Comparison of EEG derived from sphenoidal, infrazygomatic, anterior temporal, and midtemporal electrodes during complex partial seizures

Abstract

A prospective study was performed to determine whether complex partial seizures are better, or differently, recorded by sphenoidal (SP) or infrazygomatic (IZ) electrodes. Two seizures in each of 20 patients were recorded from radiographically documented SP and IZ, as well as anterior temporal (AT) and mid-temporal (MT) electrodes. Initial ictal bipolar EEG changes appeared at means of 0.57 s (SP) and 0.16 s (IZ) before, and 0.06 s (AT) and 2.36 s (MT) after, the onset of clinical signs. Mean first lateralized ictal bipolar EEG discharges appeared 0.11 s (SP), 0.88 s (IZ), 2.98 s (AT), and 3.94 s (MT) after behavioral seizure onsets. These changes occurred earlier (statistically significant) at SP than at other electrodes. Referentially, mean first ictal EEG changes occurred 0.28 s (SP) before to 0.20 s (MT) after, and ictal lateralization appeared 0.68 s (IZ) to 1.19 s (MT) after, the appearance of clinical seizure onsets. Ictal EEG amplitudes were largest (statistically significant) at SP and progressively smaller at IZ, AT, and MT electrodes. Overall, however, SP electrodes closer to the foramen ovale did not consistently reveal earlier ictal features or higher EEG amplitudes than SP electrodes farther from this landmark. For clinical purposes, SP and IZ electrodes were virtually equivalent.