Multiple Subpial Transection

Surgical procedures used to treat chronic drug-resistant epilepsy fall into two groups. The first group, resective surgery, comprises procedures in which cerebral tissue is removed on the basis that the patient’s epilepsy arises within that area, which can be safely removed. It is necessary to show that the seizure semiology, any structural abnormality demonstrated by brain imaging, usually MRI, and the results of appropriate neurophysiological investigations are all concordant and indicate that the epilepsy originates from an epileptogenic zone within the area. In these circumstances up to 80% of patients will have a significant reduction in the seizure frequency, with a high proportion free of seizures, and a concomitant improvement in other areas such as education, employment and quality of life. The second group of surgical procedures, functional surgery, is made up of operations which aim to modify the way in which the brain deals with the pathophysiology associated with chronic epilepsy. In various ways these operations try to modify the effect of the epileptic discharges so as to reduce this activity and thus reduce the clinical seizure manifestations in the patient. Whereas the rationale behind resective surgery is fairly simple, namely, that an epileptogenic zone is identified which can be safely resected, that underlying functional surgery is more complex.