• Journal of Korean Neurosurgical Society
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• 제56권6호
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• pp.455-462
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• 2014

Objective : To propose a new measure for effective monitoring of intraoperative somatosensory evoked potentials (SEP) and to validate the feasibility of this measure for evoked potentials (EP) and single trials with a retrospective data analysis study. Methods : The proposed new measure (hereafter, a slope-measure) was defined as the relative slope of the amplitude and latency at each EP peak compared to the baseline value, which is sensitive to the change in the amplitude and latency simultaneously. We used the slope-measure for EP and single trials and compared the significant change detection time with that of the conventional peak-to-peak method. When applied to single trials, each single trial signal was processed with optimal filters before using the slope-measure. In this retrospective data analysis, 7 patients who underwent cerebral aneurysm clipping surgery for unruptured aneurysm middle cerebral artery (MCA) bifurcation were included. Results : We found that this simple slope-measure has a detection time that is as early or earlier than that of the conventional method; furthermore, using the slope-measure in optimally filtered single trials provides warning signs earlier than that of the conventional method during MCA clipping surgery. Conclusion : Our results have confirmed the feasibility of the slope-measure for intraoperative SEP monitoring. This is a novel study that provides a useful measure for either EP or single trials in intraoperative SEP monitoring.

• Annals of Clinical Neurophysiology
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• 제1권2호
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• pp.160-167
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• 1999

Although somatosensory evoked potentials(SSEPs) have been utilized as the useful diagnostic tools in evaluating the wide variety of pathological conditions, such as focal lesions affecting the somatosensory pathways, demyelinating diseases, and detecting the clinically occult abnormality, their neural generators is still considerably uncertain. To appreciate the basis for uncertainties about the origins of SSEPs, consider criteria that must be met to establish a causal relationship between activity in a neural structure and a spine/ scalp-recorded potential. Electrode locations and channel derivations for SSEPs recordings are based on two principles:(1) the waveforms are best recorded from electrode sites on the body surface closest to the presumed generator sources along the somatosensory pathways, and(2) studies of the potential-field distribution of each waveform of interest dictate the best techniques to be used. In this article, authors will describe followings focused on ;(1) the concepts of near field potentials(NFPs) and far field potentials(FFPs) - the voltage of NFPs is highly dependent upon recording electrode position, FFPs are unlike NFPs in that they are widely distributed, their latencies and amplitudes are independent of recording electrode.(2) appropriate montage settings to detect the significant potentials in the median nerve and posterior tibial nerve SSEPs(3) neural generators of various potentials(P9, N13, P14, N18, N20, P37) and their clinical significance in interpretating the results of SSEPs. Especially, Characteristics of N18(longduration, small superimposed inflection) suggested that N18 is a complex wave with multiple generators including brainstem structures and thalamic nuclei. And N18 might be used as the parameter of braindeath. Precise understanding on these facts provide an adequate basis utilizing SSEPs for numerous clinical purposes.

• The Journal of Korean Physical Therapy
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• 제16권3호
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• pp.72-85
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• 2004

We have few assessment tool in physical therapy. Recently, there is increasingly a concern of electrophysiologic examinations. They includes electomyography; needle and surface, evoked potentials; somatosensory evoked potentials; brainstem auditory evoked potentials; visual evoked potentials, nerve conduction velocity, blink reflex, H-reflex, and F-wave. The purpose of this study is understanding of electrophysiologic examinations. So we hope many physical therapist to use electrophysiologic examinations in research.

• Annals of Clinical Neurophysiology
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• 제1권2호
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• pp.106-111
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• 1999

Backgroud : The generators of N37 and P37 of posterior tibial nerve somatosensory evoked potential(PTSEP) have not been exactly known. Recently, some reports suggested that P37 and N37 might have different generator. We conducted a study to know the generators of P37 and N37 of PTSEP using gating mechanism. Methods : We evaluated subcortical and cortical somatosensoy evoked potentials(SEPs) in response to posterior tibial nerve stimulation in 3 experimental conditions of foot movement and compared them with PTSEPs in full relaxation of foot. The experimental conditions were: (a) active flexion-extention of stimulated foot, (b) isometric contraction of the stimulated foot, (c) passive flexion-extention of the stimulate foot. We analyzed the latencies and amplitudes of following potentials; P30, N37, P37, and N50. Results : The amplitude of P30 potential did not change during at any paradigms. The amplitudes of P37 and N50 were significantly attenuated in all condition. However, the amplitude of N37 showed no significant change during at any paradigms. Conclusions : These results suggest that the generators of P37 and N37 of PTSEP be different in cortex.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.481-488
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• 1994

