• Korean Journal of Clinical Laboratory Science
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• v.51 no.4
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• pp.453-461
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• 2019

Intraoperative neurophysiological monitoring (INM) examination identifies the damage caused to the nervous system during surgery. This method is applied in various surgeries to validate the procedure being performed, and proceed with confidence. The assessment is conducted in an operating room, using subdermal needle electrodes to optimize the examination. There are no textbooks or guides for the correct stimuli and recording areas for the surgical laboratory test. This article provides a detailed description of the correct stimuli and recording parts in motor evoked potential (MEP), somatosensory evoked potential (SSEP), brainstem auditory evoked potentials (BAEP) and visual evoked potentials (VEP). Free-running Electromyography (EMG) is an observation of the EMG that occurs in the muscle, wherein the functional state of most cranial nerves and spinal nerve roots is determined. In order to help understand the test, an image depicting the inserting subdermal needle electrodes into each of the muscles, is attached. Furthermore, considering both the patient and the examiner, a safe method is suggested for removal of electrodes after conclusion of the test.

• Journal of Korean Neurosurgical Society
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• v.51 no.5
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• pp.286-291
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• 2012

Objective : To investigate the change of latency of cervical dermatomal somatosensory evoked potential (DSEP) according to stimulation intensity (SI) and severity of carpal tunnel syndrome (CTS). Methods : Stimulation sites were the C6, C7, and C8 dermatomal areas. Two stimulation intensities $1.5{\times}$sensory threshold (ST) and $2.5{\times}ST$ were used on both normal and CTS patients. Results : In moderate CTS, the latencies of C6 and C7 DSEP during $1.5{\times}ST$ SI and those of C7 DSEP during $2.5{\times}ST$ SI were significantly delayed compared with the values of normal subjects. Significant correlation between the latency of C7 DSEP of $2.5{\times}ST$ stimulation and the median sensory nerve conduction velocity was observed. Conclusion : We suggest that these data can aid in the diagnosis of cervical sensory radiculopathy using low stimulation intensity and of those who have cervical sensory radiculopathy combined with CTS patients.

• Annals of Clinical Neurophysiology
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• v.5 no.2
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• pp.181-186
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• 2003

Background: Somatosensory evoked potential (SSEP) is valuable for the evaluation of the central pathway. However, peripheral neuropathy sometimes renders the test useless by preventing the conduction from reaching the CNS. We postulated that the peripheral conduction problems could be overcome by proximal stimulation in SSEP and wanted to verify this in the study. Methods: Twenty patients with diabetic sensorimotor polyneuropathy were included. SSEP was elicited by stimulating the median and posterior tibial nerves. We compared the effect of distal and proximal stimulations in each SSEP in the aspect of presence/absence and various latencies of resultant waves. Results: Among the 40 cases, proximal stimulation caused reappearance of subsided waves in 10 cases (25%). In the median nerve SSEP, proximal stimulation made EN1 and CN2 visible which were not evident when distally stimulated. In the posterior tibial nerve SSEP, there was also improvement of forming waves when proximally stimulated. Conclusions: In the diabetic polyneuropathy, proximal stimulation of SSEP is more effective than the conventional distal stimulation in evaluating central pathway.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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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.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.262-268
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• 2016

Hemifacial spasm is a disease caused by involuntary facial muscles with repeated unilateral convulsive spasms. It involves contraction of multiple muscles at the same time (synkinesia). The pathogenesis appears to be the pressure on the vessel by the facial nerve. This study included hemifacial spasm patients, who received microvascular decompression surgery. Brainstem auditory evoked potential and the examination time were carefully noted when using brain surgical retractor. The facial nerve electromyography tests for the identification of artifacts and EMG waveform when the facial nerve damage, about the importance of the maintenance of anesthesia in the lateral spread response and in a somatosensory evoked potential propose a new method. Based on the above test, it will be more effective.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.4
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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 Korean Neurosurgical Society
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• v.29 no.8
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• pp.985-994
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• 2000

Objective : There are some advantages of trigeminal evoked potential(TEP) recording compared to other somatosensory evoked potential(SSEP) recordings. The trigeminal sensory pathway has a pure sensory nerve branch, a broader receptive field in cerebral cortex, and a shorter pathway. Despite these advantages, there is little agreement as to what constitutes a normal response and what wave forms truly characterize the intraoperative TEP. This study presents the normative data of TEP recorded on the epidural surface of the rat with a platinum ball electrode. Materials & Methods : Under general anesthesia with urethane, the adult Sprague-Dawley male rats(300-350g) were given electrical stimulation with two stainless steel electrodes which were inserted into the subcutaneous layer of the area around whiskers. A reference electrode was positioned in the temporalis muscle ipsilateral to the recording site. Results : TEPs were recorded in the Par I area of somatosensory cortex and recorded most apparently on the point of 2mm posterior from the bregma and 6mm lateral from the midline. The typical wave form consisted of 5 peaks (N1-P1-N2-P2-N3 according to emerging order, upward negativity). Each latency to corresponding peaks was not influenced by the different intensities of stimulation, especially from 1 to 5mA. Average latencies of 5 peaks were in the following order ; 7.7, 11.1, 15, 22.3, 29.4ms. There was also no significant difference between latencies before and after administration of muscle relaxant(pancuronium). For the electrophysiological localization of recorded waves, the action potential of a single unit was recorded with glass microelectrode(filled with 2M NaCl, $3-5M{\Omega}$) in the thalamus of rat. A sharp wave was recorded in the VPM nucleus, in which the latency was shorter than that of N1. This suggests that all 5 peaks were generated by neural activities in the suprathalamic pathway. Conclusion : In terms of recording near-field potentials, our data also suggests that TEP in the rat may be superior to other SSEPs. In overall, these results may afford normative data for the studies of supratentorial lesions such as hydrocephalus or cerebral ischemia which can have an influence on near-field potentials.

