Burr-hole electrocorticography.

In 17 epileptic patients, most of them with seizures of partial type but with diffuse or focal alternating abnormalities in the electroencephalographic recordings, chronic implantation of subarachnoid electrodes was performed. Through two bicoronal burr-holes and under fluoroscopic control, 13 to 19 insulated monopolar flexible electrodes were introduced in the subarachnoid space, conducting them either to standardized cortical targets, or concentrating them in that area of interest showed by conventional EEG. The electrodes were placed bilaterally and symmetrically, and remained implanted for 10 days. During this period, the activity of multiple foci, the reciprocal dependence between them, its reaction to cortical electric stimulation, barbiturate administration and sleep, were studied. No morbidity was found. Because of the simplicity and safety of this technique, it appears to be a good diagnostic method placed between conventional EEG and stereoelectroencephalography.