The efficacy of neuromuscular electrical stimulation with alternating currents in the kilohertz frequency to stimulate gait rhythm in rats following spinal cord injury

Three-dimensional analysis of the characteristics of joint motion and gait pattern in a rodent model following spinal nerve ligation

BACKGROUND

The spinal nerve ligation (SNL) rat is well known as the most common rodent model of neuropathic pain without motor deficit. Researchers have performed analyses using only the von Frey and thermal withdrawal tests to evaluate pain intensity in the rat experimental model. However, these test are completely different from the neurological examinations performed clinically. We think that several behavioral reactions must be observed following SNL because the patients with neuropathic pain usually have impaired coordination of the motions of the right-left limbs and right-left joint motion differences. In this study, we attempted to clarify the pain behavioral reactions in SNL rat model as in patients. We used the Kinema-Tracer system for 3D kinematics gait analysis to identify new characteristic parameters of each joint movement and gait pattern.

RESULTS

The effect of SNL on mechanical allodynia was a 47 ± 6.1% decrease in the withdrawal threshold during 1-8 weeks post-operation. Sagittal trajectories of the hip, knee and ankle markers in SNL rats showed a large sagittal fluctuation of each joint while walking. Top minus bottom height of the left hip and knee that represents instability during walking was significantly larger in the SNL than sham rats. Both-foot contact time, which is one of the gait characteristics, was significantly longer in the SNL versus sham rats: 1.9 ± 0.15 s vs. 1.03 ± 0.15 s at 4 weeks post-operation (p = 0.003). We also examined the circular phase time to evaluate coordination of the right and left hind-limbs. The ratio of the right/left circular time was 1.0 ± 0.08 in the sham rats and 0.62 ± 0.15 in the SNL rats at 4 weeks post-operation.

CONCLUSIONS

We revealed new quantitative parameters in an SNL rat model that are directly relevant to the neurological symptoms in patients with neuropathic pain, in whom the von Frey and thermal withdrawal tests are not used at all clinically. This new 3D analysis system can contribute to the analysis of pain intensity of SNL rats in detail similar to human patients' reactions following neuropathic pain.

Comparison between Russian and Aussie currents in the grip strength and thickness muscles of the non-dominant hand: A double-blind, prospective, randomized-controlled study

Objectives

This study aims to compare the Russian and Aussie currents in the force gain and hypertrophy of the forearm muscles responsible for the grip.

Patients and methods

This double-blind, prospective, randomized-controlled study included a total of 30 healthy women (mean age: 20.2±1.7 years; range, 18 to 25 years) between May 2018 and July 2018. The participants were randomly divided into three groups: control group (CG, n=10), Aussie current group (ACG, n=10), and Russian current group (RCG, n=10). All three groups underwent a force test with a gripping dynamometer and the collection of images of the superficial and deep flexor muscles of the fingers with diagnostic ultrasound. The CG received a fictious current stimulus, while the other two groups received the designated stimuli from their currents. Further evaluations were performed after 24 h of the 12th application of the current.

Results

For grip, there were no significant differences in the moment of evaluation and interaction, while the effect size yielded certain points to advantages of force gain for the group using the RCG. The thickness of the superficial muscles showed a significant difference for the first evaluation between CG and RCG (p=0.014) and between RCG and ACG (p=0.010), indicating a larger effect size for RCG.

Conclusion

Our study results show that the Russian current is proven to be the mode which yields the most optimal results.

16-Channel biphasic current-mode programmable charge balanced neural stimulation

BACKGROUND

Neural stimulation is an important method used to activate or inhibit action potentials of the neuronal anatomical targets found in the brain, central nerve and peripheral nerve. The neural stimulator system produces biphasic pulses that deliver balanced charge into tissue from single or multichannel electrodes. The timing and amplitude of these biphasic pulses are precisely controlled by the neural stimulator software or imbedded algorithms. Amplitude mismatch between the anodic current and cathodic current of the biphasic pulse will cause permanently damage for the neural tissues. The main goal of our circuit and layout design is to implement a 16-channel biphasic current mode programmable neural stimulator with calibration to minimize the current mismatch caused by inherent complementary metal oxide semiconductor (CMOS) manufacturing processes.

METHODS

This paper presents a 16-channel constant current mode neural stimulator chip. Each channel consists of a 7-bit controllable current DAC used as sink and source current driver. To reduce the LSB quantization error and the current mismatch, an automatic calibration circuit and flow diagram is presented in this paper. There are two modes of operation of the stimulator chip-namely, stimulation mode and calibration mode. The chip also includes a digital interface used to control the stimulator parameters and calibration levels specific for each individual channel.

RESULTS

This stimulator Application Specific Integrated Circuit (ASIC) is designed and fabricated in a 0.18 μm High-Voltage CMOS technology that allows for ±20 V power supply. The full-scale stimulation current was designed to be at 1 mA per channel. The output current was shown to be constant throughout the timing cycles over a wide range of electrode load impedances. The calibration circuit was also designed to reduce the effect of CMOS process variation of the P-channel metal oxide semiconductor (PMOS) and N-channel metal oxide semiconductor (NMOS) devices that will result in charge delivery to have less than 0.13% error.

CONCLUSIONS

A 16-channel integrated biphasic neural stimulator chip with calibration is presented in this paper. The stimulator circuit design was simulated and the chip layout was completed. The chip layout was verified using design rules check (DRC) and layout versus schematic (LVS) design check using computer aided design (CAD) software. The test results we presented show constant current stimulation with charge balance error within 0.13% least-significant-bit (LSB). This LSB error was consistent throughout a variety stimulation patterns and electrode load impedances.