Median Nerve Somatosensory Evoked Potentials in Patients with Chiari Malformation

Abnormal SEP reflects dysfunction of the medial lemniscus and posterior cervical cord. These structures are likely to be affected in Chiari malformation. Therefore, SEP abnormalities may provide valuable information in patients with CM. However, the consistency of SEP abnormality or normality with the damage is a matter of research. Knowing whether median nerve somatosensory evoked potential (SEP) is useful in revealing subclinical damage in patients with Chiari malformation is important in the treatment and follow-up plan of the disease. The aim of this study was to investigate the relationship between median nerve SEP values and the severity of cerebellar ectopia in patients with Chiari type 1 malformation. Median nerve SEP values were obtained from 30 healthy individuals and 146 individuals with Chiari malformation. The cerebellar ectopia degree and McRae line length were measured. SEP values were not significantly different between groups. The McRae line was found to be significantly shorter in the control group than in the Chiari malformation group (p = 0.031). There was no correlation between the degree of cerebellar ectopia and the length of the McRae line (r = 0.002, p = 0.979). Neither cerebellar ectopy degree nor McRae line length had a relationship with SEP values (r = -0.153, p = 0.066;r = -0.056, p = 0.500, respectively). There was no difference in cerebellar ectopy degree or SEP values between the groups with cerebellar ectopy with and without a syrinx (p = 0.899;p = 0.080, respectively). Likewise, McRae line length was not found to be related to the presence of a syrinx (p = 0.139). Median nerve SEP examination was not beneficial for diagnosing asymptomatic-oligosymptomatic Chiari malformation as a subclinical injury, whether accompanied by syringomyelia or not.

Identification of injury type using somatosensory and motor evoked potentials in a rat spinal cord injury model

The spinal cord is at risk of injury during spinal surgery.If intraoperative spinal co rd injury is identified early,irreve rsible impairment or loss of neurological function can be prevented.Different types of spinal cord injury result in damage to diffe rent spinal cord regions,which may cause diffe rent somatosensory and motor evoked potential signal res ponses.In this study,we examined electrophysiological and histopathological changes between contusion,distra ction,and dislocation spinal cord injuries in a rat model.We found that contusion led to the most severe dorsal white matter injury and caused considerable attenuation of both somatosensory and motor evoked potentials.Dislocation resulted in loss of myelinated axons in the lateral region of the injured spinal cord along the rostrocaudal axis.The amplitude of attenuation in motor evoked potential responses caused by dislocation was greater than that caused by contusion.After distraction injury,extracellular spaces were slightly but not significantly enlarged;somatosensory evoked potential res ponses slightly decreased and motor evoked potential responses were lost.Correlation analysis showed that histological and electrophysiological findings we re significantly correlated and related to injury type.Intraope rative monitoring of both somatosensory and motor evoked potentials has the potential to identify iatrogenic spinal cord injury type during surgery.

Correlation study between the changes of motor evoked potential and the improvement of spinal canal volume in minimally invasive transforaminal lumbar interbody fusion

Objective:To analyze the correlation between the amplitude changes of motor evoked potential(MEP),the 3D volume changes of spinal canal measuring by postoperative CT and the improvement rate of clinical symptoms after the spinal canal decompression in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF),and to explore the predictive value of the changes of both MEP amplitude and spinal canal volume in the assessment of long-term clinical prognosis in MIS-TLIF.Methods:A retrospective study of 68 patients with L4/5 spinal stenosis treated with MIS-TLIF was performed.The changes of both intraoperative MEP amplitude and 3D spinal canal volume during the spinal canal decompression,as well as the visual analogue scale(VAS)and Oswestry dysfunction index(ODI)scores in the long-term follow-up were all recorded.Results:The values of intraoperative MEP amplitude was 159.04%higher in 68 patients with MIS-TLIF after spinal canal decompression(P<0.01).The 3 postoperative 3D spinal canal volume(4.89±1.27)cm increased by 31.22%in comparison 3 with preoperative date(3.78±1.08)cm(P<0.01).The VAS and ODI scores were improved to 78.55%and 80.60%,respectively at the last follow-up(P<0.01).The improvement rate of MEP amplitude on the decompression side was positively correlated with the improvement rate of postoperative spinal canal volume(r=0.272,P=0.025).The improvement rate of postoperative spinal canal volume was positively correlated with the improvement rate of VAS and ODI at the last follow-up(r=0.656,r=0.490,P<0.01).Moreover,the improvement rate of MEP amplitude on the decompression side was also positively correlated with the improvement rate of VAS and ODI at the last follow-up(r=0.322 and 0.235,respectively,P<0.05).Conclusion:The increase of MEP amplitude after spinal canal decompression in patients with lumbar spinal stenosis treated by MIS-TLIF was closely correlated with both of the increase of spinal canal volume and the improvement of clinical symptoms.Therefore,MEP amplitude monitoring was not only the one of the important monitoring methods for predicting the prognosis of MIS-TLIF but also the reliably predictive value in the long-term clinical prognosis in MIS-TLIF.

