Authors :
Presenting Author: Darion Toutant, MSc – University of Manitoba
Graham McLeod, MD – University of Calgary
Marcus Ng, BMSc, MD(STIR), FRCPC, CSCN(EEG), FACNS, FAES – University of Manitoba
Rationale:
Recently, we showed that high-definition transcranial direct current stimulation (hd-tDCS) reduces spike rates during and after stimulation in refractory status epilepticus (RSE) resulting in a 90% discharge rate from the intensive care unit (ICU) compared to 45% historically. Investigating these beneficial effects of hd-tDCS, we hypothesize that cathodal stimulation should hyperpolarize neurons, effectively decreasing excitability, in turn reducing oscillatory activity between electrode channels to suppress excitatory epileptic events.
Methods:
10 ICU patients underwent 27 hd-tDCS sessions (1-8 sessions/patient, 2.7±1.8 average) with simultaneous 10-20 EEG recordings at 256Hz. EEGs were filtered (60Hz notch, 0.5Hz high-pass, 127Hz low-pass) using Laplacian montage to reduce volume conduction. Weighted phase lag index (wPLI) was calculated between 19-channels over 6-second periods during 20-minute timeframes pre-, during, and post-stimulation using 2-second windows with 50% overlap across delta (1-4Hz), theta (4-8Hz), alpha (8-13Hz), beta (13-30Hz), and gamma (30-80Hz) bands (Fig. 1). Connectivity matrices were thresholded using median synchronous activity per channel pair within each frequency band and timeframe per session. wPLI matrices were binarized (0=non-relevantly connected, 1=connected) and the median connected channel count was extracted between each wPLI matrix timeframe frequency. Nonparametric Friedman tests compared pre-, during, and post-stimulation connectivity across all channels and stimulation-specific channels for each frequency band (p< 0.05).