• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.99-105
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• 1999

Background and Objectives : The Motor evoked potentials (MEP) study may be useful in the evaluation of the degree of impairment in the motor nervous system and in the determination of the prognosis. The purpose of this study is to evaluate the status of central nervous system in acute and subacute state of cerebral ischemia by comparing the changes of MEP in the initial and follow-up study. Methods : Twenty patients with hemiparesis caused by ischemic stroke were recruited for this study. We tested MEP within 7 days and followed-up after 14 days after symptom onset. The cerebral motor cortex area, cervical area for upper extremity and lumbar area for lower extremity were stimulated by transmagnetic stimulator. The central motor conduction time(CMCT) was measured with the difference in MEP caused by stimulating the vertical area and spinal area. The CMCT of hemiparetic patients were classified into three groups-normal, delayed, and no evoked MEP groups. Results : The CMCT in hemiparetic side of acute ischemic stroke patients were singnificantly delayed (P < 0.05) compared with the control group. The CMCT of hemiparetic side in the follow-up study showed no sinificantly difference in comparison to the control group. The prognosis of motor improvement was better in the groups of delayed MEP than the groups of no evoked MEP. Conclusion : The CMCT of hemiparetic and contralateral sides were delayed in acute ischemic stroke, compared with control group and were returned to normal boundaries in subacute state. But in the most cases with no MEP response in the initial study, also showed no MEP response in the follow-up study. The recovery occurred in the subacute state in cases with mild hemiparesis, whereas recovery did not occur in the subacute stage in case with severe hemiparesis.

• The Journal of Internal Korean Medicine
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• v.28 no.3
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• pp.434-441
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• 2007

Objectives : Peripheral neurodegeneration occurs in diabetes mellitus (DM), both sensory and motor nerve. but we don't know exactly if DM affects central nerve pathway for all studies. Electrophysiologic study is one of the most important diagnostic tools for diabetic neuropathy. Electroneurography and electromyography are usually used. but evoked potentials (EP) is more sensitive to small nerve fiber damages and useful for central nerve evaluation in addition to peripheral nerves. Most diabetic neuropathy studies by EP have been performed with somatosensory evoked potentials (SSEP). In contrast, the objective of this study is to investigate if DM targets central motor neurons by assessing the relation between fasting blood sugar (FBS) and motor evoked potentials (MEP) latency. Methods : We inspected the medical records of 34 patients who had MEP tests during admitting days. The latency from cervical portion to abductor pollicis brevis was used as peripheral motor conduction time (PMCT). and the latency from vertex to cervical portion was used as central motor conduction time (CMCT). Then, they were correlated to FBS using correlation analysis. Results : There was a significant linear relation between FBS and PMCT (Pearson's correlation coefficient r=0.487, p<0.01), but a poor linear relation between FBS and CMCT (Pearson's correlation coefficient r=-0.l97. p>0.05). Conclusions : This study suggests that prolonged latencies of MEP in DM may be due to peripheral neuropathy rather than dysfunction of central motor pathway. therefore the clinical use of MEP to diabetic neuropathy has to be divided segmentally.

• Annals of Clinical Neurophysiology
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• v.5 no.2
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• pp.187-191
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• 2003

Purpose: MEPs elicited by transmagnetic stimulations of the motor cortex are facilitated by voluntary muscle contraction. We evaluated the effects of the imagination of the movements on latencies of MEPs and reciprocal inhibition by using transmagnetic stimulations. Methods: Twenty two healthy volunteers(eight men and fourteen women) were studied. TMSs were delivered at rest and during imagining abducting or adducting right thumb. A stimulator with a round coil and a fixed intensity of 80% of maximum was used to evoke MEPs. MEPs were evoked by magnetic stimulations over the scalp and cervical spine(C7-T1), and central motor conduction times(CMCT) were calculated by subtracting the latency of compound muscle action potentials(CMAPs) obtained by stimulating over the cervical spine from that obtained by stimulating over the scalp. The motor evoked potentials were recorded from right abductor pollicis brevis muscle(APB) and adductor pollicis muscle(AP) simultaneously. Results: Imagination of abduction resulted in a shortened latency of the CMAPs in APB, and a prolonged latency in AP. Imagination of adduction resulted in a shortened latency in AP, and a prolonged latency in APB. But the imagination caused no significant change in the latency of CMAPs elicited by stimulation over cervical spine. Therefore, the changes of the CMCTs account for these latency changes with imagination of movement. With the imagination of abduction, there are significant reduction of the CMCT's in APB(10.8%) and prolongation in AP(5.8%). On the other hand, with the imagination of adduction, prolongation of the CMCT's in APB(7.3%) and reduction in AP(5.9%) were observed. Conclusion: These findings indicate that imagination of muscle contraction increases the excitability of the human corticospinal system. Reciprocal inhibition may be accountable for the prolonged latency in the antagonist muscle.

