High gamma activity of 60–70 Hz in the area surrounding a cortical tuber in an infant with tuberous sclerosis

PURPOSE To detect the epileptogenic region causing epileptic spasms in an infant with tuberous sclerosis (TS). METHODS We applied a multiple band frequency analysis to video electroencephalographic (EEG) recordings of the infant's scalp. We also performed computed tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and magnetoencephalography (MEG) of the brain in order to ascertain the epileptic focus. RESULTS During the periodic spasms, we identified fast ictal activity with frequencies of 60-70 Hz in the right centroparietal region. This region was part of the area surrounding the largest cortical tuber that was identified on CT and MRI and was located in the right frontal lobe. An area of increased blood perfusion that was observed with SPECT and dipole sources that were determined with interictal MEG were also located in this area. In addition, ictal frequency oscillations (FOs) with high gamma activity were identified over the cortex surrounding the largest tuber. After a lesionectomy of this tuber, the periodic spasms disappeared, and no FOs were detected over this area. CONCLUSIONS Scalp EEG, which identified the ictal onset zone by detecting fast activity that was suggestive of FOs, was useful for detecting the epileptogenic region in an infant with TS.