Measuring the Severity of Neonatal Seizures: Temporal-Spatial Burden

The American Clinical Neurophysiology Society recommends measuring neonatal seizures' severity by their frequency (number of seizures-anywhere per hour), burden (percentage of time with seizures-anywhere), or on a region-by-region, temporal-spatial basis. This study compares two reduced-channel montages for temporal-spatial seizure burden analyses and examines the agreement of seizures' quantification among these three methodologies.

A convenience sample of 10 neonatal electroencephalograms was annotated for the beginnings and ends of seizures, which appeared anywhere in the full neonatal montage, then repeated on a more precise, region-by-region basis using 2 reduced-channel montages A and B. Seizure severity was measured by seizures-anywhere frequency, seizures-anywhere burden, and temporal-spatial seizure burdens using montages A and B. The results were compared by measuring their correlation and by linear regression modeling.

Seizures-anywhere frequency was correlated with seizures-anywhere burden (ρ = 0.77). However, a narrow range of seizures-anywhere frequencies corresponded with a broad range of seizures-anywhere burdens. Although there was high correlation between seizures-anywhere burdens and temporal-spatial seizure burdens (ρ = 0.92 montage A, ρ = 0.90 montage B), seizures-anywhere burdens were insensitive to variations in the spatial aspects of seizures, which were highly prevalent even in this small sample set. After adjusting for intrareader variability, the temporal-spatial seizure burdens measured by montages A and B were not significantly different (P = 0.56).

The severity of neonatal seizures is poorly represented by simple measures such as seizures-anywhere frequencies or burdens. The use of temporal-spatial seizure burden measurements is supported in work where great precision in quantifying neonatal seizures is required.