Formation mechanism of propagated sensation along the meridians,as verified by cortical somatosensory-evoked potential topographic maps

The peripheral driver stimulating theory states that as a driver passes along a certain meridian during acupuncture; the driver provokes nerve sense devices along the meridian, resulting in the nerve impulse entering the central nervous system. Accordingly, volunteers have reported propagated sensations along the meridians （PSM）. The present study was designed to utilize a cortical somatosensory-evoked potential （CSEP） topographic map for determining whether stimulation expansion occurs in somatosensory area I when sensation was provoked in individuals with obvious PSM. The sensation was blocked by mechanical compression, and the sensation was imitated in individuals without PSM. Results revealed a red, high-potential signal in the representative area of the lower limbs in individuals with obvious PSM symptoms when the Gall Bladder Meridian （GBM） sensation passed to the head and face. This representative area was near the middle line of the CSEP topographic map, and a red, high-potential signal, which jumps over the representative area of the upper limbs, also appeared in the representative face area, which was at the external region of the CSEP topographic map. However, in individuals exhibiting no PSM, only a red high-potential signal appeared in the representative lower limb area. When Hegu （LI 4） was stimulated in individuals without PSM, an obvious evoked response appeared only in the representative upper limb area. However, when Hegu was stimulated in individuals exhibiting PSM, the response area was larger in the representative upper limb area and extended to the representative face area. When Guangrning （GB 37） was stimulated in PSM individuals, the face representation response disappeared and was confined to a foot representation of the somatosensory area I when PSM was blocked by mechanical pressure. Results suggested that mechanical compression blocked PSM, and corresponding changes were exhibited in the CSEP topographic map. These results provide compelling evidence for the hypothesis that peripheral driver stimulation is the key element in producing PSM.

Cortical evoked potential changes in a rat model of acute ischemic stroke Detection of somatosensory evoked potential and motor evoked potential

BACKGROUND： Studies have shown that latency changes of some elements in a somatosensory evoked potential （SEP） and motor evoked potential （MEP） can reflect electrical activity of cerebral cortical neurons and conduction of white matter nerve fibers. However, there is a paucity of information regarding the dynamic observation of SEP and MEP following cerebral ischemic injury. OBJECTIVE： To explore SEP and MEP changes following acute ischemic stroke, and investigate the role of evoked potentials in monitoring brain function in stroke. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Chongqing Key Laboratory of Neurology, Affiliated Hospital of Chongqing Medical University from September 2007 to August 2008. MATERIALS＂ Hydrogen blood flow detector was purchased from Soochow University Medical Instrument Co., China, and Power lab system was purchased from AD Instruments, Inc., USA. METHODS A total of 36 healthy, adult, male, Sprague Dawley rats were randomly assigned to four groups （n = 9）, including three ischemia groups （12, 24 and 72 hours of ischemia） and a sham-surgery group. The rat model of acute ischemic stroke was established by middle cerebral artery occlusion （MCAO） in the left hemisphere. MAIN OUTCOME MEASURES＂ SEP and MEP of the left limbs were detected, and cerebral blood flow was measured by the hydrogen cleaning method. RESULTS： The latency of positive wave 1 （P1）, negative wave 1 （N1） and positive wave 2 （P2） waves in SEP, and latency of negative wave 1,2 （N1, N2） waves in MEP were significantly prolonged with increasing ischemic duration following MCAO （P 〈 0.01）, but cerebral blood flow was significantly decreased （P 〈 0.05, or P 〈 0.01）. CONLUSION： Ischemic stroke prolongs the latency of SEP waves （P1, N1, P2） and MEP waves （N1, N2）, and cerebral cortical evoked potential may correlate with cerebral blood flow changes. This indicates that SEP and MEP can be used to evaluate brain function following acute ischemic stroke.

