Comments on parametric and non-parametric detection of epileptiform spike activity

Parametric methods which will detect spikes in EEG signal have been suggested by many authors, and encouraging results seem to have been obtained. A main limitation is instrument complexity and most of the results have been obtained relatively slowly off line. The basic theoretical limitations of the approach apart from the factor of instrumentation do not seem to be fully recognized. In this paper we show that the parametric method is not optimum in the Weiner sense. that anamolous indications of spike activity are given when p, the number of filter parameters, is varied. that the mean square error is not an indicator of performance. that low p values, perhaps surprisingly, lead to better spike detection than high values. Non-parametric methods have been suggested by several authors and they show that significantly less instrumentation is required and on-line results can be obtained in real time using modest equipment. A 16-channel real-time spike monitor has been realized on an Apple II computer using a method attributed to Ninomija et al. The basic approach is to detect incidence of shapes, all of which could be actual spikes, and then in subsequent filtering stages remove those shapes which do not meet the criteria spelled out by the neurosurgeon.