With medical refractory epilepsy, or if seizures are secondary to a cortical malformation, surgery for disconnection or resection can be performed. Focal cortical dysplasia, an alteration of cortical development, is the most common cause of symptomatic drug-resistant epilepsy, and surgery can achieve seizure control. Even if, pre- operative imaging modalities are able to detect cortical dis­orders, the intra-operative identication and visu­alization remain a challenge [27]. For these patients, the most important factor in terms of seizure freedom is the complete removal of the dysplastic tissue, and a poor outcome may be explained by the lack of direct identication of boundaries between dysplastic and normal paren­chyma. The use of iCEUS used at our institution enables better visualization of the dysplastic area, in order to achieve a total resection. Some drug­resistant seizures are due to the presence of other lesion types, such dysembryoplastic neuroepithe­lial tumor (DNET). A DNET is a Grade I WHO tumors described as a neuronal and mixed neuro­nal–glial tumor [28]. A simple “lesionectomy” is often sufcient for seizure control, and the use of iCEUS to delineate and identify a DNET (Fig. 19.5) is essential, even when surgery is a simple disconnective procedure, where the resec­tion of parenchyma should include the lesion (Fig.19.6).