Changes of evoked potential and expression of nestin in subventricular zones in rats after focal cerebral ischemia

Objective： To study the characteristics of latency of somatosensory evoked potential （SEP） and motor evoked potential （MEP） and the expression of nestin in subventricular zones （SVZ） after persistent focal cerebral ischemia in rats. Methods： The model of cerebral ischemia in rats was made by middle cerebral artery occlusion （MCAO）. All animals of ischemia were sacrificed after 12 h, 1 d, 3 d, 7 d, and 14 d to observe the changes of latency of SEP and MEP and to detect the expression of nestin, with an immunohistochemical approach. Results： The latencies of P1 （positive wave 1）, N1 （negative wave 1） and P2 （positive wave 2） in SEP were significantly prolonged after MCAO. The latencies of N1 and N2 waves in MEP were postponed gradually and no statistical difference of latency of N1 wave was found in rats at 7 d and 14 d after MCAO. The expression of nestin increased at 12 h, and showed a significant augmentation at 3 d and peaked at 7 d, then declined slightly at 14 d after MCAO. Conclusion： The cerebral ischemia prolonged the latency of EP waves and the expression of nestin was up-regulated and reached the peak at 7 d, showing the ischemia induced the proliferation of nervous stem cells. The SEP and MEP may evaluate the proliferation in SVZ after brain ischemia.

Effect of heartbeat perception on heartbeat evoked potential waves

Objective Early researches found that different heartbeat perceivers have different heartbeat evoked potential （HEP）waves.Two tasks were considered in our experiments to get more details about the differences between good and poor heartbeat perceivers at attention and resting state.Methods Thirty channels of electroencephalogram（EEG）were recorded in 22 subjects,who had been subdivided into good and poor heartbeat perceivers by mental tracking task. Principal component analysis（PCA）was applied to remove cardiac field artifact（CFA）from the HEP.Results（1）The good heart-beat perceivers showed difference between attention and resting state in the windows from 250 ms to 450 ms after R wave at C3 location and from 100 ms to 300 ms after R wave at C4 location;（2）The difference waveforms between good and poor heartbeat perceivers was a positive waveform at FZ from 220 ms to 340 ms after R wave,which was more significant in attention state.Conclusion Attention state had more effect on the HEPs of good heartbeat perceivers than that of poor heartbeat perceivers;and perception ability influenced HEPs more strongly in the attention state than in the resting state.

Application of pudendal evoked potentials in diagnosis of erectile dysfunction

Aim: Extensive neurophysiological investigations were carried out in 100 healthy subjects and 84 patients with penileerectile dysfunction. Methods: Following examinations were performed, spinal and scalp somatosensory evoked poten-tials (SEPs) to stimulation of the dorsal nerve of penis, motor evoked potentials (MEPs) from bulbocavernosus (BC) inresponse to scalp and spinal root stimulation, and measurement of sacral reflex latency (SRL) from anal sphincter (AS).Results: In the healthy subjects, the mean sensory total conduction time (sensory TCT), as measured at the peak of thescalp P1 (P40) wave was 39.73 ms. The mean sensory central conduction time (sensory CCT = spinal-to-scalp conductiontime) was 28.98 ms. The mean peripheral conduction time (PCP) was 9.40 ins. Transcranial brain stimulation was per-formed by using a magnetic stimulator during voluntary contraction of the examined muscle. Spinal root stimulation wasperformed at rest. Motor total conduction time (motor TCT) to BC muscles was 20.48 ms. Motor central conductiontime (motor CCT) to sacral cord segments controlling BC muscles was 14.42 ms at rest. The mean SRL was 35.13 ms.Conclusion: Combined or isolated abnormalities of SEPs, MEPs, and SRL were found in patients with erectile dysfunc-tion. (Asian J Androl 1999 Sep; 1 : 145 - 150)

Prognosis in prolonged coma patients with diffuse axonal injury assessed by somatosensory evoked potential

