EEG-EMG Zeitschrift fur Elektroenzephalographie, Elektromyographie und verwandte Gebiete最新文献

VEP changes in MS patients are due to the demyelinating process which causes conduction alterations as well as inhibitory mechanisms. The pattern-shift VEP can show a delay of the main positivity, a diminished amplitude or/and an altered shape and duration. Concerning to series from the literature and own observations on more than 500 MS patients 4 different types of VEP alterations can be observed: 1. NPN complex with P2 delay; 2. broadening with loss of N2 and P2 delay; 3. bifid P2, P100-P135 complex; 4. deformation and dissociation with loss of P2, N105 dominance and amplitude reduction.

For differential, therapeutic, and prognostic reasons the recognition of early lesions in glaucoma chronicum simplex is very important. Besides sophisticated ophthalmological investigations optic nerve and retinal functions can be tested by flash and pattern-reversal evoked visual potentials and electroretinograms. 38 glaucomatous eyes were investigated by VEP and ERG applying single and flicker flashes as well as transient pattern-reversal stimuli of different check sizes. The results related to the degree of visual field disturbances show the damage of retinal and neuronal elements in a descending order affecting first of all the macular cones, then the rod system, and later on the elements of the second retinal neuron. The ganglion cells seems to be affected after all.

The method of Pattern Flash elicited P300 (PFP300) has been applied to evaluate the dynamic alterations in cognitive function of a 58 year old woman (H. C.) presenting with hepatic failure due to fulminant hepatitis Non-A-Non-B. At the time of the first investigation she complained about slight memory deficits and revealed signs of hepatic encephalopathy grade I according to Parson-Smith et al. (bilirubin 26.0 mg/dl, NH3 102 micrograms/dl, electrolytes and blood sugar normal). Psychometric tests: Number connection test (NCT): 54 s (28-53 s, greater than 2sd); Syndrom-Kurz-Test (SKT): total score = 9 (0-4), compatible with a slight "organic brain syndrome". PFP300: N250 latency 343.5 ms (276.4 +/- 14.7 ms, greater than 4sd); PFP300-latency: 442.5 ms (326.9 +/- 14.7, greater than 7sd); PFP300 amplitudes: 16.0 microV (14.4 +/- 8.4, +/- 1sd), indicating severe disturbance in visual discrimination without visual attention deficits. Due to progressive deterioration of liver function the patient had to undergo orthotopic liver transplantation. The patient was reinvestigated four weeks later. The clinical and laboratory status were normal and no signs of hepatic encephalopathy could be detected clinically or by means of the psychometric tests. The parameters of the PFP300 complex had also completely returned to normal: N250-latency: 273.0 ms (less than 1sd); PFP300-latency: 348.0 ms (less than 1sd). This observation suggests that the analysis of P300 can help to detect and follow minor cognitive deficits in cases of acute hepatic encephalopathy. It further underscores the hepatic etiology as well as the potential reversibility of this type of encephalopathy.

Noninvasive electrophysiological recordings allow to investigate various stages of human visual information processing separately. Luminance and pattern electroretinograms (ERG) contain components originating from anatomically and physiologically different retinal structures while visual evoked potentials (VEP) reflect activity in more central parts of the visual system. Simultaneous recordings of ERGs and VEPs to carefully selected visual stimuli help to relate physiological processes to neural structures, and thus may be employed as an important tool also in clinical investigations. Corresponding experimental data from both basic physiological research as well as from clinical studies are reviewed.

The application of visual evoked potentials (VEP) as a monitoring tool was studied in 40 comatose neurological intensive care patients. With increasing depth of coma, the number of detectable VEP components decreased. In deeply comatose patients, VEP were regularly displayed as a negative wave with a latency of app. 100 ms and an amplitude of app. 8 microV (N100). The administration of promethazine or flunitrazepam used as sedatives produced a decrease of amplitude and an increase of latency of N100 that was reversed within 30 or 60 min respectively. In 10 patients, in which intraventricular pressure (IVP) was measured continuously by means of an intraventricular catheter, it was found that increases of IVP produced a considerable decrease of the amplitude and area of N100; after reduction of the increased IVP, both parameters quickly recovered. These observations indicate that VEP may be a useful tool for neuro-monitoring in neurological intensive care patients.

18 patients with proven multiple sclerosis were examined by pattern reversal visual stimulation. Stimulations were carried out on full fields, foveal areas and horizontal half-fields of single eyes and on half-fields of both eyes. 77% of the patients demonstrated pathological alterations of the potentials in more than one kind of stimulation. In all patients pathological signs could be found, which pointed on the optic nerve. Only the results of three patients suggested a lesion within the central optic pathway. The demonstration of multiple lesions of the optic system in patients with multiple sclerosis is difficult and rarely possible.

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.

Evoked potential monitoring has become a widely used procedure in the evaluation of stuporous patients on neurological intensive care units. Currently BAEP and SEP are preferentially employed. VEP monitoring is a relatively uncommon procedure, because late evoked potentials tend to be relatively unstable, varying in amplitude to a moderate extend from changes of temperature, drugs, attention and the level of consciousness. A valuable approach of VEP monitoring on intensive care units are structures of the visual system at risk in vascular disease of the vertebrobasilar system or during evaluated intracranial pressure (EIP). This study uses the data of 20 stuporous patients presenting with either intracranial mass lesions or vascular diseases of the vertebrobasilar system and 20 control persons. Light emitting diode (LED)-VEP are compared with checkerboard stimulation in control persons using the technique of cross-correlation. The comparison of the control group with patients using LED-VEP allows definition of limits for normal variation as a base for identification of significant changes. Despite methodical restrictions of LED-VEP, our results are in favour of serial studies in patients with EIP. There are no corresponding findings in LED-VEP and vascular lesions of the retrochiasmatic visual system.

Saccades are fast eye movements that occur when the eye makes a refixation movement. Initially clinically relevant physiological and anatomical data are given. The two most frequently used oculographic methods are presented briefly. For clinical use it is particularly important that ocular motor disorders and effects of various drugs are compensated partially by plastic adaptation of central mechanisms. The main diagnostic fields are disorders of brain stem, cerebellum or peripheral oculomotor apparatus. Examination of horizontal and vertical saccades is a useful help in diagnosis of subclinical ocular motor disorders in encephalomyelitis disseminata.