Early prognostic assessment using evoked potentials in severe craniocerebral trauma

103 patients in acute posttraumatic coma were assessed during 72 hours following severe head injury by clinical examinations (documented with a modified Glasgow-Coma-Score and a brain-stem-score and brainstem auditory evoked potentials (BAEP) as well as short latency somatosensory evoked potentials (SEP). Patient outcomes were classified at 6 months or more, according to the following categories: good recovery, severely disabled or vegetative, and brain dead. Patients who had died by systemic complications were excluded from the study. The Glasgow-Coma-Score was reliable in forecasting a favorable outcome, but tended to produce false-pessimistic predictions. The brainstemscore and the BAEPs were reliable predictors of an unfavorable but not a favorable outcome. SEP data however, performed well as a prognostic indicant in predicting an unfavorable as well as a favorable outcome. Using the BAEP, the amplitude ratio Wave V/Wave I is more sensitive to detect a lesion than the interpeak-latency Wave I-Wave V, and--using the SEP--the amplitude ratio N20/N13b (over C2) is more sensitive than the central conduction time (N13a (over C7)--N20).     

Somatosensory evoked potentials in comatose patients: comparison with clinical findings, EEG and prognosis

21 comatose patients were examined by somatosensory evoked potentials (SSEP). The findings were correlated with the stage of brainstem herniation, the EEG and the outcome. We evaluated the early components of the SSEP (N10, N13, N14, P15, N20) in view of presence, latency and interpeak-latency of the potentials. In most cases the percentage of abnormal SSEP increased from caudal to rostral registration sites, but the potential P15 and N20 were equally abnormal. The progression of herniation correlated with increasing abnormality of the potentials. SSEP over the scalp (P15, N20) could not be registered in patients without any EEG-activity (isoelectric). Mean values of latencies and the interpeak-latencies were significantly prolonged in all cases with fatal outcome. Our findings suggest SSEP as a useful tool in the evaluation of brain-dysfunction in comatose patients.     

Primary extinct evoked cerebral potentials in the diagnosis of brain death]

In a collective of 82 patients with the clinical signs of brain death and examination of evoked cerebral potentials the incidence of primary abolished evoked potentials was studied. The initial examination occurred at the same time after onset of disease in both groups. We found a marked correlation with the clinical course of the patients. Whereas the group with primary loss of evoked potentials mainly contained patients with intracerebral and subarachnoid hemorrhages and short survival times, the other group with primary preserved evoked potentials showed a high rate of ischemic infarctions and longer survival periods. The rate of primary abolished evoked potentials can be lowered only by routine examination at the earliest time possible. Outside of neurological intensive care units the early examination of evoked potentials is hardly possible. In these units, the EEG remains the technical examination of choice in the confirmation of brain death.     

The prognosis of convulsions in the newborn--the place of EEG in comparison with echoencephalography

The routine-EEG in premature and term infants with cerebral seizures and its additional information are discussed in comparison to clinical and morphological findings. The clinical, electroencephalographic and echoencephalographic data to all 29 neonates that were treated during a four years period are presented. Three of those infants died, eight of them showed pathological results during developmental and neurological follow-up. EEG's were performed during or short by after seizures. A correlation could be shown between poor prognosis and suppression of background activity consisting in inactivity, burst-suppression pattern or moderate suppression. By contrast a normal or mildly suppressed EEG correlated with good longterm prognosis. Paroxysmal discharges in the EEG were helpful in diagnosing seizures and also for prognosis of cerebral convulsions later on. The echoencephalographic findings especially mild intracranial hemorrhages and increased periventricular echogenicity had less prognostic value. The echoencephalographic follow-up showed ventricular dilatation (e vacuo) in children who later on had developmental and neurological impairment. For assessment of prognosis in premature and term babies with cerebral seizures imaging procedures (echoencephalography and CT-scan) as well as electroencephalography are of mutual importance.     