A total of 43 prolonged coma patients with diffuse axonal injury received the somatosensory evoked potential examination one month after injury in the First Affiliated Hospital, School of Medicine, Zhejiang University in China. Somatosensory evoked potentials were graded as normal, abnormal or absent （grades I-III） according to N20 amplitude and central conduction time. The outcome in patients with grade III somatosensory evoked potential was in each case unfavorable. The prognostic accuracy of grade III somatosensory evoked potential for unfavorable and non-awakening outcome was 100% and 80%, respectively. The prognostic accuracy of grade I somatosensory evoked potential for favorable and wakening outcome was 86% and 100%, respectively. These results suggest that somatosensory evoked potential grade is closely correlated with coma severity and degree of recovery. Somatosensory evoked potential is a valuable diagnostic tool to assess prognosis in prolonged coma patients with diffuse axonal injury.

Monitoring somatosensory evoked potentials in spinal cord ischemia-reperfusion injury

It remains unclear whether spinal cord ischemia-reperfusion injury caused by ischemia and other non-mechanical factors can be monitored by somatosensory evoked potentials. Therefore, we monitored spinal cord ischemia-reperfusion injury in rabbits using somatosensory evoked potential detection technology. The results showed that the somatosensory evoked potential latency was significantly prolonged and the amplitude significantly reduced until it disappeared during the period of spinal cord ischemia. After reperfusion for 30-180 minutes, the amplitude and latency began to gradually recover; at 360 minutes of reperfusion, the latency showed no significant difference compared with the pre-ischemic value, while the somatosensory evoked potential amplitude in- creased, and severe hindlimb motor dysfunctions were detected. Experimental findings suggest that changes in somatosensory evoked potentia~ ~atency can reflect the degree of spinat cord ischemic injury, while the amplitude variations are indicators of the late spinal cord reperfusion injury, which provide evidence for the assessment of limb motor function and avoid iatrogenic spinal cord injury.

Characteristics of Pattern Visual Evoked Potential in Two Eyes with Varying Visual Acuity in One Eye and Forensic Application

In this study, we aimed to study the pattern visual evoked potentials （P-VEPs） in two eyes with varying visual acuity in one eye and to provide an objective estimation of visual acuity by comparing P-VEPs in one and two eyes. Thirty subjects were chosen, who had one eye with an acuity of 5.0, 4.85, 4.6, 4.0, or scieropia and obstructed vision and the other eye with an acuity of 5.0, respectively. P-VEPs were detected under the large grating stimuli at 3x4 spatial frequency, moderate grating stimuli （12× 16 spatial frequency） and small grating stimuli （48×64 spatial frequency）. Under large grating stimuli, there was no significant difference in P100 peak latency between the groups, nor was there a significant difference between the amplitude of two eyes and the amplitude of one normal-vision eye. Under moderate and small grating stimuli, there was a significant difference in P100 peak latency between the group with both eyes having an acuity of 5.0 and the group with visual acuity below 4.0 in one eye. There was a significant difference in P100 amplitude between the group with visual acuity of 5.0 in both eyes and the group with one normal-vision eye. There was no significant difference in the amplitude of two eyes and the amplitude of one normal-vision eye between any other two groups. In forensic identification, characteristics and variability of P-VEPs in one and two eyes can be used to identify malingering or decline in visual acuity.

Comparison of isolated-check visual evoked potential and standard automated perimetry in early glaucoma and high-risk ocular hypertension

AIM：To compare the diagnostic performance of isolatedcheck visual evoked potential（ic VEP） and standard automated perimetry（SAP）,for evaluating the application values of ic VEP in the detection of early glaucoma.METHODS：Totally 144 subjects（288 eyes） were enrolled in this study.ic VEP testing was performed with the Neucodia visual electrophysiological diagnostic system.A 15% positive-contrast（bright） condition pattern was used in this device to differentiate between glaucoma patients and healthy control subjects.Signal-to-noise ratios（SNR） were derived based on a multivariate statistic.The eyes were judged as abnormal if the test yielded an SNR≤1.SAP testing was performed with the Humphrey Field Analyzer II.The visual fields were deemed as abnormality if the glaucoma hemifield test results outside normal limits;or the pattern standard deviation with P〈0.05;or the cluster of three or more non-edge points on the pattern deviation plot in a single hemifield with P〈0.05,one of which must have a P〈0.01.Disc photographs were graded as either glaucomatous optic neuropathy or normal by two experts who were masked to all other patient information.Moorfields regression analysis（MRA） used as a separate diagnostic classification was performed by Heidelberg retina tomograph（HRT）.RESULTS：When the disc photograph grader was used as diagnostic standard,the sensitivity for SAP and ic VEP was 32.3% and 38.5% respectively and specificity was 82.3% and 77.8% respectively.When the MRA Classifier was used as the diagnostic standard,the sensitivity for SAP and ic VEP was 48.6% and 51.4% respectively and specificity was 84.1% and 78.0% respectively.When the combined structural assessment was used as the diagnostic standard,the sensitivity for SAP and ic VEP was 59.2%and 53.1% respectively and specificity was 84.2% and 84.6% respectivlely.There was no statistical significance between the sensitivity or specificity of SAP and ic VEP,regardless of which diagnostic standard was based on.CONCLUSION：The diagnostic performance of ic VEP is not better than that of SAP in the detection of early glaucoma.

