听觉诱发电位及体感诱发电位在颅脑外伤致昏迷患者的应用

严重颅脑损伤昏迷患者脑功能的监测是判断预后和指导治疗的重要手段。听觉诱发电位(BAEP)及体感诱发电位(SSEP)因其方便、无创并能连续实时监测昏迷患者相关神经传导通路电生理的变化,间接反映脑干上行激活系统、大脑皮层结构与功能的完整性,越来越成为临床对严重颅脑损伤昏迷患者预测预后和指导治疗的重要手段。本文就近年来相关研究进行综述,旨在指导临床实践。     

Monitoring of somatosensory evoked potentials during carotid endarterectomy

Summary Somatosensory evoked potentials (SEPs) were monitored in the course of 368 carotid endarterectomies (CEAs) carried out in 312 patients. In an initial group of 26 patients the shunt was used routinely while in a second group, involving 342 CEAs, it was applied selectively on the basis of modifications which the SEP underwent during clamping. The criterion for shunting was the progressive reduction, up to 50%, of the N20-P25 amplitude. New postoperative neurological deficits appeared in 6 patients, all of whom displayed a transitory SEP flattening. The SEPs of 2 of these returned to normal by the time they awoke and both showed a clinical deficit homolateral to the operated side. In only 2 cases did the deficit fail to regress completely and their postoperative CT scans revealed ischaemic lesions. A positive relationship emerged between SEP changes and back pressure values; nonetheless, as many as 75% of the patients with low residual back pressure values (< 25 mm Hg) tolerated the clamping. SEP monitoring appears to provide a reliable basis for selectively applying a shunt when there is a high risk of haemodynamic ischaemia during clamping.     

The effects of focal epileptic activity on the somatosensory evoked potentials in the rat

Summary The cortical somatosensory evoked potential (SEP) of the rat, evoked by contralateral forepaw stimulation, consisted of early (P 1 and N 1) and late components (P 2 and N 2). Microelectrode recording yielded evoked unitary responses of short latencies in the range of the early components and responses of longer latencies in the range of P 2. During the development of focal epilepsy after topical application of penicillin, the late components of SEP were enhanced and the enhanced late negativity corresponded to a surface negative cortical spike. The prominent enlargement of later components was associated with prolonged, often recurrent discharges of longer latency unitary responses and with enlarged local field potentials. Early components of SEP remained relatively unaffected and so did unitary responses with short latencies.Epileptic spike-conditioned SEPs in the cuneate nucleus, thalamic sensory relay nucleus and sensory cortex were depressed from 100 ms (cuneate nucleus) to about 300 ms (thalamus and cortex) subsequent to spike discharge. Transmission in the cuneate nucleus was least affected. Thalamic and cortical early components of SEP had similar time courses of recovery, which differed markedly from that of cortical late components. Our findings suggest that two different neuronal activities generate different components of SEP and are differentially involved in the epileptic activities, which results in the different amplitude recovery following spontaneous epileptic spike discharges.This work was supported by the Deutsche Forschungsgemeinschaft (German Research Council)     

Diazepam improves recording of lumbar and neck somatosensory evoked potentials

To determine whether the decrease in muscle artifact provided by diazepam is of sufficient clinical value to justify its use, somatosensory evoked potentials recorded in examinations of 73 consecutive patients were compared with those recorded from 33 subsequent patients who were given 10 mg of diazepam orally just before the examination. With diazepam pretreatment there was clear improvement in the quality of lumbar and neck recordings--increased reproducibility and definition and ease of measurement--and also greater tolerance of the procedure and a slight shortening of time required for the test.     

Somatosensory evoked potentials in patients with thalamic lesions

Summary Somatosensory evoked potentials (SEPs) were recorded in 20 patients with thalamic lesions confirmed by CT (10 with infarction, 10 with haemorrhage). The changes in SEP configuration are discussed in their relationship to clinical symptoms. Four types of SEP abnormality produced by thalamic lesion are distinguished: (1) FF type, (2) N20/P23 dissociation type, (3) N18/N20 false shift type, and (4) reduced early component type. It was shown that clinically similar lesions might produce different SEP patterns.     

