Short latency somatosensory evoked potentials to peroneal nerve stimulation in normal Japanese children

Short latency somatosensory evoked potentials (SSEP) were elicited by stimulation of the peroneal nerve in 68 normal children of 39 weeks to 15 years old. In all subjects, three positive potentials (P1, P2 and P3) and one negative potential (N1) were consistently recorded. A further positive potential (P4) after N1 was not always observed. There was no change of wave form with development. P1, P2, P3 and N1 might be generated in subcortical structures; caudal cervical spine, brainstem, thalamus and thalamocortical pathway, respectively. The latency of each peak per one meter body length decreased with age until 5 or 6 years of age. Moreover, the latency between peaks per one meter body length also decreased with age until 5 to 6 years of age. These findings are consistent with the development of SSEP on median nerve stimulation and with the developmental phenomenon of spinal conduction velocity, and might be related to the increase in the diameter and the progressive myelination of nerve fibers.     

Short latency somatosensory evoked potentials following median nerve stimulation in children

We investigated short latency somatosensory evoked potentials (SSEP) to median nerve stimulation in normal children and children with neurological disorders. The waveform of SSEP in normal children was almost the same as that in adults. The peak latency and interpeak latency in normal children changed during their development. Moreover, after 3 years of age, each peak latency was positively correlated with the body length and arm length. Each peak latency per 1 m of body length decreased with age. We examined SSEP in children with various neurological disorders and found that SSEP was useful for evaluating sensory functions and somatosensory damages in children who were unable to cooperate in clinical examinations. Using SSEP, we could estimate the distal margin of the lesion in the somatosensory pathway, but it was difficult to determine the accurate range of the lesion.     

Maturation of cerebral somatosensory evoked potentials

Cerebral somatosensory evoked potentials (SEPs) were elicited by stimulation of the median nerve and/or posterior tibial nerve in 117 children of 1 day to 16 years old. A major negative wave (N) was consistently recorded from the parietal region of the scalp when the arm was stimulated. The peak latency, the onset latency, the rising time and the duration of H wave are closely correlated with age and body length. The latencies are shortest in the subjects of 1-3 years old. SEPs to lower extremity stimulation were inconstant in the infants before the age of one. The major positive wave (P) has a variable topographic distribution along the middle line, over the scalp. The latencies are also very variable in the different subjects of the same age as well as in the same subject with different locations of active electrode. Among the parameters studied as for N wave, only the rising time of P wave is significantly correlated with age. The latencies of P wave have the shortest value in the subjects of 1-3 years old. The comparison of SEPs to upper and to lower limb stimulations shows that there is no relationship between them in respect to their morphology and amplitude. The minimum value of the latencies of N and P waves was observed at the same age but the difference between the peak latencies of P and N waves in the same subject increases considerably after 2 years of age and reaches the adult value after 5 years of age. These resultats indicate that the maturation of the peripheral somatosensory pathways proceeds at a higher rate than that of the central somatosensory pathways, that the maturation of the somatosensory pathways of the upper limb precedes that of the lower limb, and that the rising time of N or P waves is a good index of cortical maturation. The clinical utility of these SEPs in pediatrics is discussed.     

A study of the maturation of the somatosensory pathway by evoked potentials

We investigated the somatosensory evoked potentials (SSEPs) in 62 healthy children, ten days to twelve years old. Our control group consisted of ten healthy adults, sixteen to thirty-six years old. The stimulus was applied at the median nerve at the wrist and the cerebral SSEPs were recorded by electrodes placed on the contralateral parietal scalp region, while for the cervical SSEP recording the electrodes were placed over the skin at the C6-C7 vertebral region. The reference electrode was placed at the FZ according to the 10-20 system. Our study revealed a significant change in the early components of the SSEPs (NI and PI) between groups of different ages. The latency and duration of the NI wave form and the latency of PI were inversely correlated with age. These changes in the early components of the SSEPs are most likely due to the gradual maturation of the afferent nervous system with age. From the difference in latencies between the peak of NI and the cervical SSEP we were able to calculate the sensory conduction time in the central nervous system and found a progressive decrease in relation to the increase of age. This is most likely due to the development of postnatal myelination of the sensory fibres of the central somatosensory pathway.     

