1-P-F-7. Analysis of ictal high-frequency oscillation patterns of intracranial EEGs in surgical epilepsy cases due to various etiologies

Abstract

The patterns of ictal high-frequency oscillation (HFO) of intracranial EEGs in epilepsy patients due to various etiologies were investigated. All patients underwent resective epilepsy surgery, and the pathological diagnoses were confirmed as follows: focal cortical dysplasia (FCD), 5; tumor, 3; tuberous sclerosis (TS), 2; cavernous angioma (CA), 1; and no significant alteration (NSA), 1. EEGs were recorded at a sampling rate of 1 kHz. Ictal HFOs were analyzed by visual inspection and time–frequency analysis (multiple band frequency analysis; MBFA). Ictal HFOs were divided based on the maximum frequency on MBFA: n = 1); 100–150 Hz, FCD type I ( n = 2), FCD type IIA ( n = 1), tumor ( n = 1), CA ( n = 1); 150–200 Hz, FCD type IIB ( n = 1), tumor ( n = 3), TS ( n = 1); 200–250 Hz, FCD type IIB ( n = 1) and TS ( n = 1). FCD type IIB and TS had HFO with a higher frequency, whereas FCD type I and CA had HFO with a lower frequency. The results of this study suggest that the frequency of HFO reflects the epileptogenic substrate and its pathophysiological mechanism. Further investigation of a large series is necessary to determine the relationship between HFO and ictogenesis.