The central conduction time in posterior tibial and pudendal nerve somatosensory evoked potentials

The somatosensory evoked potentials (SEPs), following stimulation of both the posterior tibial nerve (PTSEP) and pudendal nerve (PNSEP), comprise of the lumbar negative, subcortical and cortical potential. These can be used to assess the long somatosensory pathway, including peripheral, intraspinal and intracranial conduction along the entire length. This study aimed to compare the central conduction time between the PTSEP and the PNSEP, and to investigate the relationship between the intraspinal and intracranial conduction time in the SEP pathway. The SEPs following stimulation of the posterior tibial nerve at the ankle and the pudendal nerve at the shaft of the penis were analyzed in 20 normal male subjects. The central conduction of the PNSEP was found to be slower than that of the PTSEP (p <0.05). This difference is due to a delay in conduction rather than that of intracranial conduction.     

脑血管病病人感觉障碍的体感诱发电位研究

目的：探讨脑血管病（ＣＶＤ）病人感觉障碍与体感诱发电位（ＳＥＰ）异常间的关系。方法：对ＣＶＤ２８例感觉障碍的病人，２１例只有运动障碍而无感觉障碍的病人和１０例正常人进行了ＳＥＰ研究。结果：感觉障碍组患侧中枢传导时间（ＣＣＴ）延长，与非患侧和正常对照组比较，差异均有显著性意义（Ｐ＜０．０５）。感觉障碍组Ｎ２０－Ｐ２５和Ｐ１５波幅比的异常率均明显高于无感觉障碍组。结论：ＣＶＤ的感觉障碍与ＳＥＰ的异常密切相关，ＳＥＰ可以做为判断ＣＶＤ时存在感觉障碍的客观指标     

Homozygous c.359del variant in MGME1 is associated with early onset cerebellar ataxia

We ascertained a child with early onset cerebellar ataxia and identified a novel frameshift deletion, c.359del [p. (Pro120Leufs*2), NM_052865.2] in exon 2 of MGME1 (mitochondrial genome maintenance exonuclease 1) by exome sequencing. Variations in MGME1 have been reported to cause mitochondrial DNA (mtDNA) depletion syndrome 11 (MIM #615084) in an earlier work. The phenotype included progressive external ophthalmoplegia, emaciation, respiratory failure and late onset progressive ataxia. However, the child presented here has early onset progressive ataxia, speech delay, microcephaly, cerebellar atrophy and fundus albipunctatus. This is the second report of a mutation in MGME1 and describes a more severe phenotype.     

Differential enhancement of early and late components of the cerebral somatosensory evoked potentials during forced-paced cognitive tasks in man

1. Cerebral potentials evoked by random sequences of electrical stimuli to four fingers were recorded in intact man performing selective attention tasks. Eye movements and other artifacts were excluded from the averaged traces. Different finger stimuli were designated as targets to be mentally counted in alternate runs of each experiment. The high mean random rate of stimuli (150/min) fully involved the processing capacities of the subject. Vigilance changes or differential expectancy effects were excluded by the reciprocal random design with four different sensory channels. Task-related enhancements of somatosensory evoked potentials (s.e.p.) components were estimated by comparison with the s.e.p.s to physically identical finger stimuli recorded in runs when the subject attended signals in the opposite hand. The experimental design avoided subject's fatigue.

2. The primary s.e.p. components N₂₀ and P₄₅ were not significantly influenced and this excluded centrifugal gating of the corticipetal signals as a mechanism.

3. The earliest task-related changes in s.e.p. occurred 55-135 msec (mean 77·7 msec) after the target finger stimuli. In most cases the negative N₁₄₀ component was markedly enhanced both for target signals and for non-targets in the adjacent finger of the same hand. However, in several subjects the targets elicited a positive P₁₀₀ component instead. Both N₁₀₄ and P₁₀₀ were larger at the contralateral parietal focus than ipsilaterally. They were definitely smaller at the vertex and frontal scalp locations.

4. Enhancements of N₁₄₀ were not observed in similar random four-finger experiments carried out at a 4 times slower mean rate, but they occurred in a bisensory paradigm with finger shocks and acoustic clicks at that slower rate.

5. A large positive P₄₀₀ component was only elicited by target stimuli. Its voltage was maximum over the parietal region and was equal on both sides.