The effects of sleep on median nerve short latency somatosensory evoked potentials

The effects of sleep on median nerve short latency somatosensory evoked potentials were studied in 7 subjects made up of 6 patients being evaluated for seizure disorders by all-night electroencephalograms and 1 normal healthy volunteer. The median nerve was stimulated at the wrist, and the peripheral (N9), subcortical (P13) and early cortical (N1, P2) evoked potentials were recorded during full wakefulness and natural night-time sleep. Sleep-wake state was monitored by the simultaneously obtained polysomnogram. The latencies of the cortical responses were prolonged during non-rapid eye movement (NREM) sleep. In 3 of the subjects P2 was consistently bifid during NREM sleep only. The second component of the bifid potential, 3-4 msec longer in latency than the first, appeared to be selectively enhanced during NREM sleep whereas the first component tended to become less prominent or even disappear. This suggests that the 2 peaks have different generators that are affected differently by NREM sleep. These are clinically relevant findings for interpretation of routine clinical studies.     

Stage II sleep alters infants' short latency somatosensory evoked potentials

To evaluate the effects of stage II sleep on short latency somatosensory evoked potentials (SLSEP) to median nerve stimulation, we studied 16 normal infants from two to twelve months of age. SLSEP were recorded during waking and stage II sleep. Four channels of parasagittal EEG and behavioral observations were used to classify states. Compared with SEP in the waking state, cerebral potentials in stage II sleep were of much lower amplitude, even vanishing entirely in several infants. In addition, the change from waking to stage II sleep produced significantly longer latencies of the peaks N1, P1, and P2. We suggest performing SLSEP in infants in the waking state in order to assess cerebral somatosensory function.     

Human somatosensory cortical activation strengths: comparison between males and females and age-related changes

The amplitudes of many scalp-recorded evoked potential (EP) deflections are higher in females than in males, and in elderly than in young subjects. Since EPs critically depend on the electric conductivity of the cranium, it is not known whether these differences reflect age- and gender-dependent changes in the intensity of neuronal activation, or changes in the volume conductor. Evoked magnetic fields are not significantly affected by the conductivities of the cranial tissues and therefore reflect more directly the neuronal activation than EPs. We report here on the effects of age and gender on somatosensory evoked fields (SEFs) from the primary somatosensory cortex (SI) in 43 healthy subjects (21 males) aged from 20 to 73 years (males 51+/-18 years, females 51+/-14 years). The intensity of neuronal activation was estimated with equivalent current dipoles (ECDs) found at the peaks of the N20m, P35m and P60m deflections from the left SI after right median nerve stimulation. The peak latencies of N20m and P35m (but not of P60m) were shorter in females than in males. The N20m latency was positively correlated with age in males, but otherwise the latencies did not correlate with age. The ECD amplitudes did not differ between males and females for any of the deflections. The N20m ECD strength showed a significant positive correlation (r=0.39, p<0.01) with age while P35m and P60m ECD strengths did not. The results thus did not disclose gender differences in the activation strengths of the somatosensory cortex, implying that such differences in evoked potentials may possibly be due to gender differences in the volume conductor. On the other hand, the results suggest a slight age-related increase in cortical excitability.     

Developmental and aging changes in somatosensory, auditory and visual evoked potentials

To assess developmental and aging changes in human sensory systems, components of short-latency somatosensory, brain-stem auditory and pattern-reversal visual evoked potentials, thought to originate in specific structures of these systems, were recorded in 286 normal subjects ranging in age from 4 to 95 years. Analysis was primarily restricted to peak and interpeak latencies; visual evoked potential amplitudes were also analyzed. Major results and conclusions are: (1) 'Developmental' changes (that is, decreases in latency attributable to decreased conduction time in younger subjects) were not seen in the median nerve, in brain-stem auditory pathways, or in some portions of visual cortex. Small developmental changes were seen in the somatosensory afferent pathway from the cervical spinal cord to thalamus, and large changes were seen in somatosensory and visual cortex. Cortical developmental changes appeared not to be complete until 17 years of age or later. (2) 'Aging' changes (that is, increases in latency attributable to increased conduction time in older subjects) were observed in the median nerve, cervical spinal cord, brain-stem auditory pathways, and somatosensory and visual cortex. (3) Visual evoked potential amplitudes tended to decrease with age, particularly during development; amplitude and latency effects were dissimilar for most components. (4) Males tended to show larger aging effects than females. (5) The results suggest that age-related changes in human sensory systems are not uniform, but rather are different in specific portions of these systems, different at particular epochs of the life span, and stronger in males than in females.     

