Association of attention deficit hyperkinetic disorder and epilepsy: Further explored.

Sir,

It is well known that there is a bidirectional relation between attention deficit hyperkinetic disorder (ADHD) and epilepsy. Several studies have established the prevalence of ADHD ranging from 8% to 77% in children with epilepsy.[1] One study[2] hypothesized that if these two conditions have common pathogenetic mechanisms, then the demographic profile, clinical correlates and psychiatric co-morbidities in either group should also be similar.

We tried to further explore this association in our study. We aimed to compare the clinical profile, ADHD symptoms and psychiatric co-morbidities in ADHD children with or without epilepsy and also analyze the correlation of the seizure characteristics with ADHD profile. It was designed as a case-control study.

In our study, 25 ADHD children with epilepsy (cases) were compared with 17 ADHD children without epilepsy (controls). Their demographic profile, antenatal, birth and developmental history and IQ were compared. They were analyzed with Vanderbilt Diagnostic Parent Rating Scale and Child Behavior Checklist. The cases were further classified according to seizure characteristics and compared with one another, so as to find the differences, if any, among their ADHD profiles. We used Chi-square test, Fisher's exact test and Pearson's correlation for statistical analysis.

We found that ADHD children without epilepsy had more number of preterm delivery (P = 0.092) and lower IQ (P = 0.06). ADHD has been known to be associated with preterm births.[3] In this study, as it was found that children with epilepsy have lesser preterm births, it can be speculated that the maturation of neurons attained at term may be disrupted later by epileptogenetic mechanisms leading to ADHD in these children. The lower IQ, found in controls, may be due to the possibility that ADHD children with associated lower IQ were more likely to seek medical attention.

Prior studies in ADHD and epilepsy showed a predominance of ADHD-inattentive type.[14] This study showed ADHD-combined type to be more common, similar to the control group. Among the associated co-morbidities, oppositional defiant disorder and rule breaking behavior (P = 0.03) were more common in controls. Comparison of the seizure characteristics with ADHD and other psychiatric symptoms revealed no significant differences.

The antiepileptic medications most commonly used in these patients were sodium valproate (56%) and carbamazepine (44%). It was also observed that none of the children with epilepsy were on stimulant drugs for the treatment of ADHD. The drugs for treatment of ADHD preferred in children with epilepsy were valproate, carbamazepine and clonidine.

No specific guidelines are available to manage ADHD, when it co-occurs with epilepsy. From this present study, given that the underlying mechanisms may be very similar in either group, it seems likely that similar drugs will be useful in both the situations.

Hence, we conclude that the demographic profile, ADHD symptoms and pattern of psychiatric co-morbidities are almost similar in both groups. This gives indirect evidence that both disorders have common underlying mechanisms. Similar studies with larger sample size along with detailed neuropsychological assessment and advanced neuroimaging techniques may further enlighten us. This will help in better pharmacological and psychological management of these children.