• Journal of Yeungnam Medical Science
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• v.11 no.2
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• pp.248-261
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• 1994

This study was undertaken to evaluate the clinical usefulness of magnetic motor evoked potential (MEP) in the diagnosis of stroke and predicting the motor improvement following stroke. The cortical, cervical and lumbar stimulations were performed in the case of 24 healthy controls and 24 ischemic stroke patients. The central motor conduction time (CMCT) was represented by the difference of latency to a target muscle between after transcranial stimulation and after cervical or lumbar stimulation. There was no case showing no response in controls. But in 11 out of 24 ischemic patients, we could not get cortical MEP. Mean CMCT of abductor pollicis brevis muscle was not significantly different in controls and stroke patients in whom MEPs were recorded. There were significant differences between mean CMCT of normal controls and that of stroke patients showing MEPs in AH Muscle. MEP Results from testing the stroke patients were correlated with site of lesion, degree of motor weakness and motor improvement after 1 to 2 months. These results suggest that magnetic MEP is easy and useful in electrophysiological test of central motor pathway and is useful indicator for representing the motor weakness and predicting the motor outcome in acute ischemic stroke patients.

• Annals of Clinical Neurophysiology
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• v.2 no.2
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• pp.107-113
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• 2000

Background & Objectives : Motor evoked potentials(MEPs) to magnetic trans cranial stimulation were performed to evaluate upper motor neuron involvement and relationship to lower motor neuron involvement in motor neuron disease patients. Method : MEPs were obtained in the 17 consecutive patients with motor neuron disease. These patients were divided into three group based on clinical evidence of upper and lower motor neuron involvement, bulbar symptom; amyotrophic lateral sclerosis(ALS), progressive muscular atrophy(PMA), progressive bulbar palsy(PBP). MEPs were recorded from abductor pollicis brevis and abductor hallucis muscles. Abnormal MEPs were defined by delayed central motor conduction time or absent MEP. Results : MEPs were abnormal in 64%(11/17) of patients; 100%(7/7) in ALS, 64%(4/7) in PMA, 0%(0/3) in PBP respectively. In 68 total recording muscles, 34 muscles had evidence of motor weakness and showed abnormal responses in 59%(20/34). Whereas 34 muscles with normal strength, only 3%(1/34) of muscles showed abnormal response. Conclusion : MEPs are well correlated with upper motor neuron signs in ALS and may detect masking upper motor neuron signs in PMA. The muscles with lower motor neuron sign(weakness) usually relate with abnormal MEPs reponses.

• The Journal of Korean Medicine
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• v.28 no.3 s.71
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• pp.289-298
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• 2007

Objectives : Electrical acupoint stimulation (EAS) has been used to treat motor dysfunction of stroke patients with reportedly effective results. The purpose of this study was to evaluate the efficacy of EAS with different frequencies in treating motor dysfunction of ischemic stroke patients. Methods : The subjects of this study were sixty-two ischemic stroke patients with motor dysfunction at Kyunghee Oriental Medicine Hospital who were hospitalized for one week to one month from onset. They were treated with 2Hz or 120Hz EAS for two weeks, and motor evoked potentials (MEP) were measured before and after EAS treatment. To compare the effect of 2Hz EAS with 120Hz, we measured latency, central motor conduction time (CMCT) and amplitude of MEP before and after EAS treatment. Results : After two weeks of treatment, we compared MEP data of the affected side between the 2Hz group and the 120Hz group. The 2Hz group showed more significant improvement than the 120Hz group in latency, CMCT and amplitude (P=0.008, 0.002, 0.002). In case of the affected side MEP data divided by normal side MEP data, the 2Hz group also showed improvement on latency, CMCT and amplitude with significant differences (P=0.003, 0.000, 0.008). Conclusions : These results suggest that low frequency EAS activates the central motor conduction system better than high frequency EAS, and it means that EAS with low frequency is more helpful for motor recovery after ischemic stroke than that with high frequency.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.11-15
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• 2018

Torque tubes in High Temperature Superconducting (HTS) motor transfer torque from superconducting field winding rotor to the room temperature shaft. It should have minimum heat conduction property for minimizing the load on cryo-refrigerator. Generally, these torque tubes are made with stainless steel material because of high strength, very low outgassing and low thermal contraction properties at cryogenic temperatures and vacuum conditions. With recent developments in composite materials, these torque tubes could be made of composites such as Kevlar and S-Glass, which have the required properties like high strength and low thermal conductivity at cryogenic temperatures, but with a reduced weight. Development and testing of torque tubes made of these composites for HTS motor are taken up at Bharat Heavy Electricals Limited (BHEL), Hyderabad in collaboration with Central Institute of Plastics and Engineering Technology (CIPET), Chennai and Indian Institute of Technology (IIT), Kharagpur. As these materials are subjected to vacuum, it is important to measure their outgassing rates under vacuum conditions before manufacturing prototype torque tubes. The present study focusses on the outgassing characteristics of Kevlar and S-Glass, using an Outgassing Measurement System (OMS), developed at IIT Kharagpur. The OMS facility works under vacuum environment, in which the test samples are exposed to vacuum conditions over a sufficient period of time. The outgassing measurements for the composite samples were obtained using pressure-rise technique. These studies are useful to quantify the outgassing rate of composite materials under vacuum conditions and to suggest them for manufacturing composite torque tubes used in HTS motors.

