FVEPs in Creutzfeldt-Jacob disease: Waveforms and interaction with the periodic EEG pattern assessed by single sweep analysis
Department of Neurophysiology, C. Besta National Neurological Institute, Via Celoria 11, 20133 Milan, Italy. Clinical Neurophysiology
(Impact Factor: 3.1).
04/2005; 116(4):895-904. DOI: 10.1016/j.clinph.2004.11.019
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.
Available from: Sophie Hamelin
- "During flash stimulation at 1 Hz , Visani et al . ( 2005 ) observed the occurrence of large wave complexes that replaced spontaneous periodic sharp wave complexes . This phenomenon was present in nine CJD patients , eight of whom filled the criteria for giant VEPs ( Visani et al . , 2005 ) . Giant VEPs may be explained by the loss of cortical inhibition as a result of diffuse neuronal dropout with consecutive hyperexcitability . In rare cases , such as ours , giant VEPs in CJD may lead to LFPPR ."
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ABSTRACT: Intermittent photic stimulation is performed during an EEG to evoke photoparoxysmal response. When they appear triggered by low-frequency stimulation in children, they are suggestive of rare diagnosis, that is, neuronal ceroid lipofuscinosis. Among adults, their significance is less well understood. Low-frequency (<5 Hz) intermittent photic stimulation was performed over a period of 5 years during adult standard EEG. This retrospective study included all patients exhibiting low-frequency photoparoxysmal response. Five cases were identified. Three of them presented with active epilepsy (two progressive myoclonus epilepsy, one unclassifiable), two had visual deficiency, and three had dementia. The etiologies were MELAS (two), Creutzfeldt-Jakob disease (one), Kufs disease (one), and remained undetermined for one patient. In all patients, low-frequency photoparoxysmal response was observed years or months before the final diagnoses have been reached. Low-frequency photoparoxysmal response, classically associated with childhood progressive myoclonus epilepsy, seems to have a wider etiological spectrum in adult population. Moreover, this neurophysiological feature could be present before the final diagnosis in most cases. Systematically testing low frequencies during intermittent photic stimulation even during adult EEG seems warranted, particularly in a context of severe progressive neurologic deterioration.
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Based on the current criteria, the diagnosis of “possible” or “probable” variant Creutzfeldt–Jakob disease (vCJD) implies the absence of periodic sharp wave complexes (PSWCs) in the electroencephalogram (EEG). To verify this point, we investigated the development of the EEG changes along the course of the disease in a pateint with vCJD.Methods
Long-lasting EEG-polygraphic recordings were performed once a month during the last year of illness.ResultsWe found the occurrence of a typical EEG periodic pattern in the late clinical stage of the vCJD patient.InterpretationIn the light of our finding, the diagnostic criteria for vCJD should be amended to include the possibility of a typical periodic EEG in advanced stages of disease in cases with long survival. Ann Neurol 2006;59:423–427
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ABSTRACT: Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common human prion disease. EEG is the method of choice to support the diagnosis of a human prion disease. Periodic sharp wave complexes (PSWCs) on the EEG usually indicate a progressive stage of CJD. However, PSWCs only become obvious at around 8 to 12 weeks after the onset of clinical symptoms, and in a few cases, even later. Independent component analysis (ICA) is a new technique to separate statistically independent components from a mixture of data. This study recruited seven patients who fit the criteria of CJD between 2002 and 2005 and 10 patients with Alzheimer's disease (AD) as control subjects. Using an ICA algorithm, we were able to split typical PSWCs into several independent temporal components in conjunction with spatial maps. The PSWCs were not observed in the initial EEG studies of patients with either AD or CJD. However, the ICA algorithm was able to extract periodic discharges and epileptiform discharges from raw EEG of patients with CJD at as early as 3 to 5 weeks after disease onset. Such discharges otherwise could hardly be discerned by visual inspection. In conclusion, ICA may increase the sensitivity of EEG and facilitate the early diagnosis of CJD.
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