Value of early acoustic and somatosensory evoked potentials in monitoring and prognostic assessment of coma in barbiturate therapy--comparison with clinical aspects and EEG

25 comatose patients suffering from severe cerebral lesions of different etiology were examined during barbiturate-therapy by Glasgow-Pittsburg-Coma-Scoring-System (GPCS), EEG, somatosensory and brainstem acoustic evoked potentials. The findings were correlated in view of prognostic prediction and importance for monitoring. A modified form of the Glasgow-Outcome-Score (GOS; independent-survival, dependent-survival, dead) was used for evaluating the outcome. In case of an initial GPCS less than 10 points none of the patients survived, in case of GPCS greater than 10 points 11 out of 19 patients survived. The latter relation of survival was also found in patients with improving or impairing scores during the observation period. In case of initial burst-suppression pattern in the EEG 7 out of 11 patients survived, in case of diffuse abnormalities with or with-out additional focal signs - 4 out of 10 patients survived, but in the latter there was none with an outcome of independent survival. All patients with an isoelectric EEG died. In case of bilateral recording of scalp- SEP 7 out of 11 patients survived, in case of unilateral loss of scalp-EP 4 out of 8 patients survived, but in the latter cases none with an outcome of independence. All patients with initial bilateral failure of scalp-SSEP or loss during the observation period died. In case of bilateral registrable BAEP (wave I to V) 11 out of 17 patients survived. All patients with initial uni- or bilateral failure of those potentials or loss during the observation period died.(ABSTRACT TRUNCATED AT 250 WORDS)     

Somatosensory evoked potentials in moderate hyperthermia]

The effects of moderate whole-body hyperthermia on the cervical and cortical somatosensory evoked potentials (SEP) were studied in healthy male subjects, aged 22-32 years. They were immersed in hot water and heated to a median rectal temperature of 39.0 degrees C. Serial SEPs to median nerve stimulation were recorded during cooling at intervals of 0.1 degrees C. The general wave form and the amplitudes did not systematically change. For a 1 degrees C drop there was a median latency increase of 2.6-3.7% in cervical and 1.5-7.4% in cortical SEP components. In individual cases significant latency delays of cervical N13 and cortical N20 could already be observed at differences of 0.2 degrees and 0.5 degrees respectively. All other components showed significant latency changes at temperature intervals of 0.6 to 0.8 degrees C.     

The prognostic value of evoked potentials in early neurologic rehabilitation of patients with the apallic syndrome

In 22 patients with apallic syndrome brainstem auditory and somatosensory evoked potentials were recorded, in 8 patients the course during rehabilitation was observed. Clinically the patients were scored with Glasgow-coma scale, Karnofsky-index and Goldenberg-scale. The outcome of rehabilitation was estimated by the "Glasgow-outcome scale". No correlation was found between results of evoked potentials and clinical state. First evoked potentials measurements of apallic patients allowed no prognosis. Evoked potentials are an important prognostic factor after severe head trauma, but have no value for the prognosis of apallic patients.     

事件相关电位与视觉诱发电位诊断帕金森病的价值

目的　探讨事件相关电位 (ERPs)和视觉诱发电位 (VEP)在帕金森病中 (PD)的诊断作用。方法　对 6 0例正常对照组和 5 8例无认知障碍的 PD患者组进行了 ERPs和 VEP检测。结果　 PD组 ERPs的 P30 0 波潜伏期较对照组的明显延长 (P<0 .0 5 ) ,波幅则较对照组明显降低 (P<0 .0 5 ) ;PD组 VEP的 P1 0 0 波潜伏期较对照组明显延长 (P<0 .0 5 ) ,而波幅则无显著性差异 (P>0 .0 5 )。结论　 ERPs的 P30 0 和 VEP对帕金森病的亚临床认知功能障碍及视觉传导通路功能的检测具有独特的诊断价值     

Correlation of visual evoked potentials with dementia in Parkinson's disease]

There has been some debate regarding abnormalities in visual evoked potentials (VEP) in Parkinson's disease (PD). To elucidate the mechanism causing abnormal VEP, we investigated the relationship between VEP and mental function in PD patients. Pattern reversal VEP was recorded in PD patients (n = 27) and age-matched control subjects (n = 14). PD patients consisted of two subgroups; PD without dementia (nD-PD; n = 17) and PD with dementia (D-PD; n = 10). Dementia was evaluated according to the criteria for dementia assigned in DSM III-R, and mental faculties were estimated by using the mini-mental state examination (MMSE). In pattern VEP recordings, P100 latency and amplitude were measured for each eye stimulated. No patient or control subject had impairment of corrected visual acuity or ophthalmological disease. There was no significant difference in age among the three groups (D-PD, nD-PD and control subjects). D-PD patients showed significantly prolonged P100 latency compared to nD-PD patients and control subjects (p less than 0.05). With respect to P100 amplitude, no significant difference was shown among the three groups. In PD patients, there was a rough correlation between P100 latency and MMSE score. No correlation was found between P100 amplitude and MMSE score. In control subjects, P100 latency did not correlate with advancing age. In PD patients, nD-PD patients showed a significant correlation between P100 latency and age, whereas D-PD patients presented no correlation. Abnormal VEP in PD has been mostly ascribed to dopaminergic deficiency in the retina.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alzheimer 病的脑诱发电位初步探讨

