Auditory evoked potential index: a quantitative measure of changes in auditory evoked potentials during general anaesthesia

We describe a novel index derived from the auditory evoked potential, the auditory evoked potential index, and we compare it with latencies and amplitudes related to clinical signs of consciousness and unconsciousness. Eleven patients, scheduled for total knee replacement under spinal anaesthesia, completed the study. The initial mean (SD) value of the auditory evoked potential index was 72.5 (11.2). During the first period of unconsciousness it decreased to 39.6 (6.9) and returned to 66.8 (12.5) when patients regained consciousness. Thereafter, similar values were obtained whenever patients lost and regained consciousness. Latencies and amplitudes changed in a similar fashion. From all parameters studied, Na latencies had the greatest overlap between successive awake and asleep states. The auditory evoked potential index and Nb latencies had no overlap. The consistent changes demonstrated suggest that the auditory evoked potential index could be used as a reliable indicator of potential awareness during propofol anaesthesia instead of latencies and amplitudes.     

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.     

Localized echo-volume imaging methods for functional MRI

To perform true three-dimensional activation experiments in the human brain, dedicated localized echo-volume imaging (L-EVI) methods were developed. Three-dimensional acquisition allows generation of activation maps with minimal vascular enhancement related to inflow effects. The rapid acquisition of the L-EVI (～100 msec) reduces signal instabilities caused by motion, facilitating the detection of the small intensity changes expected with brain activation. Single-shot L-EVI was performed on normal volunteers at 1.5 T, imaging a three-dimensional predefined volume (240 × 45 × 45 mm³) in the superior portion of the brain with a spatial resolution of 3.75 × 5 × 5 mm³. Increased brain coverage was achieved with a multi-volume imaging (three-shot) version, which simultaneously achieved effective suppression of signals from cerebrospinal fluid. In addition, both asymmetric spin-echo (ASE) and spin-echo (SE) versions of the technique were used to detect blood oxygenation level dependent (BOLD) signal changes in the motor cortex with a finger-tapping paradigm. Images obtained by the L-EVI sequence were qualitatively comparable to standard multislice two-dimensional echo-planar images. Both ASE and SE functional MRI (fMRI) experiments showed consistent activation in the contralateral primary sensorimotor cortex. Furthermore, significant differences in location and magnitude of activation was observed between the two methods, confirming theoretical predictions.     

60例老年椎—基底动脉供血不足的脑干听觉诱发电位分析

对60例临床诊断为椎—基底动脉供血不足的老年人进行脑干听觉诱发电位(BAEP)检查,51例异常者(异常率为85％)均在发作期检查,9例颈性眩晕病人于缓解期检查(BAEP)正常。BAEP异常提示老年人可能由于长期椎—基底动脉供血不足造成脑干内有影响听觉通路的微小梗塞灶。证明BAEP检查叫老年性椎—基底动脉供血不足的诊断很有价值。     

Wistar大鼠运动皮层代表区的微刺激测定

在１５例氯胺酮麻醉的Ｗｉｓｔａｒ大鼠利用皮层内微刺激技术测定了躯体的运动皮层代表区。电刺激为３５０Ｈｚ的阴极串脉冲，电流最大值限为８０μＡ。结果表明大多数皮层点诱发对侧肌肉反应。虽然代表区的大小有很大个体差异，分区的相对位置是恒定的。但在分区内部未见分域排列。部分大鼠存在前部前肢区，但无一例发现前部后肢区。比较文献结果提示Ｗｉｓｔａｒ大鼠的运动皮层的分化程度比Ｌｏｎｇ－Ｅｖａｎｓ黑顶鼠低。     

Effects of systemic clonidine on auditory event-related potentials in squirrel monkeys

Event-related potential (ERP), electroencephalographic (BEG), and behavioral data were collected from squirrel monkeys (Saimiri sciureus) in a 90−10 auditory oddball paradigm. Background or target tones were presented once every 2 s, and responses to the targets were rewarded. ERPs were recorded from epidural electrodes following systemic administration of clonidine (0.1 mg/kg) or a saline placebo. EEG power spectra and behavioral performance were assessed simultaneously as indices of behavioral state. Clonidine significantly decreased the area and increased the latency of a P300-like potential. The amplitudes and areas of the earlier P1, N1, and P2 components and a later slow wave-like potential were not reduced, nor were their latencies altered. Clonidine produced increased EEG power in the alpha range (7.5–12 Hz) and decreased power in the upper beta range (20–40 Hz) but did not affect performance in the oddball task. Because two major effects of clonidine are to substantially reduce activity in the noradrenergic nucleus locus coeruleus (LC) and to reduce norepinephrine (NE) release from axons, the present results support the hypothesis that the LC and its efferent projection system are important in modulating the activity of P300-like potentials.     

