Purpose: Arousal is the most primitive, powerful instinct with survival benefit present in all vertebrates. Even though the arousal systems are classically viewed as "ascending" brainstem phenomena, there is a "descending" cortical feedback system that maintains consciousness. In this study, we provide electrophysiological confirmation that seizures localized to the anterior cingulum can behaviorally manifest as paroxysms of arousal from sleep.
Methods: Temporal dynamics of arousal induced by anterior cingulate seizures were analyzed by using multiple modalities including stereoelectroencephalography (phase lag index and phase amplitude coupling), lead-1 ECG (point-process heart rate variability analysis) and diffusion tractography (DTI).
Results: The ictal arousal was associated with an increase in synchronization in the alpha band and an increase in local theta or alpha-gamma phase-amplitude coupling. In comparison to seizures that lacked clinical manifestations, ictal arousal was associated with an increase in heart rate but not heart rate variability. Finally, DTI demonstrated degeneration in white fiber tracts passing between the anterior cingulum and anterior thalamus ipsilateral to the epileptogenic cortex. The patient underwent resection of the anterior cingulum, and histopathology confirmed focal cortical dysplasia type II.
Conclusion: Anterior cingulate seizures inducing behavioral arousal have identifiable autonomic and EEG signatures.
Keywords: Anterior cingulate; Arousal; Heart rate variability; Hypnopompic seizure; Phase lag index; Phase-amplitude coupling.