The authors bring their first results of the electroencephalographic studies on localisation of brain tumors surgically verified. They worked with the Grass apparatus of 6 ink-writers. They present 9 cases. The first one is a deep left frontal abscess with the EEG showing delta waves and reverse figures on the left frontal lobe and generalised disturbances on the same side hemisphere in relation with the brain edema. The second case showed very slow waves in all the hesmisphere, with reverse figures and theta waves on pre-fronto-parietal area where was located a diffuse glioma. The third case was a convulsive with paroxystic dysrhythmia predominantly on both frontal pole and operated upon a falx meningioma at the anterior third. The fourth case showed slow waves through all the hemisphere, predominantly on frontal region, due to a very large subfrontal and fossa media metastatic tumor. The fifth case showed electroencephalographic modifications on the left parieto-occipital area due to meningioma at same localisation. The sixth case with delta waves and reverse figures on the frontal and temporal regions was due to a calcified spongioblastoma polare localised anterior to the ventricular carrefour and going so far as the plan of the sphenoid ridge. The seventh case showed diffuse left EEG disturbance with right frontal repercussion, indicating precentral lesion; at the operation, a biopsy indicated tissue near glioma. In this case the EEG was according the clinical, ventriculographic and macroscopic surgical findings. The eighth and ninth cases showed normal EEG and are cases of pituitary adenoma and acoustic neurinoma. The EEG graphics present focal alterations, as delta waves, very slow waves with reverse figures, theta waves and convulsive disrhythmias localised in cases of well limited tumors. In cases of infiltrative tumors, the modifications were diffuse and with repercussion for symetric regions of the other hemisphere. The EEG, outside of the localisation, can give elements for the type of the tumors, limited or infiltrative. The AA. believe in the value of the EEG as an element in the diagnosis of the brain tumors.
