Abstracts

Fourteen and six positive spiking is an electroencephalographic phenomenon first described by Gibbs and Gibbs in 1951 as bursts of arch-shaped surface positive waves at 14 [amp] 6 Hz seen during drowsiness in the posterior temporal leads. It was originally associated with headache, head trauma, epilepsy, behavioral disorders, vomiting and dizziness. However, it can be accepted as a pattern appearing in normal children and adolescents. Here we describe a series of patients with unilateral temporal lobe epilepsy (MTLE) which revealed 14 and 6 Hz positive spikes during video-EEG. We analyze the relative frequency and lateralization value of this EEG pattern. [underline]Video-EEG analysis.[/underline] Electrodes were placed over the scalp according to the international 10-20 system, added to temporal electrodes positioned according to the 10-10 system and sphenoidal electrodes.
[underline]14 and 6 Hz positive spikes definition.[/underline] The EEG was visually assessed by a board-certified electroencephalographer (TRV) for the presence of 14 [amp] 6 Hz positive spikes, defined as arch shaped waves at 13-17 and/or 5-7 Hz seen generally over the posterior temporal region. The sharp peaks of its component need to be positive in respect to other regions.
[underline]Side of epileptogenic temporal lobe (TL).[/underline] The side of epileptogenic TL was defined by high resolution MRI, ictal SPECT, and neuropsychological examination, and ictal video-EEG. The ictal onset zone (IOZ) was assessed on ictal video-EEG by two investigators, and when the results were discordant, they were reviewed together to achieve agreement about the localization and lateralization of seizure onset. When the IOZ could not be localized noninvasively, intracranial EEG recordings were performed. From 359 patients examined, 22 had 14 [amp] 6 Hz positive spikes (6,12%). The localization of EEG pattern was in the lateral posterior temporal leads, with maximum amplitude in the T5-T6 and P7-P8 electrodes. In the temporal lobe the mesio-basal region discloses the minimum amplitude (sphenoidal electrodes). In one patient with foramen ovale electrode, we observed high amplitude 14 and 6 Hz positive spikes, probably related to intracranial positioning of electrodes than due to mesio-basal origin. In 21 patients, 14 and 6 Hz positive spikes were lateralized contralateral to the side of MTLE (p[lt]0.01). Our findings indicate that 14 [amp] 6 Hz positive spikes are uncommon. The high frequency of lateralized pattern in patients with unilateral MTLE and the fact that occurred consistently in the TL contralateral to the side of hipocampal sclerosis is in agreement with the theory that 14 [amp] 6 Hz positive spikes can be a normal EEG pattern and suggest that the origin of 14 [amp] 6 Hz positive spikes locate in temporal lobe. Although uncommon, the EEG pattern is a reliable method for lateralization of epileptogenic temporal lobe. (Supported by Fapesp, CAPES and CnPq.)