Evoked potentials

ABSTRACT- A survey is given of my studies of evoked potentials in patients with multiple sclerosis (MS) and in control subjects. Potentials were recorded following random low-rate auditory stimulation (BAEP), checkerboard pattern-reversal stimulation (VEP), somatosensory stimulation (SEP); blink reflexes (BR) were recorded following electrical stimulation of the supraorbital nerve. Normal data had to be related to age and sex in evaluating BAEPs and VEPs.
In 160 MS patients, a total of 421 recordings were obtained. Changes by repeated BAEP and VEP tests might reflect changes in the clinical state, but they also did occur in clinically stable patients. In patients with definite MS, high incidences of abnormality were shown, supporting the clinical findings. The diagnostic value was greatest when clinically silent lesions were demonstrated in patients with suspected or possible MS. In these patients, either BAEP or VEP gave evidence of subclinical lesions in about 50%, and when combined, in 71% of the patients, thus making a transfer to a more certain diagnostic classification possible and invasive examinations unnecessary. When SEP and BR tests were added, subclinical lesions were found in 74% of the patients. The SEP recordings did show a high incidence of abnormality, but only few silent lesions; the BR test was the least sensitive. The VEP was abnormal in all patients with signs of optic neuritis and in all but one with a history of optic neuritis.
The present results are compared to those obtained in other laboratories and with other types of examinations in MS patients. It is concluded that although the tests are not specific for MS, they give valuable information in the majority of patients with a clinically uncertain diagnosis. This information will most often not be given by other types of examination. The combination of VEP and BAEP is recommended, but it should be supplemented by SEP recording in patients without spinal signs.     

The value of brain stem auditory, visual and somatosensory evoked potentials and blink reflexes in the diagnosis of multiple sclerosis

Cervical and cortical somatosensory evoked potentials (SEP) following electrical stimulation of the median nerve and blink reflexes (BR) following electrical stimulation of the supraorbital nerve were recorded in 30 normal subjects aged 20–49 years. Subjects aged 40–49 had longer SEP latencies than subjects aged 20–39 years.
A total of 29 slightly affected patients with multiple sclerosis (MS) aged 26–49 years, including four patients without clinical signs (suspected MS) and 19 patients with signs indicating only one lesion (possible MS) were examined by low-rate random-stimulated brain stem auditory (BAEP), checkerboard pattern-reversal visual evoked potentials (VEP), SEP and BR. Abnormal recordings by at least one of the examinations were found in all but three patients, and by all four tests in five patients.
In patients with definite or probable MS, demonstration of clinically recognized or subclinical lesions was of minor diagnostic value, in contrast to the importance such findings had in patients with suspected or possible MS. Silent lesions were shown by at least one of the tests in the four suspected and in 13 of the possible MS patients, so these 17 patients could be transferred to a more certain diagnostic category. This reclassification was most often due to the BAEP recording.
In patients with spinal signs, the combination of BAEP and VEP recording was sufficiently efficient. In patients with optic neuritis a combination of BAEP and SEP was preferred. No abnormal recordings were found in 15 normal subjects examined by all four tests.     

Visual, early auditory and somatosensory evoked potentials in multiple sclerosis (917 cases)