Somatosensory evoked potentials to posterior tibial nerve stimulation in children

The somatosensory evoked potentials (SEPs) to stimulation of the tibial nerve were studied in 88 children ranging in age from 1 day to 16 years. SEPs were not evidenced in 10 out of 44 infants less than 1 year old. In others it was a major positive wave (P) with a variable topographic distribution on the midline. The onset and peak latencies of this P were highly variable in different subjects of the same age or body-size, and in the same subject with the active electrode placed in different locations. The lowest values for latency were in subjects about 3 years old. The ascending time of P was the only parameter strictly correlated with age. The results are compared with SEPs to upper limb stimulation, which are constant and more reliable. These results indicate: that the maturation of the peripheral somatosensory pathway proceeds at a faster rate than that of the central somatosensory pathway; that the maturation of the somatosensory pathway of the upper limb precedes that of the lower limb; and that the ascending time of P is a good index of thalamo-cortical maturation. The clinical utility of these SEPs in pediatrics is discussed.     

Brain stem auditory, pattern-reversal visual, and short-latency somatosensory evoked potentials: latencies in relation to age, sex, and brain and body size

To determine standards of normality for auditory, somatosensory and visual evoked potentials commonly used in the assessment of neurological disease, 8 AEP, 1 VEP and 12 SEP components were recorded to stimulation of left and right ears, eyes, and median nerves in 286 normal subjects ranging in age from 4 to 95 years. Peak and interpeak latencies, and left-right differences in latency, were analyzed as a function of age, sex, and estimates of brain and body size. Major features of the results were: (1) Peak latencies of all components showed statistically significant increases in latency with age except that VEP P100 latency decreased significantly between 4 and 19 years and did not change between 20 and 59 years. (2) In adults the peak latencies of all components were significantly later in males than in females. For AEPs and VEPs these differences were explained by sex differences in brain size, and for adult SEPs were explained by sex differences in arm and shoulder dimensions. No significant sex differences in VEP and SEP latencies were seen in children. (3) Most interpeak latencies showed significant differences in relation to age or sex. (4) Age and sex are useful predictors of latency for nearly all peak and interpeak latencies; in addition, height is a useful predictor of SEP peak latencies. (5) Left-right latency differences showed little age-related, and no sex-related, change. The interlaboratory use of these or other normative data was discussed. It was concluded that these AEP and SEP norms can probably be used in other laboratories if stimulating and recording conditions are similar. However, VEP results are difficult to transfer due to the poorly understood effects of variation in stimulus conditions. Some issues regarding the optimal characterization of norms were also discussed.     

Somatosensory evoked potentials from posterior tibial nerve and lumbo-sacral dermatomes

Techniques for recording the somatosensory evoked potential following stimulation of the skin of L5 and S1 dermatomes are described and validated. Normal data and their range are given for 54 subjects (108 legs). The latency of the peak of the first positive wave (P40) can be predicted from the subject's height from the regression formulae: P40 latency in msec = height in metres X 23.7 + 8.6 for the L5 dermatome. P40 latency in msec = height in metres X 24.5 + 8.7 for the S1 dermatome. P40 latency in msec = height in metres X 15.0 + 14.6 for the posterior tibial nerve. The standard deviations are 2.90 for L5; 2.95 for S1 and 1.60 for the posterior tibial nerve. Age and sex of the subjects had no significant effect. The data will have value when dermatomal somatosensory evoked potentials are used to investigate radiculopathies.     

Somatosensory evoked potentials in healthy volunteers and in patients with dementia

In 56 healthy volunteers short, middle and long latency somatosensory evoked potentials were recorded bilaterally. The median nerve was electrically stimulated at the wrist. The impact of arm length and age on the peak latencies of the identified SEP components was investigated. Arm length relates to shoulder and neck SEP and to the N20, the primary cortical response. Age relates to all components of the SEP. A pilot study was performed in a small number of patients with senile dementia. A significant delay of the middle and long latency potentials compared to healthy volunteers was shown.     

Conduction time in central somatosensory pathways in man.

Simultaneous recording of the somatosensory evoked potential (SEP) from the neck and from the scalp allows investigation of conduction of somatosensory impulses within the central nervous system alone. The early components of the SEP produced by stimulation of the median nerve at the wrist were recorded from standardized electrode locations on the scalp and neck in 21 normal subjects. The peak latency of both the initial negative potential from the scalp, N20 (19.4 +/- 1.1 msec), and the major negative negative potential from the neck, N14 (13.8 +/- 0.9 MSEC), CORRElated positively with arm length and with height. The difference between the peak latencies of N20 and N14 (5.6 +/- 0.5 msec) was independent of both arm length and height. As the latency and distribution of N14 indicate that this potential probably arises from the dorsal column nuclei, the N20--N14 latency difference provides a measure of conduction time within central pathways which is independent of conduction time in the limbs and spinal cord. Recording of the SEP from the neck, simultaneously with that from the scalp, also facilitates clinical investigation of the somatosensory system.     