6. At least three categories of components can be differentiated in the cortical s.e.p. on the basis of their time domains (roughly 18-70 msec, 70 to 200-250 msec and over 200 msec after the finger stimuli), cerebral hemispheres topography and cognitive parameters. Verbal instructions defining specific perceptual tasks can to a large extent switch on and off the components of the second and third categories when the processing resources of motivated subjects are fully committed in a well designed forced paced paradigm. In certain individuals physiological evidence for a different `stimulus set' processing of target (P₁₀₀) and non-target (N₁₄₀) signals was documented for the first time.

     

Genetic analysis of early onset cerebellar ataxia with retained tendon reflexes in four Tunisian families

Spinocerebellar ataxias comprise a poorly understood group of inherited degenerative neurological diseases. Attempts to classify hereditary ataxias on the basis of the neurological features or specific clinical signs such as tendon reflex changes have proven to be unsatisfactory. Early onset cerebellar ataxia (EOCA) is generally inherited as an autosomal-recessive trait. Thus far, we do not have accurate answers to several questions about its classification. However, significant clinical heterogeneity observed in four Tunisian families with typical EOCA clinical features reinforces the hypothesis of genetic heterogeneity underlying this phenotype. We have demonstrated that three of the four families studied were not linked to Friedreich's ataxia (FA), vitamin E deficiency ataxia (AVED), and autosomal dominant cerebellar ataxia (ADCA) loci. The fourth family showed homozygosity for a large pathological expansion of GAA repeat in all patients, the parents being heterozygous for this mutation. We have also noted, in the case of the family studied, that there was instability in the transmission of the mutation, along with a phenomenon of anticipation comparable to that observed in dominant triplet repeat diseases. EOCA is thus clinically indistinguishable from FA, yet genetically independent of all known candidate genes. Genetic mapping is required for research into the causal gene and an understanding of the disease's physiopathologic mechanisms.     

Kinesthetic and somatosensory evoked potentials in patients with Parkinson's syndrome

In patients with Parkinson's syndrome the early components of kinesthetic evoked potentials recorded from the brain differ significantly from those in healthy subjects, whereas the components of somatosensory evoked potentials do not. The observed differences appear to reflect enhanced pyramidal descending influences on the transmission of inhibitory kinesthetic afferent impulses in order to compensate for the excessive excitation in the extrapyramidal system. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny Vol. 117, N ^o 3, pp. 230–231, March, 1994 Presented by O. S. Adrianov, Member of the Russian Academy of Medical Sciences     

Deletion mapping of chromosome 1 in early onset and late onset breast tumors--a comparative study in eastern India

Younger women exhibit more aggressive pathologic features of breast cancer (BC) compared to their older counterparts. Young age has been shown to be an independent predictor of adverse prognosis. These findings have raised the question of whether these differences are also present at the genetic level. Twenty-five early onset (age < or = 40 years) tumors including 4 bilateral tumors, and 26 late onset (>40 years) breast tumors, including 2 bilateral tumors, were examined for loss of heterozygosity (LOH) at chromosome 1 using 11 polymorphic microsatellite markers. A comparative study revealed high frequencies of LOH in chr. 1p36 (61%), 1p31.3 (40%), 1p21.3 (50%) and 1q22-23.2 (56%) in a younger group, and chr. 1p36 (46%), 1p34.2 (48%), and 1q22-23.2 (52%) in an older group. These differences in LOH frequency in these two age groups were significant for chr. 1p21.3 (p = 0.025) only. These data suggest that the deletion pattern in early onset breast tumors is not fully identical to late onset breast tumors. Similar differential deletion patterns of LOH in the 5 highly deleted regions were seen in premenopausal and postmenopausal groups. An association was seen between LOH at chr. 1p34.2 and chr. 1q22-23.2 and higher grade of the tumors in older women. Among the highly deleted regions, the deletion at chr. 1p36 was found to occur early in both groups because of common allelic loss in the bilateral tumors.     

视神经炎的体感诱发电位研究

目的：探讨视神经炎患者的亚临床损害情况。方法：利用短潜伏期体感诱发电位对３０例视神经炎患者进行四肢分侧检查。结果：下肢中枢传导异常率５０％（１５／３０），明显高于上肢７％（２／３０）；下肢中枢传导异常单侧（１２／１５）多于双侧（３／１５）；同时还发现有外周传导异常（１７％）。提示脊髓胸段频繁地不对称地受累。结论：视神经炎可能是多发性硬化的一个临床亚型表现，或者说视神经炎时往往有脊髓的亚临床损害     

