Multiple electrodes for detecting spikes in partial complex seizures.

The contribution of various electroencephalographic electrodes in detecting spikes from patients with seizures of suspected anterior temporal origin was prospectively studied with a standard protocol. The following electrodes were studied: International Standard 10-20 positions F7-8 and A1-2, sphenoidal (SP), nasopharyngeal (NP), anterior temporal (T1-2), mandibular notch surface (MNS), and mandibular notch subdermal (MNSD). Twenty patients were recorded of whom 16 demonstrated anterior temporal spikes. There was no difference in the number of spikes detected by SP, MNS, MNSD, or T1-2 electrodes (p less than 0.05); however these electrodes detected significantly more spikes than NP, F7-8, or A1-2. The SP electrode recorded spikes of highest amplitude (p less than 0.05). We conclude that for patients suspected of having seizures of anterior temporal origin, (1) a substantial number of spikes will be missed if only the International Standard electrode system is employed; (2) in comparison to SP electrodes the non-invasive and easily applied MNS or T1-2 electrodes will detect almost all spikes and should be used in outpatient EEG recordings; (3) NP electrodes provide no information that cannot be obtained by more reliable and better tolerated electrodes.