Applications of the isolated-check visual evoked potential in primary open angle glaucoma with or without high myopia

AIM:To explore the diagnostic performance of isolatedcheck visual evoked potential(ic VEP)for primary open angle glaucoma(POAG)in both highly myopic and nonhighly myopic populations and compare it with those of optical coherence tomography(OCT)and Heidelberg retinal tomography(HRT)parameters.METHODS:A total of 126 participants were recruited,including 31 highly myopic participants with POAG(HM-POAG),36 non-highly myopic participants with POAG(NHM-POAG),25 highly myopic participants without POAG(HM)and 34 controls without high myopia(Normal).All the participants underwent a complete ophthalmic examination.The signal-to-noise ratio(SNR)was used to assess the ic VEP.Both qualitative and quantitative diagnostic performances of OCT,HRT and the ic VEP were analyzed and compared.RESULTS:Based on the criterion of SNR≤1,the diagnostic performance of the ic VEP in highly myopic subjects[area under the receiver operating characteristic curve(AUC)=0.862]was better than that in non-highly myopic subjects(AUC=0.789),and the SNR had fairly good specificity.In distinguishing the HM-POAG and HM groups,the AUC of the SNR was not different from those of the OCT and HRT parameters(P>0.05)in either the qualitative or quantitative comparison.In the qualitative analysis,the ic VEP showed good consistency with damage to the central 10°of the visual field(kappa=0.695-0.747,P<0.001).CONCLUSION:The ic VEP has the potential to discriminate individuals with and without POAG,especially in populations with high myopia.

Effect of sodium tungstate on visual evoked potentials in diabetic rats

AIM： To evaluate the effect of sodium tungstate on visual evoked potentials（VEPs） in diabetic rats.· METHODS： Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin（50 mg/kg）. Sodium tungstate [40 mg/（kg·d）]was administered for 12 wk and then VEPs were recorded.Additionally, thiobarbituric acid reactive substance（TBARS） levels were measured in brain tissues.·RESULTS： The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group.· CONCLUSION： Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.

Benefits of combination of electroencephalography, short latency somatosensory evoked potentials, and transcranial Doppler techniques for confirming brain death

Objective: Optimization of combining electroencephalography (EEG), short latency somatosensory evoked potentials (SLSEP) and transcranial Doppler (TCD) techniques to diagnose brain death. Methods: One hundred and eleven patients (69 males, 42 females) from the major hospitals of Zhejiang Province were examined with portable EEG, SLSEP and TCD devices. Re-examinations occurred ≤12 h later. Results: The first examination revealed that the combination of SLSEP and EEG led to more sensitive diagnoses than the combination of SLSEP and TCD. Re-examination confirmed this and also revealed that the combination of TCD and EEG was the most sensitive. Conclusion: The results show that using multiple techniques to diagnose brain death is superior to using single method, and that the combination of SLSEP and EEG is better than other combinations.