Intrathalamic non-propagating generators of high-frequency (1000 Hz) somatosensory evoked potential (SEP) bursts recorded subcortically in man.

OBJECTIVES: Recently, bursts of high-frequency (1000 Hz) median nerve somatosensory evoked potential (SEP) wavelets were recorded subcortically near and inside the thalamus from deep brain electrodes implanted for tremor therapy. This study aimed to clarify whether these subcortical SEP bursts reflect evoked axonal volleys running in the thalamocortical radiation or a locally restricted intrathalamic response.METHODS: During deep brain electrode implantation, median nerve SEP were recorded in 7 patients sequentially along the subcortical stereotactic trajectory at sites +20 and +10 mm above the respective target nucleus (ventral intermediate thalamus or nucleus subthalamicus). Low- and high-frequency SEP components (corner frequency 430 Hz) were analyzed separately with respect to peak latency and amplitude as they changed along the recording trajectory.RESULTS: Individual wavelets of the subcortical 1000 Hz SEP burst showed fixed peak latencies independent from the depth of the electrode penetration; they increased markedly in amplitude with decreasing distance to the thalamus. In contrast, the amplitude gradient between the two recording sites was shallower for the low-frequency SEP component, which peaked earlier at the lower recording site.CONCLUSIONS: Subcortically recorded 1000 Hz SEP wavelet bursts predominantly reflect locally restricted near-field activity, presumably generated in the somatosensory relay nucleus. In contrast, the variable peak latency of the subcortical low-frequency component could reflect postsynaptic potentials sequentially evoked during passage of the lemniscal afferences curving through the thalamus and contributions from the thalamocortical radiation.     

Evoked potential studies in mitochondrial encephalomyopathy

Evoked potentials were studied in a patient with a mitochondrial encephalomyopathy revealing a defect of nicotinamideadenine dinucleotide dehydrogenase and cytochrome C oxidase in the mitochondria of a muscle biopsy specimen. The biopsy specimen showed myopathic changes with ragged-red fibers and markedly decreased cytochrome C oxidase in the muscle fibers. Subcortical somatosensory evoked potentials to median nerve stimulation were normal in the peak latencies of N9, N11, and N13. Cortical somatosensory evoked potentials to median nerve stimulation revealed significantly delayed peak latencies of N20, P20, P25, and N26, although N16 latency was normal. In particular, the interpeak latency between N16 and N20 was significantly delayed. In topographic maps, N20 and P20 were delayed in the peak latencies with normal scalp distributions. Dysfunction of somatosensory cortex indicated by the delay of cortical somatosensory evoked potentials may be related to a cortical mitochondrial abnormality. The absence of responses to auditory stimulation within 10 milliseconds could be related to the dysfunction of peripheral acoustic nerves.     

Increased cortical hyperexcitability and exaggerated myoclonus with aging in benign adult familial myoclonus epilepsy

The clinical implications of enlarged early cortical components of somatosensory evoked potentials in benign adult familial myoclonus epilepsy remain unknown. Somatosensory evoked potentials following electrical stimulation of the median nerve at the wrist were studied in 16 patients with a clinical diagnosis of benign adult familial myoclonus epilepsy (7 men and 9 women; mean age, 51 ± 18 years) and 19 age‐matched apparently healthy control subjects (11 men and 8 women; mean age, 49 ± 18 years). Giant somatosensory evoked potentials were observed in 13 of the 16 patients. P25 and N35 amplitudes in the patient group were 11.4 ± 6.1 and 19.2 ± 11.5 μV, respectively, and both were significantly larger compared with those in control subjects (P = 0.008 for P25 and P < 0.0001 for N35). There was a significant positive relationship between age at somatosensory evoked potential examination and N20, P25, and N35 amplitudes, both in the patient and in the control groups (P < 0.05). The linear regression gradient of the N35 amplitude with respect to age was significantly larger in the patient group than in the control group (P = 0.04). Furthermore, regression analysis showed a significant positive relationship between the myoclonus rating scale and age at time of somatosensory evoked potential examination (R = 0.645, P = 0.007). Somatosensory evoked potential amplitude increased with age in patients with benign adult familial myoclonus epilepsy to a greater extent than in the control subjects, which suggests a progressive increase in cortical excitability based on progressive pathophysiology in benign adult familial myoclonus epilepsy. © 2011 Movement Disorder Society     

