脑干听觉反应在轻度认知功能障碍老年人和阿尔茨海默病中的应用

目的探讨轻度认知功能障碍老年人(MCI)和阿尔茨海默病(AD)在脑干听觉反应(ABR)检测中的特点,为早期痴呆的诊断提供帮助.方法应用美国Nicolet Bravo脑电生理仪及Click短声刺激,测查36例MCI和30例阿尔茨海默病(AD)和45名健康老人(NC)的ABR.结果 MCI组、AD组及NC组在绝对潜伏期波Ⅲ(Pz脑区),绝对波幅波Ⅲ(Pz脑区),波V(Pz脑区)上有差异极显著性(P＜0.01).与NC组和MCI组相比,绝对潜伏期波Ⅲ(Pz脑区)上,AD组延迟于NC组和MCI组(P＜0.01).波幅分析所见,绝对波幅波Ⅲ(Pz脑区)和绝对波幅波V(Pz脑区)AD组低于NC组和MCI组.MCI组与NC组比较,差异有显著性(P＜0.05).结论 ABR对临床辅助诊断AD和MCI有参考价值.     

Alzheimer病事件相关电位P300亚成份变化

目的分析Alzheimer病(AD)患者与正常老人(NC组)的事件相关电位P300亚成份构成的特性.方法应用丹麦仪器和听觉oddball范式,记录了39例AD组和40例NC组在Fz、Cz、Pz三点上P300,进一步分析P3亚成份.结果P3是一个复合波,NC组波形分化好,P3a、P3b双峰明显,稳定.在Fz、Cz、Pz点双峰波出现率分别为55%、42.5%和52.5%.在Cz和Pz点,AD组P3双峰波出现率低于NC组,有显著性差异(P＜0.05).本测试结果,在Fz点P3a潜伏期,Pa、P3b波幅,Cz点P3a、P3b波幅以及Pz点P3b潜伏期、P3b波幅上,AD组表现为同一趋势,即潜伏期延迟和波幅低于NC组,有显著性差异(P＜0.05或P＜0.01).结论提示P3a和P3b可能是一个可信赖的指标,oddball范式属于一种比较简单的认知作业,宜于老年患者和精神病患者完成,较适合精神科临床应用.     

阿尔茨海默病的听觉脑干反应异常变化

目的　探讨阿尔茨海默病(Alzheimer′sdisease,AD)患者与正常老人在听觉脑干反应 (ABR)检测中的不同特点。方法　应用美国NicoletSpirit电生理仪和click短声刺激,对39例正常老人 和32例AD患者的ABR作了检查。结果　31.3%AD患者ABR波形带有切迹。AD患者ABR诸指标 在Fz、Cz和Pz三个脑区记录点上无差异(P>0.05)。在中央区,AD患者ABR绝对潜伏期波Ⅵ右侧长 于左侧,绝对波幅波Ⅴ左侧低于右侧(P<0.05)。与正常老人相比,AD患者ABR绝对波幅波Ⅲ和波Ⅵ 降低(P均<0.05)。结论　本组AD患者ABR异常在听神经区域,有待进一步随访。     

康复期男性海洛因依赖者诱发电位P300研究

目的:探讨康复期男性海洛因依赖者(MPHD)听觉诱发电位P300(AEP-P300)与视觉诱发电位P300(VEP-P300)的特点. 方法:以Neuroscan脑诱发电位仪检测38例康复期MPHD(MPHD组)和14名健康对照者(对照组)前额区(Fz)、中央区(Cz)及顶区(Pz)AEP-P300与VEP-P300. 结果:MPHD Cz点AEP-P300波幅平均秩次为23.1μV,显著低于对照组的35.8μV(P<0.05).与对照组比较,在以动物图片为靶刺激(AT)时,MPHD组Fz点波幅显著升高,Cz、Pz点潜伏期显著缩短(u=2.37、2.56、3.10,P<0.05或P<0.01);在以药物图片为靶刺激(DT)时,两组VEP-P300各指标均差异无显著性(P>0.05).与以AT为靶刺激比较,在以DT为靶刺激时,MPHD组上述各点的Fz、cz、Pz点的VEP-P300潜伏期均显著缩短,Pz点波幅显著升高(t=3.39,P<0.01). 结论:康复期MPHD者仍然存在明显的神经电生理功能的紊乱,对药物相关刺激呈现一定的偏好.     

