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。     

The diagnostic value of motor evoked potentials.

OBJECTIVE: To assess the diagnostic usefulness of motor evoked potentials (MEPs) and to identify the optimal method for calculating the central conduction time. The test results were evaluated in a prospective study of 1023 neurological patients. METHODS: We evaluated the correlation between clinical and electrophysiological findings, the accuracy, the sensitivity, the percentage of subclinical abnormalities and the false negative rates of MEPs in different neurological disorders. In patients with lower motor neuron involvement, we compared the central conduction time calculated as the difference between the latency of the cortical and magnetic root stimulation responses with that calculated using the F-wave method. RESULTS: The agreement index between electrophysiological and clinical findings was 87%. The overall accuracy of the test was 0.97. The higher sensitivity values were demonstrated in spinal cord disorders (0.85), hereditary spastic paraplegia (0.80) and motor neuron diseases (0.74). The higher percentages of subclinical abnormalities were found in motor neuron disorders (26%) muscular diseases (24%), multiple sclerosis (13.5%) and spinal cord diseases (12.5%). The higher false negative rates were found in sylvian stroke (0.36) and hereditary spastic paraplegia (0.16). Central conduction study using magnetic paravertebral stimulation but not using the F-wave method, resulted in 12% and 10% of false positive values in lower limb multiradiculopathies and in neuropathies, respectively. CONCLUSIONS: MEPs represent a highly accurate diagnostic test. MEP clinical value is maximum in motor neuron, muscle and spinal cord diseases. In patients with lower motor neuron involvement, the gold standard for central conduction determination is the F-wave method.     

A study of clinical, MRI and multimodality evoked potentials in neurologic Wilson disease

The aims of this study were evaluate motor, somatosensory, visual and auditory brainstem evoked potential (MEP, SEP, VEP, ABER) changes in Wilson disease (WD) and correlate these with magnetic resonance imaging (MRI) and clinical findings.
Neurologic WD diagnosed on the basis of clinical, ceruloplasmin and Kayser–Fleischer ring were evaluated including pedigree charting, hepatic, renal, hematologic and osteoarticular manifestations. Blood counts, serum chemistry, MRI, MEP to tibialis anterior, tibial SEP, VEP and ABER were performed. Evoked potential (EP) changes were correlated with clinical and MRI findings.
Eighteen WD patients were recruited from 17 families whose mean age was 16 years. Movement disorders were present in 14, cognitive decline in 12 and pyramidal signs in 12 patients. MRI revealed involvement of basal ganglia in 80%, thalamus in 40%, brain stem in 46.7% and subcortical white matter in 53.3%. MEP was abnormal in 35.7%, SEP in 30.8%, VEP in 57% and ABER in 61.5% patients; the latter three EP changes were subclinical. Frequency and number of EP abnormalities were higher with increasing severity of illness.
SEP, VEP and ABER reveals subclinical abnormality and MEP helps in documenting both clinical and subclinical abnormalities. Number of EP abnormalities increases with increasing clinical severity of WD.     

Restraint stress modulates sensory evoked potentials

The present experiment investigated whether repeated exposure to an acute stressor elicits changes in sensory evoked responses recorded from awake rats. Animals were restrained for four hours per day on each of four consecutive days. Recordings were obtained on the day prior to the first restraint and following the first and fourth day of restraint. Restraint generally resulted in an increase in the amplitude of sensory evoked responses recorded from the medial basal hypothalamus (MBH), dorsal hippocampus (DH), and superior colliculus (SC) without changing any other characteristics of the recording. A persistent increase in the averaged evoked response amplitudes seen on both the first and fourth daily presentation of the stressor indicates that no significant adaptation to the stressor occurred over this time period as measured electrophysiologically.     

Visual evoked potentials and sensory dimensions

Concomitant variations of physical stimulus characteristics and variations of responses elicited in the human adult subject were studied under conditions of adaptation to darkness or light in order to stimulate the B or the D sub-system described by Jung. Temporal processing in these two systems was compared by analysing output variables (VEPs and sensory ratings) in response to a range of electrophysiological and perceptual responses run in parallel: the temporal summation law, which is a basic code in the nervous system, is found to be obeyed in both B and D subsystems. But asymmetries are also observed, indicating specific characteristics of B and D functioning.     