Origin of the early components of somatosensory evoked potentials by the posterior tibial nerve stimulation--a comparative study of median nerve stimulation in clinical cases

In order to determine the generation sites of short latency somatosensory evoked potentials to the posterior tibial nerve stimulation, scalp topography was performed on 10 normal subjects in the two different band-pass recordings, i.e., wide band-pass filter (5-3000 Hz) and narrow band-pass filter (100-1000 Hz). Furthermore, comparative study of the changes of evoked potentials between posterior tibial nerve stimulation and median nerve stimulation was carried out in 22 cases with well localized lesion of the central nervous system in the same wide band-pass filter setting. The early components of somatosensory evoked potentials elicited by the posterior tibial nerve stimulation were obtained as P 30, N 34, and P 38 in the wide band-pass filter, and P 29, N 32, P 36 in the narrow band-pass filter. Components P 30, N 34 and components P 29, N 32 were widely distributed on the scalp, but were disappeared on the scalp-scalp recording. These results suggested all those components were generated from the deep subcortical structures. In the case with high cervical lesion, component P 30 at the posterior tibial nerve stimulation was remarkably prolonged in latency, and component P 13 at the median nerve stimulation was disappeared. P 30-N 34 interpeak latency at the posterior tibial nerve stimulation was prolonged in the case with pontine lesion, while P 13-N 16 interpeak latency at the median nerve stimulation was also prolonged. In the cases with thalamic and internal capsular lesion, P 30 and N 34 at the posterior tibial nerve stimulation and P 13 and N 16 at the median nerve stimulation were all preserved in normal range. These results revealed that components P 30 and N 34 were almost identical to components P 13 and N 16, respectively. On the other hand, component P 38 at the posterior tibial nerve stimulation was suppressed or disappeared in the cases with well localized lesion at the midcentro parietal region, that includes the primary foot sensory area.(ABSTRACT TRUNCATED AT 400 WORDS)     

体感诱发电位在急性脑卒中后的变化观察和意义探讨

目的观察急性脑卒中患者体感诱发电位（SEP）改变特点，评价其对于脑功能监测的价值。方法对58例脑梗死、27例脑出血和11例蛛网膜下腔出血患者，检测发病后不同时期（1～12d）SEP和血清神经元特异性烯醇化酶（NSE）改变，结合中国卒中量表评分（CSS）、Barthel指数、Glasgow-Pittsburgh昏迷量表评分以及颅脑影像学检查结果，分析与临床神经功能缺失的关系。25例年龄和性别匹配的正常人作为对照。结果发病后4d内各型脑卒中患者的SEP—P15、N20、P25和P40峰潜伏期较正常对照显著延长（P〈0．01）。脑出血和脑梗死患者发病后4d内SEP异常率高于发病后5～12d测定结果。发病后4d内，幕下脑出血和后循环脑梗死患者SEP—N20峰潜伏期与其病灶大小呈正相关（P〈0．01）。脑出血和脑梗死患者SEP—N20峰潜伏期与其血清NSE水平和CSS评分呈正相关（P〈0．01）。各型脑卒中患者SEP—N20峰潜伏期与其Glasgow-Pittsburgh昏迷量表评分呈负相关（P〈0．01）。结论SEP—N20峰潜伏期异常反映脑出血和脑梗死患者脑损伤和神经功能缺失严重程度，并可作为评估蛛网膜下腔出血患者昏迷程度的指标。     

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?     

Subcortical and cortical somatosensory potentials evoked by posterior tibial nerve stimulation: normative values

Cortical somatosensory evoked potentials to posterior tibial nerve stimulation were obtained in 29 normal controls varying in age and body height. In obtaining these potentials we varied recording derivations and frequency settings. Our recordings demonstrated the following points: N20 (dorsal cord potential) and the early cortical components (P2, N2) were the only potentials that were consistently recorded. All other subcortical components (N18, N24, P27, N30) were of relatively low amplitude and not infrequently absent even in normals. All absolute latencies other than N2 were correlated with body height. However, interpeak latency differences were independent of body height. Below the age of 20, subcortical but not cortical peak latencies correlated with age, but this appeared to be due to changes in body height in this age group. Absolute amplitudes and amplitude ratios (left/right and uni/bilateral) showed marked interindividual variability and have very limited value in defining abnormality. The use of restricted filter windows facilitated the selective recording of postsynaptic potentials (30-250 Hz) and action potentials (150-1500 Hz).