Contribution of Cross-Phase-Amplitude Coupling to Relapse in Infantile Epileptic Spasms Syndrome

Relapse poses a significant challenge after the initial effectiveness of adrenocorticotropic hormone treatment in infantile epileptic spasms syndrome (IESS), involving complex neuronal oscillations interactions. Phase-amplitude coupling (PAC) extensively characterizes mutual interactions among rhythmic activities in pathological conditions. However, the relapse-related PACs between brain regions across various frequencies remain unclear. Here, noise-assisted multivariate empirical mode decomposition based cross-PAC was utilized to evaluate the long-term prognosis of IESS. Our results revealed that stronger cross-PACs at relatively lower frequencies in the relapse group compared to the nonrelapse group, while the trend was reversed for higher frequency cross-PACs. The hub regions within functional networks were identified as frontal and occipital lobes. Combining cross-PAC with the burden of amplitudes and epileptiform discharges score demonstrated optimal performance in identifying relapse in IESS. We suggested the significance of cross-PAC in assessing the outcome of IESS.