良性阵发性位置性眩晕患者脑干听觉诱发电位分析

目的探讨脑干听觉诱发电位(BAEP)对良性发作性位置性眩晕的诊断价值。方法对51例良性发作性位置性眩晕者进行BAEP检查,并以47名正常健康受试者作对照。结果 (1)良性阵发性位置性眩晕组BAEP异常率为49.02%;(2)与对照组相比,病例组右侧Ⅰ-Ⅴ峰间潜伏期延长,有统计学差异(P<0.05);(3)病例组左右两侧相比,右侧Ⅰ、Ⅲ、Ⅴ波潜伏期延长,有统计学差异(P<0.05)。结论 BAEP对于良性发作性位置性眩晕的诊断有一定价值。     

脑梗死患者的认知性电位P300亚成分实验研究

目的 分析脑梗死(CI)患者与正常老年人(NC)的认知性电位P300亚成份构成的特性.方法 应用美国仪器和听觉oddball范式,记录了31例CI和40例NC在Fz、Cz、Pz三点上P300,进一步分析P3亚成分.结果 NC组在Fz、Cz、Pz点双峰波出现率分别为55%、42.5%和52.5%.CI组在Pz点,P3双峰波出现率低于NC组.CI组潜伏期延迟和波幅低于NC组,有显著性差异.结论 P3a和P3b是一个可靠的指标值得进一步研究.     

阿尔茨海默病患者脑电图和多项脑诱发电位的变化研究

目的探讨阿尔茨海默病患者自发和诱发脑电特征。方法应用脑电图和多项脑诱发电位检测方法对26例阿尔茨海默病患者及15名正常对照者进行脑电图(EEG)、脑干听觉诱发电位(BAEP)、视觉诱发电位(VEP)和P300等检测。结果(1)轻度阿尔茨海默病患者的EEG异常率及异常者的EEG表现与对照组基本一致;但随着阿尔茨海默病程度的加重,EEG异常率及异常者的EEG表现与对照组间相比,差异具有显著性意义(P<0.01);(2)与对照组相比,中、重度阿尔茨海默病患者的BAEPⅢ波和Ⅴ波绝对波潜伏期延长及绝对波幅降低,VEP的P200波潜伏期明显延长,差异具有显著性意义(P<0.05或P<0.01);(3)与对照组相比,阿尔茨海默病患者的P300潜伏期明显延长(P<0.05或P<0.01),且轻、中、重度患者间差异亦有显著性意义(P<0.05)。结论脑电图和多项脑诱发电位相结合的检测方法能较为客观地反映阿尔茨海默病患者的脑功能状态,有可能作为阿尔茨海默病辅助的脑电生理诊断方法,也是近年来提出病因假说的间接佐证。     

焦虑症和抑郁症患者认知电位P300对照研究

目的探讨焦虑症(AD)和抑郁症(CD)在事件相关电位(ERP)P300检测中的不同表现。方法收集符合CCMD-3诊断标准的37例焦虑症患者和32例抑郁症患者以及36例健康成人对照组(NC),使用美国仪器以及“听觉靶-非靶刺激序列”为诱发事件,完成P300检测。结果(1)AD组、CD组和NC组在靶潜伏期Pz脑区P3以及在靶波幅Pz脑区P2、P3和非靶波幅Pz脑区P2上均有显著差异(P<0.01)。(2)AD组主要成分P3表现为延迟,与NC组和CD组有极显著性差异(P<0.01)。(3)AD组和CD组靶波幅P3和非靶波幅P2均见降低,与NC组比较也有显著性差异(P<0.05)。结论P300有可能作为AD组和CD组辅助诊断的一个脑电生理学标志。     

