Anterior nucleus of thalamus deep brain stimulation for medication refractory epilepsy modulates theta and low-frequency gamma activity: a case study

A 35-year-old gentleman with a traumatic brain injury was diagnosed with refractory epilepsy with electroencephalogram and imaging findings supporting a broad seizure onset pattern in bilateral frontotemporal regions. He therefore received a Medtronic Percept PC Deep Brain Stimulator (DBS) placed bilaterally in the anterior nucleus of the thalamus (ANT). While most refractory epilepsy patients' stimulation parameters use the SANTE trial standard clinical settings of 145 Hz, 90 μs, with cycling 1-min stimulation on and 5 min stimulation off, this participant underwent 7 different stimulation parameter tests at home following testing in the clinic of 24 different stimulation parameters across 12 neurologist visits. This device allows for simultaneous stimulation of the ANT while recording the ANT local field potential (LFP) response under different stimulation parameters. Slepian multitaper analysis, modified Fitting Oscillations, and One Over F method for detrending the aperiodic component were performed to analyze neural oscillations in the frequency domain captured in the clinic. This participant was participating in a clinical study examining the effectiveness of nonstandard DBS settings to minimize broadband neural activity in the ANT. Statistically significant neuromodulatory suppression of gamma oscillations was observed in the clinic under multiple stimulation settings. We compared the ability of these research stimulation parameters to suppress at-home ANT neural activity against the standard clinical settings and examined the effects of both sets of parameters on LFP power nonstationarity. At home, theta/alpha LFP power suppression was statistically significantly reduced under the 125 Hz, 50 μs setting as opposed to the clinical setting of 145 Hz, 90 μs. The participant has achieved greater than 50% seizure reduction for over 1 year since the last neurology visit. Suppression of gamma in the clinic in the right hemisphere and suppression of theta at home in the left hemisphere show promise as quantitative feedback biomarkers for ANT-DBS. Understanding the local and network relationships of theta and slow gamma oscillations in the thalamus would further explain how these modulated oscillations may relate to the onset and propagation of seizures.