Investigating higher-order cognitive functions in temporal lobe epilepsy: cognitive estimation.

Cognitive estimation, an ability to attribute measurements to concrete things, is relevant to adaptive behavior. This study evaluated cognitive estimation in patients with temporal lobe epilepsy (TLE) with the goal of verifying its relationship to temporal lobe damage and age of seizure onset. One hundred and eight patients with drug-resistant TLE and 51 healthy controls were evaluated using the Cognitive Estimation Task (CET), which requires simple and complex estimations providing the Total and Bizarreness scores. Different tests assessed reasoning, attention, executive, visuospatial, and lexical-semantic abilities. Patients with right TLE had earlier age of seizure onset than patients with left TLE and lower education than controls. Compared with controls, both patient groups obtained worse CET Total and Bizarreness scores, but only patients with right TLE were significantly impaired. Patients with seizure onset before age 12 showed worse scores than patients with later seizure onset irrespective of the side of TLE. The CET Total and Bizarreness scores were predicted by age of seizure onset and semantic fluency; the Bizarreness score also related to education, chronological age, and visual attention. Results highlight the complexity of the cognitive pattern associated with TLE. Cognitive estimation deficit primarily reflects early age of seizure onset and semantic difficulties. An involvement of visual mental operations mediated by the right hemisphere may accentuate the deficit, while cognitive reserve may play a protective role.