Cognitive outcomes and predictive factors in epilepsy.

Although most patients with epilepsy have normal cognitive abilities, they are at increased risk for cognitive deficits. Multiple factors contribute to this risk including antiepileptic drugs (AEDs), which not only reduce neuronal irritability but may also impair neuronal excitability. The major cognitive effects of AEDs are impaired attention, vigilance, and psychomotor speed, but secondary effects on other cognitive functions can be seen. The adverse cognitive effects of AEDs are offset in part by reduced seizures. In general, the cognitive effects of AEDs are less than the sum total of other factors, but because AEDs are the major therapeutic modality for epilepsy, they are of special concern. AED-induced cognitive side effects are increased with rapid initiation, higher dosages, and polytherapy. Differential cognitive effects can be seen (e.g., worse performance on phenobarbital), but the magnitude of cognitive effects is relatively modest effects for most AEDs. However, even this modest effect can be clinically significant and impact the patient's quality of life. In addition, some patient groups may be at particular risk (e.g., elderly, children, fetus). The ultimate therapeutic goal is to control seizures with no or minimal side effects. The cognitive profile of an AED is but one factor in the selection of therapeutic options. Ongoing seizures can be detrimental to both cognition and quality of life. Patients who are refractory or intolerant to AED therapy should be referred for video EEG monitoring to confirm the seizure diagnosis and determine if the patient is a candidate for epilepsy surgery.