Effects of halothane on sensory evoked potentials

Intraoperative monitoring of central nervous system functions is useful for safe neurosurgical operations. For such a purpose, some kinds of sensory evoked potentials play significant roles, but their reliability during general anesthesia have not yet been established. The authors conducted experimental and clinical studies to reveal effects of halothane, a most popular anesthetic, on sensory evoked potentials. Eight adult cats, weighing 2.8-4.0 kg, were induced to anesthesia with thiopental and ether, and after tracheostomy and venous cannulation, they were immobilized with succinylcholine and artificially ventilated with mixture of oxygen, nitrous oxide halothane. The concentration of halothane was increased up to 4.0% by 0.5% steps. The body temperature, systemic blood pressure and carbon dioxide concentrations in expires gas were monitored continuously, and maintained within normal ranges as much as possible. The hypotension induced by halothane was easily corrected by dopamine infusion initially, but later became difficult to be controlled as the halothane concentration increased. In each concentration, short latency somatosensory evoked potentials by median nerve stimulations (SL-SEP), and brain stem auditory evoked potentials (BAEP) were recorded. Active electrode was placed on the bregma, and reference electrodes were placed on a hindlimb for SL-SEP, on the tongue for BAEP recordings. Peak amplitudes of SL-SEP were gradually decreased and finally disappeared without apparent dose dependency. Relatively the peaks with longer latencies were more affected than those with shorter latency such as P1 and N1. In BAEP, decrement of the amplitude was apparent in the peaks with longer latencies with an obvious dose dependency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Abnormal sensory evoked potentials in amyotrophic lateral sclerosis

We have reviewed sensory evoked potential (EP) findings in 17 patients with amyotrophic lateral sclerosis (ALS). Somatosensory EPs were abnormal in 7 of 16 patients after lower-extremity stimulation and in 2 of 16 patients after upper-extremity stimulation. Brainstem auditory EP abnormalities were found in 2 of 12 patients. No abnormalities were noted on pattern reversal visual EPs in 12 patients. Overall, 47% of all ALS patients studied had at least one EP abnormality. EP evidence of CNS sensory dysfunction in ALS is more frequent than that noted clinically or pathologically and offers further support to previous observations of sensory system involvement in ALS.     

Cerebral MRI and evoked potentials in Wilson disease. Comparison of findings in patients with neurological follow-up

Wilson's disease is caused by toxic copper accumulation, which leads predominantly to hepatic and basal ganglia damage. Characteristic findings in MRI and electrophysiologic examinations are described according to the occurrence of neurological symptoms. In the present study, 28 patients suffering from Wilson's disease (neurological type) were investigated. The results of MRI are compared with abnormalities of evoked potentials (BAEP, MSEP, T-VEP, MEP). All patients show hypodensities in the basal ganglial area (putamen and GI. pallidus) regularly combined with atrophy of the cerebrum and cerebellum in MRI. Signal abnormalities in the mesencephalic region (46% occurrence) and Nc. dentatus (36% occurrence) are combined with the other findings in variable patterns. Only slight changes are found in the pontine region. BAEP are disturbed in 71% of all cases and MSEP in 46%. Combined abnormalities of BAEP and MSEP were found in 39%. Pathological values occurred with a lower frequency in T-VEP (36%) and MEP (39%). The comparison of MRI findings with electrophysiological data done separately for each patient reveals no strong correlation between both methods. Individual MRI findings do not correspond with the patterns of disturbed evoked potentials and vice versa. Therefore we conclude that these methods, MRI and electrophysiological evaluation, supplement each other. Magnetic resonance imaging and electrophysiological evaluation should be performed simultaneously for therapy monitoring.     

Somatosensory evoked potentials,sensory nerve potentials and sensory nerve conduction in hereditary motor and sensory neuropathy type I

Summary Thirty-nine patients from six families with hereditary motor and sensory neuropathy type I and control subjects were included in this study. A neurological deficit score (NDS) was derived from a neurological examination and compared with neurophysiological test findings. Further, sensory nerve conduction velocities (SNCV) were compared with the motor nerve conduction velocities (MNCV). Five patients whom peaks of N11/N13 complex and N20 of the median nerve sensory evoked potential (SEP) could be recorded showed normal interpeak latency. The interpeak separation P14 N20 measured in six patients was normal. These findings point to the normal function of the central conductive pathways. Erb and cervical potentials of the median nerve SEP could be recorded in 10% and 12% of the patients, respectively. In contrast, about half of the patients showed a scalp N20, while in most of them no SNCV could be measured. In six patients far-field potential P14 of the median nerve SEP was the first detectable potential. Therefore, we argue in view of the anatomical structure of the thalamus, that the first generator for synchronizing and amplification of impulses is probably located in the thalamus. A third of the patients had a cortical sural nerve SEP, while no sural nerve potentials could be recorded. No association was found between the SEP findings and the NDS. There was an inverse correlation between median SNCV and the NDS, but no relationship between the former and sensory deficit alone. In 40% of the patients median SNCV and in 13% sural SNCV could be recorded and considered to be severely decreased. In contrast, the majority of the patients had mild to moderate sensory deficit. Furthermore, patients with measurable SNCVs had higher MNCVs and lower NDS than patients without measurable SNCVs.     

