An important factor in the diagnosis and treatment of Autism spectrum disorder (ASD) is prescribed Electroencephalography (EEG). EEG changes may show the following: slowing, asymmetry, sharp waves or spikes, sharp and slow waves, generalized sharp and slow waves, or generalized polyspikes in a distributed or general area, multifocal or focal, unilateral or bilateral, and they may be located in many different areas of the brain. There is a need to look for a EEG phenotype typical of patients with ASD. The importance of gamma waves, rhythm mu, mirror neurons, and their role in patients with ASD was discussed. Epilepsy is reported to occur in one third of ASD patients. In ASD, seizures and EEG paroxysmal abnormalities could represent an epiphenomenon of a cerebral dysfunction independent of apparent lesions. This article reviews ASD and EEG abnormalities and discusses the interaction between epileptiform abnormalities and cognitive dysfunction.
Autism spectrum disorder (ASD) is a complex neurological disorder that has been observed, defined, and diagnosed for many years (Griffin & Westbury, 2011). The prevalence of ASD in the general population is around 1 in 88. (Bagasra, Golkar, Garcia, Rice, & Pace, 2013). It is a disorder of the brain and is manifested in three areas: impaired social interaction, difficulties with verbal and nonverbal communication, and a limited number of interests and activities. Symptoms usually appear during the first three years of life and can persist throughout a patient's lifetime. Recent researches on autism have led to the development of the concept of ASD, which allows diagnoses to include individuals with varying degrees of impairment and levels of functioning (Bluestone, 2005). Ancillary symptoms may encompass obsessive-compulsive disorder, sleep disturbances, hyperactivity, attentional problems, mood disturbances, gastrointestinal symptoms, self-injurious behavior, ritualistic behavior, and sensory integration disorders. ASD is generally considered a lifelong disability of yet undetermined etiology without an established confirmatory laboratory test and, to date, without universally established, curative pharmacological or behavioral therapies (Duffy & Als, 2012). Many studies suggest that ASD is a connectivity disorder (Assaf et al., 2010 and Belmonte et al., 2004). Furthermore, changes in brain development are known in at least some cases to precede observable changes in behavior. It is thus reasonable to conjecture that electroencephalography (EEG) signals may demonstrate discernible patterns, reflecting information about the underlying neural networks that precede changes in behavior (Bosl et al., 2011a and Bosl et al., 2011b). These data, appropriately, have spawned much research into the exploration of potential etiologies as well as the development of diagnostic tests, particularly in terms of neuroimaging and EEG (Bluestone, 2005 and Duffy and Als, 2012).
Early detection of abnormalities in EEG signals may be an early marker for the development of cognitive impairment. The differences seem to be the greatest between the ages of 9–12 months. Using several machine-learning algorithms with assessment of the size of the entropy as a feature vector, infants were classified with over 80 percent accuracy with the control group and high risk of autism at the age of 9 months. Classification accuracy for boys was close to 100 percent at the age of 9 months and remained high (70–90 percent) at ages 12 and 18 months. For girls, the classification accuracy was highest at the age of 6 months but declined in subsequent years (Coben et al., 2008, Linden, 2006 and Sohal et al., 2009).
In children with ASD, EEG changes may show the following: slowing, asymmetry, sharp waves or spikes, sharp and slow waves, generalized sharp and slow waves, or generalized polyspikes in a distributed or general area, multifocal or focal, unilateral or bilateral, and they may be located in many different areas of the brain. Autism is one of the risk factors for epilepsy. In patients with epilepsy, ASD is reported to occur in one-third of patients. Epilepsy is one of the negative factors for cognitive, adaptive, and behavioral/emotional outcomes for individuals with autism. The literature indicates several features that appear to be associated with the presence of epilepsy in ASD including IQ, additional neurogenetic disorders, developmental regression, age, and gender. In ASD, seizures and EEG paroxysmal abnormalities could represent an epiphenomenon of a cerebral dysfunction independent of apparent lesions. Early detection of abnormalities in EEG signals may be an early marker for the development of cognitive impairment in patients with ASD.