Short-latency somatosensory evoked potentials in brain death

Summary Simultaneous recording of somatosensory evoked potentials to median nerve stimulation above the upper and lower neck in brain-dead patients revealed that all cervical responses were preserved in 10%, whereas a marked reduction in amplitude or even loss of N 13b at the level of the C2 spinous process was observed in 90%. Of the patients, 55% revealed an additional loss of N 13a, recorded at the level of the C7 spinous process; in 15% all cortical and spinal evoked potentials were missing, but Erb's point waves were still normal. These results suggest two different origins of the main negative waves (N 13a and N 13b), recorded above the upper and lower cervical spinal cord. N 13a (C7) is supposed to arise in the dorsal horn at the C6/7 level, N 13b (C2) in the cervicomedullary junction.     

运动诱发电位联合体感诱发电位监测在脊髓髓内肿瘤手术中的应用

目的 探讨全静脉麻醉下运动诱发电位(MEP)联合体感诱发电位(SEP)术中监测应用于脊髓髓内肿瘤手术的优越性、可靠性及临床应用价值.方法 对72例脊髓髓内肿瘤患者术中行SEP和MEP联合监测,参照McCormick评分标准对术前、术后脊髓功能的改变和诱发电位变化之间的关系进行统计分析.结果 14例脊髓神经功能改善,18例术后脊髓神经功能下降者与诱发电位监测结果具有一致性(P＜0.05).结论 对脊髓髓内肿瘤手术进行SEP与MEP监测有利于避免"假阴性/假阳性"结果及术后神经功能障碍的发生.     

The effects of halothane on somatosensory and flash visual evoked potentials during operations

Abstract

Intraoperative use of somatosensory evoked potentials (SEP’s) to monitor intracranial aneurysm surgery and flash visual evoked potentials (F-VEP’s) for parasellar surgery have been routinely employed in our clinic. We found that both EP modalities are sensitive to the changing concentration of our standard hypotensive agent, halothane. The prolongation of the N14-N20 interpeak latency to median nerve stimulation at the wrist, and prolongation of P100 latency with altered configuration of early VEP components to flash light stimulation, appear to be the results of direct pharmacological effects of the agent and not an effect of secondary hypotension. VEP is found easily abolished by halothane at a concentration of 2.0%, while the SEP is more resistant. Halothane is not ideal however when monitoring intraoperative VEP.     

Steady-state vibration somatosensory evoked potentials: physiological characteristics and tuning function.

OBJECTIVE: The steady-state somatosensory evoked potentials (S-SEPs) to vibratory stimulation were recorded to characterize their physiological properties. METHODS: Vibratory stimuli were applied to the right palmar surface in 10 normal subjects. A total of 200 responses were recorded from electrodes at 2 cm posterior to C3, Cz and C4 and 2 cm anterior to C3. All responses were Fourier analyzed and the amplitudes of the first (1F) and second (2F) harmonic components were thus obtained. The effects of modulation frequency (5-30 Hz) and stimulus intensity (0.001-0.1 Newton (N)) on S-SEPs were studied. RESULTS: The amplitudes of 1F and 2F were greatest at the electrode 2 cm posterior to C3, 1F being predominant. The mean 1F amplitudes as a function of modulation frequency showed a bimodal distribution with a trough at 14 Hz and a peak at 21 Hz. The mean 1F amplitudes showed a linear increase of up to 0.05 N and thereafter reached a plateau against the logarithmic stimulus intensity axis. CONCLUSION: Vibratory S-SEPs may originate from the primary somatosensory cortex and provide information on the fast-adapting mechanoreceptive afferents. The temporal resonance at 21 Hz places the somatosensory system between the visual and auditory systems.     

肌萎缩性侧索硬化症患者体感诱发电位研究

目的 研究肌萎缩性侧索硬化症(ALS)患者体感诱发电位(SEP)变化。方法 采用正中神经及肠后神经体感诱发电位(mSEP、tSEP)对30例患者进行检测，并与27例健康人作对比。结果 mSEP和tSEP的异常率分别为43．3％(13／30)及28％(7/5)，除N9、PF(腘点)、LP(T12点)峰潜伏期和对照组相比无显著差异外，其余各峰潜伏期及峰间期和对照组相比均有显著性差异。结论 ALS患者存在感觉通路损害，且中枢的改变较周围更明显，SEP检查对患者感觉损害的定位有一定价值。     