Visual (VEP), brainstem auditory (BAEP) and somatosensory (SEP) evoked potentials were recorded over a 6 year period in 917 patients with or suspected of multiple sclerosis according to Mc Alpine's criteria. Evoked potentials provided information of diagnostic relevance in detecting clinically unsuspected lesions (spatial dissemination). They also gave valuable informations in patients with atypical or borderline clinical features. When abnormal, VEP indicated clinically silent lesions in 45.1 p. 100 of patients with definite MS, 66 p. 100 of those with probable MS and 78 p. 100 of the possible MS. Less than 15 p. 100 of SEP and/or BAEP abnormalities were found in 83 patients with a simple or recurring retrobulbar optic neuritis. Thirteen patients with acute transverse myelopathy and no prior history of neurological disease were studied. All had normal visual and brainstem auditory evoked potentials. Abnormal VEPs helped to the clinical assessment of 88 patients with progressive spastic paraparesis 46,6 p. 100 of whom had abnormal VEPs demonstrating disseminated lesions and 36,1 p. 100 had abnormal BAEPs. The frequency of the various types of VEP, BAEP and SEP abnormalities was studied as well as their course on repeated recordings. Results of multivariate analysis are given. It was found that the longer the time interval between the first MS relapse and the evoked potential recording, the higher the incidence of abnormalities. The incidence of evoked potentials abnormalities was lower in patients with normal CSF and higher in patients with inflammatory CSF. The abnormalities were more frequent when patients had clinical evidence of lesions of the sensory pathways explored by the tests.     

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.     

Brain-stem auditory evoked potentials in multiple sclerosis: the relation to VEP,SEP and CSF immunoglobulins

Summary One hundred patients with multiple sclerosis (MS) were analysed retrospectively with respect to investigations of brain-stem auditory evoked potentials (BAEP), pattern reversal visual evoked potentials (VEP), somatosensory evoked potentials (SEP), and cerebrospinal fluid immunoglobulins (CSF-IG). BAEP were abnormal in 42% of those with normal VEP and SEP examinations, and in 38% of patients with normal CSF-IG. The chance of obtaining at least one abnormal EP was lower in patients with normal CSF-IG than in patients with abnormal CSF. When a dispersion ratio was included in the criteria for BAEP abnormality, the sensitivity increased compared with conventional BAEP criteria. We recommend that BAEP should still be included in the EP test battery for patients with suspected MS.     

Middle latency auditory evoked potentials (MLAEPs) in (MS)

Middle latency auditory evoked potentials (MLAEPs) were studied in 30 definite multiple sclerosis (MS) patients in addition to brain-stem auditory evoked potentials (BAEPs). BAEP abnormalities were detected in 18 (60%) patients. MLAEPs were abnormal in 22 (73%) of them. In 15 patients BAEPs and MLAEPs were both abnormal. MLAEPs were found abnormal in 7 of the 12 patients with normal BAEPs. In 18 patients with abnormal BAEPs only 3 had normal MLAEPs. MLAEPs abnormalities are consistent with a rostral auditory pathway involvement. Therefore, they can be used in combination with BAEPs to examine the whole auditory system to improve the sensitivity.     

Short term neurophysiological monitoring in multiple sclerosis bouts. Evaluation of steroid treatment

Visual (VEP) and brainstem auditory (BAEP) evoked potentials (EP) were recorded in 21 multiple sclerosis (MS) patients in acute relapse before and after steroid treatment. VEPs were abnormal in 14/21 patients and BAEPs in 10/21 patients before treatment. In 4 patients with acute optic neuritis (ON), an improvement of VEPs paralleled clinical evolution in 3 cases. Substantial and contrasting changes in VEPs or BAEPs, with no clinical counterpart, were related to a spontaneous fluctuation of EPs in acute relapses of MS. These changes suggest frequent subclinical (multifocal and, possibly, sequential) central nervous system involvement in MS bouts. Group analysis showed nonsignificant changes in EP parameters before and after treatment. Our results indicate that evoked potentials (EPs) are of limited value for monitoring the short-term effect of steroid treatment in MS in bouts.

