EP 65. DBS-induced alpha desynchronization in the subthalamic nucleus of PD patients. Issue 9 (September 2016)

• Record Type: Journal Article
• Authors: Castaño-Candamil, S.; Coenen, V.A.; Reinacher, P.; Piroth, T.; Tangermann, M.
• Is Part Of: Clinical neurophysiology. Volume 127:Issue 9(2016:Sep.)
• Page Start: e202
• Page End: e203
• Publication Date: 2016-09
• Subjects: Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2016.05.252
• Languages: English
• ISSNs: 1388-2457

Abstract

Abstract : Question: Deep brain stimulation of the subthalamic nucleus (STN DBS) has developed into a standard therapy for treatment refractory stages of Parkinson's disease (PD). Oscillatory components play an important role in the functioning of the brain through the control of neuronal firing (Engel and Fries, 2010 ). The power of the beta-band (12–30 Hz) in the STN is an informative biomarker for PD. It is reduced under L-Dopa medication and DBS (Kühn et al., 2008; Bronte-Stewart et al., 2009 ). However, the impact of DBS onto other oscillatory components and their relevance as PD biomarkers is less explored (Rosa et al., 2014; Beudel and Brown, 2016 ). In the present contribution, we investigate the effect of DBS upon the power of the alpha-band (8–12 Hz). Methods: For three PD patients (S1–S3), intraoperative microelectrode recordings were acquired as part of the implantation procedure for DBS. For one hemisphere three MER electrodes were lowered into the target region simultaneously (anterior, central, lateral) over a Ben's gun approach (FHC, USA). Stimulating on a singular macro-tip of the telescopic FHC electrode (FHC, USA) with increasing currents allowed to record signals with 5 kHz sampling rate from two other MER positions. Overall, seven recording constellations were measured. Starting with stimulation off, stimulation intensity was ramped up in steps of 0.5 mA and 1 mA. Each intensity was delivered for at least 20 s at a rate of 130 Hz. Five out of seven recording constellations showed a clear alpha baseline activity prior to stimulation onset. These were used for an offline bandpower analysis. The analyzed frequency band was centered onto the individual alpha frequency of each patient and had a width of 3 Hz. The log-bandpower intensity was extracted from 10 non-overlapping consecutive time windows of one second duration each, overall covering the interval of [0, 10]s relative to the onset of a novel stimulation intensity. To represent baseline activity, ten values were extracted from the interval [−15, −5]s relative to the stimulus onset. Results: For 2 out of 3 patients and 2 out of 5 recording constellations (see plots for S2 left and S3 right in Fig. 1 ), DBS onset caused a significant reduction of the alpha power relative to the baseline activity. Increasing the stimulation current (and overall stimulation time) beyond 2 mA for S2 and beyond 5 mA for S3 lead to a rebound effect. The resulting higher alpha power of higher stimulation intensities, however, still remained significantly below the baseline level. For recordings of S1 [left] and S3 [left], an alpha reduction was observed after stimulation onset as well, but it did not reach significance over all levels of stimulation intensity. Conclusions: Alpha band power of the STN may represent a biomarker for PD, which is sensitive to DBS and deserves further investigation along with the classical biomarkers beta and gamma. The rebound effect observed in this pilot study, however, suggests to test nonlinear analysis methods to assess the alpha activity.