TECHNIQUE AND EVALUATION OF THE ELECTROENCEPHALOGRAM

Abstract

The measurement of specific features of the EEG is described. A system of evaluating the EEG pattern as a whole on a 5-point scale from normality to abnormality is described. The underlying quality of stability versus instability of pattern is the basis of this system of evaluation. Normal patterns are divided into types as follows A patterns are dominated on the 3 recorded areas (frontal, precentral, and occipital) by clearly countable [alpha] sequences. B patterns lack a sequences. [image] patterns are composed of a mixture of frequencies of slow, [alpha] and fast waves, no one of which clearly dominates. MS patterns are composed of mixed frequencies but those toward the slow range are more evident. MF patterns are those in which the fast frequencies are more prominent, particularly in the precentral and frontal areas. The [image] group, though regarded as normal, is intermediate between the normal and abnormal. The abnormal features of the EEG known at present are described as "episodal" or as "continuously dysrhythmic." They include every gradation of dysrhythmia up to the well-recognized epileptic patterns; the "choppy" quality obscuring a normal pattern (associated with brain damage in 3 cases); and localized slow-wave activity associated with tumors or focal lesions. The method has been validated on selected groups of adult individuals which are compared with one another, such as a known normal group, a presumably normal or avg. group, and known abnormal groups. In the known normal group there are no EEGs rated 5, which is a rating given an EEG considered diag-nostically abnormal. In the known abnormal group the rating of 1, which is normal, appears in only a very few, whereas those rated 4 and 5 are relatively numerous.