시각 및 손가락의 전기자극에 의해 머리표면에서 발생하는 유발전위를 검출하여 Source Tracing Method를 이용하여 뇌의 시각인지영역 및 손가락 감각인지영역을 추정하였다. 본 과정에서 유발전위 검출방식은 average method를 이용하였고, 흥분뉴런군에 대한 물리적 모델로 Single Current Dipole Model을 이용하고, 머리기하에 대한 3중구각모델을 이용하여 Forward Problem을 풀었다. Inverse Problem은 current dipole의 6개의 parameter에 대한 Least Square Error Method를 이용하여 신견흥분의 위치를 추정하였다. 이러한 결과와 생리학적으로 밝혀진 시각 및 체성감각 신경로와의 비교결과 유사성이 확인되었다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제18권4호
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• pp.652-672
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• 1996

Dysfunction of the inferior alveolar nerve may result from trauma, diseases or iatrogenic injury. The development and refinement of an objective method to evaluate this clinical problem is highly desirable and needed, especially concerning for an increasing medico-legal issue. Evoked potential techniques have attracted considerable attention as a means of assessing the function and integrity of nerve pathways. The purpose of this study was to characterize the Sensory Evoked Potentials(SEPs) and Somatosensory Evoked Potentials(SSEPs) elicited by electrical stimulation of mental nerve. SEPs and SSEPs were measured and analyzed statistically before and after needle injury on the inferior alveolar nerve of Sprague-Dawalye rats. Measuring SEPs was more sensitive in evaluation of the recovery of sensory function from inferior alveolar nerve injury then measuring SSEPs but we measured SSEPs in the hope of providing a safe, simple and objective test to check oral and facial sensibility, which is acceptable to the patient. We stimulated mental nerve after needle injury on the inferior alveolar nerve and SEPS on the level of mandibular foramen and SSEPs on the level of cerebral cortex were recorded. Threshold, amplitude, and latency of both of SEPs and SSEPs were analyzed. The results were as follows ; 1. Threshold of SEPs and SSEPs were $184{\pm}14{\mu}A$ and $164{\pm}14{\mu}A$ respectively. 2 SEPs were composed of 2 waves, i.e., N1 N2 in which N1 was conducted by II fibers and N2 was conducted by III fibers. 3. SSEPS were composed of 5 waves, of which N1 and N2 shower statistically significant changes(p<0.01, unpaired t-test). 4. SEPs and SSEPs were observed to be abolished immediately after local anesthesia and recovered 30 minutes later. 5. SEPs were abolished immediately after injury. N1 of SSEPs was abolished immediately and amplitued of N2 was decreased($20.7{\pm}12.2%$) immediately after 23G needle injury, but N3, N4 and N5 did not change significantly. Recovery of waveform delayed 30 minutes in SEPs and 45 minutes in SSEPs. 6. The degree of decrease in amplitude of SEPs and SSEPs, after 30G needle injury was smaller than those with 23G. SEPs recorded on the level of mandibular foramen were though to be reliable and useful in the assessment of the function of the inferior alveolar nerve after injury. Amplitude of SSEPs reflected the function and integrity of nerve and measuring them provided a safe, simple and abjective test to check oral and facial sensibility. These results suggest that measuring SEPs and SSEPs are meaningful methods for objective assessment in the diagnosis of nerve injury. N1 and N2 of SSEPs can be useful parameters for the evaluation of the nerve function following a needle injury.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제27권3호
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• pp.250-257
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• 2001