载脂蛋白E基因对轻度认知障碍患者听觉诱发电位的影响

目的探讨载脂蛋白(ApoE)基因型对轻度认知障碍(MCI)患者听觉诱发电位(AEP)的影响。方法健康老年对照60名,MCI患者60例,其中MCI低危组(未携带ApoE ε4基因的MCI患者)和高危组(携带ApoEε4基因的MCI患者)各30例。对所有观察对象均进行AEP和ApoE基因检测,并对脑干AEP Ⅰ波、Ⅲ波、Ⅴ波潜伏期和波峰间潜伏期,N200、P300潜伏期和波幅进行比较。结果 (1)MCI低危组、高危组与健康对照组Ⅰ、Ⅲ、Ⅴ波潜伏期及波峰间潜伏期均无统计学差异(P0.05)。(2)与健康对照组[N200、P300波幅分别为(5.97±0.76)、(10.69±1.57)μV、潜伏期分别为(240.20±16.45)、(300.06士20.50)ms]比较,MCI高危组患者N200、P300波幅[分别为(5.36±0.62)、(9.95±1.20)μV]降低、潜伏期[分别为(246.97±11.6)、(313.34士26.19)ms]延长(P0.05)。与MCI低危组N200波幅[(5.81士0.62)μV]相比,高危组N200波幅降低(P0.05)。高危组、低危组及健康对照组三组间N200、P300波幅比较均有统计学差异(分别P0.01、P0.05)。结论携带ApoEε4基因的MCI患者N200、P300波幅减小,潜伏期延长。AEP有可能作为个人认知功能变化的测量指标。     

59例听神经瘤患者脑干听觉诱发电位分析

目的 分析听神经瘤(acoustic neuroma,AN)患者的脑干听觉诱发电位的变化特征及健侧耳峰间期改变.方法 对59例听神经瘤(AN)患者进行脑干听觉诱发电位(BAEP)检测,测定Ⅰ、Ⅲ、Ⅴ波潜伏期(PL)、峰间期(IPL),双耳PL、IPL之间差值(ILD)等数值.结合MRI、CT影象学资料进行分析,并与36例健康者对照.结果 AN组与正常对照组BAEP各波PL、IPL测值比较差异有极显著性(P＜0.01).AN患侧BAEP异常率98.3%(58/59);主要表现:①Ⅰ、Ⅲ、Ⅴ波缺失;②Ⅲ、Ⅴ波PL延长;③Ⅰ～Ⅲ、Ⅲ～Ⅴ、Ⅰ～Ⅴ波IPL延长.AN患者健侧BAEP的异常率69.5%(41/59),主要表现:①Ⅴ波PL延长;②Ⅲ～Ⅴ及Ⅰ～Ⅴ波IPL延长;③Ⅲ～Ⅴ/Ⅰ～Ⅲ波IPL比值＞1.肿瘤直径＞2cm,BAEP的异常率有显著提高.不同大小肿瘤组间健侧BAEP测值比较:健侧Ⅴ波PL差异有显著性(P＜0.05),Ⅲ～Ⅴ及Ⅰ～ⅤIPL差异有极显著性(P＜0.01).结论 BAEP对AN诊断具有重要意义,它为病变提供了定位诊断依据,尤其健侧Ⅲ～Ⅴ/Ⅰ～Ⅲ波IPL比值异常,是脑干受压的敏感指标.     

Far-field potentials in circular volumes: evidence to support the leading/trailing dipole model.

