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Objective: To characterise flash visual evoked potentials(FVEPs) in 20 patient s with Creutzfeldt-Jacob disease (CJD),and assess the relationships between spo ntaneous EEG patterns and the responses to individual stimuli. Methods: We analy sed the shape and time course of periodic sharp wave complexes(PSWCs) and respon ses to 1 Hz flashes. In nine patients, we applied an algorithm based on an autor egressive model with exogenous input (ARX) to estimate responses to individual r andom flashes and their interaction with PSWCs. Results:The FVEPs included P1 an d N1 components in all patients, and the P2 peak in 18. Eight patients showed gi ant FVEPs (N1-P2 > 60 V), all of whom had an MM polymorphism in codon129 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 ave rage 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 stimul us and previous PSWC, but their amplitude had an inverse relationship with the i nterval length.Conclusions: Giant responses to flash stimuli are a common findin g in CJD patients (40%of our cases). Single sweep ARX analysis showed that PSWC s were followed by a period of partial refractoriness, which prevented most of t he 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. Significance: 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.
Objective: To characterise flash visual evoked potentials (FVEPs) in 20 patient s with Creutzfeldt-Jacob disease (CJD), and assess the relationships between spo ntaneous EEG patterns and the responses to individual stimuli. Methods: We analy sed the shape and time course Of nine patients, we applied an algorithm based on an autor egressive model with exogenous input (ARX) to estimate responses to individual r andom flashes and their interaction with PSWCs. Results: The FVEPs included P1 an d N1 components in all patients, and the P2 peak in 18. Eight patients showed gi ant 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 pati ents with a normal or slightly enlarged a rage 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 interval between the stimul us and previous PSWC, but their amplitude had an inverse relationship with the i nterval length. Conclusions: Giant responses to flash stimuli are a common findin g in CJD patients (40% of our cases). Single sweep ARX analysis showed that PSWC s were followed by a period of partial refractoriness, which prevented most of t he 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 favored neuronal synchronisation. Significance: 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.