Abstracts

Rationale: Intracranial electrical stimulation is increasingly used as a treatment for refractory epilepsy, but few studies discuss its effects on memory and cognition in detail. In addition, there is a significant variation in population demographics, stimulation parameters, neuropsychological battery used for testing, and reported change in cognitive profile.


Methods: We searched Pubmed with the keywords “epilepsy” and “ memory” for articles published between 2012 and 2024 and found 8162 entries. Next, we added the keywords “DBS” and “ RNS” and narrowed the list to 59 and 20 results respectively. We reviewed the studies and removed review articles, studies that discussed short-term or non-invasive stimulation, and studies that did not have adequate neuropsychological testing data. Three studies that discussed the effect of DBS on memory and two studies on RNS in patients with epilepsy were included in the final analysis.



The following tests were used: WAIS(Wechsler adult intelligence scale), full scale IQ, perceptual reasoning index score, WAIS-III informational, total IQ, performance IQ, verbal IQ, pegboard test, trail making tests A and B. D-KEFS (Delis Kaplan executive function system). VCI (Verbal Comprehension Index Score), Boston naming test, Category word fluency test, COWA (Controlled oral word association test), BVMT-R (Brief Visuospatial Memory Test): total, delayed recall, recognition hits, and discrimination. Digital span (forward, backward). CVLT(California verbal learning test): discriminability, recognition hits, long delay-free recall. KMAS(Korean memory assessment): short-term memory, visual memory, verbal memory, full memory. MQ (memory quotient). RKMT: figure delay call, figure immediate recall, delay verbal recall, immediate verbal recall, verbal recognition, figure drawing. Selective reminding test. WMS(Wechsler memory scale)- visual reproduction. Frontal assessment battery. MMSE.




Results: The mean age of the study population was 35.6 years and the mean age of seizure onset was 17.78. The sample size in the studies ranged from 9-175 and 49.42% were females. The mean duration of epilepsy was 17.28 years (range:3.4 - 22.3). The patients were followed up for 14.2 to 60 months. Approximately 58.28% (range: 33.1-71.3%) of patients reported an improvement in seizures and 10.12 % of patients achieved an Engel class 1 outcome.



The detailed results are noted in Table 1.




Conclusions: An improvement in neurocognitive evaluation (IQ, language, memory, cognitive flexibility) was noted after long-term invasive electrical stimulation of the brain. In contrast, a decline in visual-spatial abilities and visual memory was noted. Larger studies with longer follow-up and detailed assessment are needed to understand the variation and etiology of neurocognitive outcomes in this population.


Funding: None.