Ultrasonography was attempted to be utilized intraoperatively in 14 patients with medically intractable epilepsy. In nine of these 14 patients, epileptogenic foci were identified directly by intraoperative ultrasonogra-phy. All of the lesions with cystic components were clearly demonstrated. However, intraoperative ultrasonography could not depict satisfactorily all of the calcified lesions which had been demonstrated distinctly on preoperative CT and MRI. Even if ultrasonography could not demonstrate epileptogenic lesions, it was useful for determining localization of the lesions intraoperatively by three dimensional measurements of their location and extent by referring to sonographically identifiable structures, such as the ventricles, choroid plexus, falx, cerebellar tentorium and so on. Ultrasonography is considered to be useful as an intraoperative complement of structural studies in the surgical treatment of epilepsy.
