Cns, Inc.

Frederick T Strobl

Daniel E Cohen

A method and apparatus for obtaining an indication of the extent and duration of reduced power in electroencephalographic signals as a basis for determining whether blood flow to the human brain providing such signals needs to be increased.

Electroencephalographic monitoring

An electroencephalograph (EEG) signal analyzer allows the examination of the changes in EEG cerebral activity at various sites in response to an event (e.g. a stimulus or task). The analyzer includes one or more signal processing modules which periodically sample the EEG signal from each of the sites, convert the sampled signals to digital sample values, and store those values. Digitized waveforms based on the stored digital sample values and having a length equal to or greater than the period of the lowest frequency of interest are transformed from the time to the frequency domain. For each of a plurality of epochs, a frequency spectrum is produced having frequency content which has a content uniquely due to the digital sample values from that epoch. A weighted means frequency value for each site during each epoch is derived from the corresponding frequency spectrum. Based upon the weighted mean frequency values, output signals are provided to a display and a printer to produce graphical representations of cerebral activity with time at the various sites in response to the event.

EEG signal analysis system

An electroencephelograph (EEG) signal analysis system automatically determines and displays, on a real-time basis, the frequency content of spontaneous EEG signals from the brain. The analog EEG signals from a plurality of channels are sampled and converted to digitized EEG waveforms during a continuing sequence of epochs of predetermined time duration. The digitized EEG waveform for each epoch and channel is transformed from the time domain to the frequency domain to produce a frequency spectrum representing amplitude of the EEG signal as a function of frequency. The digital data is screened both prior and subsequent to the transformation to identify those epochs which contain artifacts. During each update period, the frequency spectra for each channel from the artifact-free epochs are averaged. The amplitudes of each averaged frequency spectrum for frequencies in each of four basic frequency bands are then summed. The result is an amplitude value for each of the four frequency bands at each channel. The four amplitude values are used to update a display which contains a graphical representation of the amplitude in each of the four bands in a different color. The amplitude values are also compared with previously recorded base line values, and an audible or visual warning indication is provided when predetermined variances from the base line values occur.

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Chaska, MN, United States of America

Frederick T Strobl