Electroencephalographic studies in multiple sclerosis. Specific changes in benign multiple sclerosis

EEG changes were analysed in a group of 260 patients with definite multiple sclerosis, 156 women and 104 men, average age 38.8, at different stages of the disease. Among 103 patients with an evolution up to 5 years, 34% had significantly abnormal EEG'S while in 157 patients with an evolution from 5 to 45 years abnormal records were obtained in 47.8%. The larger group showed EEG differences between benign (66 patients), malignant (23 patients) and moderate courses (68 patients) patients. The frequency of abnormal and doubtful EEGs was highest in the benign group (80.4%) and largest in the malignant group (24.1%). The main characteristic in malignant multiple sclerosis in the steadily progressive stage was a flat EEG. There was also a significant correlation between a flat EEG and intellectual deficit. In benign multiple sclerosis the dominant activities were slow (6-10 c/sec) and high voltage (80-180 muV) alpha-theta rhythms spreading all over the cortex, usually associated with "centrencephalic" discharges. A self-limiting effect of lesions around the 3rd ventricle on auto-agressive immunological processes is proposed.