Cognitive impairment--is it inevitable?

Neuropsychological dysfunction in children and adults with epilepsy is common and has several possible interrelated causes, including the underlying pathophysiology, possible cerebral pathology, the effects of subclinical discharges, sleep disorders, status epilepticus and drug therapy. Of these factors the effects of subclinical discharges and those of medication are potentially remediable. In up to 50% of patients with subclinical epileptiform EEG discharges, these are associated with transitory cognitive impairment. When the discharges are focal, the cognitive deficits usually reflect the normal neuropsychological functions of the affected brain region. Most antiepileptic drugs, with the exception of the benzodiazepines (which themselves adversely affect cognition) and lamotrigine, do not suppress inter-ictal discharges. Although well-designed clinical trials of the effects of antiepileptic drugs are difficult to perform, there is convincing evidence that phenobarbitone and phenytoin cause cognitive impairment. Drugs which control both the seizures and inter-ictal discharges should improve cognitive function, provided the drugs themselves do not have a cognitive penalty. Lamotrigine provides effective control of both overt and subclinical seizures, without adversely affecting cognition.