Effects of Centromedian Nucleus Stimulation on Interictal Scalp EEG Burden in Lennox-Gastaut Syndrome

Deep brain stimulation (DBS) of the centromedian (CM) thalamic nucleus is a potential therapy for Lennox-Gastaut syndrome (LGS), a severe and drug-resistant epileptic encephalopathy. While long-term seizure outcomes with CM-DBS have been described, its acute electrophysiological effects and predictive value remain uncertain. We examined whether short-term changes in interictal epileptiform discharges (IEDs) following CM-DBS relate to seizure outcomes at 1 year.

Ten patients with LGS underwent CM-DBS implantation. About 1 month post-surgery, each patient had a 1-h scalp EEG. After a 10-min baseline, stimulation began at 1 V for 5 min, increasing in 1 V increments to 5 V or until paresthesias occurred. IEDs were detected automatically (Persyst v14c) and verified by an expert reviewer. Patients were followed for 1 year, with clinical response defined as ≥50% seizure reduction, i.e., responder. Correlations between acute IED change and seizure outcomes were assessed using Spearman's rank correlation.

Nine of 10 patients showed reduced IED burden during acute stimulation (31%-100%). At 1 year, 8 were responders and 2 nonresponders. Overall, acute IED reduction did not correlate with seizure outcome (Spearman's ρ = 0.3, p = 0.35). A ≥50% reduction in IED burden was seen in 7 of 7 responders versus 1 of 3 nonresponders, suggesting a nonsignificant trend toward predictive value (p = 0.06).

Acute CM-DBS reduced IED burden in most patients with LGS but did not significantly predict long-term seizure outcomes. A trend toward greater IED reduction in responders suggests possible biomarker potential, though findings are preliminary and hypothesis-generating. Limitations include small sample size, high responder rate, and short EEG duration. Larger studies with extended monitoring are needed to clarify the clinical utility of acute EEG changes as predictors of CM-DBS efficacy.