Abstracts

Rationale: Semantic knowledge refers to facts about the world acquired through experience. Among individuals who undergo left anterior temporal lobe resection (ATR) for control of complex partial seizures (CPS), those who have greater presurgical semantic knowledge are at the greatest risk for postsurgical decline of semantic knowledge. Patients with greater presurgical semantic knowledge are often those whose seizures started later in life. Individuals with seizure onset in childhood or in teenage years can also adequately learn factual information over the course of their lives. The present study evaluated change in semantic knowledge from before to after ATR in two groups: patients with age at onset of CPS in childhood or as a teenager (<18 years-old) versus patients with age at onset of CPS as an adult (18 years-old). Methods: Ninety-eight individuals who underwent unilateral ATR (43 left, 55 right) participated in the study. Mean age of childhood/teenage onset CPS was 9.6-years (range from 3-month-old to 17-year-old), and 26.6-years for the adult onset CPS group (range from 18 to 44-years-old). The Boston Naming Test (BNT) was used to quantify semantic knowledge. Results: There was no statistically significant difference in chronological age between the groups at the time of surgery (mean age for childhood/teenage group = 31 years-old at time of surgery; mean age for adult group = 35-years-old at time of surgery). Repeated measures ANOVA indicated a significant side of surgery by age group interaction for semantic knowledge as a function of time (F[1,94]=4.38, p=0.039). The largest decline in semantic knowledge after surgery was for individuals with adult onset CPS who underwent left-ATR (see Figure below; this group lost an average of 9 words after surgery). Based on the Reliable Change Index method, 62% of left-ATR patients with adult onset showed meaningful declines in semantic knowledge versus 30% of left-ATR patients with childhood/teenage onset and 5% of right-ATR patients. Conclusions: The risk of semantic knowledge loss is greatest in adult onset CPS after left-ATR. Presurgical counseling and postsurgical rehabilitation referrals may benefit patients who undergo left-ATR.