Abstracts

Rationale: Deep Brain Stimulation (DBS) has become a promising therapeutic alternative for patients with refractory epilepsy who are unsuitable candidates for resective surgery. Although numerous clinical studies have demonstrated the efficacy of DBS targeting the anterior thalamic nucleus (ATN-DBS) and hippocampus (Hip-DBS), there is a paucity of research focusing on the long-term cognitive outcomes associated with these two targets. Moreover, direct comparisons between ATN-DBS and Hip-DBS in terms of cognitive outcomes are lacking. This study aims to fill this gap by analyzing long-term cognitive function data from a single-center cohort of patients with drug-resistant epilepsy, comparing the outcomes of ATN-DBS and Hip-DBS treatments.

Methods: Between 2018 and 2022, thirty patients were enrolled in our DBS cohort, comprising 18 patients who underwent ATN-DBS and 12 who received Hip-DBS. Of these, 16 patients (10 with ATN-DBS and 6 with Hip-DBS) completed both pre- and post-operative formal neuropsychological testing (NPT) and had a minimum follow-up period of 18 months after surgery. The NPT battery included 12 categories evaluating a variety of cognitive functions for our patients.

Results: Participants were divided into non-depressed (ND) and depressed (D) groups due to the well-known impact of depression on cognitive function. In the ND group of ATN-DBS (n=7), statistically significant improvements were observed in PRI scores following ATN-DBS therapy (p = 0.046, Wilcoxon signed-rank test). Additionally, significant improvement was noted in BDI scores (p = 0.043) and a favorable trend in PRI scores (p = 0.066) in the ND group of Hip-DBS (n=5).

In the D group (ATN-DBS: 3, Hip-DBS: 1), cognitive outcomes were more variable. One ATN-DBS patient experienced worsening depression and cognitive outcomes due to an accidental traumatic intracerebral hemorrhage that occurred one year post-ATN-DBS surgery. However, the other two ATN-DBS patients demonstrated cognitive improvements, particularly in PRI. The single depressed patient with Hip-DBS showed significant cognitive deterioration across all measured parameters, but this did not significantly interfere with daily functioning.

Conclusions: The Perceptual Reasoning Index (PRI) consistently emerged as a reliable indicator of cognitive improvement in both ATN-DBS and Hip-DBS groups, including those with comorbid depression. PRI, associated with visuospatial processing and nonverbal reasoning, underscores its potential as a marker for cognitive enhancement following DBS in refractory epilepsy.

However, the study emphasizes the need for cautious interpretation of cognitive outcomes, especially in patients with depression, who exhibited declines in language-related cognitive functions. These findings highlight the importance of larger-scale studies to validate these preliminary results and to further explore the complex interplay between depression and cognitive outcomes in DBS-treated epilepsy patients.


Funding: This study was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute, and funded by the Ministry of Health and Welfare, Republic of Korea (HI23C1532).