目的探讨Ａｌｚｈｅｉｍｅｒ病（ＡＤ）脑诱发电位变异及临床应用价值。方法记录３９例ＡＤ患者和４０例健康老年人的脑干听觉反应（ＡＢＲ）、听觉诱发电位（ＡＥＰ）、视觉诱发电位（Ｆ－ＶＥＰ）以及事件相关电位Ｐ３００。结果与健康对照组相比,ＡＤ组的脑诱发电位变异为：（１）波幅下降（ＡＢＲ－Ⅴ,ＡＥＰ－Ｐ２,Ｆ－ＶＥＰ－Ｐ２,靶Ｐ３００－Ｐ２、Ｐ３,非靶Ｐ３００－Ｐ２）;（２）潜伏期延长（ＡＢＲ－Ⅲ,ＡＥＰ－Ｐ１、Ｎ１、Ｐ２）;（３）部分潜伏期提前（靶和非靶Ｐ３００－Ｎ１）。相关分析提示：除靶Ｐ３００－Ｎ１潜伏期外,以上指标均与ＡＤ的认知功能评定（ＣＡＳＩ分）有显著线性相关,部分指标同时又与被试者的教育年限显著相关。Ｋ－Ｍｅａｎｓ聚类分析表明：与ＣＡＳＩ和教育年限皆相关的脑诱发电位指标（ＢＥＰｓ）区分两类被试者的特异性高（１００．０％）而敏感性低（５１．７％）;仅与ＣＡＳＩ评分相关的ＢＥＰｓ指标则敏感性高（９３．６％）而特异性低（５５．６％）。结论ＡＤ患者的脑诱发电位指标变异程度基本上与其认知功能受损程度相平行;根据不同临床应用目的可选择相应的ＢＥＰｓ指标     

Brain mapping--topographic demonstration of the EEG and evoked potentials in psychiatry and neurology

Brain mapping of EEG and evoked potentials permits the topographic display of electrical activity of the brain and is superior to conventional polygraphic procedures. Data from 16 scalp electrodes and two ear reference electrodes were worked up. The spontaneous EEG and the EEG during different testing conditions to activate particular brain regions was measured. 2 s EEG data segments were subjected to spectral analysis by a fast Fourier transformation (FFT). For late evoked potentials (VEP, AEP, SEP and P300) a single value representing the amplitude of EP at each 2-ms poststimulus latency point served for subsequent topographic mapping. Statistical techniques (Student's t-test) have been used in conjunction with EEG and EP data to render visible the regions where a clinical population differ from normal subjects. The results show abnormalities of EEG and EP in patients with psychical und neurological diseases.     

Visual evoked potentials in Alzheimer's and Parkinson disease]

Harding et al. suggested at first that an increase of P2 latency in flash VEP without an increase of P2 latency in pattern reversal VEP may be a diagnostic marker of Alzheimer's disease. Up to now there is no convincing evidence for this hypothesis. The purpose of the present study was to examine this hypotheses in an extended group of patients with Alzheimer's disease (n = 36). In addition, a group of patients with Parkinson's disease (n = 8) without dementia syndrome and a group of healthy elderly controls (n = 46) was investigated in order to determine the sensitivity and specificity of these VEP parameters. The results confirmed significant group differences between patients with Alzheimer's disease and healthy controls concerning the increase of Flash P2 latency and unchanged latency of P2 in the pattern reversal VEP. No significant correlations were found between duration of illness and mental test scores. The group differences of P2 latency in the flash VEP for patients with Parkinson's disease and healthy controls were also significant. Therefore, the increase of flash P2 latency in VEP does not seem to be specific for Alzheimer's disease nor for dementia syndrome. The pathological mechanism causing the flash P2 latency increase in a remarkable number of neuropsychiatric patients should be elucidated in further experimental investigations.     

Cross correlation functions of acoustic evoked brain stem potentials

A method for the analysis of brainstem acoustic evoked potentials (BAEP) is presented. The calculation of the normalized cross correlation function between BAEP recordings of the right and left side yields a quantitative and objective valuation of the symmetry of the electrical brainstem activity. Contrary to the usual interpretation of latencies and amplitudes the BAEP waveform is also considered. To demonstrate the regular properties of the normalized cross correlation function 20 healthy subjects were tested. Different stimulus and recording conditions, the influence of the BAEP signal length on which the calculation of the cross correlation function is based as well as filtering of the BAEP with varying cutoff frequencies are studied.     