65例颈椎型脊髓病体感诱发电位分析

目的研究颈椎型脊髓病皮质体感诱发电位（ＳＥＰ）变化。方法对６５例颈椎型脊髓病患者和２６例正常人进行正中神经和胫后神经刺激的ＳＥＰ对照研究，并对１０例患者作治疗前后对照观察。结果本组异常率为４５％，主要表现为各波替伏期和波间期（Ｎ２０—Ｐ２５，Ｐ２５—Ｎ３５，Ｐ４０—Ｎ４５）延长，且下肢的延长更加明显，部分患者出现波形分化不良。经保守治疗后６例正常，２例好转，且ＳＥＰ的好转先于临床的改善。结论ＳＥＰ对评判颈椎型脊髓病的脊髓传导功能具有重要的意义，且有助于临床预后的评价。     

Nerve conduction changes during lower limb lengthening. Somatosensory evoked potentials (SEPs) and F-wave results

The effect of lower limb lengthening on nerve conduction was investigated in 5 achondroplastic subjects who underwent callotasis on a "cross-over" basis. Somatosensory evoked potentials (SEPs) and F waves from the posterior tibial nerve (PTN) were studied preoperatively and then after removal of the axial fixators. SEPs at the end of lengthening showed that both the latency of the plexus potential (P9) and, albeit to a lesser extent, the interpeak time between the plexus and the spinal cord (N15) potentials were significantly increased. The central conduction time (N15-P33) and the amplitude of the scalp responses were not modified. The latencies of the F waves were much longer at the end of bone distraction than in basal conditions. The increases in both PTN SEPs and F-wave latencies are consistent with a slowing of conduction The extent of these latency shifts correlated closely with the degree of limb lengthening. We calculated that, on average, each cm of lengthening could produce 0.21 msec and 0.22 msec delays respectively, suggesting a similar effect of the stretching on both sensory and motor fibers. Our findings indicated that the damage could be widely distributed along the whole length of the nerve, affecting both the peripheral (trunk) and proximal (plexus and root) segments. The electrophysiological changes were not associated with any persistent clinical complaint.     

A comparative magnetoencephalographic study of cortical activations evoked by noxious and innocuous somatosensory stimulations

We recorded somatosensory-evoked magnetic fields and potentials produced by painful intra-epidermal stimulation (ES) and non-painful transcutaneous electrical stimulation (TS) applied to the left hand in 12 healthy volunteers to compare cortical responses to noxious and innocuous somatosensory stimulations. Our results revealed that cortical processing following noxious and innocuous stimulations was strikingly similar except that the former was delayed approximately 60 ms relative to the latter, which was well explained by a difference in peripheral conduction velocity mediating noxious (Adelta fiber) and innocuous (Abeta fiber) inputs. The first cortical activity evoked by both ES and TS was in the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulated side. The following activities were in the bilateral secondary somatosensory cortex (SII), insular cortex, cingulate cortex, anterior medial temporal area and ipsilateral SI. The source locations did not differ between the two stimulus modalities except that the dipole for insular activity following ES was located more anterior to that following TS. Both ES and TS evoked vertex potentials consisting of a negativity followed by a positivity at a latency of 202 and 304 ms, and 134 and 243 ms, respectively. The time course of the vertex potential corresponded to that of the activity of the medial temporal area. Our results suggested that cortical processing was similar between noxious and innocuous stimulation in SI and SII, but different in insular cortex. Our data also implied that activities in the amygdala/hippocampal formation represented common effects of noxious and tactile stimulations.     

Whole exome and targeted gene sequencing to detect pathogenic recessive variants in early onset cerebellar ataxia

Over 100 genetically distinct causal known loci for hereditary ataxia phenotype poses a challenge for diagnostic work-up for ataxia patients in a clinically relevant time and precision. In the present study using next-generation sequencing, we have investigated pathogenic variants in early-onset cerebellar ataxia cases using whole exome sequencing in singleton/family-designed and targeted gene-panel sequencing. A total of 98 index patients were clinically and genetically (whole exome sequencing (WES) in 16 patients and targeted gene panel of 41 ataxia causing genes in 82 patients) evaluated. Four families underwent WES in family based design. Overall, we have identified 24 variants comprising 20 pathogenic and four likely-pathogenic both rare/novel, variations in 21 early onset cerebellar ataxia patients. Among the identified variations, SACS (n = 7) and SETX (n = 6) were frequent, while ATM (n = 2), TTPA (n = 2) and other rare loci were observed. We have prioritized novel pathogenic variants in RARS2 and FA2H loci through family based design in two out of four families.     

