Anticonvulsant serum levels: relationship to impairments of cognitive functioning.

Twenty-eight patients with epilepsy were seen on two occasions at an interval of three months. On one session anticonvulsant serum levels were high and on the other session the serum levels were lower. On each of the two sessions patients performed a series of psychological tests and had a blood sample taken for the analysis of anticonvulsant serum concentrations. Seizure frequency in the previous three months was documented and several patients had an EEG recording made. Deficits in psychological test performance were found at high serum concentrations. Furthermore, lower serum level concentrations did not appear to be accompanied by worsened seizure control.