The soleus late response elicited by transcranial magnetic stimulation reflects agonist-antagonist postural adjustment in the lower limbs.

OBJECTIVES: We studied the origin and underlying mechanism of the soleus late response (SLR) at a mean latency of 90 ms following transcranial magnetic stimulation. METHODS: The soleus primary response (SPR) and SLR were recorded from the soleus (SOL) muscle in 27 normal subjects under various conditions using a double-cone coil. We also tested 28 patients demonstrating neurological disorders with postural disturbance. RESULTS: The amplitude of the SPR gradually increased and its latency gradually decreased against the voluntary contraction (0-80%) of the tibialis anterior (TA) muscle. In contrast, the SLR amplitude was the greatest at a 20% TA contraction while the SLR latency was the shortest at a 40% TA contraction. The preactivation of SOL enhanced the SPR response but did not evoke the SLR. The SPR amplitude was significantly augmented while standing, however, the SLR amplitude tended to decrease. The SLR was never obtained following the stimulation of the brainstem, lumbar roots and peroneal nerve. The SLR was abnormal in patients with cerebellar ataxia and Parkinson's disease while the SPR was normal. CONCLUSIONS: A lack of any correlation between the SPR and SLR suggests that the SLR does not originate in the corticospinal tract. The SLR may thus be a polysynaptic response related to the postural control of the agonist and antagonist organization between the TA and SOL.     

Contribution of transcranial magnetic stimulation to assessment of brain connectivity and networks

The goal of this review is to show how transcranial magnetic stimulation (TMS) techniques can make a contribution to the study of brain networks. Brain networks are fundamental in understanding how the brain operates. Effects on remote areas can be directly observed or identified after a period of stimulation, and each section of this review will discuss one method. EEG analyzed following TMS is called TMS-evoked potentials (TEPs). A conditioning TMS can influence the effect of a test TMS given over the motor cortex. A disynaptic connection can be tested also by assessing the effect of a pre-conditioning stimulus on the conditioning-test pair. Basal ganglia-cortical relationships can be assessed using electrodes placed in the process of deep brain stimulation therapy. Cerebellar-cortical relationships can be determined using TMS over the cerebellum. Remote effects of TMS on the brain can be found as well using neuroimaging, including both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The methods complement each other since they give different views of brain networks, and it is often valuable to use more than one technique to achieve converging evidence. The final product of this type of work is to show how information is processed and transmitted in the brain.     

Effects of deep brain stimulation on the primary motor cortex: Insights from transcranial magnetic stimulation studies

Deep brain stimulation (DBS) implanted in different basal ganglia nuclei regulates the dysfunctional neuronal circuits and improves symptoms in movement disorders. However, the understanding of the neurophysiological mechanism of DBS is at an early stage. Transcranial magnetic stimulation (TMS) can be used safely in movement disorder patients with DBS, and can shed light on how DBS works. DBS at a therapeutic setting normalizes the abnormal motor cortical excitability measured with motor evoked potentials (MEP) produced by primary motor cortical TMS. Abnormal intracortical circuits in the motor cortex tested with paired-pulse TMS paradigm also show normalization with DBS. These changes are accompanied with improvements in symptoms after chronic DBS. Single-pulse DBS produces cortical evoked potentials recorded by electroencephalography at specific latencies and modulates motor cortical excitability at certain time intervals measured with MEP. Combination of basal ganglia DBS with motor cortical TMS at stimulus intervals consistent with the latency of cortical evoked potentials delivered in a repetitive mode produces plastic changes in the primary motor cortex. TMS can be used to examine the effects of open and closed loop DBS. Patterned DBS and TMS delivered in a repetitive mode may be developed as a new therapeutic method for movement disorder patients.     

