Interictal cognitive changes in epilepsy.

There is little evidence for significant intellectual deterioration in well-controlled seizure disorders. With recurrent convulsive seizures, the picture is less clear and depends on severity, type, age of onset, and frequency of toxic levels of antiepileptic drugs (see Table 1). In the interictal state, deficits in verbal language and memory have been observed, especially in patients with complex partial seizure foci in the left (dominant) hemisphere. The memory deficits appear to affect new learning and retention of material; the verbal deficits are more subtle, affecting word-finding, verbal fluency, and comprehension abilities. Both of these changes may either go unnoticed by the patient in day to day activities or be attributed to the effects of antiepileptic medication. Antiepileptic drugs can also affect interictal cognitive functioning. The worst of these appears to be phenobarbital; phenytoin has an intermediate effect; valproic acid and carbamazepine as single agents seem to produce fewer adverse effects. However, individual patients may be particularly sensitive to cognitive side effects of certain drugs. Finally, attention deficits and slowing of cognitive processes, either chronically or intermittently, appear to affect all seizure patients to some extent. The syndrome is more prominent in frontal or generalized seizure patterns. The intermittent nature of these disturbances has been emphasized in recent research on subclinical interictal spike-wave electrical phenomena.