the low- and high-frequency stimulation groups. rTMS may be helpful in improving upper extremity motor function even in post-stroke patients with severe upper-limb motor impairment.

Transcranial magnetic stimulation relieves pain and improves cortical excitability after stroke / 中华物理医学与康复杂志

Objective To investigate the effect of repeatedly applying transcranial magnetic stimulation (rTMS) in treating post-stroke pain (CPSP).Methods Forty stroke survivors experiencing CPSP were randomly divided into a treatment group and a control group,each of 20.All of the patients received conventional rehabilitation.In the treatment group,20 patients received 10 Hz rTMS at 80％ of their resting motor threshold applied over the primary motor cortex on their affected side,while those in the control group received sham stimulation.Both groups were treated once a day,6 times a week for 4 weeks.Before and after the treatment,both groups were assessed using a pain score self-assessed on a visual analogue scale (VAS).Their resting motor thresholds (RMTs),cortical silent periods (CSPs) and motor evoked potentials (MEPs) were also recorded.Results After the intervention,the average VAS score,RMT,CSP and M EP latency of the treatment group were (3.1±1.2),(51.3±4.8)％,(188.9± 63.0) ms and (27.9±5.7)ms,all significantly better than those before the intervention [(5.1± 1.3),(60.1±5.9)％,(239.7±43.5) ms and (35.5±4.4)ms] (P＜0.05).They were also significantly better than those of the control group after the intervention [(4.7±1.0),(57.6±5.1)％,(241.7±33.9)ms and (31.7±5.2)ms] (P＜0.05).Conclusion Transcranial magnetic stimulation can relieve post-stroke pain.The mechanisms might be related to positive changes in cortical excitability in the affected hemisphere.

Changes in Intracortical Excitability of Affected and Unaffected Hemispheres After Stroke Evaluated by Paired-Pulse Transcranial Magnetic Stimulation

OBJECTIVE: To assess the altered pattern of intracortical excitability of the affected and unaffected hemispheres in stroke patients using paired-pulse transcranial magnetic stimulation (TMS). METHODS: We evaluated intracortical inhibition (ICI) and intracortical facilitation (ICF) in both hemispheres at acute and subacute stages of 103 stroke patients using paired-pulse TMS. The patients were divided into two groups: mild-to-moderate patients whose motor evoked potential (MEP) was recorded in the affected hemisphere; and severe patients whose MEP was not recorded in the affected hemisphere. RESULTS: In mild-to-moderate patients, the value of ICI in the affected hemisphere was increased from 70.3% to 77.9% and the value of ICI in the unaffected hemisphere was decreased from 74.8% to 70.3% with eventual progression in acute to subacute stages of stroke. In severe patients, the value of ICI in the unaffected hemisphere was increased from 65.4% to 75.6%. The changes in ICF were not significantly different in this study. CONCLUSION: We conclude that the unaffected hemisphere was more disinhibited than the affected hemisphere in acute phase of mild-to-moderate stroke, and the affected hemisphere was more disinhibited in the subacute stage. The unaffected hemisphere was inhibited in severe cases in acute-to-subacute phases of stroke. This finding facilitates appropriate neuromodulation of acute-to-subacute phases in mild-to-severe stroke patients.

Effect of 1 Hz Repetitive Transcranial Magnetic Stimulation on Upper Limb Motor Function after Stroke / 中国康复理论与实践

@#Objective To observe the effect of 1 Hz repetitive transcranial magnetic stimulation (rTMS) on upper limb motor function after stroke. Methods 40 patients with ischemic internal carotid artery (ICA) stroke were randomly divided into treatment group (n=20) and control group (n=20). Both groups received conventional rehabilitation and medication. The treatment group received rTMS while the control group received pseudo stimulation, 1 Hz at 100% resting motor threshold (RMT) over contralesional motor cortex (unaffected side). The treatment group was tested with motor evoked potentials (MEPs), and both groups were assessed with Fugl-Meyer Assessment (FMA) and grip strength after treatment. Results The amplitude of MEPs of the unaffected cortex increased in the treatment group after treatment (P< 0.001). The treatment group improved in grip strength and the scores of FMA in the affected side compared with the control group after treatment (P<0.001). No serious side-effect was found. Conclusion rTMS was safe and feasible for patients with ischemic ICA stroke to improve the upper limb motor function.

Effect of 1 Hz Repetitive Transcranial Magnetic Stimulation on Upper Limb Motor Function after Stroke / 中国康复理论与实践

Objective To observe the effect of 1 Hz repetitive transcranial magnetic stimulation (rTMS) on upper limb motor function af-ter stroke. Methods 40 patients with ischemic internal carotid artery (ICA) stroke were randomly divided into treatment group (n=20) and control group (n=20). Both groups received conventional rehabilitation and medication. The treatment group received rTMS while the con-trol group received pseudo stimulation, 1 Hz at 100%resting motor threshold (RMT) over contralesional motor cortex (unaffected side). The treatment group was tested with motor evoked potentials (MEPs), and both groups were assessed with Fugl-Meyer Assessment (FMA) and grip strength after treatment. Results The amplitude of MEPs of the unaffected cortex increased in the treatment group after treatment (P<0.001). The treatment group improved in grip strength and the scores of FMA in the affected side compared with the control group after treat-ment (P<0.001). No serious side-effect was found. Conclusion rTMS was safe and feasible for patients with ischemic ICA stroke to im-prove the upper limb motor function.