Serial changes in motor and somatosensory evoked potentials in putaminal haemorrhage

Little is known about evoked potential changes in putaminal haemorrhage. In this study, somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) have been serially evaluated and their role in the prognosis of putaminal haemorrhage is now reported. Nineteen patients with CT- or MRI-proven putaminal haemorrhage were examined after a mean duration of 13 days (range 2–30); there were 4 females and 9 males, ranging in age between 25 and 70 years. The haematomas were of medium size in 13 and large or small in 3 patients each. The changes in the clinical picture and the SEPs and MEPs were evaluated on admission, and after 30 and 90 days. Central motor conduction time (CMCT) could not be recorded in 13, but was prolonged in 2 and normal in 4 patients. Median SEPs revealed the absence of near field potentials in 11 and prolongation of N9–N20 conduction time in 1 patient. In the follow-up period MEP and SEP abnormalities only changed in 5 patients; MEPs changed in 4 and SEPs in 2. The period of normalisation of MEPs ranged between 1 and 6 months. CMCT correlated with motor and N9–N20 conduction time with sensory impairment. Eight patients had poor, 6 partial and 5 complete recovery. Power, sensation, CMCT, and size and location of haematoma made positive contributions to recovery.     

Differential influence of posture and intentional movement on human somatosensory evoked potentials evoked by different stimuli

Somatosensory evoked potentials (SEP) recorded from humans were elicited by a cutaneous shock to the index finger or with a ramp displacement of the finger that stretched the first dorsal interosseous muscle. A somatosensory stimulus was presented while a subject maintained a steady posture of the metacarpophalangeal joint or during a rapid voluntary abduction of the index finger. Both activities were performed against a constant opposing load of 0.15 Nm or without a load. SEPs were recorded over the postcentral arm area, together with the electromyogram of the first dorsal interosseous muscle. The major components of the SEPs were P56, N130, P174, N232 and P294. The amplitudes of all components were diminshed substantially during active movement. A constant load opposing postural fixation or active movement did not influence the SEP amplitude. The amplitude of the P56 component was differentially affected by the shock or ramp stimuli. The findings demonstrate that active movement gates sensory input, while sustained tonic muscular activity with an opposing constant load does not, and that different somesthetic inputs may be processed differently during movement.     

Topographic analysis of somatosensory evoked potentials in patients with well-localized thalamic infarctions

After stimulation of the median nerve, three major negative peaks (NI, NII and NIII) of somatosensory evoked potentials (SEP) have different latencies along the longitudinal array of scalp electrodes: NI and NII at frontal electrodes have the shortest latency (N17, N29). There is a progressive delay toward the central (N19, N32) and parietal areas (N20, N34). NIII (N60) latency differs from one electrode to another but without consistent anterior-posterior latency shift. A variety of SEP abnormalities was observed in 17 patients with non-hemorrhagic thalamic lesions reflecting a disturbance of the complex intra-thalamic and afferent and efferent thalamic pathways. When the lesions were classified into 5 groups according to the presumed vascular territories involved, there were general but not specific characteristics of SEP abnormalities in each group of patients. In four patients with lesions involving primary sensory nuclei and presenting with the thalamic syndrome or the loss of all modalities of sensation, all SEP components after P14 were absent when the affected arm was stimulated. NI peaks were intact in two patients with thalamic sensory lacunes but NII was delayed. NI was present but delayed in three patients with anterior thalamic lesions not involving primary sensory nuclei. In patients with medial thalamic lesions, delayed central NIII was a common finding. In patients with posterior capsule or lateral thalamus lesions either NII and NIII or NIII alone were affected. NI was also affected in some with sparing of the frontal component (N17). These complex relationships between the types of SEP abnormalities and thalamic lesions are compatible with the presence of multiple, at least partially independent, thalamic generators and thalamocortical projection systems mediating regionally specific SEP components.     

