Authors :
Presenting Author: Soudeh Mostaghimi, MS – University of California - Irvine
Makoto Miyakoshi, PhD – Department of Psychiatry – University of Cincinnati Collage of Medicine; Daniel Shrey, MD – Children’s Hospital Orange County; Shaun Hussain, MD – Division of Pediatric Neurology – University of California, Los Angeles; Beth Lopour, PhD – Biomedical Engineering – University of California-Irvine
Rationale:
Infantile Epileptic Spasms Syndrome (IESS) is a rare form of epilepsy that typically begins before the age of one. In addition to early diagnosis, minimizing the time to effective treatment can decrease the severity of developmental delays associated with the condition. However, there are no established quantitative biomarkers of treatment response to guide clinical decision making. Phase-amplitude coupling (PAC) in the electroencephalogram (EEG), which is believed to reflect the dynamic integration of neural activity, is elevated in patients with IESS relative to healthy controls, but the impact of treatment on PAC is unknown. Therefore, our goal was to test PAC as a candidate biomarker of treatment response in IESS.
Methods:
Scalp EEG recordings during sleep were retrospectively obtained from patients at UCLA Children's Hospital. Data were collected from 40 children with epileptic spasms, both before and after treatment, as well as 20 control subjects approximately matched in age. As candidate metrics of treatment response, we tested two PAC methods: mean vector length (MLV) from Canolty et al. (2006) and modulation index (MI) from Tort et al. (2010). Using these two methods, we measured the strength of coupling between the delta band (3-4 Hz) phase and the gamma band (35-70 Hz) amplitude in both IESS and control subjects. We compared pre- and post-treatment IESS values to the controls, and we tested for differences in post-treatment values for those that did and did not respond to treatment.
Results:
Consistent with prior results from Miyakoshi et al. (2021), individuals with IESS (prior to treatment) had significantly higher PAC values than control subjects, as measured by MI and MVL (Table 1). This difference was statistically significant in nearly all channels. Across all IESS subjects, pre-treatment MI and MVL were significantly higher than post-treatment values (Table 1). However, individuals who did not respond to treatment (post-treatment non-responders) had higher MI and MVL values compared to those who responded (post-treatment responders; Table 1).
Table 1. PAC as a biomarker of treatment response in IESS. For each comparison, the channels with significant differences are listed for the Bonferroni-corrected significance level (P< 0.0026) and uncorrected significance level (P< 0.05).