Efficacy of nerve growth factor on the treatment of optic nerve contusion Evaluation with visual evoked potential

BACKGROUND： Pattern- visual evoked potential （PVEP） can reflect the functional status of retinal ganglial cells （RGC） and visual cortex, and is an objective examination for visual pathway function. It is a unique method for objectively examining the optic nerve function of optic ganglion cells. OBJECTIVE： To observe the effects of nerve growth factor （NGF） on PVEF in the treatment of optic nerve contusion, evaluate the clinical efficacy of NGF, and make an efficacy comparison with vitamin B12. DESIGN： A randomly grouping, controlled observation. SETTING： Department of Ophthalmology, Tangshan Gongren Hospital Affiliated to Hebei Medical University. PARTICIPANTS： Forty patients with optic nerve contusion caused by eye trauma, who received the treatment in the Tangshan Worker Hospital Affiliated to Hebei Medical University between January 2006 and June 2007, were recruited in this study. The involved 40 patients, including 34 males and 6 females, were aged 14-59 years. They were confirmed to have optic nerve contusion by ophthalmologic consultation combined with history of disease and orbital CT examination. Informed consents of treatments and detected items were obtained from all the patients. The patients were randomly divided into 2 groups with 20 in each： NGF group and vitamin B12 group. METHODS： Conservative treatment was used in the two groups. In addition, patients in the NGF group were intramuscularly injected with NGF solution 18 μg /time, once a day. Those in the vitamin B12 group were injected by the same method with common vitamin B12 of 500 μg combined with vitamin B1 of 100 mg, once a day. MAIN OUTCOME MEASURES： PVEP examination was conducted in all the patients before, one and two weeks after treatment, and latency and amplitude at P100 were detected. RESULTS： Forty patients with optic nerve contusion participated in the final analysis. Before treatment, significant differences in the latency and amplitude at P100 were not found in patients between two groups （P 〉 0.05）. For each patient in the NGF group, the latency of PVEP at P100 was significantly shortened, and the amplitude was significantly increased one and two weeks after treatment as compared with vitamin B12 group（t =2.06-2.34, P 〈 0.05）. CONCLUSION： NGF treatment can obviously improve the visual function of patients with optic nerve contusion. The curative effect of NGF is superior to vitamin B12.

Evaluation of degree of nerve root injury by dermatomal somatosensory evoked potential following lumbar spinal stenosis

BACKGROUND： Computed Tomography （CT） and Magnetic Resonance Imaging （MRI） can display the site of lumbar spinal stenosis and predict nervous compression at the morphological level; however, pure morphological changes cannot reflect functional alterations in a compressed nerve root. Dermatomal somatosensory evoked potential （DSEP） provides a means to assess the functional state of a nerve root. OBJECTIVE： To evaluate the clinical significance of DSEP, assessing the degree of nerve root injury following lumbar spinal stenosis. DESIGN, TIME AND SETTING： A case-control study was performed in the Department of Orthopaedic Surgery, Hainan People＇s Hospital, China, between September 2004 and December 2007. PARTICIPANTS： Forty-seven patients diagnosed with lumbar spinal stenosis by CT or MRI were selected as the case group; fifty healthy subjects were collected as the control group. METHODS： A KEYPOINT myoelectric evoked potential apparatus （DANTEC Company, Denmark） was used to measure DSEP, and stimulative spots were determined in accordance with the skin key sensory spot standards established by The American Spinal Injury Association： L4 in the medial malleolus, L5 in the third metatarsophalangeal joint of the dorsum of foot and S1 in the lateral heel. The needle electrode used as the recording electrode was located at the Cz point of the cranium, and the reference electrode at the Fz point. MAIN OUTCOME MEASURES： Latency of the P40 peak of DSEP, P1-N1 amplitude, P40 waveform and differentiation and disappearance of various waves. RESULTS： The sensitivity and diagnostic concurrence with surgery of nerve root injury following lumbar spinal stenosis evaluated by DSEP was 95.7 %. P40 latencies at L4, L5 and S1 in the case group were significantly longer than in the control group （P 〈 0.05）, and the P1-N1 amplitude in the case group was significantly lower than the control group （P 〈 0.05-0.01）. Nerve root injury was categorized according to DSEP latency as follows： severe damage （disappearance of the P40 wave in 103 dermatomes）, moderate damage （prolongation of the P40 peak latency ≥ 3.0 times the standard deviation of the normal mean in 60 dermatomes） and mild damage （prolongation of the P40 peak latency ≥ 2.5 times the standard deviation of the normal mean in 31 dermatomes）. CONCLUSION： DSEP can be used to determine the severity of nerve root injury following lumbar spinal stenosis with high sensitivity and specificity.

