Abstracts

We tested the hypothesis that differential activation of interictal spikes between wakefulness and sleep, measured during intracranial EEG (icEEG) monitoring, can distinguish between patients with medial temporal and temporal neocortical onset of seizures., A total of 17 patients with medial temporal (N=11) or temporal neocortical (N=6) seizure onset were selected from 55 consecutive patients who underwent intracranial EEG monitoring at Yale New Haven Hospital. The medial temporal group consisted of patients in whom seizure onset was recorded in medial temporal structures (electrode contacts in hippocampal formation or entorhinal cortex). All patients had multiple additional neocortical regions recorded simultaneously. Two 4-hour icEEG epochs were selected from each patient, one during wakefulness (8am-12 noon) and one during sleep (midnight to 4am). The selected epochs were separated by at least 6-hours from seizures. The sleep period was selected from the first night where characteristic sleep structure was observed with continuously evaluated delta power. The wakeful period was taken from either the same day or from the previous day. Spikes during each EEG epoch from selected contacts in the medial temporal (MT), occipital (O), frontal (F), parietal (P), lateral temporal (LT), and inferior temporal (IT) areas were detected with Reveal (Persyst Development Corporation, Prescott, AZ), a commercially available program., In the medial temporal group, there was significantly higher spiking in MT structures (p [lt] 0.05) in the sleep relative to awake state. The medial temporal and temporal neocortical groups could be distinguished by the change in number of spikes between the awake and sleep states in MT structures (p [lt] 0.001). In the medial temporal group, a greater number of spikes were observed in MT, IT and LT areas than the O, P, and F areas. In temporal neocortical patients, a greater number of spikes were observed in F, IT and LT than MT, O and P areas. There were more spikes in the F lobe in the temporal neocortical group than the medial temporal group (p [lt] 0.05)., Medial temporal and temporal neocortical onset groups differed in the change of the spiking rate between wakefulness and sleep in medial temporal structures as well as in the number of interictal spikes in the frontal lobe. The differential activation of interictal spikes between wakefulness and sleep may aid in distinguishing patients with medial temporal and temporal neocortical onset of seizures., (Supported by NIH R01-NS044102.)