Effect of 1 Hz Repetitive Transcranial Magnetic Stimulation on Upper Limb Motor Function after Stroke / 中国康复理论与实践

@#Objective To observe the effect of 1 Hz repetitive transcranial magnetic stimulation (rTMS) on upper limb motor function after stroke. Methods 40 patients with ischemic internal carotid artery (ICA) stroke were randomly divided into treatment group (n=20) and control group (n=20). Both groups received conventional rehabilitation and medication. The treatment group received rTMS while the control group received pseudo stimulation, 1 Hz at 100% resting motor threshold (RMT) over contralesional motor cortex (unaffected side). The treatment group was tested with motor evoked potentials (MEPs), and both groups were assessed with Fugl-Meyer Assessment (FMA) and grip strength after treatment. Results The amplitude of MEPs of the unaffected cortex increased in the treatment group after treatment (P< 0.001). The treatment group improved in grip strength and the scores of FMA in the affected side compared with the control group after treatment (P<0.001). No serious side-effect was found. Conclusion rTMS was safe and feasible for patients with ischemic ICA stroke to improve the upper limb motor function.

Cortico-Cortical Modulation Induced by 1-Hz Repetitive Transcranial Magnetic Stimulation of the Temporal Cortex

BACKGROUND AND PURPOSE: Repetitive transcranial magnetic stimulation (rTMS) has potential as a noninvasive neuromodulation treatment method for various neuropsychiatric disorders, and repeated sessions of rTMS are more likely to enhance the therapeutic efficacy. This study investigated neurophysiologic and spatiodynamic changes induced by repeated 1-Hz rTMS of the temporal cortex using transcranial magnetic stimulation (TMS) indices and fluorodeoxyglucose positron emission tomography (FDG-PET). METHODS: Twenty-seven healthy subjects underwent daily 1-Hz active or sham rTMS of the right temporal cortex for 5 consecutive days. TMS indices of motor cortical excitability were measured in both hemispheres daily before and after each rTMS session, and 2 weeks after the last stimulation. FDG-PET was performed at baseline and after the 5 days of rTMS sessions. RESULTS: All subjects tolerated all of the sessions well, with only three of them (11.1%) reporting mild transient side effects (i.e., headache, tinnitus, or local irritation). One-Hz rTMS decreased motor evoked potential amplitudes and delayed cortical silent periods in the stimulated hemisphere. Statistical parametric mapping of FDG-PET data revealed a focal reduction of glucose metabolism in the stimulated temporal area and an increase in the bilateral precentral, ipsilateral superior and middle frontal, prefrontal and cingulate gyri. CONCLUSIONS: Repeated rTMS sessions for 5 consecutive days were tolerated in all subjects, with only occasional minor side effects. Focal 1-Hz rTMS of the temporal cortex induces cortico-cortical modulation with widespread functional changes in brain neural networks via long-range neural connections.

Short-term Modulation of Scalp Acupuncture on Cortical Excitability and Motor-related Cortical Potential / 世界科学技术-中医药现代化

This study was aimed to investigate short-term modulation mechanism of scalp acupuncture according to the experimentation of cortical excitability and motor-related cortical potentials in ten normal volunteers.Through scalp needle stimulation in specific theoretical areas related to underlying cerebral surfaces,scalp acupuncture can be used as an effective therapy by changes in relative cerebral function,which is the basic principle.According to the available neurophysiological data in our study,the modulation of scalp acupuncture displayed in late part of motor-related cortical potential noticed mainly in the motor and sensory cortexes,contralateral to the needle stimulate site.Also,acupuncture can develop inhibition at longer interstimulus intervals,in paired pulse magnetic stimulation,from the somatosensory input of contralateral sensory cortex via scalp needle stimulation.In our study,it might be difficult to produce more acupuncture inhibition.The maintaining of scalp needles subcutaneously without other management after achieving needling sensations cannot achieve the requested strength of the acupuncture stimulation.

