The comorbidity of ADHD and epilepsy is reviewed by researchers at the Universities of Rome and Chieti, Italy. In ADHD children the prevalence for epileptiform EEG discharges ranges from 5% to 60%; 14% of ADHD children with epileptiform EEG abnormalities are at risk of developing seizures [1]. In children with epilepsy the prevalence of ADHD is 30-40% (Dunn DW, 2005), much higher than that in the general pediatric population (Schubert R, 2005). Studies differ in the number of patients, severity and type of epilepsy, and ADHD diagnosis. The types of epilepsy associated with comorbid ADHD include frontal lobe, absence, and Rolandic epilepsies. Prolonged focal epilepsy, as occurring in electrical status epilepticus during slow wave sleep, is associated with attention deficits and hyperactivity. [2]

Treatment of comorbid ADHD and epilepsy is a challenge because some AEDs may cause behavioral abnormalities, and stimulant medications may lower the seizure threshold. Choice of AEDs for seizure control that may improve behavior and attention in children with epilepsy and ADHD include carbamazepine or oxcarbazepine, and valproate, lamotrigine or levetiracetam. AEDs that can exacerbate behavioral disorders and should be avoided include barbiturates and topiramate. For treatment of ADHD in children with epilepsy, studies show that methylphenidate is safe in patients whose epilepsy is controlled with AEDs (Gross-Tsur V et al, 1997). Atomoxetine is recommended as an alternative to methylphenidate in some patients with ADHD and epilepsy or epileptiform discharges in the EEG (Hernandez A et al, 2005; Wernicke JF et al, 2007). Atomoxetine does not interact with AEDs while methylphenidate may increase phenytoin serum concentrations. Methylphenidate serum concentrations are lowered by carbamazepine, leading to a loss of efficacy against ADHD. (Schaller JL et al, 1999). Methylphenidate is considered the most effective and safest treatment for ADHD. [3]

COMMENT. Children with ADHD are at increased risk for seizures, and children with epilepsy are at significant risk for ADHD. Management of the comorbid disorder presents a challenge because treatments for ADHD may lower seizure threshold and AEDs may exacerbate symptoms of ADHD. CNS stimulants should be avoided in children with seizures and used with caution in those with an abnormal EEG (PDR, 2009). Studies show that methylphenidate (MPH) for ADHD is safe provided that comorbid epilepsy is under control with AEDs. In patients with epileptiform EEG untreated with AEDs, the safety of MPH is less well established. Low-dose MPH does not increase the incidence of EEG epileptiform discharges. In a patient who fails to respond to low-dose stimulant, the demonstration of epileptiform discharges by utilization of a sleep-deprived sleep EEG should aid in the choice of alternative non-stimulant medication (Millichap JJ, Stack C. Millichap JG, unpublished observations).