To apply granger causality analysis to investigate changes in directional information flow associated with altered consciousness during psychogenic non-epileptic seizures (PNES).

Impairment of consciousness is one of the most disabling aspects of epilepsy as well as PNES. Mechanisms underlying conscious awareness remain poorly understood. Change in directional flow of information has been suggested as a biomarker for states of consciousness in several studies, such as increased feedback (anterior-to-posterior) flow in awake states and feedforward (posterior-to-anterior) flow in an anesthetized state.

Scalp EEG was recorded from three subjects with suspected PNES undergoing video EEG monitoring for standard clinical care, which confirmed the PNES diagnosis. A reduced bipolar montage was utilized, consisting of the following electrode pairs: F3-F7, P3-T5, F4-F8, and P4-T6, to capture anterior-posterior (frontal-parietal) information flow. Feedforward was defined as posterior to anterior directionality, and feedback was defined as anterior to posterior directionality. Granger causality was calculated over sequential 2 second non-overlapping sliding windows, providing directional flow between anterior and posterior regions.

Ten PNES attacks were recorded in 3 patients (2 females, 1 male, ages 32, 54, & 57). All patients had normal EEG recordings. Increased directionality of feedforward occurred consistently when comparing pre-PNES states to transition to PNES. Of note, all PNES occurred at time of drowsiness or transition to sleep. In all subjects, anterior-posterior information flow was dynamic and changed overtime.

These preliminary findings suggest dynamic changes in the brain occurring during PNES. These results suggest dissociative flow dynamics underlie transition from wakeful state to loss of consciousness during PNES.  In addition, drowsy and sleep state may be more susceptible for transition to PNES. Inclusion of a larger cohort will help further elucidate the relationship of anterior to posterior information flow during states of impaired consciousness.