Cerebellar transcranial magnetic stimulation: The role of coil type from distinct manufacturers

BackgroundStimulating the cerebellum with transcranial magnetic stimulation is often perceived as uncomfortable. No study has systematically tested which coil design can effectively trigger a cerebellar response with the least discomfort.ObjectiveTo determine the relationship between perceived discomfort and effectiveness of cerebellar stimulation using different coils: MagStim (70 mm, 110 mm-coated, 110-uncoated), MagVenture and Deymed.MethodsUsing the cerebellar-brain inhibition (CBI) protocol, we conducted a CBI recruitment curve with respect to each participant’s maximum tolerated-stimulus intensity (MTI) to assess how effective each coil was at activating the cerebellum.ResultsOnly the Deymed double-cone coil elicited CBI at low intensities (−20% MTI). At the MTI, the MagStim (110 mm coated/uncoated) and Deymed coils produced reliable CBI, whereas no CBI was found with the MagVenture coil.Conclusions: The Deymed double-cone coil was most effective at cerebellar stimulation at tolerable intensities. These results can guide coil selection and stimulation parameters when designing cerebellar TMS studies.     

Early and late motor evoked potentials reflect preset agonist–antagonist organization in lower limb muscles

A single transcranial magnetic stimulus can evoke two involuntary muscle responses in lower limb muscles of healthy humans. The purpose of the present study was to find out if these responses, when evoked during the processing period of a simple or choice reaction time task, such as ankle dorsiflexion, have specific characteristics related to the task. During the auditory reaction time, a transcranial magnetic stimulus was delivered to observe changes in the excitability of the central nervous system. A dual-cone coil was used, which effectively stimulated the fairly deep-lying lower limb motor cortex. Stimuli were delivered in a random order with 20–300-ms delays from the auditory gosignal. Motor evoked potentials (MEP) in right and left anterior tibial and soleus muscles were analyzed while early MEPs were observed invariably in both muscles; late MEPs occurred consistently only in soleus muscles. Both early and late MEP amplitudes were larger in simple reaction time trials than in choice reaction time trials. The late MEP appeared earlier in the simple reaction time task than in the choice reaction time task, reflecting faster central processing of simple reaction time tasks. The amplitude of the soleus late MEP in the simple reaction time task followed closely the amplitude of anterior tibial early MEP, suggesting a preset agonist–antagonist organization. This relationship was not present in the choice reaction time task.© 1995 John Wiley &Sons, Inc.     

The long-term effect of repetitive transcranial magnetic stimulation in the treatment of intractable insomnia

ObjectiveTo explore the differences in clinical efficacy of different courses of repetitive transcranial magnetic stimulation (rTMS) in the treatment of intractable insomnia and the duration of clinical efficacy after cessation of treatment.Method70 patients with intractable insomnia were randomly divided into 1 treatment course group and 2 treatment courses group. The rTMS course consisted of daily sessions of 1200 stimuli for the r-DLPFC at a frequency of 1 Hz and 800 stimuli for parietal lobe (CPZ) at a frequency of 1 Hz. The pitchburg sleep index (PSQI), Hamilton depression scale (HAMD), Hamilton anxiety scale (HAMA), and cardiopulmonary coupled sleep (CPC) were assessed for 35 patients in each group at baseline, at 2 weeks, and at 1 and 3 months after treatment.ResultThe scores of PSQI, HAMD and HAMA in the 2 groups were significantly improved after 1 month of follow-up after rTMS treatment (p < 0.01). The long-term effect of different treatment courses is different. After 2 consecutive courses of treatment, there was still a significant difference between the 3-month follow-up and the pre-treatment period (p < 0.05). However, there was no statistical difference between the 3-month follow-up of one course of treatment and the pre-treatment period. The results of CPC test showed that the improvement of total sleep time (TST), and deep sleep time (DST) was basically consistent with the assessment of PSQI, HAMD and HAMA that the clinical efficacy of the 3-month follow-up was better than that of one course of treatment after 2 consecutive courses of treatment.ConclusionThe treatment of refractory insomnia by rTMS is effective, and the duration of the curative effect is related to the course of treatment. 2 consecutive courses of treatment still have a certain effect after 3 months, which is worthy of clinical promotion.     