椎旁定位腰骶体感诱发电位对腰椎间盘突出症的诊断意义

目的探讨椎旁定位腰骶体感诱发电位（LSSEP）在腰椎间盘突出症中的变化及其诊断意义。方法对84例有L4、L5和S1神经根损害表现的腰椎间盘突出症的患者进行胫后神经体感诱发电位（SEP）、皮节体感诱发电位（DSEP）和椎旁定位LSSEP检查，测定其N40的潜伏期，并对多水平突出症患者的LSSEP与腰椎MRI比较。结果胫后神经SEP检测异常率为42．86％；L5、S1 DSEP检测的异常率为90．48％；椎旁定位LSSEP异常率为95．24％，比胫后神经SEP检测异常率明显增高（P〈0．005）。在L3。椎间盘突出中，以L4的LSSEP异常为主；在L4-5椎间盘突出中以L5的LSSEP为主。结论椎旁定位LSSEP检测可能是诊断腰椎间盘突出症快捷、可靠、敏感的检测方法，其结果与神经根受累水平相一致。     

Effects of psychotropic drugs on somatosensory evoked potentials in cerebral ischemia

Several authors have demonstrated a correlation between short latency somatosensory evoked potentials (short latency SEPs) and cerebral blood flow (CBF). It is also known that ischemia may modify the amplitude of the cortical SEP while its latency is less sensitive to CBF fluctuations. Phychotropic drugs — Oxiracetam, SAMe, Naloxone, L-acetylcarnitine and GM1 — affect some parameters of the early components of cortical SEPs, chiefly the amplitude, which makes SEP recording a useful method for monitoring pharmacological activity in acute stroke.

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Sommario Molti studi hanno dimostrato l'esistenza di una relazione fra potenziali evocati a breve latenza (Short-latency SEP) e flusso ematico cerebrale (CBF). è anche noto che condizioni d'ischemia possono modificare l'ampiezza del SEP corticale, mentre la latenza si dimostra meno sensibile a fluttuazioni del flusso ematico cerebrale. La somministrazione di farmaci nootropi — Oxiracetam, SAMe, Naloxone, M-Acetilcarnitina, GM1 —altera alcuni parametri delle componenti precoci del SEP corticale, principalmente l'ampiezza, facendo di tale metodica un utile mezzo per monitorare l'attività farmacologica, nella fase acuta dello stroke.

     

2型糖尿病体感诱发电位研究

目的 通过对2型糖尿病（DM）患者进行刺激正中神经（MN）和胫后神经（PTN）诱发的体感诱发电位（SEP）的检查,了解病人躯体深感觉通路功能状态,早期发现病人的神经病变。方法 用Nicolet Viking　TV型肌电图/诱发电位仪对30例2型DM患者进行SEP的检测并与正常人对照。应用SPSS统计软件采用t检验、卡方检验及多元逐步回归分析比较两组间SEP各项参数的差异,分析DM组SEP参数变化与血糖、血脂、肾功能之间的关系。结果①DM组MNSEP异常20例（66.7％）,PTNSEP异常22例（73.3％）,表现为波形缺失、波潜伏期延长及波幅下降。②DM组MNSEP的N9～N20潜伏期、波幅异常（P<0.05）;PTNSEP的N9～P38潜伏期、波幅异常（P<0.05）。③DM组SEP异常与病程、血糖、血脂、肾功能有关P<0.05）。结论①SEP是检测2型DM神经病变的敏感指标。②控制血糖、血脂、保护肾功能有利于阻止神经病变的发展。     

Changes in somatosensory evoked responses by repetition of the median nerve stimulation

OBJECTIVE: We investigate the synaptic factor for the recovery function of evoked responses using a repetitive stimulation technique. METHODS: Somatosensory evoked cortical magnetic field (SEF) was recorded following stimulation of the median nerve using single to 6-train stimulation in 8 healthy subjects. The SEF responses after each stimulus in the train stimulation were extracted by subtraction of the waveforms. RESULTS: An attenuation of the SEF components was recognized after the second of the stimuli, but there was no significant attenuation with the third or later stimulations. The root mean square (RMS) of the 1M (peak latency at 20 ms after stimulation) and 4M (70 ms) components were smaller than that of the single stimulation during the train stimulation, while the 2M (30 ms) and 3M (45 ms) components were not attenuated, but the 3M was facilitated at the fourth to sixth stimulation. CONCLUSION: The synaptic factor was not responsible for the attenuation of the SEF components during repetitive stimulation in healthy subjects. The SEF change disclosed a functional difference among the SEF components during the train stimulation, especially among the later components.     