Significance of sensory evoked potentials in the diagnosis of polyneuropathy

In 172 patients suffering from neuropathies of different aetiologies (diabetic, uraemic, inflammatory, hereditary, alcoholic, cryptogenic) the SEP findings (cortical median and sural nerve SEP, cervical median nerve SEP, Erb's point potential) were compared with the results of conventional sensory and motor electroneurography (ENG) and with clinical signs. SEP's yielded a high percentage of abnormalities. Thus in 5 of the 6 groups the sural nerve SEP presented an unequivocal latency prolongation in 55 to 75% of the patients, in HMSN-I-patients even in 100%. Also well over 50% of the median nerve evoked potentials were outside the normal range. In many cases the delay of the SEP's simply reflected the impairment of conduction within the peripheral nerve fibres as documented by ENG; here the ENG was naturally even more sensitive in detecting slight distal conduction disturbance, which did not shift the SEP latency outside the normal range. However, in a certain percentage that varied in the different aetiological groups, the SEP's demonstrated an impairment of conduction within the proximal segments of the sensory system not accessible to conventional ENG technique. Thus, in 15 to 25% of the patients with diabetic, uraemic, inflammatory and cryptogenic neuropathies, pathological SEP findings were combined with normal results of the ENG examination. In no case this "proximal" conduction disturbance affected the "central conduction" between the cervical spinal cord and the cortex. A more detailed differentiation was often impossible: A prolonged conduction time between brachial plexus and cervical cord could not be subdivided further due to the lack of the SEP component representing the "spinal entry of the afferent volley". SEP's--especially the cortical SEP's--can be reliably recorded even if a peripheral sensory nerve action potential is lacking; in these cases the extent of the conduction disturbance is documented only by the--practically always demonstrable--delay of the SEP. Nearly without exception, pronounced latency prolongations were seen only in cortical SEP's because in these cases the subcortical components could no longer be identified. Two types of considerably delayed cortical SEP's could be distinguished: Potentials of abnormal shape, where the complete extinction of the initial complex had to be assumed: the latency prolongation cannot be equated with the actual conduction delay. Completely normal-shaped potentials whose latency times evidently reflected the real delay.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of thiopental on sensory evoked potentials in the cat

Noninvasive electrophysiological evaluation with sensory evoked potentials would be of clear diagnostic and prognostic value in evaluating comatose patients with stroke or severe head injury. In order to protect the brain from such kinds of insults, barbiturate coma therapy has been employed and its effectiveness has been already established. However, in the barbiturate coma therapy, it is occasionally difficult to distinguish the pharmacological effect of barbiturate from the preexisting brain dysfunction caused by the underlying process of the disease. In adult cats, authors studied changes of sensory evoked potentials following cumulative intravenous administration of thiopental which is used clinically for barbiturate coma therapy. P1 and N1 of cortical SEP showed tendency of gradual decrease in amplitude. However, no significant changes occurred in latency by stepwise increment of thiopental dose. Changes in amplitude of P1 and N1 of cortical SEP preceded to the flattening on electroencephalogram. Around at the level of the concentration where EEG changes began, I-II interpeak latency of BAEP and latency of wave I of short latency SEP started to increase. BAEP and early components of SEP (I.II.III.IV) persisted even in by far the higher level of serum concentration of thiopental than that of clinical use. Furthermore, most of these parameters showed no statistically significant change neither in amplitude nor in latency. These experimental results suggest that sensory evoked potentials will provide us with useful information in the assessment of the brainstem function in patients under thiopental induced deep coma.     

Effects of signal probability on sensory evoked potentials in cats

The present experiment was designed to follow the evoked potential (EP) changes recorded from the association cortex and A II area of the auditory cortex and from the vertex of the freely moving cat. The EPs elicited by clicks of different probabilities used as warning stimuli during aversive conditioning were analyzed. It was found that the EPs recorded from the auditory cortex and the vertex showed different changes during the aversive conditioning to the rare clicks of 3 and 10% probabilities. The N50 and P100 components of the auditory cortical (A II area) EPs increased significantly at both signal probabilities. On the vetex and association cortical EPs, elicited by the rare signals, a broadly distributed positivity, the P250 wave could be detected. The amplitude increase of the P250 was inversely proportional to the used probability of the signal.