Abstracts

Rationale: Autism spectrum disorder (ASD) is a neurodevelopmental disorder frequently with comorbid epilepsy, and sudden unexpected death in epilepsy is a leading cause of death in ASD patients.  Despite growing interest in genetic, neurophysiological and clinical overlaps between ASD and epilepsy, data on ictal electroencephalographic (EEG) recordings in ASD are lacking; behavioral disorders often make it difficult or impossible to obtain EEG recordings.  We examined ictal EEG features in a consecutive series of patients with ASD and epilepsy. Methods: We retrospectively identified 400 consecutive patients with ASD and epilepsy at our Level 4 Epilepsy Center between 2015 and 2019; 45 had at least one EEG-recorded seizure seen.  Demographics, age of nonfebrile seizure onset, age of ASD diagnosis, language, magnetic resonance imagining (MRI) findings, genetic testing and EEG studies were reviewed. Seizures were classified by semiologic and electrographic features. Ictal findings were analyzed. Results: A total of 497 seizures were captured in 45 patients ages 2 – 60 years old: 20 patients with focal onset epilepsy had 126 seizures (median: 1, range: 1-30), 17 patients with generalized onset epilepsy had 88 seizures (median: 2, range: 1-15), 7 patients with Lennox-Gastaut Syndrome had 270 seizures (median: 12, range: 1-74) and 1 patient had both right hemisphere focal and generalized onsets (12 focal, 1 generalized). Among the 20 with focal epilepsy, 2 had seizure onsets in multiple locations. Focal ictal onsets were localized to frontal (16.7%) or temporal lobes (50%) or multilobar/hemispheric (33%). Rhythmic activity (RA) at focal onset included delta (2), theta (60), alpha (10), mixed frequencies (2) or obscured by artifact (6). Focal seizure onsets included repetitive epileptiform activity (REA) in 35 cases. Polyspikes (36), sharps (9), spike wave (39) and spikes (13) were most commonly seen at generalized seizure onset. RA at generalized onset included delta (4) and unspecified (37).  Generalized motor tonic-clonic seizures (GTC) were captured in 7 patients lasting an average of 59 seconds (R: 10-78sec). Of the 21 GTC (1 in 6 patients, 2 in 1 patient, 13 in 1 patient), four seizures in four separate patients resulted in postictal generalized suppression. MRI studies were performed in 28 patients: normal (46.4%), related abnormal (10.7%; lissencephaly, lobulated lesion from tuber cinereum, mesial temporal sclerosis), unrelated abnormal (n=42.9%)). Of the 14 patients who underwent genetic sequencing, pathogenic variants were found in 71.4% all with epilepsy onset before 17 years of age. Conclusions: Our study is the first to analyze a large set of ictal data in patients with autism spectrum disorder, a population in which it is traditionally difficult to obtain ictal recordings. Our results confirm the diverse spectrum of seizure types and provide clinical-EEG correlates of seizures in ASD patients, including the presence of postictal generalized EEG suppression in 13% of tonic-clonic seizures. The finding of temporal and frontal focal onsets raises possibility of epilepsy surgery, responsive neurostimulation, or deep brain stimulation.  The presence of both focal and generalized epilepsies indicates there is not a single epilepsy mechanism in non-lesional ASD.  EEG to classify seizures and epilepsies is important to determine therapeutic options and every effort should be made to obtain EEG in this population. Funding: No funding