Changes in Dermatomal Somatosensory Evoked Potentials according to Stimulation Intensity and Severity of Carpal Tunnel Syndrome

Objective

To investigate the change of latency of cervical dermatomal somatosensory evoked potential (DSEP) according to stimulation intensity (SI) and severity of carpal tunnel syndrome (CTS).

Methods

Stimulation sites were the C6, C7, and C8 dermatomal areas. Two stimulation intensities 1.5×sensory threshold (ST) and 2.5×ST were used on both normal and CTS patients.

Results

In moderate CTS, the latencies of C6 and C7 DSEP during 1.5×ST SI and those of C7 DSEP during 2.5×ST SI were significantly delayed compared with the values of normal subjects. Significant correlation between the latency of C7 DSEP of 2.5×ST stimulation and the median sensory nerve conduction velocity was observed.

Conclusion

We suggest that these data can aid in the diagnosis of cervical sensory radiculopathy using low stimulation intensity and of those who have cervical sensory radiculopathy combined with CTS patients.     

Multi-locus transcranial magnetic stimulation—theory and implementation

Background

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation method: a magnetic field pulse from a TMS coil can excite neurons in a desired location of the cortex. Conventional TMS coils cause focal stimulation underneath the coil centre; to change the location of the stimulated spot, the coil must be moved over the new target. This physical movement is inherently slow, which limits, for example, feedback-controlled stimulation.

Antidepressant-like effect of magnetic resonance imaging-based stimulation in mice

INTRODUCTION: It has been reported that a novel type of magnetic resonance imaging (MRI) scan called echo planar magnetic resonance spectroscopic imaging (EP-MRSI) may show antidepressant effects. We examined whether the two routine diagnostic protocols of MRI [T1 and echo planar diffusion weighted imaging (EPI-DWI)], have antidepressant-like effects in an animal model of depression. METHODS: The effects of standard EPI-DWI and T1 MRI on immobility, swimming and climbing times in the modified forced swimming test (FST) in mice were examined. After exposure to the first session of modified forced swimming test, we randomly divided the mice into four groups. The first group (T1 MRI group, n=21) received a 15-minute stimulation of T1 sequence. The second group (EPI-DWI MRI group, n=21) received a 15-minute stimulation of EPI-DWI protocol. The third group (sham group, n=21) spent 15 min in a tunnel similar to the MRI gantry in terms of size, temperature and light intensity and received recorded sounds from a normal session of EPI-DWI with similar duration and intensity. The fourth group acted as controls (n=21).The second session of the modified FST was conducted twelve hours later. The mean of immobility, swimming and climbing times in this session were compared to the control group. RESULTS: T1 weighted and EPI-DWI MRI groups showed a reduction in immobility time compared to the control group (P value<0.002, P value<0.017 respectively). This effect is comparable to that seen in the FST after the administration of antidepressant agents. The climbing time in the group subjected to EPI-DWI MRI was longer than the control group (P value<0.035). Previous studies showed similar effects after the administration of antidepressant drugs affecting the catecholamine systems. The swimming time in the T1 MRI group was significantly longer than the control group (P value<0.037). Previous studies showed qualitatively similar effect to that of anti-depressant drugs affecting the serotoninergic systems. The swimming, climbing and immobility times in the sham and control groups showed no significant difference. CONCLUSIONS: Our findings raise the possibility that MRI-based stimulation may have antidepressant-like effects in mice. This is likely to be through different mechanisms in T1 weighted and EPI-DWI protocols. However the possible biological basis of this effect is not yet understood and we would advocate further studies of MRI-based stimulation effects on transmitters in the different organs in the body specially the brain.     

脑皮质电刺激对癫痫大鼠脑皮质兴奋性的影响

目的 观察重复脑皮质电刺激对氯化铁诱发慢性癫痫大鼠模型脑皮质兴奋性的影响.方法 通过在运动感觉区脑皮质注射氯化铁建立慢性癫痫大鼠模型,给予脑皮质低频(1 Hz)低强度(0.1 mA)和低频(1 Hz)高强度(1.0 mA)、高频(100 Hz)低强度(0.1 mA)和高频(100 Hz)高强度(1.0 mA)不同的重复电刺激,检测电刺激前后脑皮质后放电阈值、后放电时程和行为学评分.假刺激慢性癫痫大鼠作为对照组.结果 后放电阈值低频低强度组(2.10±0.38)mA与对照组(1.50±0.33)mA相比差异有统计学意义(P＜0.05).行为学评分和后放电时程各组与对照组相比差异无统计学意义.行为学评分与后放电阈值的比值低频低强度组(1.88±0.60)和低频高强度组(2.18±0.38)与对照组(3.22±0.67)相比差异有统计学意义(P＜0.01和P＜0.05).结论 重复低频低强度脑皮质电刺激可以升高氯化铁诱发慢性癫痫大鼠模型的脑皮质后放电阈值,降低脑皮质兴奋性,提示合适参数的脑皮质电刺激对氯化铁诱发大鼠癜痫具有抑制作用.     

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

ObjectiveSystematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).MethodsPubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.ResultsERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.ConclusionsWhile there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.SignificanceThe review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.     

