The discussion of the relationship between autism and epilepsy and how this relationship has contributed to our current understanding of the pathophysiology of autism needs to be considered within our present definitions of autism and epilepsy. Autism includes a heterogeneous number of conditions that affect the developmental trajectory of social cognition and verbal and non-verbal communication [9
]. Repetitive behaviors and narrow interests are characteristic of individuals with autism. Autism spectrum disorders (ASD) or pervasive developmental disorder (PDD) are the common terms used to include children with autistic disorder (AD), pervasive developmental disorders not otherwise specified (PDD-NOS) and those with Asperger syndrome (AS). Children with disintegrative disorder (DD) and Rett syndrome (RS) are also included under the umbrella term of PDD but have features, specifically when discussing the relationship of epilepsy to autism, that distinguish them from children with AD, PDD-NOS, and AS [10
]. With the exception of RS, these disorders are all behaviorally defined and most recent studies use the term autism interchangeably with that of ASD to include children with AD, PDD-NOS, AS, and DD, but not RS.
Epilepsy is a paroxysmal disorder characterized by abnormal electrical brain activity associated with a variety of behavioral manifestations. Seizures have been classified into different epilepsy syndromes based on the semiology of the symptoms experienced and characteristics of the convulsive or motor manifestations, and also on the specific EEG patterns associated with the behaviors. The term sub-clinical or non-convulsive seizure is used to refer to electrographic seizure patterns without clinically recognizable cognitive, behavioral, or motor functions or apparent impairment of consciousness; it requires a concurrent EEG with behavioral testing. Epileptiform abnormalities is a term used to describe spikes or spike and wave discharges on an EEG [11
Autism and epilepsy are not single diseases or disorders. There is no single etiology for autism or for epilepsy. It is, therefore, more accurate to refer to these disorders as the autisms and the epilepsies. The core clinical feature that defines autism and related disorders and differentiates autism from other developmental disorders is a disturbance of social interaction. The hallmark of epilepsy is recurrent seizures, i.e., clinical events characterized by paroxysmal, stereotyped, relatively brief interruptions of ongoing behavior, associated with electrographic seizure patterns [11
]. Both autism and epilepsy are associated with a range of behavioral manifestations, cognitive strengths and weaknesses, and variable outcomes.
Autism and epilepsy are not rare disorders, as the estimated prevalence per 1000 children is 5.8 for autism and 7.1 for epilepsy [12
]. Approximately 30% of children with autism have epilepsy [13
] and 30% of children with epilepsy, at least those seen in a tertiary epilepsy clinic, have autism [14
]. Children with both autism and epilepsy have a worse developmental trajectory than those with either autism or epilepsy alone [15