Design of an intracranial electrode for monitoring

Direct recording of the electric brain activity gives more information than conventional electroencephalogram. Several authors have designed a variety of electrodes in order to solve the different problems of electrocorticography but in our opinion none of these fulfil the following features: easy implantation and extraction with minimal trauma; flexibility to allow placement over regions of the brain cortex that are difficult to access (interhemispheric fissure, medial aspect of the temporal lobe, frontobasal region, etc.), good quality recording. A multiple contact electrode which we think matches these features has been designed. Initially this electrode was tested in the postoperative monitoring of ten patients with supratentorial malignant tumours and in one case of intractable epilepsy. In two patients complications of treatment were detected, one had an epileptic seizure and the other had bleeding in the tumoural bed. In the first case a right temporal focus was delineated and posteriorly excised. Implantation of the electrode was always very simple, either from the craniotomy or from a burr hole, and its flexibility allowed us to place it over the regions above mentioned. Also the extraction was easy with a simple traction and without the need for a second intervention. In all cases the recording quality was excellent.