Summary
Objective
Long‐term recording with intracerebral electrodes is commonly utilized to identify brain areas responsible for seizure generation (epileptogenic zone) and to tailor therapeutic surgical resections in patients with focal drug‐resistant epilepsy. This invasive diagnostic procedure generates a wealth of data that contribute to understanding human epilepsy. We analyze intracerebral signals to identify and classify focal ictal patterns.
Methods
We retrospectively analyzed stereo‐electroencephalographic (EEG) data in a cohort of patients either cryptogenic (magnetic resonance imaging negative) or presenting with noncongruent anatomoelectroclinical data. A computer‐assisted method based on EEG signal analysis in frequency and space domains was applied to 467 seizures recorded in 105 patients submitted to stereo‐EEG presurgical monitoring.
Results
Two main focal seizure patterns were identified. P‐type seizures, typical of neocortex, were observed in 73 patients (69.5%), lasted 22 ± 13 seconds (mean +SD), and were characterized by a sharp‐onset/sharp‐offset transient superimposed on low‐voltage fast activity (126 ± 19 Hz). L‐type seizures were observed in 43 patients (40.9%) and consistently involved mesial temporal structures; they lasted longer (93 ± 48 second), started with 116 ± 21 Hz low‐voltage fast activity superimposed on a slow potential shift, and terminated with large‐amplitude, periodic bursting activity. In 23 patients (21.9%), the L‐type seizure was preceded by a P seizure. Spasmlike and unclassifiable EEG seizures were observed in 11.4% of cases.
Significance
The proposed computer‐assisted approach revealed signal information concealed to visual inspection that contributes to identifying two principal seizure patterns typical of the neocortex and of mesial temporal networks.
NOV