[EEG anomalies in the prodromic phase of Rasmussen's syndrome. Report of two cases]

Electroencephalographic (EEG) recordings were studied at disease onset in two subjects presenting with Rasmussen's syndrome. Particular attention was paid to abnormalities detected during the prodromic phase before clinical outcome suggested the existence of chronic encephalitis. EEG recordings showed focal, polymorphic abnormalities associated with slow biphasic complexes (SBC). These complexes that are composed of two slow waves with opposite polarity, a 150- to 250-mV peak-to-peak amplitude and a 500-ms duration have only been described in inflammatory syndromes of the central nervous system. Their occurrence at onset of Rasmussen's syndrome are discussed.