• Journal of Korean Physical Therapy Science
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• v.3 no.1
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• pp.907-918
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• 1996

Evoked potentials(EP) are defined as electric responses of the nerves system to sensory stimulation. EPs are used mainly to test conduction in the visual, auditory, and somatosensory systems, especially in the central parts of these systems. Somatosensory evoked potentials (SEP) are the potentials elicited by stimulation of peripheral nerves and recorded at various sites along the sensory pathway. SEPs types consist mainly of SEPs to electric stimulation of arm or leg nerves. SEPs to arm stimulation are usually recorded simultaneously from clavicular, cervical, and scalp electrodes; SEPs to leg stimulation are recorded from lumbar, low thoracic, and scalp electrodes. Subject variables that have practical impotance are age, limb length, body height, and temperature. General clinical interpretation of abnormal SEPs wave decreases of peripheral conduction time, and abolition of SEPs recorded from different levels to identify lesions of peripheral nerves, plexus, nerve root, spinal cord, cauda equina, hemispheric brainstem, and cerebral parts of the somatosensory pathway.

• Annals of Clinical Neurophysiology
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• v.19 no.2
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• pp.136-140
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• 2017

A 77-year-old male with amyotrophic lateral sclerosis had a hypoxic event. After resuscitation, generalized myoclonus appeared and resolved after two days. Five days after the hypoxic event, myoclonic seizures re-emerged right after performing a somatosensory evoked potential and persisted for ten days. Electroencephalogram revealed frequent bi-hemispheric synchronous spike and waves in the central areas. We suggest that somatosensory evoked potential testing may trigger myoclonic status epilepticus. Underlying cortical degeneration associated with amyotrophic lateral sclerosis could attribute to this phenomenon.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.481-488
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• 1994

In this paper a study of neuro-pathway estimation based on visual and somatosensory evoked potential is given. The evoked potentials which are caused by visual and somatosensory stimulation are detected by an average method. The forward problem that is estimating a scalp potential from a given electrical source in the brain is solved by using a triple concentric spherical shell model of the head and a single current dipole model of the neuron activity. The inverse problem which calculates a source position is solved by a least square fit between the model predicted potential and a given evoked potential measurement. The similarities between estimated sensory neuro-pathways and physiological brain function regions are verified.

• Korean Journal of Veterinary Research
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• v.42 no.3
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• pp.397-402
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• 2002

Clinical usefulness of somatosensory evoked potentials (SSEP) as a prognostic tool was evaluated with three dogs showing clinical signs associated with intervertebral disc diseases. Prior to measure SSEP, history taking, physical examination, radiological study and neurological examination were performed. In case 1, poor prognosis was predicted because deep pain was not observed and loss of sensory function was observed in SSEP. And the clinical signs persisted with the conservative treatment. However, in cases 2 and 3, good prognoses were predicted by normal conduction velocity in SSEP that meant the presence of sensory function. The clinical signs of cases 2 and 3 disappeared at days 18 and 13 after treatment, respectively. These results suggest SSEP be used clinically as a prognostic tool in dogs with intervertebral disc diseases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1441-1442
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• 2013

• Journal of Korean Neurosurgical Society
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• v.29 no.1
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• pp.5-14
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• 2000

Objective : Somatosensory evoked potential(SSEP) has been known to be a good method for evaluating brain stem function, but it is not sufficient to check the fine changes of cortical functions. A fine change of cortical function can be expressed with somatosensory evoked cortical field potential(SSEFP) rather than general SSEP. To confirm the usefulness of SSEFP for evaluating the cortical function, the authors simultaneously measured SSEFP and the intracranial pressure-volume index(PVI) in kaolin-induced hydrocephalic rats. Method : Hydrocephalus was induced with injection of 0.1ml kaolin-suspended solution into the cisterna magna in 60 Sprague-Dawley rats. The authors measured PVI and SSEFP 1 week after injection of kaolin-suspended solution. To evaluate the severity of induced hydrocephalus, we measured the transverse diameter of the lateral ventricle on the coronal slice of the rat brain 0.40mm posterior to the bregma. Result : The typical wave form of SSEFP in control rats showed a negative-positive complex wave at early latency. In SSEFP of normal rats, N0 is 10.0 msec, N1 15.3 msec, P1 31.2 msec and N1-P1 amplitude $15.4{\mu}V$. As hydrocephalus progressed, the peak latency of N1 and P1 were delayed. In mild hydrocephalus, negative peak waves were split. The N1-P1 amplitude was decreased only in severe hydrocephalus. The changes of the characteristics of SSEFP according to the severity of hydrocephalus were well correlated with the changes of PVI. Shunting normalized the characteristics of SSEFP in relation to ventricular sizes and PVI in hydrocephalic rats. Conclusion : SSEFP may be useful for evaluating the impairment of cortical function in hydrocephalus.

