Abstracts

To characterize the relationship between dynamic changes of ictal high-frequency oscillations (HFOs) recorded by subdural EEG and ictal clinical behaviors in children with intractable localization-related epilepsy., We retrospectively studied 22 children (12 girls; 10 boys; mean age, 12 years; range, 2 to 17 years) who presented with intractable localization-related epilepsy and who underwent extraoperative video subdural EEG (1000 Hz sampling rate) and cortical resection between July 2004 and June 2006. We reviewed slow waves and repetitive spikes without low frequency filter and HFOs using 60Hz low frequency filter on the raw subdural EEG. We performed multiple band frequency analysis (MBFA) to evaluate the frequency, distribution and patterns of ictal HFOs on power spectrograms of MBFA. We compared ictal HFO changes and ictal clinical semiologies., Sixteen (73%) of 22 patients had abnormalities on MRI consisting of cortical dysplasia in 11, mesial temporal sclerosis, multiple tubers, a small cystic lesion, old infarction, post cortical resection in one each. Six patients had normal MRI. All 22 patients had ictal HFOs. The peak frequency of HFOs ranged from 90 to 250 Hz (mean, 160 Hz). MBFA using power spectrograms and EEG revealed three patterns of ictal HFOs : A) wide-band HFOs consisting of a mixture of various HFOs with or without repetitive spikes; B) wide band HFOs with superimposed slow waves; C) sustained narrow-band HFOs consisting of an isolated HFOs ([lt]30Hz band range) with sudden electrodecremental event. We observed the wide-band HFOs (1[sim]250Hz, [sim]120electrodes) in 16 patients either with partial seizures alone (10 patients, pattern A) or with epileptic spasms (6 patients, pattern B). Six patients (pattern A+C) with partial seizures that secondarily generalized had wide-band HFOs (1[sim]170Hz, pattern A) before clinical onset and sustained narrow-band HFOs (60[sim]164Hz, pattern C) with electrodecremental events after clinical onset ([sim]28 electrodes). Four patients showed mixtures of seizure types (partial seizures and epileptic spasms, partial seizure with or without secondarily generalized in two each)., Wide-band HFOs with or without repetitive spikes corresponded to partial seizures without secondarily generalized tonic clonic seizures. Wide-band HFOs with superimposed slow waves were correlated to epileptic spasms. Sustained narrow-band HFOs with electrodecremental events after the wide-band HFOs accompanied generalized tonic-clonic seizures following partial seizures. Patterns, distribution and time course of HFOs by MBFA were associated with the clinical seizure expressions.,