Conference Coverage

EEG abnormalities may indicate increased risk for epilepsy in patients with autism



Abnormal findings on overnight continuous EEG in patients with autism spectrum disorder (ASD) are associated with a significantly increased risk of subsequent epilepsy, according to research presented at the annual meeting of the American Epilepsy Society. In addition, a positive family history of febrile seizures also is associated with an increased risk of epilepsy in this population.

Dr. Divya Nadkarni, Ronald Reagan UCLA Medical Center in Los Angeles

Dr. Divya Nadkarni

The literature suggests that the prevalence of epilepsy in patients with ASD ranges from 5% to 40%. This broad range may result from the heterogeneity of epilepsy risk factors among patients with ASD. These risk factors include intellectual disability, age, and syndromic forms of ASD such as tuberous sclerosis complex. Regardless of whether they have epilepsy, approximately 60% of patients with ASD have EEG abnormalities. The prognostic implications of these abnormalities are uncertain.

Investigators reviewed patients’ charts retrospectively

Divya Nadkarni, MD, a neurologist at Ronald Reagan UCLA Medical Center in Los Angeles, and colleagues sought to clarify the relationship between risk factors such as EEG abnormalities and subsequent epilepsy in patients with ASD. They retrospectively identified patients who were followed jointly at UCLA and at Pediatric Minds, a neurodevelopmental clinic in Torrance, Calif. Eligible patients had a diagnosis of ASD, based on criteria from DSM-IV, DSM-5, or the Autism Diagnostic Observation Schedule. In addition, patients had overnight, continuous video EEG evaluation and a minimum follow-up of 1 week after EEG. Patients with a history of epilepsy before the initial EEG evaluation were excluded. Dr. Nadkarni and colleagues collected clinical and electrographic data by chart review.

The study’s primary outcome was time to onset of epilepsy. Among the variables that the investigators analyzed were EEG abnormalities, which they defined as focal slowing or generalized or focal epileptiform discharges. The other variables were history of febrile seizures, family history of epilepsy, family history of febrile seizures, and family history of ASD. Dr. Nadkarni and colleagues analyzed the data using the Kaplan–Meier method and Cox proportional hazards models.

In all, 164 patients met the study’s inclusion criteria. The population’s median age at the initial EEG evaluation was 4.5 years. The median follow-up after this evaluation was 2.4 years. The investigators found 63 patients (38.4%) with abnormal EEGs, and 18 patients (11%) subsequently developed epilepsy after a median of 1.9 years.

Family history of febrile seizures was associated with time to epilepsy onset

The time to epilepsy onset was associated with abnormalities on the initial overnight continuous EEG. The hazard ratio of epilepsy among patients with EEG abnormalities was 8.0. Approximately one-third of patients with EEG abnormalities developed subsequent epilepsy, compared with approximately 5% of patients without EEG abnormalities, said Dr. Nadkarni.

In addition, time to epilepsy onset was independently associated with a positive family history of febrile seizures. This finding was unexpected, said Dr. Nadkarni. The hazard ratio of epilepsy among patients with a positive family history of febrile seizures was 12.6.

The patient’s own history of febrile seizures was not associated with time to epilepsy onset. One potential explanation for this result is that it is difficult to distinguish between febrile seizure and seizure with fever in the general pediatric population. Making this distinction in children with ASD, who may have atypical febrile seizures, might be still more difficult, said Dr. Nadkarni.


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