Abstracts

Epileptic aphasias (EA) such as Landau-Kleffner syndrome can be difficult to distinguish from autism spectrum disorders (ASD) when patients present with paroxysmal behaviors or frank seizures. Previous investigations emphasize the activating effect of state on EEGs in EA, as interictal epileptiform discharges (IED) may only appear in sleep.
We tested the hypothesis that state is activating for the occurrence of IED in cases of ASD. We retrospectively reviewed EEG data from a sample of 112 children with ASD with paroxysmal behaviors of unclear etiology whom were referred for EEG study between 1998 and 2004. The sample included only those in which IEDs were present. Exclusion criteria included a clinical diagnosis of EA, recording time [gt]1hr, or pharmacological sedation.
Digital EEG data was reformatted into a modified polysomnographic montage. Sleep scoring of 30 sec epochs was performed with standardized criteria adapted from Rechtschaffen and Kales. The presence of IEDs was identified within epochs. Interrater reliability in preliminary studies was calculated as kappa 0.87 Data from ten subjects (9M, 1F/ mean age 6.5 yrs[plusmn]2.0 yrs) were studied, yielding 587 epochs. Sleep (stage I: 15.7%, stage II: 10.6%, stage: III/IV-3.9%) occurred in 175 (30%) of the epochs. The proportion of sleep epochs containing IED during wakefulness of 229/412 (55%) was identical to that in sleep, 98/175 (56%) [[chi][sup2]=0.99]. Only one child had IED restricted to sleep. All IED were focal with variable inter-subject lobar localization, with 6/10 children having temporal EEG discharges. While 2 of 3 (66%) EEGs with IED occurring during wakefulness were nontemporal, only 2/7 (28%) EEGs with IED occurring during sleep were nontemporal. In this highly selected group of children with ASD, sleep was neither an overall nor obligate activator of IED. The differential distribution of IEDs by state may be helpful in the distinction between EA and ASD and may provide insight into each syndrome[apos]s underlying pathophysiology.