High frequency EEG activity associated with ictal events in an animal model of infantile spasms

Department of Neurology Neuroscience, Baylor College of Medicine, Houston, Texas, USA.
Epilepsia (Impact Factor: 4.57). 01/2011; 52(1):53-62. DOI: 10.1111/j.1528-1167.2010.02887.x
Source: PubMed


To describe high frequency (HF) electrographic activity accompanying ictal discharges in the tetrodotoxin (TTX) model of infantile spasms. Previous studies of HF oscillations in humans and animals suggest that they arise at sites of seizure onset. We compared HF oscillations at several cortical sites to determine regional differences. Methods:  TTX was infused for 4 weeks into the neocortex of rats beginning on postnatal days 11 or 12. Electroencephalography (EEG) electrodes were implanted 2 weeks later and video-EEG recordings were analyzed between postnatal days 31 and 47. EEG recordings were digitally sampled at 2,048 Hz. HF EEG activity (20-900 Hz) was quantified using compressed spectral arrays and band-pass filtering.
  Multiple seizures were analyzed in 10 rats. Ictal onset was associated with multiple bands of rhythmic HF activity that could extend to 700 Hz. The earliest and most intense discharging typically occurred contralaterally to where TTX was infused. HF activity continued to occur throughout the seizure (even during the electrodecrement that is recorded with more traditional filter settings), although there was a gradual decrease of the intensity of the highest frequency components as the amplitude of lower frequency oscillations increased. Higher frequencies sometimes reappeared in association with spike/sharp-waves at seizure termination.
The findings show that HF EEG activity accompanies ictal events in the TTX model. Results also suggest that the seizures in this model do not originate from the TTX infusion site. Instead HF discharges are usually most intense and occur earliest contralaterally, suggesting that these homologous regions may be involved in seizure generation.

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    • "Another model that has provided significant insights is the model produced via intracerebral chronic infusions of tetrodotoxin (TTX) for several weeks starting from the 10th day of life in rat pups. This leads to the development of spontaneous recurrent brief spasm-like seizures in adulthood (Frost et al., 2011. The seizures are characterized by brief extensor or flexor spasms; the ictal EEG pattern consists of an initial generalized, high amplitude, slow wave followed by an electrodecrement with superimposed fast activity. "
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