Autism and related autism spectrum disorders (ASD) are lifelong, often severely impairing neurodevelopmental syndromes involving deficits in social relatedness, language, and behavior. Reports of increasing prevalence, the lack of well controlled studies on treatment efficacy, and the immense costs of education and care for these patients all combine to make autism a public health crisis. However, despite a large body of careful pharmacological, pathological, electrophysiological, and imaging investigations, the etiology of autism remains unclear. Known medical conditions account for only a fraction (5-20%) of autism (1
). Co-morbidity with other neurological disorders, demonstrated widespread neuropathological changes, and an emerging literature of structural and functional neuroimaging differences in autism all herald an underlying central nervous system (CNS) abnormality.
One of the best-known associations with CNS dysfunction is the high risk of epilepsy. This has been known since the first cases of autism (4
) and is commonly reported to occur in 1/3 of individuals with ASD. However, the exact prevalence remains unknown and the literature presents a wide range of estimates from 5% (5
) to 46% (6
). ASD is also increased in epilepsy populations, with as high as 32% (7
) meeting diagnostic criteria.
There is no primary seizure type or syndrome associated with autism. Complex partial (with or without secondarily generalized seizures), absence, and generalized tonic-clonic have all been reported (8
). The diagnosis of seizure activity in autistic individuals is made more difficult because the behavioral abnormalities associated with complex partial and/or absence seizures (e.g., staring and non-responsiveness with or without repetitive motor behaviors) can all be attributed to the autism. Recently, there have also been reports of high rates of epileptiform EEGs in children with autism without a history of seizures or epilepsy (13
The increased prevalence of epilepsy and/or epileptiform EEG abnormalities in individuals with ASD may be an important clue to an underlying neurological abnormality, at least for a subset of autism patients. However, there are no definitive data to help predict which children will develop epilepsy and/or EEG abnormalities and to what degree cognition, behavior and other phenotypic characteristics are affected. Fundamental questions regarding the relationship among the occurrence of epilepsy, and the cognitive, language and behavioral deficits seen in autism are still unanswered: is this just an epiphenomenon of the underlying neural dysfunction in autism, or is there a causal relationship (15
A critical review of the literature points to several characteristics that appear to be associated with the presence of epilepsy in ASD including: IQ, additional neurogenetic disorders, age, developmental regression, and gender. This paper evaluates the association of these features with both clinical epilepsy and epileptiform EEG abnormalities in individuals with autism in an attempt to identify risk factors. We also review treatment strategies and discuss emerging ideas in this area.