皮节体感诱发电位在诊断腰骶神经根损害中的临床研究

目的:探讨皮节体感诱发电位(DSEP)在诊断腰骶神经根受损及其严重程度中的临床应用价值.方法:将47例具有长期腰痛,伴有双侧下肢放射痛及间歇性跛行症状,经CT或MRI确诊有腰椎管狭窄(LSS)需要入院进行手术治疗的病例设为病例组.对照组为50例无腰腿痛和无中枢神经系统疾病的健康成年人.分别对两组进行双侧L4、L5、S1神经根DSEP检测.DSEP的异常诊断标准:P40波(即P1波)消失,和(或)P40波潜伏期延长超过正常均数+2.5倍标准差(>+2.5 s).结果:病例组中,P40波潜伏期明显延长91个皮节,P40波形消失103个皮节.分别将左右两侧三个皮节(L4、L5、S1)的P40潜伏期与正常对照组相对应皮节的P40潜伏期进行统计学分析,差异有显著意义(P<0.01).DSEP诊断LSS神经根其灵敏度和符合率均为95.7%.结论:DSEP能反映LSS时神经根受损及其严重程度,与CT或MRI能互为补充,作为需要进行手术的证据,具有重要的临床应用价值.     

局限性癫痫患儿体感诱发电位特征及临床应用

目的：探讨局限性癫痫患儿体感诱发电位特征及应用价值。方法：依据头颅ＣＴ结果分组观测５１例局限性癫痫患儿及３０例正常儿童的双侧正中神经短潜伏期体感诱发电位（ＳＬＳＥＰ）各指标的差异，并与常规脑电图结果进行了比较。结果：与对照组相比，脑部ＣＴ未发现病变组Ｎ２０波幅在癫痫灶侧明显高于对侧；而癫痫灶侧大脑病变组的病灶侧Ｎ２０波幅却明显低于对侧。在部分脑电图未显示局灶性异常的病例也同样显示了这种差异。结论：对于局限性癫痫患儿进行正中神经ＳＬＳＥＰ检查可有助于早期判断症状性癫痫和特发性癫痫，在某种意义上它可能较常规脑电图检查具有更高的敏感性     

Cortical somatosensory evoked potentials. II. Effects of excision of somatosensory or motor cortex in humans and monkeys

1. To clarify the generators of human short-latency somatosensory evoked potentials (SEPs) thought to arise in sensorimotor cortex, we studied the effects on SEPs of surgical excision of somatosensory or motor cortex in humans and monkeys. 2. Normal median nerve SEPs (P20-N30, N20-P30, and P25-N35) were recorded from the cortical surface of a patient (G13) undergoing a cortical excision for relief of focal seizures. All SEPs were abolished both acutely and chronically after excision of the hand area of somatosensory cortex. Similarly, excision of the hand area of somatosensory cortex abolished corresponding SEPs (P10-N20, N10-P20, and P12-N25) in monkeys. Excision of the crown of monkey somatosensory cortex abolished P12-N25 while leaving P10-N20 and N10-P20 relatively unaffected. 3. After excision of the hand area of motor cortex, all SEPs were present when recorded from the cortical surface of a patient (W1) undergoing a cortical excision for relief of focal seizures. Similarly, all SEPs were present in monkeys after excision of the hand area of motor cortex. 4. Although all SEPs were present after excision of motor cortex in monkeys, variable changes were observed in SEPs after the excisions. However, these changes were not larger than the changes observed after excision of parietal cortex posterior to somatosensory cortex. We concluded that the changes were not specific to motor cortex excision. 5. These results support two major conclusions. 1) Median nerve SEPs recorded from sensorimotor cortex are produced by generators in two adjacent regions of somatosensory cortex: a tangentially oriented generator in area 3b, which produces P20-N30 (human) and P10-N20 (monkey) [recorded anterior to the central sulcus (CS)] and N20-P30 (human) and N10-P20 (monkey) posterior to the CS; and a radially oriented generator in area 1, which produces P25-N35 (human) and P12-N25 (monkey) recorded from the postcentral gyrus near the CS. 2) Motor cortex makes little or no contribution to these potentials.     