Reliability of dermatomal somatosensory-evoked potential in the evaluation of lumbosacral nerve root injury A concurrent case-control study

BACKGROUND： It has been reported that dermatomal somatosensory evoked potential （DSEP） can be used for diagnosing nerve root injury in patients with lumbar disc herniation （LDH）, and that 83% 95% of patients suffer from the disease. Body height correction is not performed prior to determinations of latency and latency difference between the healthy and affected sides. However, latency noticeably correlates to body height. OBJECTIVE： This study aims to determine the lumbosacral nerve root injury in patients with LDH by DSEP, and to evaluate the sensitivity of the DSEP difference between the healthy and affected sides using a diagnostic index following body height correction. DESIGN： A case-control observation. SETTING： Department of Orthopedic Surgery, Hainan Provincial People＇s Hospital. PARTICIPANTS： Ninety-six patients, comprised of 67 males and 29 females, with an average age of 43 years and a mean body height of 1.65 m （range 1.48-1.81 m）, were recruited for this study. These patients suffered from unilateral lower limb radiation pain and received treatment at the Department of Orthopedic Surgery, Hainan Provincial People＇s Hospital between January 2004 and December 2006. All patients were confirmed to suffer from LDH at the L3-4, L-5, and/or Ls-SI by CT and/or MRI examinations. Central nervous system diseases were excluded. In order to obtain a normal reference value, DSEP was determined for a group of 50 subjects, who concurrently received health examinations in the same department. The subjects had no previous history of back leg pain or nervous system disease. The group of healthy controls included 26 males and 24 females, with an average age of 37 years and a mean body height of 1.63 m （range 1.50-1.80 m）. Written informed consent was obtained from all subjects for laboratory samples. The protocol was approved by the Hospital＇s Ethics Committees. DSEP was determined with myoelectricity-evoked potential equipment （Keypoint, Batch No. 9020A0042591, Dantec Company, Denmark）. METHODS： DSEP of patients with LDH was determined. Constant-voltage square pulse stimulation was used to determine DSEP, with the following parameters： a pulse wave width of 0.2 milliseconds; a saddle-like stimulating electrode; a stimulation intensity 3 times greater than the sensation threshold; a stimulation frequency of 1.5 Hz; mean superposition greater than 100 times; and inter-electrode impedance 〈 5 k Q. The stimulation point was a skin key sensation point confirmed by the American Spinal Injury Association, i.e. L4 at medial malleolus, L5 at the third metatarsophalangeal joint on the dorsum of the foot, and SI at the lateral heel. The recording electrode was a needle electrode, the recording point was Cz, and the reference electrode was Fz. DSEP latency of P40, and latency differences of P40, between the healthy side and the affected side, were determined. DSEP at L4, L5, and S1 nerve roots of the lower limbs of 50 healthy controls were bilaterally determined. The normal values of P40 latency and P40 N50 amplitude were statistically obtained. MAIN OUTCOME MEASURES： Determination of DSEP values. RESULTS： Ninety-six patients with LDH and fifty healthy controls participated in the final analysis. In the healthy controls, the amplitude of DSEP varied greatly, with a mean amplitude co-efficient of variation of 58% for L4, L5, and SI dermatomes. P40 latency was stable, with a mean latency coefficient of variation of 4.7%. In patients with LDH, the P40 wave disappeared. P40 latency was 2.5 times prolonged compared to normal mean value. P40 latency difference between the healthy and the affected side was 2.5 times higher than the normal mean value of the healthy side. CONCLUSION： DSEP can reflect the functional status of lumbosacral nerve root. P40 latency difference between the healthy side and the affected side is the most sensitive diagnosis index for patients with LDH suffering from unilateral lower limb radiation pain.

Electroencephalogram and evoked potential parameters examined in Chinese mild head injury patients for forensic medicine

