Contribution of different somatosensory afferent input to subcortical somatosensory evoked potentials in humans

ObjectivesTo investigate the subcortical somatosensory evoked potentials (SEPs) to electrical stimulation of either muscle or cutaneous afferents.MethodsSEPs were recorded in 6 patients suffering from Parkinson’s disease (PD) who underwent electrode implantation in the pedunculopontine (PPTg) nucleus area. We compared SEPs recorded from the scalp and from the intracranial electrode contacts to electrical stimuli applied to: 1) median nerve at the wrist, 2) abductor pollicis brevis motor point, and 3) distal phalanx of the thumb. Also the high-frequency oscillations (HFOs) were analysed.ResultsAfter median nerve and pure cutaneous (distant phalanx of the thumb) stimulation, a P1-N1 complex was recorded by the intracranial lead, while the scalp electrodes recorded the short-latency far-field responses (P14 and N18). On the contrary, motor point stimulation did not evoke any low-frequency component in the PPTg traces, nor the N18 potential on the scalp. HFOs were recorded to stimulation of all modalities by the PPTg electrode contacts.ConclusionsStimulus processing within the cuneate nucleus depends on modality, since only the cutaneous input activates the complex intranuclear network possibly generating the scalp N18 potential.SignificanceOur results shed light on the subcortical processing of the somatosensory input of different modalities.     

Enlarged high frequency oscillations of the median nerve somatosensory evoked potential and survival in amyotrophic lateral sclerosis

ObjectiveA large N20 and P25 of the median nerve somatosensory evoked potential (SEP) predicts short survival in amyotrophic lateral sclerosis (ALS). We investigated whether high frequency oscillations (HFOs) over N20 are enlarged and associated with survival in ALS.MethodsA total of 145 patients with ALS and 57 healthy subjects were studied. We recorded the median nerve SEP and measured the onset-to-peak amplitude of N20 (N20o-p), and peak-to-peak amplitude between N20 and P25 (N20p-P25p). We obtained early and late HFO potentials by filtering SEP between 500 and 1 kHz, and measured the peak-to-peak amplitude. We followed up patients until endpoints (death or tracheostomy) and analyzed the relationship between SEP or HFO amplitudes and survival using a Cox analysis.ResultsPatients showed larger N20o-p, N20p-P25p, and early and late HFO amplitudes than the control values. N20p-P25p was associated with survival periods (p = 0.0004), while early and late HFO amplitudes showed no significant association with survival (p = 0.4307, and p = 0.6858, respectively).ConclusionsThe HFO amplitude in ALS is increased, but does not predict survival.SignificanceThe enlarged HFOs in ALS might be a compensatory phenomenon to the hyperexcitability of the sensory cortex pyramidal neurons.     

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

ObjectiveSystematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).MethodsPubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.ResultsERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.ConclusionsWhile there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.SignificanceThe review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.     

神经外科麻醉对体感诱发电位的影响

目的探讨神经外科手术麻醉对体感诱发电位（SEP）的影响,以期为麻醉和手术处理提供依据。方法随机抽取我科17例全麻手术病人,分成颅内疾病手术组（A组）与脊柱、脊髓疾病手术组（B组）,于术前、麻醉（诱导完成）、术始、术中、术毕和术后6个时程连续监测SEP的潜伏期、波幅及波形并记录。结果麻醉后SEP潜伏期延长5.96%,波幅下降24.00%,未出现波形消失的情况。结论麻醉抑制SEP,表现为潜伏期延长和波幅下降,但未出现波形消失的情况。     

