Authors :
Presenting Author: Marla Hamberger, PhD – Columbia University
William MacAllister, PhD – Alberta Children's Hospital
Robyn Busch, PhD – Cleveland Clinic
Nahal Heydari, PhD – Columbia University
Mary Lou Smith, PhD – University of Toronto
Rationale:
Multiple studies show that general intellectual abilities remain stable following pediatric, focal epilepsy surgery. However, both naming and verbal memory may be at risk, particularly for children whose seizures arise from the language-dominant hemisphere. Although both naming and verbal memory are known to be supported primarily by the left temporal-perisylvian region, it is unknown whether decline in one domain carries a risk of decline in the other. We examined the relation between changes in naming and changes in verbal memory in children following focal epilepsy surgery involving the dominant (left) or nondominant (right) hemisphere, and in children with atypical (i.e., right or bilateral) language organization.
Methods:
Participants were 76 children, ages 6-16, who had epilepsy surgery (Left, n=28: resection: 15, laser ablation: 3, lesionectomy: 9, gamma knife: 1; Right, n=31: resection: 22, laser ablation: 4, lesionectomy: 5; Atypical n=17: resection: 11, laser ablation: 2, lesionectomy: 4) and pre and postoperative testing including the Children’s Auditory (ANT) and Visual (VNT) Naming tests; 67 children also had pre and postoperative word memory testing (CVLT-C: 35, CAVLT-2: 27, CHAMP: 4, CVLT-2: 1). Naming was assessed by “Speed Index” scores (i.e., Number of items named rapidly [< 2 sec] – Number of items named after a delay [2-20 sec]). Memory was assessed by delayed free recall. Multivariate ANOVA compared groups on demographic and clinical variables; paired t-tests compared pre and postoperative test scores. Pearson correlations assessed associations between variables.
Results:
Across groups, there were no differences in age, IQ, or seizure outcome (left: age: 11.9±2.7, IQ: 95.8±10.3, Engel outcome: 1.3±0.7; right: age: 12.0±2.7, IQ: 92.9±13.3, Engel outcome: 1.3±0.8; Atypical: age: 11.7±2.9, IQ: 86.1±12.2, Engel outcome: 1.4±0.9, all p > .05). Preoperatively, ANT scores were lower in children with left compared to those with right hemisphere seizures (p=.02), whereas VNT and memory scores did not differ among groups. However, postoperatively, VNT scores declined in children who had left hemisphere surgery (p=.006), ANT scores improved in children who had right hemisphere surgery (p=.005), and the atypical group exhibited a nonsignificant decline in VNT scores (p=.07). Verbal memory tended to decline only among those who had left hemisphere surgery (p=.052). Interestingly, there were no significant correlations between changes in naming and changes in memory, and neither correlated with age, IQ, or seizure outcome (all p’s > .25). Using 1SD to denote significant decline, only 4/28 of the left hemisphere group declined in both naming and verbal memory.Conclusions:
Like adults, children who undergo dominant hemisphere surgery may be at higher risk for visual naming and verbal memory decline. However, a decline in naming does not imply decline in verbal memory (or vice versa); rather, few children exhibited decline in both domains, suggesting dissociable neurofunctional mechanisms underlying naming and verbal memory in children with focal epilepsy.
Funding:
NIH R01 NS35140