Abstracts

Full array EEG remains the gold standard for the diagnosis and quantification of neonatal seizures (NS). However, amplitude-integrated EEG (aEEG) is currently being introduced into the USA as an adjunct for NS detection. aEEG displays a single, highly processed EEG channel interpreted at the bedside by neonatologists to reveal background activity and NS. This study was designed to measure the theoretical and practical limits of NS detection by a single channel of standard EEG, as well as aEEG.
Objectives: a) To describe the characteristics (site of onset, duration, and peak-to-peak (p-p) amplitude) of a large number of NS recorded by full array EEG. b) To determine which NS characteristics are associated with their visibility in a single channel (C3-C4), used to simulate the raw signal from which aEEG tracings are derived. c) To determine the sensitivity of NS detection by neonatologists using aEEG tracings., Full array neonatal EEGs with NS were obtained from a library of digital EEGs and were reviewed for EEG background and NS characteristics. The study was powered to obtain a 95% confidence interval of [plusmn] 5% around the percentage of seizures identified using aEEG. The presence, duration, and p-p amplitude of each seizure were simultaneously noted in a single EEG channel derived from C3-C4. aEEGs were generated from this same channel and were independently reviewed by neonatologists for background and NS., A total of 851 seizures from 125 full array EEGs recorded from 121 neonates were analyzed. The conceptional ages were 34 to 50 weeks. Mean seizure duration was 132 seconds (range: 10-2314 seconds). Mean seizure frequency was 7 NS per hour (range: 0.5 to 21 NS per hour). Mean seizure burden (the percent of time that the full array EEG showed NS at any location) was 24.8% (range: 0.7 to 86.9%). Seizure frequency did not predict seizure burden (r=0.21; NS). Since 94% of the 125 full array EEGs had at least one NS visible at C3-C4, and 78% of all 851 seizures appeared in the C3-C4 channel, the theoretical ceilings of sensitivity of NS detection in a single EEG channel and aEEG were high. However, NS were significantly briefer and lower in amplitude at C3-C4 compared to NS seen on full array EEG (p [lt]0.001). Status epilepticus (SE) occurred in 18/125 (14.4%) of full array EEGs, but in only 8/125 (6.4%) of the single channel studies (p=0.038). Furthermore, some neonatologists detected NS in just 22-42% of the aEEG records. Likewise, only 12-22% of individual seizures were detected on aEEG., Electrographic seizure burden in sick neonates is high. Accurate measurement of seizure burden requires detailed characterization, rather than simple seizure counts. Although the theoretical ceiling on sensitivity for NS detection in the C3-C4 channel is high, neonatologists detected fewer than one quarter of seizures using aEEG tracings derived from this channel.,