Age at onset and neuropsychological function in frontal lobe epilepsy

Purpose: Previous studies into the cognitive consequences of frontal lobe epileptic dysfunction may have proved inconclusive, due to a factor not commonly accounted for: Damage or disturbance during different epochs of development may give rise to different levels of neuropsychological dysfunction. In this study, we investigated the influence of age at onset on cognitive performance in a group of subjects with frontal lobe epilepsy (FLE). Methods: Seventy-four subjects (42 with left, and 32 with right) FLE were classified into early (0-6 years), intermediate (7-11 years) or late onset (greater than or equal to 12 years) and their performance recorded on a battery of measures assessing both executive and motor skills. Results: On the measures of executive functioning, no consistent pattern emerged, whereas on the measures of motor skill, the results suggested that a right-sided early onset (i.e., 0-6 years) did not impair performance compared to a later lesion within the same hemisphere. Furthermore, this sparing of performance was not observed within the left hemisphere. Conclusions: Overall, the results suggest that individuals with differing ages of epilepsy onset will be differentially impaired on certain cognitive tasks. Several tentative ramifications of these results are suggested.