Epilepsia Open (Feb 2024)

EEG‐based spatiotemporal dynamics of fast ripple networks and hubs in infantile epileptic spasms

  • Ioana M. A. Samfira,
  • Aristea S. Galanopoulou,
  • Hiroki Nariai,
  • Jonathan M. Gursky,
  • Solomon L. Moshé,
  • Berj L. Bardakjian

DOI
https://doi.org/10.1002/epi4.12831
Journal volume & issue
Vol. 9, no. 1
pp. 122 – 137

Abstract

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Abstract Objective Infantile epileptic spasms (IS) are epileptic seizures that are associated with increased risk for developmental impairments, adult epilepsies, and mortality. Here, we investigated coherence‐based network dynamics in scalp EEG of infants with IS to identify frequency‐dependent networks associated with spasms. We hypothesized that there is a network of increased fast ripple connectivity during the electrographic onset of clinical spasms, which is distinct from controls. Methods We retrospectively analyzed peri‐ictal and interictal EEG recordings of 14 IS patients. The data was compared with 9 age‐matched controls. Wavelet phase coherence (WPC) was computed between 0.2 and 400 Hz. Frequency‐ and time‐dependent brain networks were constructed using this coherence as the strength of connection between two EEG channels, based on graph theory principles. Connectivity was evaluated through global efficiency (GE) and channel‐based closeness centrality (CC), over frequency and time. Results GE in the fast ripple band (251–400 Hz) was significantly greater following the onset of spasms in all patients (P central > anterior, Kruskal‐Wallis P < 0.001), with maximum CC over the centroparietal channels in 10/14 patients. Additionally, this anteroposterior gradient in CC connectivity is observed during spasms but not during the interictal awake or asleep states of infants with IS. In controls, anteroposterior gradient in fast ripple CC was noted during arousals and wakefulness but not during sleep. There was also a simultaneous decrease in GE in the 5–8 Hz range after the onset of spasms (P < 0.05), of unclear biological significance. Significance We identified an anteroposterior gradient in the CC connectivity of fast ripple hubs during spasms. This anteroposterior gradient observed during spasms is similar to the anteroposterior gradient in the CC connectivity observed in wakefulness or arousals in controls, suggesting that this state change is related to arousal networks.

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