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Sommario I potenziali evocati visivi (VEP) ed acustici troncoencefalici (BAEP) sono stati eseguiti in 21 pazienti affentti da sclerosi multipla (SM) in fase di poussée, prima e dopo un ciclo di trattamento con steroidi. Prima del trattamento i VEP edi BAEP sono risultati alterati in 14 e 10 pazienti rispettivamente. 4 pazienti presentavano una neurite ottica (ON) in fase acuta; in 3, dopo il trattamento, è stato rilevato un significativo miglioramento dei VEP e dell'acuità visiva. Significative, ma contrastanti, modificazioni dei VEP e BAEP, riscontrate in altri 5 pazienti, non correlate all'evoluzione clinica, sono suggestive di un interessamento subclinico, multifocale e possibilmente sequenziale, durante una poussée della SM. L'analisi per gruppi non evidenzia differenze statistiche significative tra prima e dopo il trattamento. I nostri risultati indicano che i potenziali evocati sono di limitata utilità ai fini di un monitoraggio a breve termine della SM in poussée.

     

Evoked potentials and CSF-immunoglobulins in MS: relationship to disease duration, disability, and functional status

In 100 MS patients, BAEP and tibial SEP abnormality rates increased significantly with disease duration and clinical disability. VEP correlated non-linearly with disease duration, and median nerve SEP correlated with disability. In multifactorial analysis, however, BAEP correlated significantly only with clinical brainstem and cerebellar signs. These results suggest that evoked potentials correlate more strongly with neurological status of the functional subsystems than either overall disability or disease duration. These findings indirectly suggest that evoked potentials may be useful monitors during large therapeutical trials in MS patients.     

Variations of brain stem auditory evoked potentials correlated to duration and severity of multiple sclerosis

A total of 158 recordings of brain stem auditory evoked potentials (BAEPs) were obtained in 121 patients with multiple sclerosis. A statistically significant increased incidence of abnormality and diffusely abnormal recordings was found with increasing duration and severity of symptoms. Alterations in follow-up recordings might reflect changes in the clinical state, but also occurred in clinically stable patients. These findings suggested that transition from normality of BAEPs might occur either by successive disappearance of the later waves or by uniformly decreasing amplitudes of all the waves to diffusely abnormal recordings. It was concluded that the main value of BAEP recording in patients with multiple sclerosis was to indicate clinically silent lesions, and its value in monitoring the clinical condition of the individual patient was dubious.     

Diagnostic investigations in MS: which is the most sensitive?

In an attempt to establish the efficacy of the different diagnostic tests, 41 multiple sclerosis (MS) patients at different stages of the disease were studied by means of visual evoked potential (VEP) recording, T-lymphocyte subset determination cerebrospinal fluid (CSF) analysis and magnetic resonance (MR) imaging. MR and CSF oligoclonal bands (OB) were the most sensitive techniques for the diagnosis of MS, being positive in 88% of patients, while VEP and helper/suppressor (H/S) T-cell ratio were altered in 54% and 46% of patients respectively. Low significant agreement coefficient were found among the 4 tests and the major value, even though "fairly" significant, was between MR and OB.     

多系统萎缩44例的临床与神经电生理特点分析

目的 探讨临床和神经电生理检查对于多系统萎缩(MSA)的诊断价值。方法 对44例MSA患者分组分析其临床特点、肌电图(EMG)、神经传导速度(NCV)、躯体感觉诱发电位(SEP)、运动诱发电位(MEP)、脑干听觉诱发电位(BAEP)及视觉诱发电位(VEP)。并比较临床表现和电生理检查结果在各组间的差异。结果 本组患者以自主神经功能障碍和小脑生共济失调的异常率最高(88．6％)。帕金森综合征出现率在各组间差异有显著意义(P值分别为0．027、0．007、0．025)，卧立位血压异常在拟诊组和可能组间差异有显著意义(76．5％、18．2％)。EMG和NCV的异常率为38．1％，各组间出现率有不同。各种诱发电位的异常出现率在分组比较中无显著性差异。结论 仅凭临床表现无法对：MSA进行分组。各项神经电生理检查中以BAEP的阳性率最高。EMG和NCV结果在各组之间的差异提示该项检查对于MSA的分组可能有一定的帮助。     

