Theta Power Spectral Analysis of Electroencephalography in Infantile Spasms: Before and After ACTH Treatment

Background: Infantile spasms (ISs) were thought to be a kind of intractable seizure, and diagnosed with one or many of the following: nodding spasm clusters, mental retardation, or showing up as interictal hypsarrhythmia on electroencephalograms. While these spasms represent a major therapeutic challenge, limited parameters are available to evaluate their status before and after treatment. The American Academy of Neurology/Child Neurology Society recommends that administration of adrenocorticotropic hormone (ACTH) is effective for short-term treatment of children with IS. To determine whether there were differences in EEG manifestations, we performed a power spectral analysis of the EEG of hypsarrhythmia to determine the effects of ACTH, before and after its administration. Methods: After obtaining informed consents from guardians, we recruited children younger than 3 years of age, who fulfilled both the definition of IS and were receiving other antiantiepileptic drugs (valproic acid, vigabatrin, lamotrigine, etc.) in Taipei Medical University-affiliated hospitals from November 2009 to June 2012. Patients with IS were administered synthetic ACTH subcutaneously for 2 weeks following a 6-week tapering-off period. The data were later analyzed by fast Fourier transformation (FFT) analysis. Results: The average EEG voltage of five patients before ACTH treatment for all the brain regions ranged from 92.21 to 153.02 μV (mean: 106.64 ± 12.36 μV; n= 5). We found that the frequency corresponding to the theta wave power (7.8. Hz) showed a prominent elevation in all of the five IS patients with hypsarrhythmia. Before commencing ACTH treatment, the theta wave power was in the range of 14.77-27.52 μV (mean: 21.05 ± 2.15 μV; n= 5). Two weeks after ACTH treatment, the theta wave power decreased to a range of 1.81-6.01 μV (mean 3.81 ± 0.67; n= 5). Thus, we conclude that administration of ACTH induced a significant decrease in the theta wave power (mean decrease: -80.95 ± 3.42%; p<0.05; n= 5). Conclusion: Performing an FFT spectrum analysis of an EEG such as EEG of the hypsarrhythmia can serve as an objective tool to understand specific signal processing in children with IS. This is the first finding to discover the inhibitory effect of ACTH on the theta wave power. The inter-relationship between ACTH and theta power needs to be elucidated in the future studies.