Objective To evaluate the usefulness of quantitative electroencephalogram （QEEG）, flash visual evoked potential （F-VEP） and auditory brainstem responses （ABR） as indicators of general neurological status. Methods Comparison was conducted on healthy controls （N=30） and patients with brain concussion （N=60） within 24 h after traumatic brain injury. Follow-up study of patient group was completed with the same standard paradigm 3 months later. All participants were recorded in multi-modality related potential testing in both early and late concussion at the same clinical setting. Glasgow coma scale, CT scanning, and physical examinations of neuro-psychological function, optic and auditory nervous system were performed before electroencephalogram （EEG） and evoked potential （EEG-EP） testing. Any participants showed abnormal changes of clinical examinations were excluded from the study. Average power of frequency spectrum and power ratios were selected for QEEG testing, and latency and amplitude of F-VEP and ABR were recorded. Results Between patients and normal controls, the results indicated： （1） Highly significance （P 〈 0.01） in average power of α1 and power ratios of θ/α1, 0/α2, α1/α2 of EEG recording; （2） N70-P 100 amplitude of F-VEP in significant difference at early brain concussion; and （3） apparent prolongation of Ⅰ～Ⅲ inter-peak latency of ABR appeared in some individuals at early stage after concussion. The follow-up study showed that some patients with concussion were also afflicted with characteristic changes of EEG components for both increments of α1 average power and θ/α2 power ratio after 3 months recording. Conclusion EEG testing has been shown to be more effective and sensitive than evoked potential tests alone on detecting functional state of patients with mild traumatic brain injury （MTBI）. Increments of α1 average power and θ/α2 power ratio are the sensitive EEG parameters to determining early concussion and evaluating outcome of postconcussion symptoms （PCS）. Follow-up study associated with persistent PCS may be consistent with the postulate of substantial biological, rather than psychological origin. The study suggests that combination of EEG and EP parameters can contribute to the evaluation of brain function as a whole for clinical and forensic applications.

Characteristics of brainstem auditory evoked potentials of students studying folk dance

BACKGROUND： Previous experiments have demonstrated that brainstem auditory evoked potential is affected by exercise, exercise duration, and frequency. OBJECTIVE： Comparing the brainstem auditory evoked potential of students studying folk dance to students studying other subjects. DESIGN： Observational contrast study. SETTING： Physical Education College, Shandong Normal University PARTICIPANTS： Fifty-five female students were enrolled at Shandong Normal University between September and December in 2005, including 21 students that studied folk dance and 34 students that studied other subjects. The age of the folk dance students averaged （19 ± 1） years and dance training length was （6.0 ± 1.5） years. The students that studied other subjects had never taken part in dance training or other physical training, and their age averaged （22 ± 1） years, body height averaged （162 ± 5） cm, body mass averaged （51 ± 6） kg. All subjects had no prior ear disease or history of other neurological disorders. All students provided informed consent for the experimental project. METHODS： The neural electricity tester, NDI-200 （Shanghai Poseidon Medical Electronic Instrument Factory） was used to examine and record Brainstem Auditory Evoked Potential values of the subjects during silence, as well as to transversally analyze the Brainstem Auditory Evoked Potential values. The electrode positions were cleaned and degreased with soapy water, followed by ethanol. The selected bipolar electrodes were situated on the head： recording electrodes were placed at the Baihui acupoint, and the reference electrode was placed at the mastoid of the measured ear, with grounding electrodes in the center of the forehead. Brainstem Auditory Evoked Potential values were elicited by monaural stimulation of a ＂click＂ though an earphone; the other ear was sheltered by the white noise. The click intensity was 102 db, the stimulation frequency was 30 Hz, the bandpass filters were 1 000-3 000 Hz, the sensitivity was 5 ta V, and a total of 2 000 sweeps were averaged. Waveform identification and analysis： various components of the Brainstem Auditory Evoked Potential values were identified, and the peak latencies and peak-peak values were analyzed. MAIN OUTCOME MEASURES： Latency of Ⅰ , Ⅱ, Ⅲ, Ⅳ, Ⅴ and Peak-Peak Value of Ⅰ, Ⅲ, Ⅴwere measured. RESULTS： Fifty-five subjects were enrolled in the final analysis, without any loss. Compared to the students who studied other subjects ① Ⅰ -Ⅴ peak latencies （PL）： Ⅳ PL of the right ear of the folk dance students was obviously longer （P 〈 0.05）; ② Ⅰ, Ⅲ, V peak-peak values：Ⅰ peak-peak values of the right ear were obviously higher （P 〈 0.05）. CONCUSION： ① PL of the right ear of the folk dance students was obviously longer, which indicates that dancing results in a stronger sensibility to auditory stimuli. ②. Peak-peak values were obviously higher, which indicates that long-term exercise enhances the music senses and synchrony of auditory nerve impulses.