Changes of somatosensory evoked potential accompanying ischaemia and hypoxia in cats

Changes of evoked potential accompanying haemorrhagic hypotension and hypoxia were investigated on cats to evaluate the usefulness of SEP as a monitor in an intensive care unit (ICU), and the following results were obtained. (1) Positive-negative diphasic potential was elicited at posterior sigmoid gyrus (PSG) by contralateral superficial radial nerve stimulation.

This potential was recorded at the restricted area of the posterior border of PSG and regarded as primary somatosensory evoked potential. (2) In the initial stage of haemorrhagic hypotension, both positive and negative components of SEP occasionally increased in amplitude. In profound hypotension in which CBF fell to less than the critical level of 30 ml 100 g^–1 min^–1, the latency was retarded and the amplitude was decreased. At CBF less than 10 ml 100 g^–1 min^–1, SEP disappeared. Within the range of CBF between 10 and 30 ml 100 g^–1 min^–1, a close correlation was noted between CBF and SEP amplitude. Transient increase of SEP amplitude was also observed during hypoxia induced by inhalation of nitrogen gas. (3) In normal state SEP was decreased in amplitude by conditioning stimulation of the nucleus lateralis posterior (LP nucleus) of the thalamus. This might be explained by the fact that intracortical inhibitory interneurons were activated by stimulation of LP nucleus, After haemorrhagic hypotension and hypoxia, however, the inhibitory effect on SEP elicited by LP nucleus stimulation attenuated or disappeared. Because of the initial impairment of the inhibitory interneurons by ischaemia and hypoxia, the amplitude of SEP might increase transiently.

In conclusion, the authors thought that SEP might be less useful than EEC in ICU, because of its insensible change to hypoxia and ischaemia.     

Low and high-frequency somatosensory evoked potentials recorded from the human pedunculopontine nucleus

ObjectiveTo investigate the generators of the somatosensory evoked potential (SEP) components recorded from the Pedunculopontine Tegmental nucleus (PPTg).MethodsTwenty-two patients, suffering from Parkinson’s disease (PD), underwent electrode implantation in the PPTg area for deep brain stimulation (DBS). SEPs were recorded from the DBS electrode contacts to median nerve stimulation.ResultsSEPs recorded from the PPTg electrode contacts could be classified in 3 types, according to their waveforms. (1) The biphasic potential showed a positive peak (P16) whose latency (16.05 ± 0.61 ms) shifted of 0.18 ± 0.07 ms from the lower to the upper contact of the electrode. (2) The triphasic potential showed an initial positive peak (P15) whose latency (15.4 ± 0.2 ms) did not change across the DBS electrode contacts. (3) In the last SEP configuration (mixed biphasic and triphasic waveform), the positive peak was bifid including both the P15 and P16 potentials.ConclusionWhile the P16 potential is probably generated by the somatosensory volley travelling along the medial lemniscus, the P15 response represents a far-field potential probably generated at the cuneate nucleus level.SignificanceOur results show the physiological meaning of the somatosensory responses recorded from the PPTg nucleus area.     

Association between somatosensory evoked potentials and EEG in comatose patients after cardiac arrest

ObjectiveTo analyze the association between SSEP results and EEG results in comatose patients after cardiac arrest, including the added value of repeated SSEP measurements.MethodsContinuous EEG was measured in 619 patients during the first 3–5 days after cardiac arrest. SSEPs were recorded daily in the first 55 patients, and on indication in later patients. EEGs were visually classified at 12, 24, 48, and 72 h after cardiac arrest, and at the time of SSEP. Outcome at 6 m was dichotomized as good (Cerebral Performance Category 1–2) or poor (CPC 3–5). SSEP and EEG results were related to outcome. Additionally, SSEP results were related to the EEG patterns at the time of SSEP.ResultsAbsent SSEP responses and suppressed or synchronous EEG on suppressed background ≥24 h after cardiac arrest were invariably associated with poor outcome. SSEP and EEG identified different patients with poor outcome (joint sensitivity 39% at specificity 100%). N20 responses were always preserved in continuous traces at >8 Hz. Absent SSEPs did not re-emerge during the first five days.ConclusionsSSEP and EEG results may diverge after cardiac arrest.SignificanceSSEP and EEG together identify more patients without chance of recovery than one of these alone.