Effect of thoracic epidural etidocaine 1.5% on somatosensory evoked potentials, cortisol and glucose during cholecystectomy

The effect of thoracic (T7-8) epidural etidocaine 1.5%, 9 ml, and continuous per- and postoperative epidural infusion of etidocaine 1.5%, 4 ml/h, on early (less than 500 ms) somatosensory evoked potentials (SEPs), and cortisol and glucose in plasma during cholecystectomy, was examined in ten patients. Spread of analgesia (pin-prick) was T3 (T1-T3) to L2 (T11-L3) 35 min after injection of etidocaine, and T3 (T2-T4) to T12 (T8-L4) 3 h after surgical incision (median (range)). Before operation, epidural etidocaine had no significant effects on peak-to-peak amplitude of SEPs to electrical stimulation at the L1, T10 or T6 dermatomal level (P greater than 0.09). SEPs were abolished in only two patients at T6, and no patient had SEPs abolished at T10 or L1. The plasma concentrations of cortisol and glucose were significantly increased 20 min after surgical incision and remained increased throughout the study. No correlation was found between the block-induced decrease in the peak-to-peak amplitude at T6 or T10 and increase in plasma cortisol, except for a negative correlation at T10 and the initial increase in cortisol (Rs = 0.72, P = 0.03). In conclusion, thoracic epidural administration of 9 ml of etidocaine 1.5% does not provide total afferent somatic blockade assessed by SEP and the stress response to cholecystectomy.     

不同检测方法预测白内障术后视力的观察

目的 评价各种检测方法在预测白内障术后视功能恢复的作用。方法 白内障197例(214眼)术前行闪光视网膜电图(F-ERG)、闪光视诱发电位(BVEP)、视网膜计、光定位、色觉及注视性质等综合检测，术后3月复查最佳矫正视力。结果 术前F—ERG的b波、F—VEP的P1波、潜视力、色觉均与术后视力存在显著相关性，其中F-ERG、F—VEP、潜视力预测术后视力的可靠性分别为62．6％、79．0％、60．6％。但排除白内障完全成熟及高龄者(超过80岁)，潜视力预测的可靠性则达82．6％。结论 对于非完全成熟及非高龄者，视网膜计是术前预测白内障术后视力比较理想的方法，而对于完全浑浊及高龄者，视网膜计检查结果的准确性欠佳，应结合F-ERG、F-VEP、色觉及注视性质等多方面因素进行综合讲价。     

事件相关电位和脑电图在痴呆早期诊断中的意义

目的 研究血管性痴呆（vascular dementia，VD）患者ERP和EEG的变化特征，并与神经心理学及痴呆程度进行相关性分析。方法 测定68例VD患者及37例健康志愿者的事件相关电位（ERP：N100，P300）、脑电图（EEG），同时采用MMSE进行认知功能评定，并进行相关性分析。结果 68例VD组患者的P300潜伏期明显延长，波幅明显降低，与正常对照组比较有明显差异性（P〈0.01，P〈0.05），N100潜伏期。波幅变化不是很大（P〉0.05），脑电图异常率，VD组94%，正常对照组18%，2组比较有明显差异性（P〈0.01）。VD组患者ERP异常程度与EEG异常程度经相关性分析无相关性。VD组MMSE与正常对照组比较有明显差异（P〈0.05），VD组MMSE评分与P300PL呈负相关（r=-0.57，P〈0.05），与P300AMP呈正相关（r=0.37，P〉0.05）。结论 ERP与认知功能存在明显相关性，提示了ERP是反映其认知功能障碍程度的客观指标之一，可作为检测高危人群普查的手段之一，ERP在判断认知功能方面敏感于其他检查手段，客观性强。