Extending applications for high-frequency oscillations

Abstract

Epilepsy is a common neurologic disorder, affecting all ages. Despite a continuous increase in available antiepileptic drugs (AEDs), as many as 40% of people with epilepsy will have pharmacoresistant seizures.1 Surgery is a highly effective treatment for many patients with pharmacoresistant seizures, but its use is limited, in part due to difficulties in delineating the epileptogenic region. Furthermore, the median proportion of patients experiencing long-term seizure freedom after epilepsy surgery is still less than optimal—66% for patients with temporal lobe resections, 46% with occipital and parietal resections, and 27% with frontal lobe resections.2 This has contributed to the underutilization of surgical treatment,3 and underscores the need for reliable biomarkers to identify potential surgical candidates early after failure of a few adequate AED trials, and to improve the cost-effectiveness of presurgical evaluation. EEG remains the most important laboratory test for the clinical diagnosis and management of epilepsy. Interictal EEG spikes are imperfect biomarkers for epilepsy, however, and do not reliably localize the extent of an epileptogenic region. Epileptologists share the impression that there are specific “red spikes” that derive from epileptogenic tissue, and nonspecific “green spikes” that are propagated, or derive from irritable tissue incapable of generating spontaneous seizures; but EEG experts have been unable to distinguish between the two.4 High-frequency oscillations (HFOs) in the 80–200 Hz (ripple) range can be recorded from normal hippocampus and parahippocampal structures …