Event-related potentials suggest slowing of brain processes in generalized epilepsy and alterations of visual processing in patients with partial seizures

Event-related potentials were recorded in two auditory tasks and in one visual task from 13 patients with partial seizures (PS), 12 patients with idiopathic generalized epilepsy (IGE), and healthy age-matched participants. IGE patients had delayed latencies in the auditory tasks, with the delay being reliable already at N1, and continuously increasing at N2b and at P3. The P3 delay correlated with duration of epilepsy both in IGE and in PS patients. In the visual task, the posterior N2 was delayed in PS patients, in particular in PS patients with temporal focus. Resembling the delays as found in healthy elderly adults, the delays with auditory stimuli might reflect a slowing of brain processes as it occurs in healthy aging. The isolated delay of posterior N2 in temporal PS patients might indicate a specific impairment of the occipito-temporal visual pathway. Taken together, event-related potentials prove to be a very sensitive instrument for measuring altered brain functioning in epileptic patients, when compared to measurement of overtly visible responses.