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

• Journal of Korean Neurosurgical Society
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• v.30 no.7
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• pp.831-841
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• 2001

Objective : Somatosensory evoked potentials(SSEPs) have been used widely both experimentally and clinically to monitor the function of central nervous system and peripheral nervous system. Studies of SSEPs have reported the various recording techniques and patterns of SSEP. The previous SSEP studies used scalp recording electrodes, showed mean vector potentials which included relatively constant brainstem potentials(far-field potentials) and unstable thalamocortical pathway potentials(near-field potentials). Even in invasive SSEP recording methods, thalamocortical potentials were variable according to the kinds, depths, and distance of two electrodes. So they were regarded improper method for monitoring of upper level of brainstem. The present study was conducted to investigate the characteristics of somatosensory evoked field potentials(SSEFPs) of the cerebral cortex that evoked by hindlimb stimulation using ball electrode and the pathways of SSEFP by recording the potentials simultaneously in the cortex, VPL nucleus of thalamus, and nucleus gracilis. Methods : In the first experiment, a specially designed recording electrode was inserted into the cerebral cortex perpendicular to the cortical surface in order to recording the constant cortical field potentials and SSEFPs mapped from different areas of somatosensory cortex were analyzed. In the second experiment, SSEPs were recorded in the ipsilateral nucleus gracilis, the contralateral ventroposterolateral thalamic nucleus(VPL), and the cerebral cortex along the conduction pathway of somatosensory information. Results : In the first experiment, we could constantly obtain the SSEFPs in cerebral cortex following the transcutaneous electrical stimulation of the hind limb, and it revealed that the first large positive and following negative waves were largest at the 2mm posterior and 2mm lateral to the bregma in the contralateral somatosensory cortex. The second experiment showed that the SSEPs were conducted by way of posterior column somatosensory pathway and thalamocortical pathway and that specific patterns of the SSEPs were recorded from the nucleus gracilis, VPL, and cerebral cortex. Conclusion : The specially designed recording electrode was found to be very useful in recording the localized SSEFPs and the transcutaneous electrical stimulation using ball electrode was effective in evoking SSEPs. The characteristic shapes, latencies, and conduction velocities of each potentials are expected to be used the fundamental data for the future study of brain functions, including the hydrocephalus model, middle cerebral artery ischemia model, and so forth.

• 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.

• Archives of Craniofacial Surgery
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• v.20 no.4
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• pp.223-227
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• 2019

Background: Neurosensory changes are frequently observed in the patients with mid-face fractures, and these symptoms are often caused by infraorbital nerve (ION) damage. Although ION damage is a relatively common phenomenon, there are no established and objective methods to evaluate it. The aim of this study was to test whether trigeminal somatosensory evoked potential (TSEP) could be used as a prognostic predictor of ION damage and TSEP testing was an objective method to evaluate ION injury. Methods: In this prospective TSEP study, 48 patients with unilateral mid-face fracture (only unilateral blow out fracture and unilateral zygomaticomaxillary fracture were included) and potential ION damages were enrolled. Both sides of the face were examined with TSEP and the non-traumatized side of the face was used as control. We calculated the latency difference between the affected and the unaffected sides. Results: Twenty-four patients recovered within 3 months, and 21 patients took more than 3 months to recover. The average latency difference between the affected side and unaffected side was 1.4 and 4.1 ms for the group that recovered within 3 months and the group that recovered after 3 months, respectively. Conclusion: Patients who suffered ION damage showed prolonged latency when examined using the TSEP test. TSEP is an effective tool for evaluation of nerve injury and predicting the recovery of patients with ION damage.