FVEPs in Creutzfeldt-Jacob disease: waveforms and interaction with the periodic EEG pattern assessed by single sweep analysis.
ABSTRACT To characterise flash visual evoked potentials (FVEPs) in 20 patients with Creutzfeldt-Jacob disease (CJD), and assess the relationships between spontaneous EEG patterns and the responses to individual stimuli.
We analysed the shape and time course of periodic sharp wave complexes (PSWCs) and responses to 1 Hz flashes. In nine patients, we applied an algorithm based on an autoregressive model with exogenous input (ARX) to estimate responses to individual random flashes and their interaction with PSWCs.
The FVEPs included P1 and N1 components in all patients, and the P2 peak in 18. Eight patients showed giant FVEPs (N1-P2>60 V), all of whom had an MM polymorphism in codon 129 of the prion protein gene; in seven cases, the presence of giant FVEPs correlated with a prominent and almost continuous periodic EEG pattern. Giant N1-P2 abnormally spread on the anterior scalp regions, and had a different waveform distribution from that of the PSWCs. In five patients with a normal or slightly enlarged average N1-P2 amplitude, single sweep (ARX) analysis revealed a period of relative refractoriness following individual PSWCs. In four patients with 'giant' FVEPs, the individual responses occurred regardless of the interval between the stimulus and previous PSWC, but their amplitude had an inverse relationship with the interval length.
Giant responses to flash stimuli are a common finding in CJD patients (40% of our cases). Single sweep ARX analysis showed that PSWCs were followed by a period of partial refractoriness, which prevented most of the individual responses to flashes, but not giant FVEPs. The association between prominent spontaneous paroxysms and giant FVEPs suggests that both are due to a common hyperexcitable change favouring neuronal synchronisation.
Our data contribute to clarifying the debated problem of the occurrence of giant FVEPs in CJD and their relationships with the spontaneous periodic EEG pattern.
- [show abstract] [hide abstract]
ABSTRACT: Serial EEG changes have been studied in three patients with histologically confirmed Jakob-Creutzfeldt disease. Periodic sharp waves are not necessarily limited to the late stages of the disease. They were found in the initial recording in all three cases and helped establish the correct diagnosis at an early stage. The sharp waves may be asymmetrical or localized early in the disease, but eventually become diffuse and bisynchronous. As the disease progresses there is gradual slowing and flattening of background activity and lengthening of the interval between periodic complexes.Serial visual evoked responses were investigated in one patient who showed an exaggerated response to visual stimuli. Initially the responses were markedly enlarged. As the disease progressed there was an increase in latency and decrease in amplitude of early components and a reversal of polarity in the late part of the response.Possible mechanisms responsible for the generation of periodic discharges and abnormal visual evoked responses are discussed, and it is suggested that many of these changes might reflect a loss of normal inhibitory influences on the cortex.RésuméL'évolution de l'electroencéphalogramme a été suivie chez trois cas de la maladie Jakob-Creutzfeldt, chacun confirmé par examen histologique. Les ondes aiguës périodiques ne sont point limitées à la période avancée de la maladie. Elles sont même apparues sur le premier tracé chez les trois cas et ont servi à etablir nettement le diagnostic au début de la maladie. Les ondes aiguës peuvent être localisées ou asymétriques au commencement mais, éventuellement, elles deviennent répandues et bisynchrones. A mesure que la maladie s'aggrave l'activité de fond devient plus lent et plus bas tandis que l'intervalle entre les complexes périodiques devient plus court.Les réponses corticales évoquées à la stimulation visuelle ont été examinées chez un malade montrant une réponse exagérée à toute stimulation visuelle. Les réponses sont nettement exagérées au début. Au fur et à mesure que la maladie progresse les premières ondes montrent un amplitude diminuée et un retard prolongé tandis que les ondes tardives changent de polarité.Les différents mécanismes possiblement responsables pour les ondes aiguës périodiques et les potentiels évoqués corticaux exagérées sont discutés. Il est suggeré que ces changements peuvent indiquer une diminution des influences inhibitrices normales du cortex.Electroencephalography and Clinical Neurophysiology 09/1973; 35(2):133-42.
- [show abstract] [hide abstract]
ABSTRACT: A parametric method of identification of movement-related brain macropotentials on a single trial basis through an ARX (autoregressive with exogenous inputs) algorithm is presented. The basic estimation of the information contained in the single trial is taken from an average carried out on a sufficient number of trials, while the noise sources, EEG and EOG are characterized as exogenous inputs in the model. The simulations as well as the experimental results confirm the capability of the model to drastically improve the signal/noise ratio in each single trial and to satisfactorily identify the contributions of signal and noise in the overall recording. This way, using the same algorithm, a particularly efficient reduction of ocular artifacts is also achieved. The movement-related brain macropotentials recorded in three subjects show a high degree of variability from trial and this effect seems to be related to programming processes and evaluation of errors.International Journal of Psychophysiology 06/1994; 16(2-3):163-74. · 2.04 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: We report two patients who developed isolated visual symptoms and signs as initial manifestations of Creutzfeldt-Jakob disease (CJD). Both patients had normal conventional T1- and T2-weighted brain magnetic resonance (MR) images; in one patient, early cortical abnormalities were detected by diffusion-weighted and fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Results from the cerebrospinal fluid assay for the 14-3-3 brain protein were also negative in one patient, despite pathologic confirmation of CJD at autopsy. The Heidenhain variant of CJD should be considered in all patients who present with isolated visual manifestations, including homonymous hemianopsia and normal conventional brain MRI. Diffusion-weighted and FLAIR MRI may demonstrate early cortical abnormalities in patients with CJD. The CSF assay for the 14-3-3 protein may be normal, even in pathologically confirmed cases.Journal of Neuro-Ophthalmology 07/2001; 21(2):99-102. · 1.63 Impact Factor