An EEG study of deep-seated cerebral and subtentorial lesions in comparison with cortical lesions

Abstract

1. 1. The comparative localizing value of EEG was determined in 50 cortical lesions of the cerebral convexity, 50 deep-seated cerebral lesions, and 50 subtentorial lesions. Because the EEG technique utilized afforded evidence with respect to certain deep pathways of neurophysiological importance, its value in the localization of deep-seated lesions was of particular interest to us. 2. 2. The EEG characteristics of deep lesions, as opposed to the characteristics of cortical lesions, were discussed. Two EEG signs, indicative of deep-seated lesions, and which have been described by others, were verified in this series: (a) Bilateral simultaneous bursts of slow wave activity occurred in two out of three deep-seated lesions and in over one half of the subtentorial lesions. (b) Shifting asynchronous bursts of slow wave activity were found predominantly in the temporal regions, occurred in more than one half of the subtentorial lesions, and were found twice as commonly in association with lesions in this region than in the deep-seated cerebral location. Such bursts occurred in ten out of fourteen extraparenchymatous lesions of the posterior fossa. These patterns rarely occurred in cortical lesions. Their correlative value with respect to other findings and parameters of study were discussed. 3. 3. The value of EEG in localizing cortical convexity lesions was 94 per cent and slightly superior to the roentgenographic diagnostic results obtained in these same patients. 4. 4. The diagnostic value of EEG diminished in proportion to the relative remoteness of the lesions from the point of scalp recording. 5. 5. A possible explanation of bilateral simultaneous bursts and of shifting asynchronous bursts was discussed in terms of the activation of deep-seated lesions, which directly or indirectly involved the “pacemaker” mechanism and its diffuse projection system.