Reproducibility (test–retest) of vestibular evoked myogenic potential

IntroductionThere is still no consensus in the literature as to the best acoustic stimulus for capturing vestibular evoked myogenic potential (VEMP). Low-frequency tone bursts are generally more effective than high-frequency, but recent studies still use clicks. Reproducibility is an important analytical parameter to observe the reliability of responses.ObjectiveTo determine the reproducibility of p13 and n23 latency and amplitude of the VEMP for stimuli with different tone-burst frequencies, and to define the best test frequency.MethodsCross-sectional cohort study. VEMP was captured in 156 ears, on the sternocleidomastoid muscle, using 100 tone-burst stimuli at frequencies of 250, 500, 1000, and 2000 Hz, and sound intensity of 95 dB nHL. Responses were replicated, that is, recorded three times on each side.ResultsNo significant difference was observed for p13 and n23 latencies of the VEMP, captured at three moments with tone-burst stimuli at 250, 500, and 1000 Hz. Only the frequency of 2000 Hz showed a difference between captures of this potential (p < 0.001). p13 and n23 amplitude analysis was also similar in the test–retest for all frequencies analyzed.Conclusionp13 and n23 latencies and amplitudes of VEMP for tone-burst stimuli at frequencies of 250, 500, and 1000 Hz are reproducible.     

听觉诱发电位指数、脑电双频指数对异丙酚麻醉下患者术中体动反应的预测

目的评价听觉诱发电位指数(AAI)、脑电双频指数(BIS)预测异丙酚麻醉下患者术中体动反应的可能性。方法择期行妇科手术全麻患者28例,ASAⅠ或Ⅱ级,年龄24-62岁,体重46- 71 kg,术前2 h口服咪达唑仑10 mg,入室后以血浆靶浓度3．5μg/ml靶控输注异丙酚、静脉注射芬太尼2μg／kg及维库溴铵0．1 mg／kg麻醉诱导,气管插管后,调整异丙酚血浆靶浓度维持BIS 40-60。切皮后不再追加肌松剂,观察患者术中头面部及四肢的体动反应,记录体动反应发生前、后2min内BIS、AAI的最大值(BISmax、AAImax)及此时段内BIS>75、AAI>40的次数及出现时间。记录术中当BIS>75、AAI>40时前、后2 min内有无体动反应发生及发生时间。结果12例出现体动反应,体动前、后2 min内BISmax为63±16(4例BIS>75,33．3％),AAImax为48±11(12例AAI>40,100％)。麻醉维持过程中,出现14次BIS>75,并发体动反应4次(28．5％),BIS反应时间较体动时间滞后(84±19)s;出现AAI>40者28次,并发体动者12次(42．8％),AAI反应时间较体动时间滞后(13±3)s。结论异丙酚麻醉下BIS、AAI反应时间较体动发生时间滞后,不能预测术中体动反应的发生。     

听觉诱发电位指数指导全凭静脉麻醉期间病人输注异丙酚的效果

目的探讨听觉诱发电位指数(AAI)指导全凭静脉麻醉期间病人输注异丙酚的效果。方法择期全麻下行腹腔镜胆囊切除术病人60例,ASAⅠ或Ⅱ级,随机分为2组(n=30):试验组(Ⅰ组)和对照组(Ⅱ组)。静脉诱导气管插管后,持续输注0．2μg·kg-1·min-1瑞芬太尼以维持合适的麻醉深度。Ⅰ组通过监测AAI调节异丙酚输注速率,使AAI维持在30以下,Ⅱ组根据病人血压及心率调节异丙酚输注速率,每5分钟增减0．01 mg·kg-1·min-1异丙酚。记录气腹前(T1)、气腹后(T2)、分离胆囊(T3)、腹腔冲洗(T4)、手术结束(T5)时2组的血压、心率、AAI和输注异丙酚的速率,同时记录2组异丙酚、维库溴铵、瑞芬太尼用量、术毕睁眼时间、应答时间和拔管时间。结果2组各时间点AAI差异有统计学意义(P<0．05),与Ⅱ组相比,Ⅰ组输注异丙酚速率以及总用量减少(P<0．05)。术后24 h随访病人均无术中知晓。结论AAI指导全凭静脉麻醉输注异丙酚用于腹腔镜胆囊切除术病人,可较好的控制麻醉深度,指导合理用药,避免病人术中知晓。     

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。     

噪声中EP信号的提取算法及研究进展

诱发电位的提取是脑电信号处理领域的前沿课题近年来 ,通过少次甚至单次试验提取诱发电位已经成为研究的主流。本文对近年来提取诱发电位的信号处理方法进行了简要的回顾 ,并分别从小波变换、神经网络、高阶累积量、独立分量分析等四个方面对算法进行了介绍     

Short-term brain ‘plasticity’ in humans: transient finger representation changes in sensory cortex somatotopy following ischemic anesthesia

