Abstracts

Rationale: Little is known about cognitive outcome in patients undergoing responsive neurostimulation for intractable epilepsy in clinical practice. Reports from randomized controlled trials identified no significant cognitive decline following RNS treatment, and modest improvements in naming and memory were reported for some patients (1). The current study compares pre and postoperative test scores in a small clinical sample of RNS patients. Methods: A consecutive series of 7 patients implanted with the RNS device (NeuroPace, Mountain View, CA) at Minnesota Epilepsy Group between 8/2016 and 6/2018 were evaluated. One patient was excluded due to poor effort on post-op testing. Localization of seizure onset varied across the 6 subjects examined, although 5 of 6 had abnormal electrographic activity in the left hemisphere. Two of these subjects were stimulated bilaterally. All patients underwent baseline neuropsychological testing and follow-up assessment 11 to 24 months following RNS surgery (mean=15.2). Tests selected for analysis included measures of attention (WAIS-IV Digit Span), language (Boston Naming Test, Auditory Naming Test, D-KEFS Verbal Fluency) verbal delayed recall (WMS-IV Logical Memory, Buschke Verbal Selective Reminding or Rey Auditory Verbal Learning) and nonverbal delayed recall (WMS-III Faces, Rey Osterrieth Complex Figure). Age and education-based standard or scaled scores were compared, with significant change defined as greater than or equal to 1 standard deviation. Results: Available preoperative FSIQ scores ranged from borderline impaired to average. Comparison of pre- to post-operative scores revealed largely stable performances across cognitive domains, including tests that showed significant impairment at baseline. 80% of all 9 scores in all 6 patients showed no significant change following approximately 1 year of RNS treatment. Two of 3 patients with involvement of the left mesial temporal structures demonstrated significant improvement on a verbal memory measure (Logical Memory II). Significant declines were observed in verbal fluency for 3/5 patients with left hemisphere seizure onset (including mesial temporal, lateral temporal and frontal lobe cases). There was no indication of improved visual naming performance in any subject. Conclusions: In this small clinical sample, cognitive performance remained largely stable across measures of attention, language, and verbal and nonverbal memory. Significant improvement in verbal memory performance for 2 of 3 patients with targeted left mesial temporal stimulation suggests that reduction of electrographic seizure activity with RNS may have the potential to improve cognitive functioning in some patients. The relationship of these cognitive changes to degree of seizure reduction and the implications for further research will be considered.1. Epilepsia, 56(11), 1836-1844, 2015 Funding: No funding