Suppression of deep brain stimulation artifacts from the electroencephalogram by frequency-domain Hampel filtering

Objective: Currently, electroencephalography (EEG) cannot be used to record cortical activity during clinically effective DBS due to the presence of large stimulation artifact with components that overlap the useful spectrum of the EEG. A filtering method is presented that removes these artifacts whilst preserving the spectral and temporal fidelity of the underlying EEG. Methods: The filter is based on the Hampel identifier that treats artifacts as outliers in the frequency domain and replaces them with interpolated values. Performance of the filter was tested with a synthesized DBS signal and actual data recorded during bilateral monopolar DBS. Results: Mean increases in signal-to-noise ratio of 7.8 dB for single-frequency stimulation and 13.8 dB for dual-frequency stimulation are reported. Correlation analysis between EEG with synthesized artifacts and artifact-free EEG reveals that distortion to the underlying EEG in the filtered signal is negligible (r(2) > 0.99). Conclusions: Frequency-domain Hampel filtering has been shown to remove monopolar DBS artifacts under a number of common stimulation conditions used for the treatment of Parkinson's disease. Significance: Application of frequency-domain Hampel filtering will allow the measurement of EEG in patients during clinically effective DBS and thus may increase our understanding of the mechanisms of action of this important therapeutic intervention. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.