Two forms of short-interval intracortical inhibition in human motor cortex

BackgroundPulses of transcranial magnetic stimulation (TMS) with a predominantly anterior-posterior (AP) or posterior-anterior (PA) current direction over the primary motor cortex appear to activate distinct excitatory inputs to corticospinal neurons. In contrast, very few reports have examined whether the inhibitory neurons responsible for short-interval intracortical inhibition (SICI) are sensitive to TMS current direction.ObjectivesTo investigate whether SICI evaluated with AP and PA conditioning stimuli (CS_PA and CS_AP) activate different inhibitory pathways. SICI was always assessed using a PA-oriented test stimulus (TS_PA).MethodsUsing two superimposed TMS coils, CS_PA and CS_AP were applied at interstimulus intervals (ISI) of 1–5 ms before a TS_PA, and at a range of different intensities. Using a triple stimulation design, we then tested whether SICI at ISI of 3 ms using opposite directions of CS (SICI_CSPA3 and SICI_CSAP3) interacted differently with three other forms of inhibition, including SICI at ISI of 2 ms (SICI_CSPA2), cerebellum-motor cortex inhibition (CBI 5 ms) and short-latency afferent inhibition (SAI 22 ms). Finally, we compared the effect of tonic and phasic voluntary contraction on SICI_CSPA3 and SICI_CSAP3.ResultsCS_AP produced little SICI at ISIs = 1 and 2 ms. However, at ISI = 3 ms, both CS_AP and CS_PA were equally effective at the same percent of maximum stimulator output. Despite this apparent similarity, combining SICI_CSPA3 or SICI_CSAP3 with other forms of inhibition led to quite different results: SICI_CSPA3 interacted in complex ways with CBI, SAI and SICI_CSPA2, whereas the effect of SICI_CSAP3 appeared to be quite independent of them. Although SICI_CSPA and SICI_CSAP were both reduced by the same amount during voluntary tonic contraction compared with rest, in a simple reaction time task SICI_CSAP was disinhibited much earlier following the imperative signal than SICI_CSPA.ConclusionsSICI_CSPA appears to activate a different inhibitory pathway to that activated by SICI_CSAP. The difference is behaviourally relevant since the pathways are controlled differently during volitional contraction. The results may explain some previous pathological data and open the possibility of testing whether these pathways are differentially recruited in a range of tasks.     

Ocular pressure waveform reflects ventricular bigeminy and aortic insufficiency

Ocular pulse amplitude (OPA) is defined as the difference between maximum and minimum intraocular pressure (IOP) during a cardiac cycle. Average values of OPA range from 1 to 4 mmHg. The purpose of this investigation is to determine the source of an irregular IOP waveform with elevated OPA in a 48-year-old male. Ocular pressure waveforms had an unusual shape consistent with early ventricular contraction. With a normal IOP, OPA was 9 mmHg, which is extraordinarily high. The subject was examined by a cardiologist and was determined to be in ventricular bigeminy. In addition, he had bounding carotid pulses and echocardiogram confirmed aortic insufficiency. After replacement of the aortic valve, the bigeminy resolved and the ocular pulse waveform became regular in appearance with an OPA of 1.6–2.0 mmHg. The ocular pressure waveform is a direct reflection of hemodynamics. Evaluating this waveform may provide an additional opportunity for screening subjects for cardiovascular anomalies and arrhythmias.     

《三指禅》之月经脉论浅析

《三指禅》是一部经典的脉学专著,《三指禅·月经脉论》对月经脉的认识比较全面,有据有例,在病因、证候以及治疗上都做出了独特的见解,对脉学研究的贡献不可磨灭,应重视其地位,更好的发挥其对临床的指导作用。     

Foreign body granuloma around implantable pulse generator for deep brain stimulation: Two case reports

We report two cases of granuloma that occurred around an implantable pulse generator (IPG) for deep brain stimulation. Both cases showed no signs of infection and disappeared after moving the IPG and removing the granulation. If a noninfectious mass is formed, the relocation of IPG may improve it.     

Noninvasive measurement of local arterial pulse wave velocity in humans by ultrasound

An improved method for noninvasive measurement of the local velocity of arterial pulse wave propagation by an echo-tracking-based ultrasound system is described. A data acquisition image interface was programmed in the ultrasound machine simultaneously to record M-mode ultrasound signals at two locations of a given distance apart along an artery. The selections of measurement sites, separation, and time resolution were performed on the control interface. The temporal sampling frequency could be as high as 10?kHz. The displacements of the blood vessel wall along the time axis were calculated from the M-mode signals by cross-correlation of the radio-frequency data and the distension waveforms were obtained. The temporal separation of the feet of the distension curves from the two measurement locations was derived to give the travel time of the pulse wave. Measurements were made in vivo on human carotid arteries. The pulse wave velocities measured from four volunteers were from 4.1 to 7.2 m/s with coefficients of variation from 5.9 to 29.5%. Some of the factors contributing to the variation in measured values of the velocity are discussed. The method is simple to implement and should be suitable for clinical research into local pulse wave velocity.     

Aortic Stiffness Assessed by Global Pulse Wave Velocity in Postmenopausal Women: An Ultrasonographic Study

Objective: The first goal of our study was to investigate major determinants of aortic stiffness in postmenopausal women using an echocardiographic method to calculate global pulse wave velocity (PWVg) rather than the less accurate carotid–femoral pulse wave velocity (PWVc). The second goal was to relate PWVg to the absolute risk of major cardiovascular (CV) events estimated by CV risk factors. Patients and methods: Two hundred forty‐four consecutive women who presented to our heart station were screened. One hundred twenty‐two were postmenopausal, either natural or surgical, whereas 122 were premenopausal. The mean age of the patients was 54 ± 13 years. Individuals were categorized as current smokers, former smokers, or nonsmokers and hypertensive or not. Hypercholesterolemia and diabetes mellitus were defined. Aortic stiffness was assessed by PWVg measured with pulsed Doppler, the interval between the beginning of QRS complex and the foot of the systolic upstroke in the Doppler spectral envelope was calculated at the aortic valve site and at the right common femoral artery. PWVg was calculated between the aortic valve and right common femoral artery by dividing the straight line distance between the two by the transit time. Results: There was a highly significant statistical difference (P < 0.0012) in PWVg between menstruating women and postmenopausal women. Similarly, this difference in PWVg was also noted among the menstruating population (P < 0.0014) when comparing normotensive women and hypertensive women. In postmenopausal women, PWVg was 6.8 m/sec in normotensive women and 7.56 m/sec in hypertensive women (P < 0.007). Conclusion: PWVg was increased in postmenopausal women compared with menstruating women. Systemic hypertension has an independent, but additive effect on aortic stiffness assessed by PWVg. Our study supports the usefulness of the assessment of aortic stiffness as a marker of CV disease and to identify subjects at risk at an early age.     

高血压病患者大动脉功能改变与血管弹性的研究

目的 探讨高血压病患者动脉弹性功能变化情况及其影响因素.方法 应用脉搏波速度自动测量系统对62例健康人和232例高血压病患者进行颈动脉-股动脉脉搏波速度(CFPWV)检测,并分析与收缩压(SBP)、舒张压(DBP)、平均压(MBP)、脉压(PP)、体重指数、年龄等指标的相关性.结果 高血压病患者的CFPWV显著高于健康人(P＜0.01).高血压病患者CFPWV显著高于健康人(P＜0.01),并与年龄、SBP、DBP、MBP、PP呈显著的负相关(P＜0.01).结论 高血压病患者的动脉弹性明显降低,检测CFPWV可观察动脉早期功能改变,对临床早期干预治疗具有重要意义.