多发性硬化患者的MRI及多种诱发电位研究

目的探讨磁共振成像(MRI)和诱发电位(EPs)在诊断多发性硬化中的价值。方法对68例多发性硬化患者的头颅MRI、脑干听觉诱发电位、视觉诱发电位以及体感诱发电位等指标进行回顾性分析和比较。结果多发性硬化患者的头颅MRI、脑干听觉诱发电位、视觉诱发电位以及体感诱发电位的异常率分别为91.2%(62/68)、80.9%(55/68)、82.4%(56/68)和77.9%(53/68),且均发现多发性硬化的亚临床病灶;两项或多项联合检查的异常率较单项检查的异常率增高,差异有统计学意义(P<0.01)。结论头颅MRI和诱发电位检查有助于临床早期确诊多发性硬化,联合应用可使其敏感性提高。     

视觉诱发电位在视神经脊髓炎中的诊断价值

目的探讨视觉诱发电位在视神经脊髓炎中的诊断价值。方法应用棋盘格反转模式对32例健康人和30例视神经脊髓炎患者进行视觉诱发电位检测,比较测量数据。结果视觉诱发电位的异常率为93.33%,P100峰潜伏期与对照组相比有显著性差异(P<0.01),P100波峰无显著性差异(P>0.01)。结论视觉诱发电位对视神经脊髓炎的早期诊断和病情程度判断具有一定的价值。     

Visual and auditory evoked potentials during long-term vigabatrin treatment in children and adolescents with epilepsy.

OBJECTIVES: The aim of the study was to estimate the effects of Vigabatrin (VGB) as add-on therapy on visual (VEP) and brain-stem (BAEP) evoked potentials. METHOD: The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these AEDs. Combination therapy was administered using add-on VGB in the recommended dose 57.4+/-26.5 mg/kg body mass/day. VEP and BAEP evoked potentials were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age matched control group. RESULTS: Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the interpeak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes. CONCLUSIONS: Adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs. Our electrophysiological studies demonstrate abnormalities in EPs parameters due to subclinical toxicity induced by AEDs. Major alterations produced bitherapy of VPA-SR + VGB and minor SR formulations of CBZ or VPA.     

多发性硬化患者头颅磁共振、诱发电位和IgG指数的对比研究

报道43例多发性硬化(MS)患者头颅磁共振成像(MRI)、诱发电位(EP)和IgG指数(IgGIndex)的对比研究结果。发现MRI的检测异常率为81.4％,而VEP仅53.7％、BAEP47.5％、IgGIndex57.5％。MRI在显示空间脱髓鞘方面是最敏感的方法,但VEP、BAEP只要有一项异常即判断为EP异常则其异常率高达79.5％,接近MRI。作者认为三者同时检查可以提高诊断的准确性。     

Multimodality evoked potentials in amyotrophic lateral sclerosis

Visual, brainstem auditory and somatosensory evoked potentials to medial nerve stimulation were recorded in 27 patients affected by amyotrophic lateral sclerosis. VEP N75, P100, N140, N75-P100 latencies and P100 amplitude, BAEP I-III, III-V and I-V interpeak-latencies were within normal limits in all ALS patients. Somatosensory evoked potentials were abnormally delayed in 8 patients: in 3 arms because of a delayed N9-N13 latency, in 9 arms because of a delayed N13-N19 latency.     

Multiple sclerosis with normal neuro-ophthalmological work-up: results of focal stimulations induced by a scanning laser ophthalmoscope

