Indications and selection criteria for invasive monitoring in children with cortical dysplasia

In order to presurgically define the anatomical location of the epileptogenic zone (EZ) and its proximity to possible cortical and subcortical eloquent areas in pediatric patients with medically intractable focal epilepsy, an array of noninvasive tools are available: recorded seizure semiology, scalp electroencephalographic (EEG) recordings (ictal and interictal epileptic patterns), magnetic resonance imaging (MRI), positron emission tomography (PET), ictal single-photon emission computed tomography (SPECT), neuropsychological testing, and/or magnetoencephalography. When the noninvasive tools fail or are insufficient in precisely localizing the EZ and its functional and anatomical interphase with potential eloquent cortical areas, invasive extra-operative monitoring procedures might be needed. In this chapter, we will discuss the main goals of extra-operative invasive evaluation for children with medically intractable epilepsy in whom cortical dysplasia is a possible etiology. We will specifically discuss the possible indications, surgical strategies, results, and morbidity associated with the placement of subdural and stereoelectroencephalography (SEEG) electrodes. The rationale behind the choice of each one of the above techniques will also be discussed.