Mesial temporal versus neocortical temporal lobe seizures: Demonstration of different electroencephalographic spreading patterns by combined use of subdural and intracerebral electrodes

`We investigated differences between spatiotemporal intracranial EEG characteristics of temporal lobe seizures with mesiolimbic versus neocortical onset, using both subdural and intracerebral electrodes. In 37 patients we analyzed 128 seizures, assessing time intervals from initial onset of a seizure in either mesial or neocortical temporal (NT) lobe structures to sequential ictal involvement of the contralateral mesiolimbic structures and the ipsi- and contralateral temporal and frontal neocortical areas. We noted significantly more rapid seizure spread from mesiolimbic temporal (MT) structures ipsilateral to contralateral in patients with NT versus MT seizure onset. Time values for total seizure duration and time of spread from ipsilateral limbic to contralateral limbic reliably discriminate between individual seizures of either type. Three different spreading patterns were noted in the MT group and two more were noted in the NT group. Theoretical considerations concerning routes of spread are presented. In neither the MT nor the NT group could a correlation be established between pattern of seizure spread and outcome of surgery.