# Distributed EEG source localization of hypsarrhythmia in west syndrome: a standardized, low-resolution, brain electromagnetic tomography (sLORETA) study

## TL;DR

This study uses EEG source localization to better understand hypsarrhythmia in West syndrome, revealing abnormal brain activity patterns in affected patients.

## Contribution

The study introduces a novel use of sLORETA to localize distributed EEG sources in West syndrome, revealing specific brain regions and frequency patterns.

## Key findings

- West syndrome patients showed significantly increased current density in all frequency bands compared to controls.
- Delta band changes were most prominent in the right frontal lobe, particularly the middle frontal gyrus.
- Abnormal activity showed a low-to-high and anteroposterior gradient in neuronal activity.

## Abstract

West syndrome is a developmental epileptic encephalopathy characterized by epileptic spasms, hypsarrhythmia, and neurodevelopmental regression. Despite well-defined clinical criteria, hypsarrhythmia remains challenging to characterize due to its disorganized nature. Recent advancements in quantitative electroencephalography (qEEG) provide a more objective approach to understanding the electrophysiology of this disorder. This study aims to use qEEG and distributed source localization to increase the understanding of hypsarrhythmia in West syndrome.

This study involved 34 participants, 17 diagnosed with West syndrome (West syndrome group) and 17 healthy controls (control group). All participants underwent 30-minute sleep EEG recordings, and data were analyzed using standardized low-resolution brain electromagnetic tomography (sLORETA) to assess the current density distribution across four frequency bands (delta, theta, alpha, and beta). Statistical non-parametric analysis was performed to compare neural activity between the West syndrome and control groups.

Significant increases in current density were observed across all frequency bands in the West syndrome group, with the most pronounced difference found in the delta band, followed by theta, alpha, and beta bands. The most prominent changes in the delta band were noted in the right frontal lobe, particularly in the middle frontal gyrus. In the theta band, the most significant differences were observed in the right middle frontal gyrus, while the alpha and beta bands showed notable changes in the left inferior frontal gyrus and the right superior frontal gyrus, respectively.

Our study demonstrates a significant increase in current density across all frequency bands, with the most pronounced differences observed in the delta band in patients with West syndrome. These changes exhibit a predominant anterior distribution, particularly within the frontal lobe. The findings provide new insights into the electrophysiology of hypsarrhythmia, highlighting the presence of a low-to-high and anteroposterior gradient in neuronal activity. These results contribute to the growing body of research on West syndrome and emphasizes the value of qEEG in enhancing the interpretation of hypsarrhythmia.