# EEG biomarkers of microstructural damage in normal-appearing white matter among patients with neuromyelitis optica spectrum disorder: A DTI-EEG combined study

## TL;DR

This study finds that EEG can detect subtle brain damage in patients with neuromyelitis optica spectrum disorder, even in areas that look normal on standard scans.

## Contribution

This is the first study to explore EEG biomarkers for white matter damage in neuromyelitis optica spectrum disorder.

## Key findings

- Seventeen of twenty main white matter tracts showed microstructural damage in patients with NMOSD.
- EEG functional connectivity indices in theta and gamma bands strongly correlated with white matter integrity.
- EEG biomarkers were linked to disease severity, disability, and cognitive performance in patients.

## Abstract

This study aimed to explore the potential of EEG in monitoring the extent of white matter microstructural damage in patients with neuromyelitis optica spectrum disorder (pwNMOSD) for the first time.

Thirty-two pwNMOSD and 20 healthy controls were recruited and all received DTI scan, while the pwNMOSD underwent also resting state EEG (rs-EEG). DTI indices were compared between two groups to identify impaired WM tracts in pwNMOSD. Correlations between the 240 rs-EEG indices (including spectral and functional connectivity indices in five frequency bands of six brain regions) and the fractional anisotropy (FA) of the impaired WM fiber tract were calculated to identify the rs-EEG biomarkers of WM microstructural damage. The relationships of the identified rs-EEG biomarkers with disease characteristics and cognitive function were further analyzed.

Seventeen of the 20 main WM tracts were found to have microstructural damage in pwNMOSD. The functional connectivity indices were significantly and positively correlated with the FA of WM tracts in pwNMOSD, especially the coherence and phase locking value strengths in the theta and gamma frequency bands (r=0.40-0.61). Different patterns between the rs-EEG indices in different frequency bands and the integrity of WM tracts were revealed. These identified rs-EEG indices were significantly related to patients’ disease characteristics (number of attacks (r=-0.44), expanded disability status scale score (r=-0.41--0.47), serum anti-glial fibrillary acidic protein level (r=-0.43)) and cognitive functions (symbol digit modality test score, r=0.46).

The functional connectivity of rs-EEG may serve as important biomarkersof WM microstructural damage in NMOSD.