Long-term results of a simultaneous trial of deep brain and motor cortex stimulation in refractory neuropathic pain

Objective: Although deep brain stimulation(DBS) and motor cortex stimulation(MCS)are effective in patients with refractory neuropathic pain, their application is still empirical; there is no consensus on which technique is better. Methods: To enhance the success rate of trial stimulation of invasive neuromodulation techniques and identify approapriate stimulation targets in individual patients, we performed a simultaneous trial of thalamic ventralis caudalis(Vc) DBS and MCS in 11 patients with chronic neuropathic pain and assessed the results of the trial stimulation and long-term analgesia. Results: Of the 11 patients implanted with both DBS and MCS electrodes, nine(81.8%)had successful trials. Seven of these nine patients(77.8%) responded to MCS, and two(18.2%) responded to Vc DBS. With long-term follow-up(56 ± 27.5 months), the mean numerical rating scale decreased significantly(P < 0.05). The degree of percentage pain relief in the chronic MCS(n = 7) and chronic DBS(n = 2) groups were 34.1% ± 18.2%and 37.5%, respectively, and there was no significant difference(P = 0.807). Five out of the seven MCS patients(71%) and both DBS patients had long-term success with the treatments, defined as >30% pain relief compared with baseline. Conclusions: With simultaneous trial of DBS and MCS, we could enhance the success rate of invasive trials. Considering the initial success rate and the less invasive nature of epidural MCS over DBS, we suggest that MCS may be a better, initial means of treatment in chronic intractable neuropathic pain. Further investigations including other subcortical target-associated medial pain pathways are warranted.

Magnetic stimulation at Neiguan(PC6) acupoint increases connections between cerebral cortex regions

Stimulation at specific acupoints can activate cortical regions in human subjects.Previous studies have mainly focused on a single brain region.However,the brain is a network and many brain regions participate in the same task.The study of a single brain region alone cannot clearly explain any brain-related issues.Therefore,for the present study,magnetic stimulation was used to stimulate the Neiguan（PC6） acupoint,and 32-channel electroencephalography data were recorded before and after stimulation.Brain functional networks were constructed based on electroencephalography data to determine the relationship between magnetic stimulation at the PC6 acupoint and cortical excitability.Results indicated that magnetic stimulation at the PC6 acupoint increased connections between cerebral cortex regions.

Disappearance of unaffected motor cortex activation by repetitive transcranial magnetic stimulation in a patient with cerebral infarct

The ipsilateral motor pathway from the unaffected motor cortex to the affected extremity is one of the motor recovery mechanisms following stroke （Jang, 2011）. Because stroke patients who had shown recovery by this mechanism usually showed poorer motor function, compared with patients who showed recovery by other mechanisms, several researchers have considered this mechanism as a maladaptive plasticity （]ang, 2013）.

Mechanisms responsible for the effect of median nerve electrical stimulation on traumatic brain injuryinduced coma: orexin-A-mediated N-methyl-Daspartate receptor subunit NR1 upregulation

Electrical stimulation of the median nerve is a noninvasive technique that facilitates awakening from coma. In rats with traumatic brain injury-induced coma, median nerve stimulation markedly enhances prefrontal cortex expression of orexin-A and its receptor, orexin receptor 1. To further understand the mechanism underlying wakefulness mediated by electrical stimulation of the median nerve, we evaluated its effects on the expression of the N-methyl-D-aspartate receptor subunit NR1 in the prefrontal cortex in rat models of traumatic brain injury-induced coma, using immunohistochemistry and western blot assays. In rats with traumatic brain injury, NR1 expression increased with time after injury. Rats that underwent electrical stimulation of the median nerve（30 Hz, 0.5 ms, 1.0 m A for 15 minutes） showed elevated NR1 expression and greater recovery of consciousness than those without stimulation. These effects were reduced by intracerebroventricular injection of the orexin receptor 1 antagonist SB334867. Our results indicate that electrical stimulation of the median nerve promotes recovery from traumatic brain injury-induced coma by increasing prefrontal cortex NR1 expression via an orexin-A-mediated pathway.

