Abstracts

Rationale: EEG can be very useful in diagnosing prion infections and has been included in the WHO diagnostic criteria for sCJD. In practice, its value can be optimized when sequential studies are performed. The presence of EEG changes, including periodic sharp wave complexes (PSWC), may vary even at advanced stage. Monitoring the evolution of these findings may alert one to the correct diagnosis as other non-invasive diagnostic modalities are limited. Methods: Observation of a patient with pathologically confirmed rapidly progressive sCJD (MM1) from the clinical onset to death, including EEG studies across 24 day period. Results: An elderly right handed female presented with dizziness, gait disturbance and forgetfulness for 3 weeks. The initial neurological examination was significant only for mildly ataxic gait. In the following 3 weeks, she deteriorated rapidly with progressive worsening of ataxia, startle myoclonus, and cognitive decline leading to akinetic mutism. She died within 10 weeks after clinical onset of her disease. Brain MRIs showed persistent diffuse gyriform hyperintensity in the right more than the left hemisphere on diffusion weighted images. Neuron specific enolase was elevated in the cerebrospinal fluid. Right frontal brain biopsy and pathological studies showed vacuolization in cerebral gray matter, presence of protease resistant prion protein (PrPsc or PrP27-30), and immunopositivity to 3F4 monoclonal antibody. Three weeks after clinical onset, the first EEG showed asymmetric attenuation of background fast activities in the right hemisphere and generalized intermittent rhythmic slowing. The asymmetry became less evident during sleep. EEG monitoring was started 18 days later and lasted for 5 days. Compared to the initial record, progressive diffuse background slowing and intermittent suppression was noted. The amount of generalized intermittent rhythmic slowing remained stable and the asymmetric attenuation in the right hemisphere persisted throughout the entire period of observation. Abundant anteriorly dominant PSWCs were observed as intermittent bursts. Their temporal and spatial features, including an initial anterior positive deflection and a striking dominance in the right hemisphere, persisted throughout the monitoring. PSWCs attenuated briefly in response to intravenous lorazepam, though no clinical change was noted. No definite electrographic seizure were identified. The patient expired at home 4 weeks after the last EEG. Conclusions: The value of EEG in diagnosing prion diseases can be improved by repeated recordings. Close monitoring of serial EEG changes and correlation with clinical symptoms may guide one to the correct diagnosis early. As in our case, PSWC, which can be asymmetric, may persist into advanced stage of sCJD and should not be confused with periodic lateralized epileptiform discharges from other causes. In some cases as in our patient, serial EEG may provide evidence of prion disease and support further definitive invasive evaluation such as a brain biopsy.