OBJECTIVE: Visual evoked potentials (VEPs) are a very useful tool in diagnosis of multiple sclerosis (MS). Nevertheless, in some cases of the disease, VEPs are normal. The aim of this study was to evaluate the diagnostic value of focal checkerboard reversal stimulation based on opto-acoustic modulation generated by a scanning laser ophthalmoscope (SLO) in patients whose standard neuro-ophthalmological work-up was normal. METHODS: We prospectively studied 185 MS patients. In this cohort we found 30 patients with definite MS and normal neuroophthalmological work-up and we studied the diagnostic yield of focal visual stimulation in these patients. We performed focal SLO-elicited VEPs with two different spatial distributions: a central 8 x 8 degrees square field and a central 8 x 8 degrees exclusion square. The results were analysed in terms of age of the patient, course of the disease, and disability evaluated on the Expanded Disability Status Scale (EDSS). RESULTS: Mean latencies of focal VEPs were increased in MS patients compared to controls. In MS, focal stimulation allowed dysfunction of the visual system to be detected in 50% of patients who have been classified as normal according to conventional VEPs. VEP abnormalities were found to be correlated with the EDSS score (P<0.001) and the course of the disease (P<0.05). CONCLUSION: We have demonstrated the value of focal VEPs in MS diagnosis using SLO-based techniques. Further prospective work in patients with possible and probable MS should enable an evaluation of the sensitivity and specificity of this method in the early diagnosis of MS.     

Visual evoked potentials in normal subjects and patients with multiple sclerosis

Visual evoked potentials (VEPs) by checkerboard pattern-reversal stimulation were recorded in 70 subjects aged 10–69 years and in 100 patients with definite, probable or possible multiple sclerosis (MS). Longer latencies and smaller amplitudes of the major positive component were found in male subjects, in old subjects and when the amplifier's band-pass was narrowed. Subjects 10–14 years old had longer latencies and higher amplitudes than mature adults. Based on findings in the normal material, the following three criteria were used in evaluating the recordings from patients: the latency, the side difference in latencies and the ratio of amplitudes between the two sides of the major positive component with various limits for the two sexes and different age groups.
The incidence of abnormal recordings was 85% for all the patients, 100% in 50 patients with definite, 70% in 50 patients with probable or possible MS, 73% in patients who had a history of spinal symptoms only, 98% if they had and 74% if they had not experienced optic neuritis. The incidence of abnormal findings increased with increasing duration of symptoms. All patients with visual acuity below 0.67 had abnormal VEPs.
The high incidence of abnormal recordings confirmed the value of the test in establishing the diagnosis, and suggested that the use of different normative values for sex and age may increase the diagnostic yield without increasing the number of false positive findings.     

Foveal interocular time thresholds and latency differences in multiple sclerosis

Summary Nineteen patients with suspected multiple sclerosis (MS) and 28 control subjects were foveally stimulated by a small cross formed by rectangular red-light-emitting diodes. By means of crossed polarizers one eye was exposed only to the horizontal bar of the cross, the other to the vertical. Stimulus onset asynchrony ranged from 0 to ±300 ms (the horizontal bar preceding or following the vertical). The task was to indicate whether the horizontal or vertical bar had appeared first. Compared with normal subjects, MS patients exhibited much higher time thresholds (ranging from –150 to +130 ms) and had considerable interocular latency differences (up to 29 ms), indicating unilateral or asymmetrical impairment of the visual pathways. The psychophysical latency differences of the patients were compared to monocular latencies and interocular latency differences of the visually evoked cortical potential (VEP) obtained by foveal stimulation. Under the stimulus conditions chosen in this study, the diagnostic value of the psychophysical measurements was equal to or, for McAlpine's classes I and II of definite and probable MS patients, better than that based on VEP recordings.     

酒精所致精神障碍患者的脑干听觉诱发电位

目的分析酒精所致精神障碍患者的脑干听觉诱发电位（ＢＡＥＰ）表现。方法对３０例长期嗜酒所致精神障碍患者进行ＢＡＥＰ检测，并与正常人进行对照。结果病例组ＢＡＥＰ各波峰潜伏期（ＰＬ）、峰间期（ＩＰＬ）延长，波形分化差，与正常对照组有显著性差异。结论ＢＡＥＰ异常与临床表现及影像学，实验室结果基本一致，提示诱发电位可作为慢性酒精中毒的诊断方法之一