Epilepsy, EEG Abnormalities in Children with Autism Spectrum Disorders

Kim, Myong A; Kim, Seung Woo; Kim, Young Key; Chung, Hee Jung

Abstract

PURPOSE:The comorbidity of epilepsy varies from 8% to 42% in autism spectrum disorders(ASD), and currently its estimate is approximately one-third of the whole spectrum. Additionally, it is reported that certain ASD patients have EEG abnormalities without epileptic history. This study was conducted to analyze the prevalence of epilepsy and EEG abnormalities in ASD patients, as well as discover the risk factors for such conditions.
METHODS
329 cases with ASD were identified from the 1252 patients who visited the Developmental Disorder Clinic at Ilsan Hospital, National Health Insurance Corporation, from April 2001 to June 2008. Among the total ASD cases, the 186 patients who have had EEG test were selected, from which 54 patients with abnormal EEG were classified as a test group and 132 patients with normal EEG as a control group. The results were analyzed and compared between the test and control groups retrospectively.
RESULTS
1) A total 186 patients of 143 males and 43 females participated in the study. Subjects were subdivided into 5 groups as follows: 14 Asperger syndrome, 70 pervasive developmental disorder, NOS, 95 autistic disorder, 7 Rett's syndrome, and no childhood disintegrative disorder. The test group was a total of 54 cases with 36 males and 18 females and average age of 56.44+/-27.51. The control group was a total of 132 cases with 107 males and 25 and its average age was 48.86+/-27.44. 2) EEG abnormalities were seen in 54 out of 186 patients(29%) and epileptic symptoms were found in 26 out of 186 patients(14%). 3) Among 186 cases of ASD patients, a total of 217 EEG were conducted and 71(32.7%) of them showed EEG abnormalities. Furthermore, it was noticed that the prevalence of abnormal EEG findings increased with the severity of the disease(P<0.05). 4) Epilepsy is directly related to the severity of ASD(P<0.05) and even higher prevalence was seen in patients with positive family history of epilepsy(P<0.05). 5) On the other hand, abnormal EEG was seen in 31 out of 160 non-epileptic patients. 6) 179 out of 186 ASD patients had taken cognitive function tests and those 156 patients with cognitive impairment were more likely to show abnormalities in EEG. Severe ASD patients were more likely show abnormal EEG and the degree of cognitive impairment was closely related to the severity of ASD(P<0.05).
CONCLUSION
Our study showed that risk factors for epilepsy comorbidity and EEG abnormalities in ASD were directly related to family history of epilepsy,the severity of ASD, the presence of cognitive impairment, and the severity of cognitive impairment. It is thought that epilepsy and EEG abnormalities are thought to be markers for underlying brain pathology that resulted in ASD. Furthermore ASD patients showed higher prevalence of EEG abnormalities than the general population, from which it can be speculated that the cause of ASD lies more closely in underlying neurobiological dysfunctions in individual patients, rather than inadequate nurturing environment.