Sensory dysfunction following the injury of the inferior alveolar nerve requires objective examination to get a reproducible data and to provide necessary treatment. This study was designed to evaluate if the SEP(somatosensory evoked potentials) of the mental nerve can be used as an objective method for the diagnosis of nerve injury and sensory disturbances. The subjects were nineteen patients ($37.4{\pm}11.3$ years old) who had been suffered from sensory disturbance of the unilateral lower lip and mental region for over 6 months after the inferior alveolar nerve injuries confirmed by the microsurgical explorations. The clinical neurosensory tests as SLTD(static light touch discrimination), MDD(moving direction discrimination), 2PD(two point discrimination), PPN(pin prick nociception) and accompanied pain were preceded to electro-physiologic examinations as SEP. The score of sensory dysfunction (sum score of all sensory tests) ranged from 0 to 8 were compared to the latency differences of the mental nerve SEPs. The correlation between clinical sensory scores and SEPs were tested by Spearman nonparametric rank correlation analysis, the differences in SEP latency by Kruskal-Wallis test and the latency differences according to PPN and accompanied pain by Mann-Whitney U test. This study resulted that the difference of the latencies between normal side and affected side was $2.22{\pm}2.46$ msec and correlated significantly with the neurosensory dysfunction scores (p=0.0001). Conclusively, the somatosensory evoked potentials of the mental nerve can be a useful diagnostic method to evaluate the inferior alveolar nerve injuries and the change of sensory dysfunction to be reproduced as an objective assessment.

• 한국임상수의학회지
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• 제17권2호
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• pp.388-394
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• 2000

이 실험은 소형견종에 대한 정상 SEPs의 범위를 알아내기 위해 실시되었다. 임상증 상이 정상인 28두를 대상으로 자극점에서 channel 1 까지의 Pl(LPI), channel 1까지의 Nl (LN1), 자극점에서 channel 2가지의 Pl(TP1), channel 2까지의 N1(TNI)의 절대잠복기와 LP1-TN1` 의 파간잠복기를 알아내기 위해서 실시하였다. 이번 실험에서 LPI, LNI, TPI, TNI의 절대잠복기 (absolute latency)의 평균값은 2.69$\pm$0.31 msec, 4.91$\pm$0.49m/sec, 4.64$\pm$0.39 msec, 5.21$\pm$0.42 msec 띠었다. LP1과 TN1 사이의 파간절대잠복기의 핑균값은 2.52$\pm$7.19 msec 이었다. 측정 치들을 속도로 변환하였을 경우 다음과 같았다. 측, LPI, LNI. Tfl, TNI 그리고 LP1-TN1 에서의 속도의 평균값은 각각 93.11$\pm$ 8.58 m/sec, 50.99$\pm$ 5.36m/sec. 80.18$\pm$ sec, 71.31$\pm$4.79m/sec그리고 49.50$\pm$3.58m/sec 이었고. 71.66m/sec, 37.79m/sec, 65.75m/ sec, 59.33 m/sec, 40.55m/sec 의 최저속도를 초과하였을 때 정상범위로 간주하였다. LPI, LNI, TPI,TN1까지의 절대잠복기와 자극전극에 시 측정전극가지의 거리 사이에는 상관관계가 있었다 LP1, LN1, TP1, TN1의 상관계수는 각각 0.621, 0.494. 0.577,0.618 이었다 요추에서 기록된 SEPs갈은 LP1의 상관계수가 LN1 보다 높았으며 흉추에서 기록된 SEPs값은 TN1의 상관계수가 TP1보다 높았다. LP1과 TN1의 파간잠복기와 channel 1과 2의 거리차이와의 상관계수는 0.571이다. 따라서 LPI, LNI. TPI, TNI그리고 LPI-TNI 들의 최저속도를 이용 하여 척수 손상 여부를 판단할 수 있다고 생각된다.

• 한국임상수의학회지
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• 제19권3호
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• pp.277-282
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• 2002

