Abstracts

Rationale: For over 90 years, physicians have been using electroencephalography, EEG, to record the electrical activity of the brain with high temporal resolution, establishing it as a potential testing method for diagnosis or prognosis of a variety of neurological disorders and disease states, including sleep disorders, dementia, and epilepsy. Various analysis methods have been proposed to quantify variances in EEG characteristics usually only subjectively described by ‘experts.’ One method derives quasi-stable topographical maps from the recording to represent the global activity of the brain at rest called microstates. Previously published studies using this method found the same four microstate classes were consistently acquired to represent the brain function of a variety of disease states and healthy controls. We applied this technique to a cohort of patients with multi-drug resistant temporal lobe epilepsy (TLE) in an effort to confirm these patients’ microstates would have topographical similarity to known microstate classes from patients without epilepsy. We evaluated statistical parameters commonly used to assess microstates: global explained variance (GEV), global field potential (GFP), duration, coverage, occurrence frequency, and transition probabilities (TP). Methods: Routine awake EEG recordings from 39 TLE patients (age range: 25-59, male and female) were collected. EEGLAB toolbox for Matlab was used for preprocessing recordings and microstate analysis. Microstates for each patient were visually sorted into four common microstate classes from previously published studies based on topographical similarity. We categorized patients as completely seizure free (SF) or not (NSF) and compared the microstate parameters between the two groups. Results: The microstates of the patients with TLE proved topographically similar to those of patients without epilepsy. However, there were no significant differences in the microstate parameters in SF versus NSF patients. There were also no significant differences in the parameters in patients with right TLE when compared to the patients with left TLE. Conclusions: Patients with multi-drug resistant TLE did have microstate classes that proved topographically similar to those of previously published studies. However, there were no significant differences in the statistical parameters in the seizure outcome comparison nor the different hemisphere comparison. Establishing variances between the statistical measures of patients with TLE in comparison to healthy controls may also have clinically relevant findings. Funding: This work prepared by employees of the Federal Government as part of their official duties.