Abstracts

Rationale: Prior work has shown conservation of language functioning and working memory (WM) skills following surgery to treat intractable seizures (Smith, Lah, & Elliott 2010). However, prior studies often included a single measure of functioning and did not use rigorous Reliable Change Index (RCI), and thus may not have captured the range of potential deficits that may be overlooked in traditional group analyses. In the present study, we explored whether patients experienced changes in language functioning and/or auditory WM following epilepsy surgery across a battery of neuropsychological tests. In addition, we sought to explore whether surgical factors predict language decline.  Methods: 27 pediatric epilepsy surgery patients (mean age at surgery = 10.23 years; range = 4.46 – 18.57) completed a neuropsychological evaluation prior to and following epilepsy surgery, with an average of 1.52+/- 1.85 years following surgery. Neuropsychological measures assessing WM and language functioning (Table 1) were included. RCI with α set at 0.20 (two-tailed) was calculated for each subtest to determine if patient scores on each task significantly changed beyond test-retest variation. A composite change variable was created to reflect a dichotomous outcome of whether patients experienced a significant change on one or more measures within either language or working memory. Logistic regressions were performed to evaluate the effects of surgery hemisphere (left vs. right) and surgery location (frontal vs. temporal) on neurocognitive decline.  Results: Paired t-tests did not identify significant changes from pre- to post-surgery on any individual neurocognitive variable (all ps>.05). However, of the 22 patients who received at least one comparable measure of language functioning at their post-operative visit relative to their pre-operative visit, 11 (50%) patients experienced a significant decline on at least one measure, with the highest percentage of patients (29.4%) exhibiting decline on a naming task (EOWPVT). Of the 13 patients who received comparable measures of WM at pre- and post-operative visits, 3 (27.3%) patients demonstrated decline.  Surgery hemisphere (χ2 (1)=0.03, p=0.86) and location (χ2 (1)=1.28, p=0.26) did not predict language decline.  Conclusions: Similar to prior studies, patients did not show group-level differences on any individual neurocognitive test pre- and post-surgery.  However, half of patients showed significant decline on at least one measure of language functioning. In contrast, fewer patients showed changes in WM function following surgery. These findings highlight the utility of including multiple measures of functioning in assessing the impact of surgery and evaluating if declines are overlooked by looking at group means. It may be more revealing to examine change at the individual level using reliable change across a range of skills.   References:Smith, Lah, & Elliott, 2010. Outcomes of pediatric epilepsy surgery and measurement issues. In C. Helmstaedter, B. Hermann, M. Lassonde, P. Kahane, & A. Arzimanoglou (Eds.), Neuropsychology in the care of people with epilepsy (pp. 239-247). John Libbey Eurotext: Montrouge.  Funding: Internal Department Funds