PMC8256673_01
EEG findings of alternating focal slowing. EEG during drowsiness, longitudinal bipolar montage (low frequency filter = 1 Hz, high frequency filter = 30 Hz). (A) During a period of left hemiplegia, continuous delta slowing was noted over the right hemispheric derivations, maximal in the right temporal head region (F8, T8, P8). Quantitative EEG (qEEG) showed accentuation of delta on the right on the asymmetry spectrogram tool (red arrow), and a denser delta band on the right on the rhythmicity spectrogram tool (blue arrows). (B) About 24 hours later, a right hemiparesis was noted. The EEG showed resolution of the right hemispheric slowing, and the presence of continuous delta slowing over the left hemispheric region, maximal in the left temporal head region (F7, T7, P7). QEEG shows increased left sided delta asymmetry (red arrow), and denser delta band on the left (blue arrows).
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Over the first several hours of the recording, a marked asymmetry developed (Fig. 1A), with resolution of the left hemispheric slowing but persistent focal slowing in the right hemisphere. Prolonged EEG monitoring was restarted and showed asymmetric slowing involving the left hemispheric derivations greater than right (Fig. 1B).
EEG findings of 14 Hz positive spike bursts. EEG during drowsiness, longitudinal bipolar montage (low frequency filter = 1 Hz, high frequency filter = 30 Hz). (A) 14 Hz positive spikes ("ctenoids") were noted throughout the recording. These have also been seen in encephalopathies due to Reye syndrome. (B) Quantitative analysis, showing a sharp peak at 14 Hz (red arrow).
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MRI brain was performed and did not show any evidence of ischemic stroke, or any other definite cause for the symptoms. 14 Hz positive spike bursts (ctenoids) were also observed throughout monitoring (Fig. 2).