Electrophysiological evaluation in 4 patients with diabetic pseudotabes

BACKGROUND: Researches on diabetic nervous system lesion are mainly focus on peripheral nerve and vegetative nerve, so there are few investigations on diabetic pseudotabes. OBJECTIVE: To investigate the electrophysiological examinations on the diagnosis of diabetic pseudotabes. DESIGN: Case study. SETTING: Department of Electrophysiology and Department of Neurology, Zhongshan Hospital Affiliated to Xiamen University. PARTICIPANTS: A total of 4 patients with type 2 diabetes mellitus, including 3 males and 1 female aged from 50 to 72 years, were selected from Department of Neurology, Zhongshan Hospital Affiliated to Xiamen University from March 2002 to February 2005. All accepted subjects met the modified diagnostic criteria of diabetes mellitus, which was set by American Diabetes Mellitus Association (ADA) in 1997. Otherwise, the subjects had typical symptoms and physical signs of spinal posterior funiculus damage. However, patients with spinal cord lesion which was caused by other factors were excluded. All accepted subjects provided the confirmed consent. METHODS: Nicolet NT electromyography (EMG)/evoked potential meter (made in the USA) was used to detect spinal cord conduction velocity (SCCV), somatosensory evoked potential (SEP) of lower limbs, motor nerve conduction velocity (MNCV) and sensory nerve conduction velocity (SNCV) of extremities. Determining criteria: Measurements were performed based on the laboratory standards. SCCV, which was less than lower limit of normal value (T2–12: 40–55 m/s, T12–L4: 20–41 m/s, T2–L4: 36–45 m/s), was regarded as abnormal. SEP value of lower limbs: P40, P60 and PF, which were more than standard deviation of normal value (x(—)+2.5), were regarded as the abnormality. Normal value of P40, P60 and PF latencies (x(—)±s) in this study: P40, P60 and PF in males were (37.6±1.9) ms, (59.8±3.9) ms and (7.6±0.9) ms, respectively; meanwhile, those in females were (35.5±1.7) ms, (55.2±2.7) ms and (6.3±0.7) ms, respectively. MNCV and SNCV, which were less than 50 m/s in upper limbs and 40 m/s in lower limbs, were regarded as the abnormality. MAIN OUTCOME MEASURES: Electrophysiological examinations. RESULTS: All 4 patients with type 2 diabetes mellitus were involved in the final analysis. ① SCCV: Among 4 patients, SCCV of three patients was decreased in T2–12, T12–L4 and T2–L4, and that of the other one was decreased in T2–12 and T2–L4; however, SCCV in T12–L4 was normal. There was significant difference as compared with normal value (P < 0.01). ② SEP of lower limbs: SEP values of lower limbs were abnormal in all 4 patients. Among them, P40, P60 and PF latencies of two patients were delayed; P40 of one patient was delayed and PF was not drained out; P40 and P60 of the last one were delayed and PF was normal. ③ MNCV and SNCV: The MNCV and SNCV were normal in one patient and abnormal in three patients. The results demonstrated that MNCV and SNCV of extremities decreased; especially, sensory nerve action potential (SNAP) of both lower extremities of one patient were not drained out. CONCLUSION: Detections of SCCV, SEP of lower limbs, MNCV and SNCV of extremities are helpful to investigate whether peripheral nerve and deep sensory passage are damaged or not and determine whether deep sensory damage is caused by peripheral nerve and spinal posterior funiculus.     

Topography of cholinergic afferents from the nucleus basalis of meynert to representational areas of sensorimotor cortices in the rat

We investigated (1) the topography of projection neurons in the nucleus basalis of Meynert (NBM) with efferents to restricted regions of the primary somatosensory (SI), the second somatosensory (SII), and the primary motor (MI) cortices in the rat; (2) the percentage of these NBM projection neurons that were cholinergic; and (3) the collateralization, if any, of single NBM neurons to different subdivisions within SI, to homotopic areas of SI and SII, and to homotopic areas of SI and MI. Retrograde single-and double-labeling techniques were used to study NBM projections to electrophysiologically identified subdivisions of SI and to homotopic representational areas of SI and SII, and of SI and MI. Choline acetyltransferase immunocytochemistry was done to identify cholinergic NBM neurons. Of the retrogradely labeled NBM neurons that projected to selective subdivisions of SI, SII, and MI, 89%, 87%, and 88%, respectively, were cholinergic. We found a rostral-to-caudal progression of retrogradely labeled NBM neurons following a medial-to-lateral sequence of injections into subdivisions of SI. Overlapping groups of single-labeled NBM neurons were observed after injections of different tracers into adjacent subdivisions within SI or homotopic areas of SI and SII, and of SI and MI. We conclude that NBM innervation to SI, SII, and MI is mostly cholinergic in the rat, that each cortical area receives cholinergic afferents from neurons widely distributed within the NBM, and that each NBM neuron projects to a restricted cortical area without significant collateralization to adjacent subdivisions within SI or to homotopic areas of SI and SII, or SI and MI. © 1993 Wiley-Liss, Inc.     

Pain-related somatosensory evoked potentials following CO2 laser stimulation in peripheral neuropathies

Pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation were examined in 30 patients with peripheral neuropathies, and the results were compared with clinical sensory findings. Pain SEP findings showed a significant correlation with the clinical impairment of pain sensation, but not with the impairment of deep sensations. In contrast, conventional electrically-stimulated SEPs (electric SEPs) showed a significant correlation with deep sensations, but not with the impairment of pain sensation. Examinations of both pain SEPs and electric SEPs, therefore, are considered to be very useful to evaluate physiological functions of sensory nerves in patients with peripheral neuropathies.     

