Interest of peroperative direct cortical and sub-cortical electrical stimulations during cerebral surgery in functional areas.

Indications of surgical treatment for lesions in functional cerebral areas depend on the ratio between the definitive neurological deficit and the ben eficial effect of resection. Defection of eloquent cortex is difficult beca use of important individual variability. Peroperative direct cortical and s ubcortical electrical stimulations (DCS) provide the most precise and relia ble method currently available allowing identification and preservation of neurons essential for motricity, sensivity and language. We report our prel iminary experience with DCS in surgery of intracerebral infiltrative tumors with a consecutive series of 15 patients operated from November 96 through September 97 in our institution. Presenting symptoms in the 15 patients (8 males, 7 females, mean age 43 yea rs) were seizures in I I cases (73%) and neurological deficit in 4 cases (2 7%). Clinical examination was normal in 11 patients and revealed hemiparesi a in 4. Magnetic resonance imaging (MRI) with three-dimensional reconstruct ion showed a precentral tumor in 10 cases, central lesion in one patient, p ostcentral lesion in two cases, right insular tumor (non-dominant hemispher e) in one case. All patients underwent surgical resection using DCS with de tection in 13 cases of motor cortex and subcortical pathways under general anesthesia, in one case of somatosensory area under local anesthesia, and i n one case of language areas also under local anesthesia. The tumor was rec urrent in two patients had been operated earlier but without DCS. Resection , verified by postoperative MRI, was total in 12 cases (80%) and estimated at 80% in 3 patients. Histological examination revealed an infiltrative gli oma in 12 cases (8 low grade astrocytomas, 3 low grade oligodendrogliomas, and one anaplastic oligodendroglioma), and metastases in 3 cases. Eight pat ients had no postoperative deficit, while the other 7 patients were impaire d, with, in all cases except one, complete recovery in 15 days to 2 months. Direct cortical and subcortical electrical stimulations offer a reliable, p recise and safe method, allowing functional mapping especially useful in ca se of infiltrative cerebral tumors in eloquent areas. This technique allows improvement in the quality of tumoral resection and concurrently a minimiz ation of the risk of definitive postoperative neurological deficit.