There is growing evidence that subcortical structures, including the thalamus, are involved in seizure networks in patients with neocortical epilepsy. Responsive neurostimulation of the centromedian nucleus of the thalamus (CMT) has been shown to terminate seizures in case reports of patients with generalized and focal neocortical epilepsy [Burdette, et al. Epilepsy and Behavior, 2020]. However, to our knowledge, no prior reports have demonstrated the utility of stimulating the thalamus during a sEEG evaluation. We present two patients with refractory neocortical epilepsy who underwent sEEG evaluation including an electrode in the CMT.

Both patients underwent real-time high frequency stimulation (HFS) at CMT during runs of interictal discharges. Patient 1 was also stimulated during seizures. Stimulation settings for both patients were 50Hz, 0.3msec pulse duration, for 3 seconds. Patient 1 underwent stimulation at 2mA while Patient 2 was 1mA. For patient 1, seizure characteristics before and after stimulation were compared using a student’s t-test (duration) and Fisher exact test (apnea).

For Patient 1, HFS of the CMT successfully aborted 4 seizures. Compared to 11 seizures prior to stimulation, those with HFS were significantly shorter (9.5 vs. 20.5 seconds, p=0.018). The patient did not develop clinical apnea in any of the 4 seizures aborted with HFS, but did with all of the 11 seizures without stimulation (p=0.001). Stimulation during runs of interictal discharges was inconclusive.  In Patient 2, HFS aborted runs of inter-ictal discharges in all 10 attempts.

These cases demonstrate that stimulation of the CMT during sEEG evaluation can abort electroclinical seizures and potentially interictal discharges. This supports the idea that the CMT is involved in focal neocortical epilepsy networks. Stimulation during sEEG may be useful in predicting efficacy of thalamic neurostimulation.