Decoding brain responses to pixelized images in the primary visual cortex: implications for visual cortical prostheses

Visual cortical prostheses have the potential to restore partial vision. Still limited by the low-resolution visual percepts provided by visual cortical prostheses, implant wearers can currently only ＂see＂ pixelized images, and how to obtain the specific brain responses to different pixelized images in the primary visual cortex（the implant area） is still unknown. We conducted a functional magnetic resonance imaging experiment on normal human participants to investigate the brain activation patterns in response to 18 different pixelized images. There were 100 voxels in the brain activation pattern that were selected from the primary visual cortex, and voxel size was 4 mm × 4 mm × 4 mm. Multi-voxel pattern analysis was used to test if these 18 different brain activation patterns were specific. We chose a Linear Support Vector Machine（LSVM） as the classifier in this study. The results showed that the classification accuracies of different brain activation patterns were significantly above chance level, which suggests that the classifier can successfully distinguish the brain activation patterns. Our results suggest that the specific brain activation patterns to different pixelized images can be obtained in the primary visual cortex using a 4 mm × 4 mm × 4 mm voxel size and a 100-voxel pattern.

Mechanism of GABA Receptors Involved in Spasticity Inhibition Induced by Transcranial Magnetic Stimulation Following Spinal Cord Injury

The effect of high-frequency repetitive transcranial magnetic stimulation（r TMS） on spasticity following spinal cord injury（SCI） and the action mechanism were investigated. SCI models were established in Sprague-Dawley rats. Five groups were set up： normal control group, SCI-7 day（7D） model group, SCI-14 D model group, SCI-7D r TMS group and SCI-14 D r TMS group（n=10 each）. The rats in SCI r TMS groups were treated with 10 Hz r TMS at 8th day and 15 th day after SCI respectively. Motor recovery and spasticity alleviation were evaluated by BBB scale once a week till the end of treatment. Finally, different parts of tissues were dissected out for detection of GABA receptors using Western blotting and polymerase chain reaction（PCR） technique. The results showed that the BBB scores after treatment were significantly higher in SCI-7D r TMS group than in SCI-14 D r TMS group（P〈0.05）. The GABA receptors were down-regulated more significantly in SCI-14 D model group than in SCI-7D model group（P〈0.05）. At different time points, r TMS treatment could affect the up-regulation of GABA receptors： The up-regulation of GABA receptors was more obvious in SCI-7D r TMS group than in SCI-14 D r TMS treatment group（P〈0.05）. It was concluded that 10-Hz r TMS could alleviate spasticity following SCI and promote the motor recovery in rats, which might be attributed to the up-regulation of GABA receptors. It was also suggested that early high-frequency r TMS treatment after SCI may achieve more satisfactory curative effectiveness.

Novel role for transcranial magnetic stimulation to study post-traumatic respiratory neuroplasticity

Transcranial magnetic stimulation-a tool used in humans：Transcranial magnetic stimulation（TMS）is a non-invasive widespread clinical tool used to stimulate cortical areas in human subjects.This technique utilizes a brief,highly intense magnetic field applied to cortical areas,which locally depolarized interneurons（Weber and Eisen,2002）.

High-frequency and brief-pulse stimulation pulses terminate cortical electrical stimulation-induced afterdischarges

Brief-pulse stimulation at 50 Hz has been shown to terminate afterdischarges observed in epilepsy patients. However, the optimal pulse stimulation parameters for terminating cortical electrical stimulation-induced afterdischarges remain unclear. In the present study, we examined the effects of different brief-pulse stimulation frequencies（5, 50 and 100 Hz） on cortical electrical stimulation-induced afterdischarges in 10 patients with refractory epilepsy. Results demonstrated that brief-pulse stimulation could terminate cortical electrical stimulation-induced afterdischarges in refractory epilepsy patients. In conclusion,（1） a brief-pulse stimulation was more effective when the afterdischarge did not extend to the surrounding brain area.（2） A higher brief-pulse stimulation frequency（especially 100 Hz） was more likely to terminate an afterdischarge.（3） A low current intensity of brief-pulse stimulation was more likely to terminate an afterdischarge.

A useful electroencephalography(EEG) marker of brain plasticity: delta waves

Plasticity is a natural property of living organisms that is crucial for adaptation and evolution.Over the last decades,the availability of sophisticated neuroimaging techniques（in particular,functional magnetic resonance imaging（f MRI）,and transcranial magnetic stimulation（TMS））,has made it possible to explore in vivo the on-line functioning of brain and its plasticity.However,