Abstracts

Rationale: Epilepsy is a prominent neurological disease that affects nearly 1% of the world’s population. Twenty-five percent of patients with epilepsy do not achieve adequate seizure control with medication. Additionally, only 20% of patients with epilepsy refractory to medication are eligible for resective surgery, and only 30-40% of eligible patients achieve complete seizure freedom (Engel Class 1 outcome). Drug resistant epilepsy (DRE) is associated with high use of medical resources, low socioeconomic status, higher risks of accidents and increased incidence of sudden unexpected death in epilepsy (SUDEP). In the absence of a safely resectable seizure focus, historical palliative treatments have failed those with DRE. In these patients, emerging treatment modalities, such as deep brain stimulation (DBS) and responsive neurostimulation (RNS), may provide a solution. The thalamus has become an increasing area of interest for neurostimulation in the treatment of epilepsy, specifically targeting the anterior thalamic nucleus (ANT) and centro-median nucleus (CM).

Methods: Two patients with drug resistant epilepsy were presented at the Spectrum Health multidisciplinary epilepsy conference. Following an in depth discussion, a consensus was reached to implant deep brain stimulation electrodes in the bilateral centro-median nuclei of the thalamus. Each patient was subsequently followed in the epilepsy clinic.

Results: Our first patient showed a significant reduction in GTCs, myoclonic seizures and FIAS at 6-month follow up and 12-month follow up. A 25% increase was noted in overall seizure frequency at 10-month follow up, however this was felt to be medication related given the decrease in lamotrigine prior to the noted increase in seizure frequency. A > 75% reduction in seizure frequency was noted for all seizure types at subsequent follow up. Of note, the patient passed away unexpectedly in late 2021. Given his significant reduction in seizure frequency, it is unclear if seizures played a role in his death.

Our second patient showed an initial 50% decrease in GTCs, 85% decrease in atypical absence seizures while tonic seizures remained unchanged at 2-month follow up. At subsequent follow-ups, there was a 100% decrease in atypical absence seizures with an increase in GTCs, prior to further optimization of DBS parameters. At 16-20 month follow up, an increase in all seizure types was observed in the setting of multiple confounding variables. All confounds were addressed by the 22-month follow-up, at which time atypical absence seizures had decreased in frequency and GTC had decreased by over 50% from baseline. Tonic seizures were also noted to be improving but remained above baseline.

Conclusions: Our study contributes to the growing body of literature regarding deep brain stimulation of the centro-median thalamic nucleus as a viable treatment option in drug resistant multifocal and idiopathic generalized epilepsy.

Our patients both showed a significant decrease in frequency for various generalized seizure types (GTCs, myoclonic and atypical absence). An increase in frontal onset generalized tonic-clonic seizures was seen in one patient, though it is hypothesized his DBS parameters have yet to be optimized. A decrease in focal impaired aware seizures was also seen in one patient. Tonic seizures remained unchanged in frequency in one patient.

Therefore, while some efficacy is shown for the use of CM-DBS in the treatment of idiopathic generalized, multifocal and potentially focal impaired aware seizures, further data is needed to draw conclusions on the efficacy of CM-DBS in the treatment of tonic seizures and those with frontal lobe origin.

Funding: Please list any funding that was received in support of this abstract.: None.