Transient rearrangements of finger representation in primary somatosensory cortex induced by an anesthetic block of the sensory information from adjacent fingers have been shown invasively in animals. Such a phenomenon has been now replicated in seven healthy human volunteers. Somatosensory Evoked Fields (SEFs) have been recorded during separate electrical stimulation of the 1st, 3rd, or 5th finger. Recordings were obtained in control conditions (stage A), following complete ischemic anesthesia of the 4 non-stimulated fingers (stage B), and after regaining sensation (stage C). SEFs were recorded using a 28-channel DC-SQUID magnetometer; a single position of the sensor was enough to identify the source of N20m, P30m and following components using the Equivalent Current Dipole (ECD) model. The amount of afferent input during stages A through C was monitored with surface electrodes placed on the nerve at wrist and elbow. No variation of the nerve compound potential was observed during stages A through C. In stage A, the localizing algorithm was able to discriminate the individual finger representation in accordance with the somatotopic organisation of the sensory homunculus. It was observed that the ECDs responsible for the cortical responses from the unanesthetized finger were significantly changing following a relatively brief period of sensory deprivation from the adjacent fingers. Such changes of the ECDs with respect to the control conditions were characterized by an increase in strength and deepening for the middle finger, and by a shift on the coronal plane for the thumb and the little finger (medial for the former, lateral for the latter). Such changes became progressively evident in stage B, but were persisting in stage C.     

Comparative effects of stimulation of the trigeminal ganglion and the superior sagittal sinus on cerebral blood flow and evoked potentials in the cat

The superior sagittal sinus (SSS) and the trigeminal ganglion (Vg) of anesthetized cats were stimulated electrically and field potentials in the upper cervical spinal cord and regional cerebral blood flow were recorded. Stimulation of the entire ganglion produced smaller field potential changes in two regions (medioventral area (MVA); dorsolateral area (DLA] of the upper spinal cord than did stimulation of the sagittal sinus (Vg/SSS response ratio = 17% for the MVA and 48% for the DLA). Stimulation of the trigeminal ganglion increased blood flow in only the frontal and parietal cortices (+93% and +33%), whereas stimulation of the sinus produced both larger changes in these areas (+137% and +139%) and also produced changes in regional cerebral blood flow in the thalamus (+122%).     

Scalp and Limbic P3 Event-Related Potentials in the Assessment of Patients with Temporal Lobe Epilepsy

Auditory oddball scalp and limbic P3s were recorded from 18 patients with unilateral temporal lobe epilepsy (TLE) prior to seizure surgery. Limbic P3s were unilaterally absent ipsilateral to the seizure focus and were present in the nonepileptogenic temporal lobe in all 18 cases studied. Scalp P3s, recorded from C3 and C4, on the other hand, were elicited bilaterally and there was no significant difference in amplitude or latency between the epileptogenic and nonepileptogenic sides. These data concur with studies of scalp P3 performed following surgery and suggest that the assessment of the contribution of limbic P3 to scalp P3 may be masked by volume conduction effects and other generators of P3. We conclude that the P3 recorded from central scalp sites, unlike its limbic counterpart, offers little clinical information in the presurgical assessment of patients with TLE.     

Evoked potentials in patients with non-neurological Wilson's disease

Summary In Wilson's disease neurological manifestations result from the damage in the basal ganglia, even if a widespread degeneration of the brain occurs. The few studies performed using evoked potentials with the aim of identifying subclinical dysfunction in the three major sensory pathways have never shown abnormalities in patients without neurological manifestations. To verify this observation we studied 12 patients suffering from Wilson's disease in a pre-neurological stage by using pattern visual evoked potentials (VEPs), somatosensory evoked potentials (SEPs) to median nerve stimulation and brainstem auditory evoked potentials (BAEPs). Four of these patients had not yet been treated with penicillamine or trientine (triethylenetetramine dihydrochloride), while the remaining 8 patients were on treatment for at least 1 year. In 3 patients of this second group and in 1 patient of the first group we observed a significant (3 SD over the mean) increase in P100 wave latency, while SEPs and BAEPs were found to be abnormal in only 1 patient, respectively.     

闪光视觉诱发电位监测甘露醇降颅压效果的临床研究

目的利用闪光视觉诱发电位监测颅内高压患者颅压水平,研究降颅压效果与甘露醇用量以及其他影响因素的关系。方法选择60例颅内高压患者,应用NIP-200型无创颅内压监测仪监测患者每日颅压,计算最高颅压与最低颅压间的差值(降颅压效果),采用多元逐步回归方法分析降颅压效果与性别,年龄,最高颅压时的心率、血压以及降至最低颅压时甘露醇总用量的关系。结果60例患者最低颅压平均值为(213·4±66·8)mmH2O(83·5~364·5mmH2O),患者的颅压水平从入院至最低值时甘露醇总用量的平均值为(1870·8±861·9)ml(375~4000ml)。降颅压效果与最高颅压时的血压(舒张压和收缩压)和心率无相关性(P>0·05),与性别、年龄显著相关(P<0·05),与甘露醇用量显著相关(P<0·01)。结论甘露醇有明显的降颅压作用,但是用到一定的剂量后,便不再有降颅压作用。女性患者比男性患者降颅压的效果好。患者年龄越小,降颅压效果越好。