PMC9792293_01
Electroencephalography upon admission. A: series of extreme delta brushes are visible in the frontopolar EEG channels showing the typical pattern of high-frequency beta activity superimposed on periodic blunt delta waves (marked with red triangles). One "extreme delta brush" (black rectangle) is highlighted in the right panels. The upper right panel shows the enlarged detail section of the EEG in an epoch of 1 s (enlarged in the right upper panel). The power spectrum of this epoch (lower right panel) displays the mixed frequency spectrum of beta activity (20-30 Hz) and delta activity (peak at 1 Hz). Importantly, the frontal intermittent fast activity is in stereotyped association with the periodic delta activity and not present in delta down-states. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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The EEG on admission displayed normal background activity, but intermittent frontal fast activity superimposed on high amplitude periodic delta waves (Fig. 1).
EEG recording 3 days (A) and 4 weeks (B) after initial presentation. A: 3 days after admission, the EDB pattern persisted. EEG shows unchanged high-frequency beta activity superimposed on periodic blunt delta waves in a 40 s EEG epoch. In this time resolution, the sinusoid beta activity is only visible as short beta bursts in the surface-negative delta up-phase (inlet in panel A shows one enlarged beta burst). Time-frequency spectrum confirms the time-locked co-occurrence of delta and beta waves (arrows). B: EEG after 4 weeks shows complete remission of the pathological EEG pattern and a normalization of background activity.
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To confirm this EEG finding, a 20-minute standard EEG in wakefulness was repeated 3 days later, showing the identical frontal EEG pattern (Fig. 2A). Follow up EEG after 4 weeks showed a complete remission of the encephalopathic EEG pattern, including the EDB (Fig. 2B).