Abstracts

Rationale: Previous studies demonstrate a relationship between impaired naming and reduced verbal cognitive abilities in patients with temporal lobe epilepsy (TLE; Mayeux et al., 1980; Hermann et al., 1988). The association may be largely related to word-retrieval impairment (Hermann et al., 1988), although this has not been directly investigated. The current study sought to determine if word-finding difficulties (WFD) are related to performance on verbal cognitive measures, including memory, in adults with TLE. Methods: One hundred and six individuals with left TLE and pathologically-confirmed mesial temporal sclerosis (MTS) completed comprehensive preoperative neuropsychological evaluations. Patients were divided into two groups based on the degree of benefit received from phonemic cueing on a confrontation naming task. WFD occurred at a higher rate for men (64%) as compared to women (43%; χ2[106]=4.28, p=0.038). There were no other differences between the groups on relevant demographic or seizure variables. Patients with and without WFD were then compared on their performance on cognitive measures. Results: One-way ANOVAs revealed that patients with WFD demonstrated poorer performance on nearly all verbal cognitive measures than those without WFD. Specifically, patients with WFD performed more poorly on measures of verbal intelligence (i.e., vocabulary, verbal abstract reasoning, and fund of information), single-word reading, phonemic verbal fluency, and select verbal memory subtests (i.e., word-pairs immediate and delayed, word-list delayed). The only verbal measures on which the two groups did not significantly differ were measures of delayed verbal recognition memory, story recall, and immediate word-list learning. Of note, these measures place relatively low demand for lexical retrieval of a specific word for competent completion of the tasks. In contrast, a dissociation existed such that there were no significant differences between groups on any of the nonverbal cognitive measures including nonverbal intelligence (i.e., attention to visual detail, block construction, nonverbal reasoning), figural fluency, face recognition memory, and visual scene recall. Chi-square analyses indicated that low average to impaired verbal memory performance occurred at a significantly higher rate for patients with WFD (42% and 46%) as compared to patients without WFD (18% and 24%; χ2[106]=7.34, p=0.007 on an immediate verbal recall index and χ2[106]=5.60, p=0.018 on a delayed verbal recall index). Conclusions: Results suggest that WFD confound performance on most verbal cognitive measures in adult patients with left TLE, particularly on measures with high demand on lexical retrieval. While extent of temporal lobe damage may have influenced both WFD and verbal performance, use of a homogenous patient group with left MTS reduced the influence of this potential confound. Thus, performance on verbal cognitive tasks, including memory measures, may be an underestimate of true cognitive ability in patients with WFD and should be interpreted with caution.