Source localization of triphasic waves: implications for the pathophysiological mechanism.

To investigate the current source location from the electroencephalograms (EEGs) of 12 patients who showed typical triphasic waves attributable to various causes, using the combination of a dipole source model and a distributed source model. The triphasic waves were explained by a single main dipole in 10 of the 12 patients, and 2 patients had two dipoles responsible for the triphasic waves. All the main dipoles had a radial orientation with respect to the frontal pole. The current density of the triphasic waves was distributed mainly in the bilateral medial frontal regions along the cingulate cortices. These findings suggest that current sources located in the medial frontal area are crucial for generating triphasic waves. The source localization may be useful for elucidating the pathophysiologic mechanism of generalized non-epileptic EEG activities, such as triphasic waves.