Neurophysiological features of fasciculation potentials evoked by transcranial magnetic stimulation in amyotrophic lateral sclerosis

We report 13 patients with amyotrophic lateral sclerosis in whom fasciculation potentials (FPs) driven by transcranial magnetic stimulation (TMS) were recorded. A total of 18 different FPs were analyzed. TMS-driven fasciculations had a simple morphology and were stable. Complex potentials were never cortically driven. Recruitment by a slight voluntary contraction was verified in 7 of 13 tested FPs. FPs were driven by threshold stimuli in 7 of 10 patients and by stimuli 5% below threshold in 3 of 6. Mapping demonstrated that FPs were driven in an area close to the center of gravity of the muscle cortical area. In one case FPs were evoked from most of the cortical representation area of a very weak muscle. Three other patients with profuse fasciculations associated with other clinical conditions were also studied. No TMS evoked fasciculation was observed in this group. The results of this systematic study suggest that cortically evoked FPs arise centrally, at spinal cord or even more proximally, and can represent a marker of increased corticomotor excitability, which is predominant at an earlier phase but can persist as the disease progresses. Received: 15 April 1999/Received in revised form: 28 July 1999/Accepted: 2 November 1999     

Predominant activation of I1-waves from the leg motor area by transcranial magnetic stimulation

We performed transcranial magnetic stimulation (TMS) to elucidate the D- and I-wave components comprising the motor evoked potentials (MEPs) elicited from the leg motor area, especially at near-threshold intensity. Recordings were made from the tibialis anterior muscle using needle electrodes. A figure-of-eight coil was placed so as to induce current in the brain in eight different directions, starting from the posterior-to-anterior direction and rotating it in 45 degrees steps. The latencies were compared with those evoked by transcranial electrical stimulation (TES) and TMS using a double cone coil. Although the latencies of MEPs ranged from D to I3 waves, the most prominent component evoked by TMS at near-threshold intensity represented the I1 wave. With the double cone coil, the elicited peaks always represented I1 waves, and D waves were evoked only at very high stimulus intensities, suggesting a high effectiveness of this coil in inducing I1 waves. Using the figure-of-eight coil, current flowing anteriorly or toward the hemisphere contralateral to the recorded muscle was more effective in eliciting large responses than current flowing posteriorly or toward the ipsilateral hemisphere. The effective directions induced I1 waves with the lowest threshold, whereas the less effective directions elicited I1 and I2 waves with a similar frequency. Higher stimulus intensities resulted in concomitant activation of D through I3 waves with increasing amount of D waves, but still the predominance of I1 waves was apparent. The amount of I waves, especially of I1 waves, was greater than predicted by the hypothesis that TMS over the leg motor area activates the output cells directly, but rather suggests predominant transsynaptic activation. The results accord with those of recent human epidural recordings.     

The effects of repetitive transcranial magnetic stimulation on depressive symptoms and the P300 event-related potential

Changes in the Hamilton Depression Rating Scale and the P₃₀₀ auditory event-related potential were assessed in 10 patients with depression before and after a treatment course of five daily sessions of 10?Hz repetitive transcranial magnetic stimulation (rTMS) over the left prefrontal cortex. The patients were initially randomly allocated either to an active or a placebo rTMS treatment. All patients received both types of treatment separated by an interval of 4?weeks. The median Hamilton score decreased by 7 points following active rTMS and by 1?point after sham (p=0.075). Active rTMS was associated with a significant increase in the P₃₀₀ amplitude compared with sham (p=0.02). There was no correlation between changes in P₃₀₀ measurements and the Hamilton scores after active treatment. We conclude that five daily sessions of left prefrontal rTMS treatment is not of sufficient duration to make a significant improvement in depressive symptoms.     

Efficacy of repetitive transcranial magnetic stimulation in depression: A review of the evidence

Repetitive transcranial magnetic stimulation (rTMS) is a novel treatment in psychiatry. We reviewed all published evidence on the efficacy of this treatment option in depressive disorders. An extensive electronic and manual search for eligible research reports identified only 12 studies that met the predetermined criteria for inclusion. rTMS was administered differently in most studies, and patient characteristics varied widely. A formal meta-analysis of the studies was thus not possible. Instead, we conducted a qualitative evaluation of the included studies. The antidepressive efficacy was not consistent, and where efficacy was demonstrated, it was modest in most studies. Some patients had good but transient responses to rTMS. Treatment gains were not maintained beyond the treatment period. Comparisons with electroconvulsive therapy (ECT) indicated the superiority of ECT. More, larger and more carefully designed studies are needed to demonstrate convincingly a clinically relevant effect of rTMS. We conclude that there is insufficient evidence for rTMS as a valid treatment for depression at present.     

