Attention-deficit disorders and epilepsy in childhood: incidence, causative relations and treatment possibilities.

At least 20% of children with epilepsy have clinical attention-deficit hyperactivity disorder (ADHD) compared to 3% to 7% of the general pediatric population. Several mechanisms may account for the high prevalence, such as a common genetic propensity, noradrenergic system dysregulation, subclinical epileptiform discharges, or even seizures, antiepileptic drug effects, and psychosocial factors. At the same time, children with attention-deficit hyperactivity disorder have a higher than normal rate of electroencephalography abnormalities (5.6-30.1% vs. 3.5%). Methylphenidate treatment is equally efficient in children with isolated attention-deficit hyperactivity disorder and in children with attention-deficit hyperactivity disorder and epilepsy (70%-77%). Electroencephalography screening in patients with attention-deficit hyperactivity disorder in the absence of other clinical indications or before starting methylphenidate treatment is not currently indicated. Methylphenidate is considered safe for use in children who are seizure-free. However, the few reports of seizure aggravation in methylphenidate-treated children with uncontrolled epilepsy have raised concern.