术中皮质体感诱发电位与电刺激术定位脑功能区

目的探讨脑功能区手术中利用脑皮质体感诱发电位(SEP)及直接皮质电刺激定位脑功能区的方法及意义。方法对10例脑功能区病变病人在唤醒麻醉下进行手术，利用皮质SEP及皮质直接电刺激定位感觉区、运动区及语占区，住保护脑功能区的前提下，手术切除病变。结果7例病人利用SEP及皮质电刺激确定出运动感觉区，其中4例利用SEP位相倒置确定出中央沟，3例病变位于左侧额颞叶的病人通过皮质直接电刺激确定出语言区?术后功能均较术前明显好转。结论术中SEP及直接皮质电刺激可准确、实时确定脑功能区，最大程度地保护功能，切除病变。     

单纯脑白质疏松症与皮质下动脉硬化性脑病的临床对比研究

目的探讨单纯脑白质疏松症(LA)和皮质下动脉硬化性脑病(BD)的临床表现、影像学及脑诱发电位的改变特征。方法(1)调查114例单纯脑白质疏松症患(LA组)和41例皮质下动脉硬化性脑病患(BD组)的发病危险因素和临床表现。(2)两组患均行CT检查，并按照脑白质异常程度分为3型。(3)LA组74例患，BD组35例患行MRI检查，根据T2WI显示的脑室周围高信号分为5型。(4)两组分别选择部分伴有高血压的患进行躯体感觉诱发电位(SEP)、脑干听觉诱发电位(BAEP)和视觉诱发电位(VEP)检查。结果(1)LA组患的危险因素呈多样化，无神经局灶体征，临床表现仅为轻度记忆力减退、步态不稳。CT显示脑白质异常以1型为主，占70．2％(80／114)；MRI脑白质异常也同样以1型为主，占71．6％(53／74)，均无脑室扩大。电生理学检查显示，SEP异常率为83．7％(36／43)，其中轻度60．5％，中度23．2％；BAEP异常率为62．8％(27／43)，潜伏期和峰间期延长；VEP异常率为53．5％(23／43)，各波潜伏期延长，均无波形消失。(2)BD组患危险因素以高血压为主(95．1％)，临床表现以神经局灶体征、明显认知功能障碍和卒中样发作为主。CT分型以3型多见，为73．2％(30／41)；MRI检查显示3型为54．3％(19／35)，4型45．7％(16／35)，41例患均有双侧脑室对称性扩大。电生理学检查显示，SEP异常率为96．7％(29／30)，其中轻度6．7％，中度46．7％，重度43．3％；BAEP异常率86．7％(26／30)，潜伏期和峰间期进一步延长，部分伴有Ⅲ、Ⅴ波缺失；VEP异常率为83．3％(25／30)，各波潜伏期进一步延长，部分P2单侧波形消失。结论单纯脑白质疏松症无特征性临床表现，诊断主要以影像学1型脑白质异常为依据；诱发电位表现为各波潜伏期延长，无波形完全缺失。皮质下动脉硬化性脑病的危险因素为高血压，临床有较明显的认知功能障碍，常见卒中样发作等特征，影像学检查CT显示3型脑白质异常，MRI显示3型或4型为诊断依据；诱发电位呈现各波潜伏期进一步延长并伴有部分波形完全缺失。     

Variability in hand surface representations in areas 3b and 1 in adult owl and squirrel monkeys

Detailed microelectrode maps of the hand representation were derived in cortical areas 3b and 1 from a series of normal adult owl and squirrel monkeys. While overlap relationships were maintained, and all maps were internally topographic, many map features varied significantly when examined in detail. Variable features of the hand representations among different monkeys included a) the overall shapes and sizes of hand surface representations; b) the actual and proportional areas of representations of different skin surfaces and the cortical magnifications of representations of specific skin surfaces, which commonly varied severalfold in area 3b and manyfold in area 1; c) the topographic relationships among skin surface representations, with skin surfaces that were represented adjacently in some monkeys represented in locations many hundreds of microns apart in others; d) the internal orderliness of representations; e) the completeness of representations of the dorsal hand surfaces; and f) the skin surfaces represented along the borders of the hand representation. Owl monkey maps were, in general, internally more strictly topographic than squirrel monkey maps. In both species, area 3b was more strictly topographic and less variable than was area 1. The degree of individual variability revealed in these experiments is difficult to reconcile with the hypothesis that details of cortical maps are ontogenetically specified during a period in early life. Instead, we propose that differences in the details of cortical map structure are the consequence of individual differences in lifelong use of the hands. This conclusion is consistent with earlier studies of the consequences of peripheral nerve transection and digital amputation, which revealed that cortical maps are dynamically maintained and are alterable as a function of use or nerve injury in these monkeys (Merzenich et al., '83a,b, '84a; Merzenich, '86; Jenkins et al., '84; Jenkins and Merzenich, '87).