[Application of topographic mapping of electroencephalogram to cerebrovascular diseases]

Abstract

Not a little difficulties lie in extraction of useful information by visual inspection alone from massive amount of data contained in multichannel polygraphic recordings of electroencephalography (EEG). Therefore, an effort to summarize conventional EEG and to demonstrate it semi-quantitatively has been made by many investigators and recently topographic mapping of EEG (TME), which is able to display equipotential maps of square roots of power spectra over each frequency band on computer-driven color video screen, has been designed. This system was clinically applied to the 16 patients who developed cerebrovascular disease with supratentorial lesions. (1) Slow wave focus was more obviously visualized on delta and/or theta bands of TME compared to visual inspection of conventional EEG in 8 cases out of 16. Also, suppression of alpha wave was beautifully demonstrated in 12 cases out of 16. The fact indicates that TME is useful as a sensitive detector of suppressed neuronal function. (2) Improvement of both TME and clinical signs after oxygenation at high pressure (case 3), carotid endarterectomy (case 1) and bypass surgery (case 6) were well correlated. The fact indicates that TME is one of the acceptable objective parameters for assessment of efficacy of various therapies. (3) TME was employed as a test evaluating effectiveness of bypass operation. This test was performed by compressing anastomosed superficial temporal artery (STA) for 10 minutes and change of TME after compression of STA was observed. In case 2 and 15, suppression of alpha activity was obviously noted in the occipital area ipsilateral to the STA compression following compression of STA, which suggested that these 2 cases depend hemodynamically on the anastomosed STA.(ABSTRACT TRUNCATED AT 250 WORDS)