Abstracts

Rationale: This study uses independent component analysis (ICA) to investigate the dynamic interactions of independent dipoles in the EEG of myoclonus. Using ICA and dipole fitting algorithm, the mixed dynamic signals of scalp recorded electroencephalography (EEG) could be statistically separated into independent dipoles, which are presumed to be the cerebral generators of the recorded EEG. The complex dynamics between the independent dipoles in myoclonus could be characterized to reveal the cerebral generators and propagation pathways. Methods: Retrospective EEG recordings from patients (n=7) with persistent myoclonus were selected according to the approved protocol by the institutional review boards. These EEGs were processed in EEGLAB (http://www.sccn.ucsd.edu/eeglab/). After computing ICA, the components of interest in generating myoclonus were identified using statistical analysis, autocorrelation. New EEGs were reconstructed and compared to the original EEGs to visually review the adequacy of component selection. Dipole fitting of these components was performed and mapped on a 2-d head model. The dynamic interactions of these components were reviewed on a video clip to review the probable propagation pathways for myoclonus. Results: In 7 subjects with myoclonus, which was confirmed by clinical inspection and video recordings during the EEG recording, the locations of the cerebral generators were identified. Most of the fitted dipoles were dispersed within the mesial frontal lobe regions and the upper brainstem, with some scattering in the occipital/temporal lobes. The interactions and dynamic relationship of the anteriorly and posteriorly located dipoles were further analyzed. It was noted that there is a general pattern of front to back propagation of the dipole activity during myoclonus. Conclusions: 1) A cerebral network involving the cerebral generators in the mesial frontal region and upper brainstem are implicated in generating myoclonus. 2) The mesial frontal region might be involved in the initiation of the myoclonus, with subsequent propagation of the activity to the upper brain stem.