Fig. 8

Seizure onset localization using an assortment of montages. Illustrative successive screenshots (A, B then C) of an evolving right frontal seizure in an average referential montage (Panel I) and in a longitudinal bipolar montage (Panel II). This is a typical seizure with “a rhythmicity that evolves in space and time”. It starts in the right frontal area (black arrow) as shown in screenshots A, then progresses to involve the whole right hemisphere with relatively slower rhythmic activity (screenshots B), and finally clearly involves the left hemisphere with bilateral rhythmic spikes (screenshots C). In Panel III, the entire almost 40 s seizure is shown on a larger timebase (white arrows indicate seizure onset and offset). This high quality and artifact-free recording was stable and not affected by the seizure even though it was accompanied by full body generalized tonic–clonic movements (Racine stage 5). In this P40 rat, with kainate-induced status epilepticus, seizures similar to the one shown here, were near continuous over a period of 4–6 h, and then frequently recurred in the first 24 h following the kainic acid administration in this model of temporal lobe epilepsy. The vigorous movements associated with kainate-induced status epilepticus did not affect the electrical continuity, stability, or quality of the EEG tracings. F3: left frontal, F4: right frontal, P3: left parietal, P4: right parietal, Av: average of the signals obtained from the 4 sampling electrodes