Abstracts

Rationale: The rate of patients with neuropsychological changes after epilepsy surgery varies across pediatric and adult studies. In addition, some neuropsychological domains such as memory and naming have been relatively well studied, whereas others have not been studied adequately. The goal of this study was to conduct a systematic review to identify the base rate of cognitive changes (decreases and increases) in neuropsychological functioning after epilepsy surgery. Methods: As part of a larger project on the development of an appropriateness and necessity rating tool for identifying surgical candidates, an extensive literature search was conducted using PubMed, EmBase and the Cochrane database, yielding 5061 articles related to epilepsy surgery. Abstracts were reviewed to ensure they met the following inclusion criteria: partial epilepsy, focal resections, English only, n >= 20, all ages except neonates (excluded: non-resective or non-cortical surgery, palliative procedures, stimulation studies). In all, 763 articles meeting eligibility criteria were hand-searched; 152 included neuropsychological outcomes. In a second stage, studies meeting further inclusion criteria consisting of use of original data, pre-post surgery design, outcomes in the form of standardized tests, and use of empirically-based methods for determining change (Reliable Change Index, standardized regression-based scores), and information on base rates of patients with reliable/significant change were included. In all, 25 articles met full inclusion criteria. Results: First, the majority of patients did not demonstrate significant post-operative declines in cognitive functioning, despite some individual heterogeneity in memory outcome across patients. Second, there was a substantial risk to verbal memory and naming with left-sided resections in the language-dominant hemisphere (30-50%) compared to a low rate of neuropsychological complications for right-sided surgeries overall (0-25%). Third, after temporal lobe surgery, there was a low rate of decline in executive functioning (0-18%) and an increased likelihood of improved executive functioning regardless of resection side (17-50%). Fourth, self-reported cognitive decline after epilepsy surgery was rare (0-20%), and changes tended not to align with objective estimates of cognitive function, but instead appeared fueled by psychological factors. Data on children were limited, apart from possible benefit to IQ and a possibly lower rate of memory decline after temporal lobe surgery. Conclusions: Studies indicated good cognitive outcomes for the majority of patients with epilepsy, with the lowest cognitive complication rate associated with right-sided surgeries. Most of the research literature on neuropsychological outcomes after epilepsy surgery is focused on adult temporal lobe patients and employs an almost exclusive focus on memory and language as outcome measures. There is a need for more research on extra-temporal surgeries and children, and a need to expand outcomes to a broader range of neuropsychological functions.