The prevalence of ADHD, its neurological correlates, and the effect of ADHD on health-related quality of life in 203 children (mean age 11.8 years, SD 3.8) with severe epilepsy were evaluated at British Columbia Children's Hospital, Vancouver, Canada. Epilepsy patients were mainly (74%) pre- or postsurgical or vagal nerve stimulator candidates; 74.4% were localization related and 16.7% were generalized epilepsies. Approximately 60% of epilepsy patients had either ADHD-Inattentive subtype (ADHD-I) or ADHD-Combined Inattentive/Hyperactive-Impulsive subtype (ADHD-C). Inattention was diagnosed in 40% and hyperactivity-impulsivity in 18%. Age of onset of seizures, epilepsy duration, and seizure frequency were not related to severity of inattention or hyperactivity-impulsivity. ADHD-C was associated with earlier onset of seizures, generalized epilepsy, and more frequent seizure intractability, compared to ADHD-I. ADHD-I was associated with a greater frequency of localization-related epilepsy, and more frequent use of AEDs with cognitive side effects (benzodiazepines, topiramate, phenobarbital). Quality of life was impaired two-fold in children with severe epilepsy complicated by ADHD-I, and four-fold with ADHD-C comorbidity, when compared to non-ADHD/epilepsy patients. 
COMMENT. Children with severe epilepsy are at high risk for inattentive symptoms with ADHD. ADHD, particularly ADHD-C, is significantly correlated with poor quality of life in epilepsy patients. Neurological correlates of comorbid epilepsy and ADHD include the age of onset of seizures, seizure frequency, seizure type, and use of AEDs with cognitive side effects. ADHD-C and epilepsy comorbidity is a marker for severe epilepsy and/or severe brain dysfunction. Characteristics of ADHD/epilepsy comorbid cases differ from those of 'primary' ADHD in the prominence of inattentiveness as a core symptom. Impulsivity and dyscontrol are more frequent as core symptoms in children with primary ADHD (Barkley, 2006).
For a comprehensive review of ADHD and epilepsy, supported by 108 references, see Schubert R, 2005, included in Ped Neur Briefs Jan 2005;19:1-2; All types of epilepsy and even children with recent onset of seizures are involved. Patients with absence epilepsy have difficulty sustaining attention despite adequate seizure control and normal IQ. Other forms of epilepsy frequently complicated by ADHD include electrical status epilepticus during slow-wave sleep, and benign rolandic epilepsy. Brief cognitive deficits (transient cognitive impairment) occur with subclinical epileptiform discharges, and may adversely affect attention and cognitive function without the occurrence of clinical seizures. AED use in these patients is controversial. Treatment of ADHD with methylphenidate (MPH) is effective and safe in patients with epilepsy, provided seizures are controlled with AEDs [2, 3]. MPH-treatment of ADHD complicated by centrotemporal (rolandic) spikes in the EEG has a risk of precipitating seizures in 16.7% compared to only 0.6% in patients with normal EEGs.