• Annals of Clinical Neurophysiology
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• v.8 no.1
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• pp.29-35
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• 2006

Background: Transcranial magnetic stimulation (TMS) is a non-invasive diagnostic method particularly suited to investigation the long motor tracts. The clinical value of TMS in most spinal cord diseases has still to be made. Diagnostic value of magnetic motor evoked potential (MEP) parameters in intramedullary spinal cord lesions was investigated. Methods: MEP elicited by TMS was recorded in 57 patients with clinically and radiologically defined intramedullary myelopathy. Twenty five patients with cervical myelopathy (CM) and 32 thoracic myelopathy (TM) were included. Recordings were performed during resting and minimal voluntary contraction at both abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. Stimulation threshold(ST), amplitude, and central motor conduction time (CCT) were measured at resting and facilitated conditions. CCT was calculated by two means; central motor latency (CML)-M using magnetic transcranial and root stimulation, and CML-F using electrical F-wave study. The results were compared between patient groups and 10 normal control group. Results: Facilitated mean ST recorded at TA was elevated in both CM and TM compared with control group. Resting mean CML-M at TA was significantly prolonged in both CM and TM, and CML-M was absent or delayed in 37.1% of CM and 8% of TM at APB with facilitation. Facilitated mean MEP amplitude at ABP was lower in CM than in TM, while MEP/M ratios were not different significantly between groups. Conclusions: Magnetic motor evoked potential has diagnostic value in intramedullary myelopathy and localizing value in differentiating between CM and TM by recording at APB and TA. It is a noninvasive way to investigate the functional status of motor tracts of spinal cord.

• Annals of Clinical Neurophysiology
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• v.6 no.1
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• pp.20-25
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• 2004

Background and Objectives: The proximal and distal nerve segments are preferentially involved in acquired demyelinating polyneuropathies (ADP). This study was undertaken in order to assess the usefulness of motor evoked potential (MEP) and somatosensory evoked potential (SSEP) in the detection of the proximal nerve lesion in ADP. Methods: MEP, SSEP and conventional NCS were performed in 6 consecutive patients with ADP (3 AIDP, 3 CIDP). MEP was recorded from abductor pollicis brevis and abductor hallucis using magnetic stimulation of the cortex and the cervical/lumbar spinal roots. SSEP were elicited by stimulating the median and posterior tibial nerves. Latency from cortex and cervical/lumbar roots, central motor conduction time (CMCT), EN1-CN2 interpeak latency were measured for comparison. Results: MEP was recorded in 24 limbs (12 upper and 12 lower limbs) and SSEP in 24 limbs (12 median nerve, 12 posterior tibial nerve). F-wave latency was prolonged in 25 motor nerves (25/34, 73.5%). Prolonged CML and PML were found in 41.7% (10/24) and 45.8% (11/24), respectively. Interside difference (ISD) of CMCT was abnormally increased in the upper extremity, 66.7% (4/6 pairs) in case of CML-PML. EN1-CN2 interpeak latency was abnormally prolonged in one median nerve (1/10) and LN1-P1 interpeak latency was normal in all posterior tibial nerves. Conclusions: MEP and SSEP may provide useful information for the proximal nerve and root lesion in ADP. MEP and SSEP is supplemental examination as well as complementary to conventional NCS.

• The Journal of Internal Korean Medicine
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• v.27 no.1
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• pp.265-275
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• 2006

Objectives : Electrical acupoint stimulation(EAS) has been used to treat motor dysfunction of stroke patients with reportedly effective results. The purpose of this study is to evaluate the efficacy of the EAS with different frequencies in treating motor dysfunction of ischemic stroke patients. Methods : The subject of this study were forty-two ischemic stroke patients with motor dysfunction in Kyunghee oriental medicine hospital who were hospitalized for one week to one month from onset. They were treated with 2Hz or 120Hz EAS for two weeks, and motor evoked potentials(MEP) were measured before and after EAS treatment. To compare the effect of 2Hz EAS with 120Hz, the number of patients who showed MEP responses after two weeks among those who had no previous response was checked. Also measured were latency, central motor conduction time(CMCT), amplitude of MEP before and after EAS treatment. Results : After two weeks of treatment, 4 out of 15 patients(27%) in the 2Hz EAS group and lout of 19 patients(5%) in the 120Hz group showed potential responses. Yet there was no significant difference between the two groups. When MEP data of the affected side between the 2Hz group and the 120Hz group was compared, the former showed more significant improvement than the latter in latency, CMCT and amplitude(P=0.040, 0.019,0.021). When the proportion of the affected side and unaffected side in MEP data was examined, the 2Hz group showed improvement on only latency and CMCT with significant differences(P=0.040, 0.014). Conclusions : These results show that EAS with low frequency is more helpful for motor recovery after ischemic stroke than that with high frequency. This suggests that low frequency EAS activates the central motor conduction system better than high frequency EAS.