Abstracts

Rationale: There have been little detailed descriptions of the intracranial ictal EEG (icEEG) patterns in children. Differences in the ictal icEEG patterns between adults and children and differences due to substrate or age dependent changes in the icEEG are unknown. We describe ictal patterns of onset recorded by intracranial electrodes in 19 pediatric patients and correlates with pathological substrates. Methods: Nineteen pediatric patients (<18 years old) with intractable epilepsy underwent monitoring with subdural grid/strip electrodes or depth electrodes for possible surgical intervention from 2003-2008. Ictal patterns from a total of 152 seizures were visually analyzed retrospectively by three separate readers and characterized by frequency, morphology, and anatomic localization (focal, regional, multifocal, or diffuse). Results: The most common pattern of ictal onset was high frequency low voltage activity (HFLV) which was seen in 9/19 patients. The next most common pattern was sinusoidal activity in the theta range with superimposed beta activity (6 patients), with the remainder of the patients (4 patients) having 4-7 Hz rhythmic spiking at the onset of their seizure. Pathologic substrates of the patients included: cortical dysplasia, infarct, cavernoma, viral encephalitis, and mesial temporal lobe sclerosis. HFLV activity and theta sinusoidal activity with superimposed beta activity were seen in the majority of patients with cortical dysplasia (14/15 patients) while rhythmic spiking was the most common ictal onset pattern in patients with substrates other than cortical dysplasia (3/4 patients). Onset was focal in 5/19 patients, regional in 8/19 patients, multifocal in 4/19 patients, non-localizable in 2/19 patients, and did not correlate with pattern of seizure-onset or region of onset. Conclusions: HFLV activity and sinusoidal activity in the theta range with superimposed beta activity are the most common ictal onset patterns in cortical dysplasia while rhythmic spiking is more commonly seen in other substrates. This will be compared to ictal icEEG in adults.