The leading/trailing dipole model explains the production of far-field potentials as an asymmetry in the leading and trailing dipole moments of a propagating action potential detected by a referential montage. This investigation documents the production of far-field potentials produced by a pure dipole generator in a circular volume conductor. Multiple equipotential waveforms are recorded in an adjoining circular volume conductor attached to the one in which the dipole generator is located. This finding substantiates the "wick electrode" effect that explains the equipotential and instantaneous distribution of far-field potentials over relatively large distances in volume conductors. The present findings support a number of the leading/trailing dipole model proposals which explain far-field potential generation.     

Far-field potentials

Far-field potentials are produced by neural generators located at a distance from the recording electrodes. These potentials were initially characterized incorrectly as being of positive polarity, widespread distribution, and constant latency; however, recent advances have clearly demonstrated that far-field potentials may be either positive or negative depending upon the location of the electrodes with respect to the orientation of the dipole generator. Additionally, peak latencies in the far-field can vary with alterations in body position and the spatial distribution of far-field potentials, while widespread, is not uniform. Recent studies of far-field potentials suggest how such waveforms are produced when the symmetry of an action potential, as recorded by distant electrodes, is broken by such factors as differing conductivities of volume conductor compartments, direction of action potential propagation, size differentials in adjoining body segments, or the termination of action potential propagation in excitable tissue. Human, animal, and computer experiments support the preceding generalizations. These new explanations are directly applicable to such far-field potentials as the short latency somatosensory-evoked potential. Furthermore, since far-field potentials can also occur in muscle tissue, one should expect that these generalizations will hold with respect to electromyographic potentials. © 1993 John Wiley & Sons, Inc.     

Far-field potentials in circular volumes: the effect of different volume sizes and intercompartmental openings.

Preliminary investigations of circular volume conductors suggested that far-field potential magnitude declines progressively slower with increasing radial distance from a current source and follows a cosine function with angular displacement of the recording electrode from the electrical generator's axis. Using circular volumes of 6 differing radii, the mathematical relationship between angle, radii, and far-field potential amplitude is determined. Previous theoretical relationships of amplitude versus dipolar spacing, current, and distance from a dipole generator in a bounded volume conducting medium are verified for the near-field. Far-field potentials in circular volumes are found to become constant at radii greater than 75% of the bounded volume's radius. Additionally, an adjoining volume conductor acts simply as a passive fluid-filled electrode (wick electrode) to the circular volume containing the generator until the intercompartmental opening to the circular volume exceeds 20% of its circumference. This finding was clinically supported by recording similar P9 somatosensory-evoked far-field potentials generated caudal to the foramen magnum from various portions of the cranium, whose connections to the torso, foramen magnum, and neck, average 6.2% and 17.8%, respectively. Finally, 3 circular volume conductors were connected in series by channels less than 20% of the volume conductor's circumference. Both adjoining circular volumes were equipotential to the far-field potential present at the boundary of the first circular volume containing the dipole generator. This observation supports the clinical finding of far-field potential transmission through multiple human bodies in conductive contact.     

Evoked potentials in multiple system atrophy (MSA)

OBJECTIVES: To study the involvement of pyramidal tracts and sensory pathways in multiple system atrophy (MSA). MATERIALS AND METHODS: Evoked potential studies were performed in 45 MSA patients suffering from either MSA of cerebellar type (MSA-C) or MSA of parkinsonian type (MSA-P). RESULTS: Motor evoked potentials were normal in all MSA patients, whereas visual and somatosensory evoked potential abnormalities were found in about 40% of the MSA patients with no significant difference between the cerebellar (MSA-C) and parkinsonian (MSA-P) subgroup. Abnormal latencies of wave III in brainstem auditory evoked potentials were significantly more frequent in MSA-C. CONCLUSIONS: Abnormalities of somatosensory, visual and auditory evoked potentials are frequent findings in MSA, whereas abnormal motor evoked potentials are not a characteristic feature of the disease.     