Pinging the brain with transcranial magnetic stimulation reveals cortical reactivity in time and space

BackgroundSingle-pulse transcranial magnetic stimulation (TMS) elicits an evoked electroencephalography (EEG) potential (TMS-evoked potential, TEP), which is interpreted as direct evidence of cortical reactivity to TMS. Thus, combining TMS with EEG can be used to investigate the mechanism underlying brain network engagement in TMS treatment paradigms. However, controversy remains regarding whether TEP is a genuine marker of TMS-induced cortical reactivity or if it is confounded by responses to peripheral somatosensory and auditory inputs. Resolving this controversy is of great significance for the field and will validate TMS as a tool to probe networks of interest in cognitive and clinical neuroscience.ObjectiveHere, we delineated the cortical origin of TEP by spatially and temporally localizing successive TEP components, and modulating them with transcranial direct current stimulation (tDCS) to investigate cortical reactivity elicited by single-pulse TMS and its causal relationship with cortical excitability.MethodsWe recruited 18 healthy participants in a double-blind, cross-over, sham-controlled design. We collected motor-evoked potentials (MEPs) and TEPs elicited by suprathreshold single-pulse TMS targeting the left primary motor cortex (M1). To causally test cortical and corticospinal excitability, we applied tDCS to the left M1.ResultsWe found that the earliest TEP component (P25) was localized to the left M1. The following TEP components (N45 and P60) were largely localized to the primary somatosensory cortex, which may reflect afferent input by hand-muscle twitches. The later TEP components (N100, P180, and N280) were largely localized to the auditory cortex. As hypothesized, tDCS selectively modulated cortical and corticospinal excitability by modulating the pre-stimulus mu-rhythm oscillatory power.ConclusionTogether, our findings provide causal evidence that the early TEP components reflect cortical reactivity to TMS.     

重复经颅磁刺激治疗伴躯体疼痛抑郁症患者的疗效观察

目的探讨重复经颅磁刺激（rTMS）治疗伴有躯体疼痛的抑郁症患者的临床疗效和安全性。方法将60例伴有躯体疼痛的抑郁症患者随机分为两组,各30例,均给予度洛西汀口服8周,研究组同时联用rTMS,对照组则予假性rTMS刺激4周,观察8周。于治疗前及治疗后第1,2,3,4,8周应用汉密尔顿抑郁量表（HAMD）、医学结局研究用疼痛量表（MOSPM）和治疗中出现的不良反应量表（TESS）评定两组的治疗效果和安全性。结果治疗结束后两组的MOSPM和HAMD评分均较治疗前显著下降（P〈0．05）;治疗第1,2,3,4周,研究组的MOSPM评分低于对照组,差异有统计学意义（P〈0．05）;治疗第2,3,4周,研究组的HAMD评分低于对照组而显效率高于对照组,差异有统计学意义（P〈0．05）;治疗第8周,两组患者的MOSPM和HAMD评分及显效率差异均无统计学意义（P〉0．05）,治疗期间无严重不良反应发生。结论rTMS能有效治疗伴躯体疼痛的抑郁症,迅速缓解疼痛改善抑郁症状,早期疗效优于单一度洛西汀治疗,且安全性高。     

Reliability of lower limb transcranial magnetic stimulation outcomes in the ipsi- and contralesional hemispheres of adults with chronic stroke

Objective

To investigate the ability of transcranial magnetic stimulation (TMS) outcomes in the chronic stroke population to (i) track individual plastic changes and (ii) detect differences between individuals. To this end, intrarater “test-retest” reliability (relative and absolute) was tested for the ipsilesional and contralesional hemispheres.

