Abstracts

Rationale: We evaluated the antiseizure efficacy, side effects and neuropsychological effects of deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT).

Methods: We retrospectively analyzed the data of our cohort of 13 patients, implanted between 2012 and 2014. Postimplantation seizure frequencies were compared with mean seizure frequencies in the 6 months before the implantation. Seizure frequency and side effects data were complete in 11 patients. Neuropsychological data was complete or deemed sufficient in 8 patients.

Results: Seven patients were responders (achieved seizure reduction of ≥50%). One achieved seizure freedom. Seizure reduction of < 50% was achieved in 1 patient (34.5%). The 4 remaining patients had a seizure frequency increase ranging from 15% to 161% (on average 75.7%). The average seizure decrease was 71% (34.5%-100%). Four patients remained implanted at the end of follow-up. Causes for explantation were lack of efficacy in 4 cases, and psychogenic dysarthria and dysphagia, electrical paresthesias along cable trajectory and the emergence of delusions in the 3 remaining cases. Among the 7 responders, the etiology was most commonly unclear, followed by structural origin. Three of the responders had multifocal epilepsy. In the non-responder group, the most common etiology was also unclear. Mean follow-up was 51.5 months. All patients underwent multiple changes in antiseizure medication during follow-up time, though this did not influence seizure frequency.

To address acute cognitive effects of DBS a baseline assessment was performed after implantation and before stimulation, and a follow-up assessment was conducted under DBS. At baseline, 4 of the 8 patients showed impairment in attention and executive functions. Regarding episodic memory, in 6 of the 8 patients a deficit was registered at baseline. All patients showed an impairment under DBS.

To analyze the long-term effects of DBS on cognition we compared the preoperative neuropsychological profile with a long-term follow-up under DBS. At the long-term follow-up, we observed significant intraindividual changes in verbal learning and memory in 5 of the 8 patients (3 deteriorated, 2 improved). Regarding figural memory, none of the patients declined, 1 patient improved. The same is valid for confrontative naming and mental rotation.

Conclusions: 53.8% of patients treated with DBS-ANT for refractory epilepsy at our center were responders, with an average seizure reduction of 71% (34.5%-100%). Non responders suffered an average seizure increase of 75.7%. Intolerable side effects arose in 3 patients, two of them were of psychiatric nature. Our results suggest that patients with multifocal epilepsies may benefit the most from DBS-ANT, in accordance with other centers’ experiences (1). All patients presented acute cognitive effects after implantation. Long-term neuropsychological effects included significant intraindividual changes in verbal learning and memory. Figural memory, confrontative naming and mental rotation were mostly unchanged, and improved in a small number of patients.

Funding: Please list any funding that was received in support of this abstract.: There are no funding sources to declare.