Occupation and communication programs for post-coma persons with or without consciousness disorders who show extensive motor impairment and lack of speech

These two studies were aimed at extending the assessment of technology-aided programs for post-coma persons with extensive motor impairment and lack of speech. Specifically, Study I assessed a new program arrangement, in which stimulation access and caregiver attention could be obtained with variations of the same response (i.e., single- versus double-hand closure) by three participants who were diagnosed at the upper level of the minimally conscious state at the start of the study. Study II was aimed at enabling two persons who had emerged from a minimally conscious state to engage in leisure activities, listen to audio-recordings of family members, and send and receive messages. The responses selected for these participants were hand pressure and eyelid closure, respectively. The results of both studies were positive. The participants of Study I increased their responding to increase their stimulation input and caregiver interaction. The participants of Study II managed to successfully select all the options the program included (i.e., the leisure options, as well as the family and communication options). General implications of the programs and the related technology packages for intervention with post-coma persons with multiple disabilities are discussed.     

Dysphagia and hemispheric stroke: A transcranial magnetic study

INTRODUCTION: Dysphagia is a common and distressing consequence of hemispheric stroke. STUDY AIM: To verify the usefulness of transcranial magnetic stimulation (TMS) studies of swallowing in healthy subjects and in stroke patients. MATERIAL AND METHODS: TMS studies of the motor cortical projections to the upper esophageal sphincter were performed in 45 patients with acute mono-hemispheric stroke (26 patients with dysphagia) and 20 healthy adult volunteers. RESULTS: TMS of either hemisphere in normal volunteers evoked motor evoked potentials (MEP) in the esophagus. The average point of optimal excitability was slightly more anterior in the right hemisphere; otherwise, MEP amplitudes and latencies were similar from both hemispheres as were the areas of the cortical map. The cortical map area and amplitude of MEPs were significantly smaller and the latencies longer after stimulation of the affected hemisphere compared with the unaffected hemisphere and pooled control data. Twenty-four dysphagic patients (92.3%) had abnormalities of MEP of the affected hemisphere, while only five non-dysphagic patients (26%) had these abnormalities. Dysphagic patients were older and had more disability compared with non-dysphagic patients. MEPs of the affected hemisphere of patients with dysphagia were later and smaller in amplitude than MEPs of non-dysphagic patients. The cortical map area was also smaller. CONCLUSION: The esophagus is represented bilaterally in motor cortex, but the hot spot lies more anterior to Cz in right hemisphere compared to left hemisphere. Both the severity of stroke and neuroplasticity of the unaffected hemisphere have implications in the development of dysphagia.     

How structural and functional MRI can inform dual-site tACS parameters: A case study in a clinical population and its pragmatic implications

BackgroundAbnormalities in frontoparietal network (FPN) were observed in many neuropsychiatric diseases including substance use disorders. A growing number of studies are using dual-site-tACS with frontoparietal synchronization to engage this network. However, a computational pathway to inform and optimize parameter space for frontoparietal synchronization is still lacking. In this case study, in a group of participants with methamphetamine use disorders, we proposed a computational pathway to extract optimal electrode montage while accounting for stimulation intensity using structural and functional MRI.MethodsSixty methamphetamine users completed an fMRI drug cue-reactivity task. Four main steps were taken to define electrode montage and adjust stimulation intensity using 4x1 high-definition (HD) electrodes for a dual-site-tACS; (1) Frontal seed was defined based on the maximum electric fields (EF) predicted by simulation of HD montage over DLPFC (F3/F4 in EEG 10–10), (2) frontal seed-to-whole brain context-dependent correlation was calculated to determine connected regions to frontal seeds, (3) center of connected cluster in parietal cortex was selected as a location for placing the second set of HD electrodes to shape the informed montage, (4) individualized head models were used to determine optimal stimulation intensity considering underlying brain structure. The informed montage was compared to montages with large electrodes and classic frontoparietal HD montages (F3-P3/F4-P4) in terms of tACS-induced EF and ROI-to-ROI task-based/resting-state connectivity.ResultsCompared to the large electrodes, HD frontoparietal montages allow for a finer control of the spatial peak fields in the main nodes of the FPN at the cost of lower maximum EF (large-pad/HD: max EF[V/m] = 0.37/0.11, number of cortical sub-regions that EF exceeds 50% of the max = 77/13). For defining stimulation targets based on EF patterns, using group-level head models compared to a single standard head model results in comparable but significantly different seed locations (6.43 mm Euclidean distance between the locations of the frontal maximum EF in standard-space). As expected, significant task-based/resting-state connections were only found between frontal-parietal locations in the informed montage. Cue-induced craving score was correlated with frontoparietal connectivity only in the informed montage (r = ?0.24). Stimulation intensity in the informed montage, and not in the classic HD montage, needs 40% reduction in the parietal site to reduce the disparity in EF between stimulation sites.ConclusionThis study provides some empirical insights to montage and dose selection in dual-site-tACS using individual brain structures and functions and proposes a computational pathway to use head models and functional MRI to define (1) optimum electrode montage for targeting FPN in a context of interest (drug-cue-reactivity) and (2) proper transcranial stimulation intensity.     

颞叶癫痫脑电图分析及病灶超微结构观察

目的 研究影像学检查无异常的颞叶癫痫患者,电生理异常与皮层棘波灶及海马超微病变的关系.方法 选择经CT或MRI检查未见异常的颞叶癫痫患者7例,术前做脑电图或24h视频脑电监测,术中在脑电监测下取颞叶大脑皮质棘波灶和海马组织,做电镜观察.结果 7例患者电生理检查均可见典型痫样放电.颞叶皮质痫灶和海马可见不同程度的神经元固缩,胶质细胞变性,胶质增生,突触数量及突触结构改变,血脑屏障破坏等改变.结论 影像学无异常的颞叶癫痫患者颞叶皮层痫灶和海马超微结构病理变化明显,特别是突触的变化,是导致癫痫患者脑电生理机能异常及癫痫反复自发性发作的形态学基础.