痉挛性斜颈体感诱发电位的研究

目的：探讨痉挛性斜颈患者大脑皮层功能的变化。方法：对30例痉挛性斜颈患者刺激正中神经后体感诱发电位（SEP）的P22、N30波潜伏期及P22、N30波幅进行比较分析,30例正常对照组仅在颈部主动向右侧扭转时对双侧P22、N30波幅进行比较分析。结果：病例组SEPP22、N30潜伏期正常,双侧比较差异无统计学意义,头部扭转方向的对侧大脑半球前中央区的P22-N30波幅比明显高于对侧,差异有统计学意义。正常对照组前中央区记录的双侧P22N30波幅比较差异无统计学意义。结论：SEP P22、N30潜伏期正常提示传导通路结构完整,头部扭转方向的对侧大脑半球前中央区的P22-N30波幅比明显高于对侧,提示患者对侧大脑皮层前中央区电活动存在异常的兴奋及抑制,即抑制性减弱,兴奋性增高,N30记录的是刺激正中神经SEP中长潜伏成分,可能来源于运动辅助区,进一步提示患者存在感觉一运动整合功能异常。     

Synaptic potentials evoked by convergent somatosensory and corticocortical inputs in raccoon somatosensory cortex: substrates for plasticity.

1. "Unmasking" of weak synaptic connections has been suggested as a mechanism for the early changes in cortical topographic maps that follow alterations of sensory activity. For such a mechanism to operate, convergent sensory inputs must already exist in the normal cortex. 2. We tested for topographic and cross-modality convergence in primary somatosensory cortex of raccoon. The representation of glabrous skin of forepaw digits was chosen because, even though it is dominated by inputs from the glabrous skin of a single digit, it nevertheless comes to respond to stimulation of other digits when, e.g., a digit is removed. 3. Intracellular recordings were made from 109 neurons in the representation of glabrous skin of digit 4. Neurons were tested for somatosensory inputs with electrical and natural stimulation of digits. 4. Excitatory postsynaptic potentials (EPSPs) were evoked in 100% of the neurons (109/109) by electrical stimulation of glabrous skin of digit 4, and in 79% (31 of 39) by vibrotactile stimulation. 5. Glabrous skin of digit 4 was not the sole source of somatosensory inputs. A minority of neurons generated EPSPs after electrical stimulation of hairy skin of digit 4 (10 of 98 neurons, 10%). Electrical stimulation of digits 3 or 5 evoked EPSPs in 22 of 103 neurons (21%). Natural stimulation (vibrotactile or hair bending) was also effective in most of these latter cases (digit 3, 6/7; digit 5, 9/10). 6. Intracortical microstimulation of the "heterogeneous zone" was used to test for corticocortical connections to neurons in the glabrous zone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of realistically shaped boundary-element and spherical head models in source localization of early somatosensory evoked potentials

Summary Source localizations of early somatosensory evoked potentials and electrical potentials produced by dipoles in the region of the central sulcus were computed using realistically shaped boundary-element head models (BEM) and compared to localizations obtained using 3-shell spherical models. Realistically shaped 3-shell boundary-element-models were constructed on the basis of the individual anatomy obtained from 3D-MR-tomography in 6 subjects. Spherical head models were fitted to the actual locations of the electrodes and to the surface of the heads, respectively. Source locations calculated within the spherical head models differed by an average of 4 mm (range: 2 to 7 mm) with respect to the 3-shell BEM, taking into account the limited accuracy of this model. This mislocation was most prominently due to deeper source locations predicted using a spherical head model and caused by incorrect modelling of the geometry of the heads, although sources were located in a favourable region of the heads.This work was supported by the Volkswagen foundation.     

脑梗死患者的运动及体感诱发电位研究

目的：研究脑梗死患者的运动诱发电位（ＭＥＰ）及体感诱发电位（ＳＥＰ）改变。方法：对３０便脑梗死患者在急性期行经颅磁刺激ＭＥＰ检测,对其中２０例同时行电刺激ＳＥＰ检测,１０例患者２月后复查ＭＥＰ,并以３０例健康者作为正常对照组。结果：急性期ＭＥＰ的异常率为９３％,主要表现为皮层ＭＥＰ消失,中枢运动传导时间（ＣＭＣＴ）延长,波形异常及阈刺激强度增高。ＳＥＰ的异常率为３０％,表现为皮层波的缺失及中枢传导时间延长。复查ＭＥＰ有９例明显改善。结论：对于脑梗死的诊断,ＭＥＰ较ＳＥＰ敏感,但将ＭＥＰ与ＳＥＰ联合应用,可从不同的两个侧面反映运动及感觉功能受损的情况,弥补了ＣＴ仅能提供颅内解剖学改变而不能反映功能状态的不足。