Newer antiepileptic drugs and cognitive issues.

Although the causes of cognitive impairment in patients with epilepsy have not been completely elucidated, three factors are clearly involved: the underlying etiology of epilepsy, the effects of seizures themselves, and the central nervous system effects of antiepileptic drugs (AEDs). All commonly used AEDS have some effect on cognitive function, and the effect may be substantial when crucial functions are involved, such as learning in children or driving ability in adults, or when already-vulnerable functions are involved, such as memory in elderly patients. The available evidence is insufficient to support definite conclusions about the cognitive effects of three of the newer AEDs, tiagabine, gabapentin, and levetiracetam. Better evidence is available for lamotrigine (LTG), topiramate (TPM), and, to a lesser degree, oxcarbazepine (OXC). OXC appears not to affect cognitive function in healthy volunteers or adults with newly diagnosed epilepsy, but its cognitive effects in children and adolescents have not been systematically studied. A relatively large number of studies are available for LTG, which has demonstrated a favorable cognitive profile overall, both in volunteers and in patients with epilepsy. Although dose and titration speed may be confounding factors in some of the studies of TPM, there is clear evidence that this agent does affect cognitive function, with specific effects on attention and verbal function. For LTG, attempts have been made to correlate cognitive effects with what is known of the drug's mechanism of action; this is an area of research that deserves further exploration with regard to other AEDs as well, especially TPM.