Localization of focal brain lesions by electroencephalography

The material presented summarizes the experience of the Electrophysiological Laboratory of the A.L. Polenov Neurosurgical Institute, Leningrad, gained in the course of years in the field of localization of brain tumours. The paper emphasizes the need for a rational use of functional tests in recording bioelectric potentials of the brain for the localization of tumours in adults and children. In addition to conventional photic stimulation, other methods of increasing the localizing value of EEG are discussed and their use is particularly recommended. These methods are: trigger photic stimulation, “adequate functional tests” and, in complicated cases, a functional test involving adaptation to darkness and drowsiness. Electroencephaloscopy may be helpful in certain cases. Electrocorticography should supplement preliminary EEG data in every case of operation for brain tumour. The proposed mathematical treatment provides objective criteria for evaluating the effectiveness of the methods employed, as well as additional material for localizing a pathological process.