• Journal of Korean Physical Therapy Science
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• v.15 no.1
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• pp.11-20
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• 2008

This study was designed to test the effects of comprehensive rehabilitation management on functional recovery after attack of cerebrovascular disease. 16 cerebrovascular disease patients applied comprehensive rehabilitation management of physical therapy at department of physical Therapy, C medical center in Gwang－ju. The collection of the data had been executed for 4months(April 15, 2007${\sim}$July 15, 2007). For evaluating, Functional Independence measure(FIM) and Somatosensory Evoked Potential(SSEP) were used to assess functional recovery. The results of this study were as follows: 1. In the comparison of latency of median nerve SSEP before and after treatment, the lat. N20 and P25 increased, the ampl. P25/N20 was decreased. In the comparison difference data of median nerve SSEP, however there was no significant difference in the group(p>0.05). 2. In the comparison of latency of Post Tibial nerve SSEP before and after treatment, the lat. P40, P50, P60 increased, the ampl. P40 was decreased. In the comparison difference data of post tibial nerve SSEP, however there was no significant difference in the group(p>0.05). 3. In the comparison of FIM scores of Self－care, Sphincter Control, Mobility: Transfer, Locomotion before and after treatment, the scores of FIM was significantly increased. In the comparison of difference of the motor part of FIM, however there was significant difference(p<0.05). 4. In the comparison of FIM scores of Communication, Social Cognition before and after treatment, the scores of FIM was significantly increased. In the comparison of difference of the motor part of FIM, however there was no significant difference in the group(p>0.05). Based on these results, it is concluded that the comprehensive rehabilitation management for cerebrovascular disease case was not significant difference in the SSEP, was significant difference in the motor part of FIM. Further study should be done to analyze the effect of intervention duration of treatment, optimal time to apply the treatment in more long period.

• Journal of Yeungnam Medical Science
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• v.18 no.1
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• pp.67-74
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• 2001

Background: Meralgia paresthetica(MP) which is characterized by paresthesias and sensory impairment without motor weakness in the anterolateral aspects of the thigh is produced by compression of the lateral femoral cutaneous nerve(LFCN). Even though the diagnosis of MP is mostly based on the clinical symptoms, electrophysiologic study is mandatory to confirm the disease objectively. It has been known that Somatosensory evoked potential(SSEP) study of LFCN is a simple and very useful method to evaluate MP, so we studied SSEP of LFCN in normal adults and offer normal values. Materials and Methods: Thirty six normal adults(23 males and 13 females) ages from 21 to 73 years old($mean{\pm}SD$:$42.06{\pm}15.74$) were studied SSEP of LFCN bilaterally. The stimulation site was anterolateral aspect of thighs and the recording site was Cz'. Results: The mean values($mean{\pm}SD$) of $LP_0$, $SP_0$, $LN_1$ and $SN_1$ of all subjects were 35.10(${\pm}2.42$), 33.80(${\pm}2.4$), 43.68(${\pm}1.88$) and 42.16(${\pm}2.12$) and the mean values($mean{\pm}SD$ of $DP_0$, $DN_1$ and DA(${\mu}V{\pm}SD$ were 1.30(${\pm}1.14$), 1.52(${\pm}1.38$) and 0.32(${\pm}0.33$). Conclusion: For the diagnosis of MP. comparison of latency difference between both sides is more reliable than simple value of latency itself because of individual differences of body types. According to our results. the latency difference should be less than 2 msec and the amplitude difference was less than 1.6 times in normal adults.

• Annals of Clinical Neurophysiology
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• v.16 no.2
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• pp.62-69
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• 2014

Background: Neuromodulation therapy has been used to an adjunctive treatment promoting motor recovery in stroke patients. The objective of the study was to determine the effect of repetitive transcranial magnetic stimulation (rTMS) on neurobehavioral recovery and evoked potentials in rats with middle cerebral artery occlusion. Methods: Seventy Sprague-Daley rats were induced permanent middle cerebral artery occlusion (MCAO) stroke model and successful stroke rats (n=56) assigned to the rTMS (n=28) and sham (n=28) group. The 10 Hz, high frequency rTMS gave on ipsilesional forepaw motor cortex during 2 weeks in rTMS group. The somatosensory evoked potential (SSEP) and motor evoked potential (MEP) were used to evaluate the electrophysiological changes. Behavioral function of the stroke rat was evaluated by the Rota rod and Garcia test. Results: Forty rats ($N_{rTMS}=20;\;N_{sham}=20$) completed all experimental course. The rTMS group showed better performance than sham group in Rota rod test and Garcia test at day 11 (p<0.05) but not day 18 (p>0.05). The amplitude of MEP and SSEP in rTMS group was larger than sham group at day 18 (p<0.05). Conclusions: These data confirm that the high frequency rTMS on ipsilesional cerebral motor cortex can help the early recovery of motor performance in permanent middle cerebral artery stroke model and it may simultaneously associate with changes in neurophysiological activity in brain.