On the estimation of silent period thresholds in transcranial magnetic stimulation

ObjectiveWe evaluated the induction of corticospinal silent period (SP) using transcranial magnetic stimulation (TMS) at stimulation intensities normalized to resting motor threshold (rMT) or silent period thresholds (SPTs). The aim was to reduce the characteristic inter-individual variation in SP measurements in healthy population to improve the sensitivity of such measurements.MethodsThe cortical representation area of the right hand musculature of 12 healthy subjects was stimulated with navigated TMS with varying stimulating intensities. Subsequently, the individual SPTs for eliciting SPs of 20, 30, and 50 ms in duration were determined from the input–output characteristics.ResultsWhile SPT for 20 and 50 ms SPs differed from rMT, the SPT for 30 ms was similar to rMT. Nevertheless, the inter-individual variation in SP duration was reduced significantly at 120% of SPT30 when compared with SP durations obtained at 120% of rMT.ConclusionsInter-individual variation in the SP duration decreases when applying TMS at stimulation intensities normalized to the individual SPTs instead to the rMT. This makes the SP duration more specific to inhibition and less affected by changes in cortical excitability.SignificanceUse of individual SPTs may improve the sensitivity of the SP measures in studies with inter-individual design.     

The novelty value of the combined use of electroencephalography and transcranial magnetic stimulation for neuroscience research

Electroencephalographic (EEG) responses measured simultaneously with transcranial magnetic stimulation (TMS) have opened a new window into the human nervous system. The combined use of TMS and EEG (TMS-EEG) provides a means for the detailed study of the reactivity of any cortical region in the intact brain; also the reactivities of non-motor cortical areas related with higher-order functions are now appreciable. A recent epochal finding concerning cortical reactivity is that neuronal activation is induced with remarkably low stimulation intensities. This knowledge is significant when optimizing experimental set-ups for maximal patient safety. Stimulation of different cortical areas evokes different patterns of remote EEG activity, confirming the viability of TMS-EEG for the study of corticocortical connections. In this review, we expand on these and other notable findings related with TMS-EEG. We discuss the possibilities of the technique for the study of cortical reactivity and connectivity. We show that TMS-EEG allows the study of interhemispheric connections with high spatiotemporal specificity and the assessment of cortical reactivity with excellent sensitivity.     

重复经颅磁刺激对抑郁障碍患者睡眠质量改善的临床研究

研究背景 目前抑郁障碍患病率呈逐年升高之趋势,综合性医院就诊的抑郁障碍患者多以躯体化症状为主诉,尤以睡眠障碍最为常见,改善睡眠质量成为迫切的需要.本研究探讨重复经颅磁刺激(rTMS)对改善抑郁障碍患者睡眠质量的疗效.方法 以躯体化症状就诊的抑郁障碍患者随机分为单纯药物治疗组(药物治疗组)和rTMS联合药物治疗组(联合治疗组),分别采用汉密尔顿焦虑量表(HAMA)和抑郁量表(HAMD)评价两种治疗方法的疗效.结果 两种治疗方法在不同观察时间点,各项评分差异均有统计学意义(P=0.000),且治疗方法与观察时间点之间存在交互作用(均P=0.000).与药物治疗组相比,联合治疗组患者治疗1、2和4周时HAMA评分、HAMD总评分和躯体化症状评分降低(均P=0.000);治疗1周时睡眠障碍评分降低(P=0.001);治疗1和2周时抑郁症状评分降低(均P=0.000).与治疗前相比,药物治疗组患者各项评分除治疗后1周差异无统计学意义(P＞0.05)外,其余各观察时间点差异均有统计学意义(P=0.000);联合治疗组患者治疗后各项评分差异均有统计学意义(P=0.000).治疗后1、2和4周,两组治疗总有效率比较,联合治疗组[63.64％(14/22)、86.36％(19/22)、90.91％ (20/22)]高于药物治疗组[20％ (4/20)、55％ (11/20)、75％(15/20)],差异有统计学意义(均P=0.000).结论 重复经颅磁刺激联合药物治疗抑郁障碍患者起效早、效果好,尤其对睡眠质量的改善优于单纯药物治疗,可以提高抑郁障碍患者的治疗依从性.     