Effect of Stimulation Polarity of Transcranial Direct Current Stimulation on Non-dominant Hand Function

OBJECTIVE: To evaluate motor excitability and hand function on the non-dominant side according to the polarity of transcranial direct current stimulation (tDCS) on the motor cortex in a healthy person. METHOD: tDCS was applied to the hand motor cortex for 15 minutes at an intensity of 1 mA in 28 healthy right-handed adults. Subjects were divided randomly into four groups: an anodal tDCS of the non-dominant hemisphere group, a cathodal tDCS of the non-dominant hemisphere group, an anodal tDCS of the dominant hemisphere group, and a sham group. We measured the motor evoked potential (MEP) in the abductor pollicis brevis and Jabsen-Taylor hand function test (JTT) in the non-dominant hand prior to and following tDCS. All study procedures were done under double-blind design. RESULTS: There was a significant increase in the MEP amplitude and a significant improvement in the JTT in the non-dominant hand following anodal tDCS of the non-dominant hemisphere (p<0.05). But there was no change in JTT and a significant decrease in the MEP amplitude in the non-dominant hand following cathodal tDCS on the non-dominant hemisphere and anodal tDCS of the dominant hemisphere. CONCLUSION: Non-dominant hand function is improved by increased excitability of the motor cortex. Although motor cortex excitability is decreased in a healthy person, non-dominant hand function is maintained. A homeostatic mechanism in the brain might therefore be involved in preserving this function. Further studies are warranted to examine brain functions to clarify this mechanism.

Motor cortex excitability in Parkinson's disease and multiple system atrophy / 中华物理医学与康复杂志

Objective To observe any differences in motor cortex excitability between Parkinson's disease (PD)patients and patients with multiple system atrophy (MSA) and to explore whether motor evoked potentials (MEPs) can be used as an electrophysiological indicator for differentiating the 2 diseases.Methods Thirty-four PD patients, 22 MSA patients and 15 age- and sex-matched healthy control subjeets were included in this study. Relaxed motor thresholds (RMTs), central motor conduction time (CMCTs) and MEP amplitudes (AMPs) were recorded in all three groups. The relationships of RMT, CMCT and AMP with the severity of the disease were observed.Results Average RMT in the PD group was significantly lower than that in the MSA and control groups. Average RMT in the MSA group was also significantly lower than that in the control group. There was no significant difference among the three groups with regard to CMCT. AMP in the PD group was significantly higher on average than in the MSA and control groups, but there was no significant difference between the MSA and control groups. RMT decreased and CMCT shortened progressively with the severity of the disease in the PD group, but not in the MSA group.Conclusions There were differences in motor cortex excitability between PD patients and MSA patients. MEP RMTs and CMCTs may be valuable for identifying PD and MSAc but the clinical significance of the amplitude differences remains to be further explored.

The Short-term Modulation of Scalp Acupuncture on the Cortical Excitability in Patients with Parkinson's Disease: A Pilot Study / 世界科学技术-中医药现代化

Acupuncture was frequently used for alternative treatments in Parkinson's disease because of its safety,but there was an argument whether acupuncture improves motor symptoms or not.Besides,few electrophysiological studies were designed for acupuncture combined with Parkinson's disease Using the technique of paired transcranial pulse magnetic stimulation,we measured the excitability of corticocortical inhibitory circuits to investigate effects of scalp acupuncture from 9 patients with Parkinson's disease.Although patients didn't take any short-term benefit in motor symptoms through the treatment of scalp acupuncture,there was no any adverse event,and some electrophysical effects developed in patients.The enhanced corticocortical inhibition on motor cortex possibly developed at longer interstimulus intervals,and there was a relatively increase in later part of motor-related cortical potentials on the central part and right-side near vertex around over sensory cortex,but was not significant in early potentials.So a further long-term study is essential to ascertain the physical mechanism and clinical effects in scalp acupuncture.

The Effect of Transcranial Direct Current Stimulation on Cortical Excitability and Motor Function in a Stroke Patient: A case report

In this case study, we investigated the change of cortical excitability and motor function recovery after transcranial direct current stimulation (tDCS). A patient with chronic right middle cerebal artery territory infarction received tDCS. We performed anodal tDCS on her ipsilesional primary motor cortex which was found by motor evoked potential and conventional occupational therapy for 2 weeks. We evaluated upper extremity function with Fugl-Meyer Assessment (FMA) before and after, one and three months after tDCS. In addition, functional magnetic resonance imaging (FMR) was carried out to evaluate the change of cortical excitability. FMA score was improved after tDCS and the improvement was prominent at one and three months later compared to pre-treatment score. And cortical excitability of ipsilesional primary motor cortex was increased after tDCS. As these results show tDCS seems to be useful tool in promoting motor recovery through increasing cortical excitability in stroke patients.

Facilitation of Cortical Excitability by Action Related Sentence

OBJECTIVE: To investigate the effect of action related visual and auditory stimuli on the motor evoked potential (MEP) of hand. METHOD: Right handed fifteen healthy adults without neurological deficit were included. Visual lingual stimulation was given on the computer monitor with the sentence and auditory lingual stimulation was given 10 repetitions of the above sentence using computer speaker with eyes closed. MEPs from transcranial and transcervical magnetic stimulation were recorded on the abductor pollicis brevis of the right hand. RESULTS: The latency of MEPs was shortened and the amplitude of MEPs with transcranial magnetic stimulation after lingual stimulation (p<0.05). However, the latency and amplitude of with transcervical stimulation did not show significant changes. CONCLUSION: Cortical excitability was enhanced by action related visual or auditory stimuli. Exercise accompanied by visual or auditory lingual stimulation rather than simple exercise might be useful for facilitating cortical excitability.