Influence of magnetic resonance imaging on somatosensory and brain-stem auditory evoked potentials in man

Summary There is still a need to prove that even static magnetic fields up to 1.5 T used in magnetic resonance imaging (MRI) are biologically safe and harmless for humans. Recordings of median and ulnar nerves and brain-stem auditory evoked potentials in 20 patients were completed prior to and after MRI investigation of the central nervous system. Neither the somatosensory nor the auditory evoked potentials exhibited any significant change of latencies, interpeak latencies or amplitudes. Since these electrophysiological parameters are highly dependent on the quality of nerve conduction and integrity of information processing in various nuclei, it may be assumed that MRI causes no lasting changes in either respect.     

Recommendations for the clinical use of somatosensory-evoked potentials

The International Federation of Clinical Neurophysiology (IFCN) is in the process of updating its Recommendations for clinical practice published in 1999. These new recommendations dedicated to somatosensory-evoked potentials (SEPs) update the methodological aspects and general clinical applications of standard SEPs, and introduce new sections dedicated to the anatomical-functional organization of the somatosensory system and to special clinical applications, such as intraoperative monitoring, recordings in the intensive care unit, pain-related evoked potentials, and trigeminal and pudendal SEPs. Standard SEPs have gained an established role in the health system, and the special clinical applications we describe here are drawing increasing interest. However, to prove clinically useful each of them requires a dedicated knowledge, both technical and pathophysiological. In this article we give technical advice, report normative values, and discuss clinical applications.     

Visual and auditory evoked potentials in the early diagnosis and follow-up of neurosarcoidosis

Visual and brainstem auditory evoked potentials (VEPs, BAEPs) were recorded in 23 patients with neurosarcoidosis. Eight patients (35%) had abnormal BAEPs, and 10 (43%) had abnormal VEPs. Four of the 8 patients with abnormal BAEPs had facial paresis, one had impaired memory and only 3 had symptoms and signs compatible with brainstem lesion. Seven of the patients with abnormal VEPs had no visual symptoms. These findings suggest that BAEP and VEP can reveal subclinical nervous system involvement in sarcoidosis and can also help in the early diagnosis of neurosarcoidosis. Successive recordings of 5 patients showed that BAEP and VEP were useful in the follow-up of these patients.     

The speech evoked potential in normal subjects and patients with cerebral hemispheric lesions

The present study deals with observations on the “speech evoked potential”-a late positive potential evoked by word repetition. These potentials, evoked by “silent” repetition of polysyllabic words, were averaged and recorded from the scalp overlying the inferior frontal regions on both sides in 20 normal healthy subjects of ages ranging from 13–58 years. The potential had a triphasic negative, positive, negative morphology and was present over both hemispheres in left as well as right handed subjects. The main positive deflection and mean latencies of 219.2 msec and 221.6 msec and mean amplitude of 6.2 μv and 6.5 μv respectively on the left and right sides. Though there were interindividual variations in latency, amplitude and morphology, there was a high degree of intraindividual similarity and reproducibility in subjects. The variations in these parameters with age, sex and handedness are discussed. In 10 patients with cerebral lesions, the evoked potential was normal in 5 cases with right frontal lesions and showed abnormalities in 3 of 5 cases with left frontal lesions. The speech evoked potential may be useful in the further study of electrical correlates of speech output in speech disorders.     

Preparation to respond as manifested by movement-related brain potentials

Ten subjects were instructed to squeeze a dynamometer in a prescribed manner in order to assess the effects of motor preparation on event-preceding brain potentials. Right and left hand responses were required in 5 different experimental conditions allowing different degrees of advance preparation. Six channels of EEG (F3, F4, C3′, C4′, P3, P4) and two channels of EMG were digitized over a 3000 msec epoch, and response-locked averages were computed. Event-preceding negative potentials were evident well in advance of movement if the subject was informed of the timing of the response. These premovement potentials were asymmetrical on the scalp (contralaterally dominant at the central sites) if the subject knew which hand would be required to respond. Thus, we conclude that the appearance and asymmetry of these potentials reflect preparation to execute specific motor acts.