본 실험은 각각의 마취방법이 체성감각유발전위 (SEPs) 파형에 미치는 영향을 알아보고 SEP의 측정에 적절한 마취방법을 찾고자 시행하였다. 임상적으로 건강하고 크기와 나이가 비슷한 다섯 마리의 잡종견을 대상으로 SEPs를 측정하고 각각의 측정값을 분석하였다. SEPs측정을 위해 후 경골신경을 자극하였고 요추 5-6번 사이에서 channel 1의 LP1과 LN1, 흉추 11-12사이에서 channel 2의 TP1, TN1을 기록하였다. 실험에 사용한 마취방법 중. Acepromazine + Thiopental Na + Isoflurane, Acepromazine + Propofol + Isoflurane, Diazepam + Xylazine, Xylazine + Ketamine, Acepromazine + Propofol infusion, 및 Propofol infusion등의 방법만이 SEPs측정이 가능하였고, 파형은 명확하였으며, 측정에 요구되어지는 일정 시간인 25분 이상 동안 마취 유지가 가능하였다. 또한 각 마취군에서의 SEPs 파형을 Acepromazine + Thiopental Na + Isoflurane군과 비교해 보았을 때 latency의 경우, Acepromazine + Propofol + Isoflurane군의 ST(stimulating point)-LN1, SP-TP1, Diazepam + Xylazine 군의 Chl-Ch2, Xylazine + Ketamine군의 Chl-Ch2, Acepromazine + Propofol infusion군의 ST-LP1와 Chl-Ch2에서 부분적으로 유의적인 차가 있었다. Conduction velocity의 경우, Acepromazine + Propofol + Isoflurane군의 ST-LN1, Diazepam + Xylazine군의 Chl-Ch2, Xylazine + Ketamine군의 Chl-Ch2, Acepromazine + Propofol infusion군의 ST-LP1, 그리고 Propofol infusion군의 ST-LN1의 측정값에서 유의적인 차가 있었지만 전반적으로는 전체적인 파형의 유의적인 변화는 없었다. 이상의 결과를 토대로 SEPs 측정시 흡입마취로는 Acepromazine + Thiopental + Isoflurane과 Acepromazine + Propofol + Isoflurane, 주사마취로는 Diazepam + Xylazine과 Xylazine + Ketamine, 점적마취로는 Acepromazine + Propofol infusion과 Propofol infusion 방법이 사용 가능한 것으로 확인되었다.

• 한국임상수의학회지
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• 제18권4호
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• pp.315-323
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• 2001

본 실험에서는 인공적으로 척수관의 20-50%를 차지하는 이물을 척수관내에 삽입한 후 이물제거 시기에 따라 somatosensory evoked potentials (SEPs) 변화상을 임상증상과 척수조영술을 이용하여 비교 관찰하였다. 실험군은 척수관의 50%를 차지하는 이물을 삽입하여 1주일 후에 제거한 군(II군), 2일 수에 제거한 군(III군), 또 척수관의 20%를 차지하는 이물을 삽입하여 1주일 후에 제거한 군(IV군), 2일 후에 제거한 군(V군), 8주 계속 유지한 군(VI군) 그리고 대조군으로 laminectomy만을 실시한 군(I군)으로 나누었다. 척수관 직경의 50%를 차지하는 큰 이물을 삽입하여 2일간 유지하였다가 제거한 후 관찰한 군(III군), 척수관 직경의 20%를 차지하는 작은 이물을 삽입하여 1주일간 유지하였다가 제거한 후 관찰한 군(IV군), 작은 이물을 삽입하여 2일간 유지하였다가 제거한 후 관찰한 군(V군)에서는 SEPs latency와 임상증상에서 거의 이상이 나타나지 않았다. 작은 이물을 8주간 계속 유지한 군(VI군)에서는 SEPs latency에서는 약간의 이상을 보였으나 임상증상에서 거의 이상이 나타나지 않았다. 척수압박 후 제거한 각각의 군에서 SEPs latency와 임상증상은 비슷한 회복추이를 보였다. 그러나 척수관 직경의 50%를 차지하는 큰 이물을 삽입하여 1주일간 유지하였다가 제거한 후 관찰한 군(II군)에서는 TN1의 SEPs latency는 기록되지 않았으며, 임상적으로 신경증상을 나타내었다. III, Iv 및 V 군에서 TP1과 TN1(T11과 T12사이)은 이물 삽입 직후에는 비정상적으로 기록되었고 처음으로 TP1과 TN1 값이 기록된 날은 이물을 삽입하였다가 제거한 후 각각 6일, 9.5일 및 3.5일째였다. VI군에서 TN1의 유발전위는 이물삽입 후 7.7일째부터 기록되었고 34일째에 정상적인 파형을 보였다. II군에서 TN1의 유발전위는 이물을 삽입하였다가 제거한 후 8주째 까지 기록되지 않았다. I군에서 TN1 값은 laminectomy 후 1일째에 처음으로 기록되었다.