Amygdala-hippocampus relationships in temporal lobe seizures: a phase-coherence study.

We analyzed temporal lobe seizures in patients with intracerebral electrodes to assess which of hippocampus and amygdala have a predominant role at seizure onset. Seizures were divided into those of mesial temporal onset, in which amygdala and hippocampus were involved but the neocortex was not (77 seizures from 17 patients), and those of regional onset in which mesial structures and neocortex were involved (89 seizures from 16 patients). We measured coherence and phase between one amygdala channel and one or two hippocampal channels during the first 10 s to determine which structure was leading the discharge.

Frequency of the electroencephalographic discharge in seizures of focal and widespread onset in intracerebral recordings.

The information provided by the EEG during an epileptic seizure is of critical importance in the localization of an epileptic focus. Localizing information is usually provided by the region of onset, by the predominance of the discharge during the seizure, and by postictal slow waves. In patients with intracerebral electrodes, we investigated another aspect of the discharge: its highest frequency.

Graphic representation of the EEG during epileptic seizures.

In seizures starting gradually, careful examination of the background is required to determine the time and region of onset. We propose a method for displaying EEG variables which characterize seizure onset: changes in amplitude and in average frequency compared to background. These variables are displayed topographically for each EEG channel so that 1 or 2 min of EEG may be viewed on a standard screen, thus representing pre-ictal and ictal periods.