Depth EEG and evoked potentials using an intravascular catheter electrode in the baboon

Obtaining an intracranial EEG, as well as a depth recording of the somatosensory evoked potentials, via a vascular approach are described. Experimentally, a directable microcatheter was placed in the middle cerebral artery of baboons. Using the catheter guide wire as electrode, intracranial electrical activity was recorded from within the cerebral vessels. Significantly, depth recordings of the SEP showed waves of thalamic origin not present in surface recordings. Advantages of this method over surface recordings are the greater gain of information possible and, over other techniques of depth recording, the comparibly lesser invasiveness.     

Computer assisted analysis of EEG, evoked potentials, EEG reactivity and heart rate variability in comatose patients

A multifunctional system for combined evaluation of EEG, visual (VEP), somatosensory (SEP) and auditory brainstem evoked potentials (BAEP) is introduced. For the light stimulation an array of light emitting diodes are used for tactile stimulation a vibration stimulus is applied to he distal digit of one finger. Stimulus-synchronous EEG segments are used for EP averaging and also for quantification of either the blocking or the activation of rhythmic EEG activity. Using this technique, alpha spindles characteristic of certain comatose states can be quantified for the first time. An important parameter is the alpha frequency, which is slowed down when there is evidence of cortical lesions, but remains unchanged in primary brain stem lesions. Comparing SEP and VEP also allows for differentiation of brain stem lesions from lesions in other areas. VEP were found to be maintained in predominant brain stem disorders. The auditory brain stem potentials and the heart rate variability are of further diagnostic significance. The importance of the individual parameters such as alpha-frequency, VEP, SEP, BAEP and alpha-spindles is demonstrated by follow-up studies in comatose patients.     

Subcortical somatosensory evoked potentials in patients with hepatic encephalopathy caused by severe acute hepatitis

We studied the median nerve stimulated somatosensory evoked potentials (SEP) of 23 patients with hepatic encephalopathy (HE) resulting from severe acute hepatitis and 22 healthy volunteers. Ten patients who improved and survived more than 60 days were classified as Group 1 and the remaining 13 patients who died shortly after the SEP studies were classified as Group 2. The mean N9-N13 interpeak latencies (IPL) were not different among control and two patient groups. The mean N13-N20 IPL of Group 2 was significantly prolonged when compared with normal controls (P < 0.001) and Group 1 (P < 0.001). Five of the six patients with abnormal N13-N20 IPL died of hepatic failure within 24 h after SEP testing. The occurrence of abnormal subcortical conduction together with cortical dysfunction suggested that brain damage in terminal hepatic encephalopathy was diffuse. The presentation of abnormal prolongation of N13–N20 IPL of SEP during the course of severe acute hepatitis indicated a poor prognosis. Peripheral somatosensory conduction is unaffected even in terminal HE.     

The place of EEG mapping in cerebral ischemia

70 patients with Completed stroke were studied and the findings of routine EEG, EEG mapping and CT were compared. It could be shown, that the EEG mapping revealed significantly more often focal changes corresponding with the clinical signs (83%) than the routine EEG (57%). Hypodense lesions in CT were seen in 54 patients. Identical results of EEG mapping and CT were found in 50 patients, EEG mapping and routine EEG were identical in 46 patients. The EEG mapping provided additional lateralisation in 12 patients with negative CT findings and in 21 patients with negative routine EEG. In patients with hypodense lesions in CT the EEG mapping revealed significantly more often focal changes (85%) than the routine EEG (59)%).     

单模式与多模式诱发电位对重症脑血管病患者的预后评估

目的探讨单模式与多模式诱发电位对重症脑血管病患者脑损伤程度的评价和预测预后的准确性。方法对42例急性中、重度（格拉斯哥昏迷评分≤12分）幕上脑血管病患者进行短潜伏期体感诱发电位（SLSEP）和听觉诱发电位（BAEP）监测，根据病后3个月的格拉斯哥预后评分分为预后良好组（8例）与预后不良组（34例），依据单模式诱发电位分级标准（Judson、Hall标准）和多模式诱发电位分级标准（Cant标准）进行分级，并进行单模式与多模式之间特异性和准确性的比较。结果单模式和多模式各分级标准与预后均有显著相关性，级别越高，预后越差。单模式SLSEP预测特异性、准确性（分别为97．1％和92．9％）高于BAEP（94．1％和90．5％）。多模式诱发电位预测准确性与单模式体感诱发电位相同。结论单模式体感诱发电位能较准确地预测幕上重症脑血管病患者的预后。