[Video-EEG evaluation complemented by spectral and EEG source analysis in patients with medication-resistant medial...

To evaluate the value of prolonged video-electroencephalographic (video-EEG) monitoring complemented with spectral and EEG source analysis in identifying the epileptogenic area in patients with medial temporal lobe epilepsy who are candidates for non-lesional resective surgery.

The electrographic patterns during the onset of seizures were evaluated in over 667 seizures from 41 patients with a clinical diagnosis of medication-resistant partial epilepsy. Analyses were performed using Harmonie software and variable resolution electrical tomography (VARETA).

Video-EEG was used to determine that 53.6% of the patients evaluated suffered complex partial seizures of a temporal origin; these were characterised by having an average frequency of 5.56 +/- 1.56 Hz, while the non-temporal seizures displayed a frequency within the range 9.17 +/- 3.32 Hz. The topographic location of the dominant ictal frequency during the period of maximum spectral energy in patients with temporal lobe epilepsy enabled us to draw a distinction between a group of patients with mesial seizures and those with non-mesial seizures that exceeded the number that was determined by visual inspection of the EEG, that is, 78.9 versus 47.3%, respectively. There was a 100% coincidence between the area where the seizures began as defined by surface EEG complemented with spectral analysis, the generator of this activity as defined by VARETA and the epileptogenic region.

The localising information provided by video-EEG complemented with spectral and EEG source analysis allows for non-invasive location of the epileptogenic region in patients with medial temporal lobe epilepsy even when structural imaging studies show an absence or bilaterality of abnormalities.