重复经颅磁刺激联合帕罗西汀治疗抑郁症首次发病患者的起效时间及对执行功能的影响

目的 探讨重复经颅磁刺激(repetitive transcranial magnetic stimulation,rTMS)联合帕罗西汀治疗抑郁症首次发病患者的起效时间及对执行功能的影响.方法 符合美国精神障碍诊断与统计手册第4版诊断标准的抑郁症首次发病患者46例,采用随机数字表法随机分为rTMS组(25例)和伪rTMS组(21例);2组性别、年龄、受教育年限、病程的差异均无统计学意义(x2检验和t检验,均P＞0.05).2组患者均接受帕罗西汀(20 ～40 mg/d)治疗.rTMS组接受左侧背外侧前额叶皮质rTMS刺激,10 Hz,80％运动阈值,刺激2s,间隔28 s,800个脉冲,每周5次,连续4周共20次.伪rTMS组应用伪刺激线圈,刺激部位、次数、频率同rTMS组;有振动声音,但不产生磁场效应.治疗前及治疗第1,2,3,4,8周末均对2组患者评估汉密尔顿抑郁量表(24项,Hamilton Depression Scale-24,HAMD),并均在治疗前和治疗第8周末完成威斯康星卡片分类测验(Wisconsin Card Sorting Test,WCST).结果 治疗前rTMS组HAMD评分[(43.64±10.05)分]与伪rTMS组[(42.58±9.29)分]的差异无统计学意义(t=0.348,P=0.730),治疗第1,2,3,4周末,rTMS组HAMD评分[(31.82±5.93),(23.82±4.05),(17.95±6.82),( 12.55±3.14)分]明显低于伪rTMS组[(37.00±8.43),(27.95±6.87),(22.11±5.23),(16.47±4.03)分],差异有统计学意义(t=-2.302,P=0.026;t=-2.382,P=0.022;t=-2.929,P=0.006;t=-3.502,P=0.001);治疗第8周末rTMS组HAMD评分[(7.77±4.12)分]与伪rTMS组[(9.05±5.07)分]的差异无统计学意义(t=-0.892,p=0.378).治疗第4周末,rTMS组的显效率和治愈率(95％和73％)明显高于伪rTMS组(63％和37％),差异有统计学意义(x2 =6.771,P=0.016;x2 =6.866,P=0.009).治疗第8周末,rTMS组的显效率和治愈率(91％和82％)与伪rTMS组(84％和74％)的差异无统计学意义(x2=0.427,P=0.649;x2=0.394,P =0.709).治疗前、治疗第8周末,2组患者WCST评分的差异均无统计学意义(P均＞0.05).结论 高频rTMS联合帕罗西汀治疗抑郁症首次发病患者起效快,对患者的执行功能无影响.     

The combination of neuronavigation with transcranial magnetic stimulation for treatment of opercular gliomas of the dominant brain hemisphere

Objective

The objective of this study is to investigate the application of transcranial magnetic stimulation combined with neuronavigation for preoperative mapping of the language area in neurosurgical interventions on the opercular area of the dominant hemisphere.

Methods

Five patients were operated upon gliomas in the opercular area. For localization of the speech area a transcranial magnetic stimulator MEDTRONIC-MagPro was used. BrainLAB-VectorVision Neuronavigation system was utilized for precise planning of the operative approach.

Results

Gross total resection was achieved in all patients. Three-month postoperative follow-up was done. Three of the patients had a transient postoperative motor aphasia which resolved within 1 month.

Conclusion

This method is useful for preoperative localization of the speech area, as well as preoperative planning of the operative approach and intra-operative planning of the direction of brain retraction and operative corridor.     

BOLD fMRI response to direct stimulation (transcranial magnetic stimulation) of the motor cortex shows no decline with age

Previous studies using BOLD fMRI to examine age-related changes in cortical activation used tasks that relied on peripheral systems to activate the brain. They were unable to distinguish between alterations due to age-related changes in the periphery and actual changes in cortical physiology. Transcranial magnetic stimulation (TMS), which allows direct, noninvasive stimulation of cortical neurons, was interleaved with BOLD fMRI to study 6 young and 5 old subjects. Three different tasks were compared: direct stimulation by TMS, indirect active stimulation produced by a motor task, and indirect passive stimulation produced by hearing the TMS coil discharge.Direct neuronal stimulation by TMS produced similar fMRI signal increases in both groups, suggesting that cortical physiology itself may not necessarily decline with age.