Figure 3

Scalp HFO rates correlate with seizure frequency and decrease after successful epilepsy surgery. (a) Scalp HFO rates in HFO area channels correlate with seizure frequency (Spearman’s rho 0.740, p < 0.001). Presurgical HFO rates are indicated by circles and postsurgical HFO rates by triangles. Pre- and postsurgical HFO rates are connected by a solid line for the patients for whom postsurgical seizure freedom was achieved (Engel I) and by a dotted line for patients for whom postsurgical seizure freedom was not achieved (Engel II–IV). The gray area on the bottom of the graph represents the HFO range corresponding to seizure freedom, based on the 0.124 HFO/min threshold, as established by the ROC curve. 17 of 28 scalp EEG recordings were classified correctly as true positive, ten as true negative, and only one was a false negative. (b) Median scalp HFO rates in HFO area channels decrease after surgery in the patients for whom postsurgical seizure freedom was achieved (Wilcoxon signed-rank: p = 0.005, z = 2.803) from 0.287 HFO/min (iqr 0.107) in the presurgical to 0.015 HFO/min (iqr 0.029) in the postsurgical EEG.